Heat Training Week 2

Looks like we are continuing to make strides towards better heat tolerance during exercise and I've decided that for week 2 I won't bore you with more tables of data.  I'm headed to Disneyland on Saturday and will be gone for a couple of days, and by the time I get back, it will be mid-week 3 of the experiment and very close to Tevis time and I'm not going to want to go back and write this up - and really, it's just more of what I saw in week 1.  

So, instead, I'm going to share some more "heat stuff" that I've learned and more tidbits for my Readers considering the heat and its effects.

Farley’s sweat DEFINITELY has a different feel to it compared to week 1.  It’s a lot more like water and less like......snot.  The sweat “lies” against the skin and in the hair coat instead of “sitting on top”.  It doesn’t glisten as much.  And when I reach down to pat and stroke her neck in the middle of a ride, there’s actually friction between my fingers and her hair - my hands don’t glide over her hair like they did in week 1. 

Being at home with no internet and a wee android screen Funder graciously looked up whether the difference I was seeing could relate directly to a difference in sweat composition.  I knew that heat conditioning can change sweat composition of horses (http://jap.physiology.org/content/87/5/1843.long) but I didn’t know if you could actually SEE that change in composition to the naked eye.

Of course, Funder got distracted by things like latherin, which is a surfactant protein completely unique to horses that is in their sweat during her quest to dig me up an answer. 

I have to admit - I rolled my eyes at Funder and graciously allowed her to go on and on about the stupid protein.  I had come across it before, filed it away as a “gee whiz” factoid and gone on with my life.  I was much more interested in that the amount of sodium decreases in sweat with heat conditioning and I was trying to figure out whether a decrease in sodium would cause a decrease in viscosity.......

And then I actually re-reviewed the latherin molecule and realized that perhaps it was worth more than just a gee whiz.....

Latherin is a surfactant protein, which is interesting because the only other biological surfactant that I’m really familiar with is a surfactant protein that is produced in the lungs that reduces the surface tension in the alveoli (tiny air spaces in the lungs) that makes it possible for these tiny “lung bubbles” to stay open and thus let us do gas exchange......in fact, pulmonary surfactant is only manufactured by the body late in gestation and the lack of surfactant is a significant issue in premature births. 

What the heck was a protein that reduces surface tension doing on the hide of a horse???????

There’s a good review article on the internet here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005726

Turns out that its surface tension reducing properties make it a “wetting” agent for hair.  Think about spraying hose of water at a horse at low velocity when the horse is dry (ie - not sweaty), or dumping water or sponging a dry horse.  At least on my horse the water that isn’t directly under pressure of the nozzle, my hand or sponge tends to bead and roll off.  Unless friction, pressure, or some other force is added to “rub” the water into the coat, the hair seems to have a natural “water repellent” nature.  The basis of this water repellence by the hair is surface tension! Adding latherin/surfactant to the liquid reduces the surface tension and allows the hair to get wet/soaked with sweat which helps it move from the skin to the coat and to the air where it cools the horse by evaporating.  Brilliant!!!!!!!

Or in fancy science talk: acts as a “wetting agent to facilitate evaporative cooling through a waterproofed pelt”.  

The structure of the sweat gland is more simple than humans - it’s more of a direct dumping line outside of the body that doesn’t conserve sodium. The extra salt, as well as the latherin alters the evaporative point of the sweat and may lead to better evaporative cooling. Lucky lucky horsey.  So, THAT’S one way horses compensate for their increased size and reduced surface area from us puny humans (puny = advantage of relatively more surface area compared to our body volume). BTW the information in this paragraph courtesy of Hinchcliff’s Equine Exercise Physiology Text.  I’m on page 336 for those of you following along......within a chapter helpfully titled “Body fluids and electrolytes: responses to exercise and training”.

So....apparently this latherin thing is more important than “making the horse lather where something rubs when it sweats”.  I kid you not - that was the level of my understanding before this week.

So......what happens to latherin as you heat condition?  I’ve found resources that say that sodium levels decrease (and of course some resources that say there is not change, because science is a messy thing, but I’m going with sodium levels in sweat decrease with heat training) but a change in surfactant levels of sweat is a much better explanation for why the sweat feels different than the sodium content.

This is what I found: The sweat of an unfit horse contains more latherin - which is why they “foam up”.

And....that’s about all I found.  Which is a bit frustrating, because a week ago Farley wasn't "foaming up" like an unfit horse - she hasn't done that since last fall. Yet, I'm sure there was a higher concentration of latherin in her sweat last week than this week.  Not enough latherin to foam last week......but enough to give her coat more "slip" under my fingers when she sweated. Apparently no one has looked at whether there is some sequential decrease in latherin as the horse gets fitter? Either in general or just heat? Bummer.

mmm....Well.....that was a lead up to a big NOTHING. 

To make it up to you, I’m going to review some concepts from my new *favorite* book by Hinchcliff (Equine Exercise Physiology), in a section promisingly titled “Heat acclimatization” and “Recommendations for preparation for exercise or competition in hot conditions”.

I really appreciate text books that cite the actual primary references that are used for their commentary, and it’s even better when they occasionally give a short summary of the study’s findings.  Often it’s a paper I was trying to find, and to have a short synoposis of it is nice (although, must be weighed against me finding and reading the paper for myself).  

OK, time for cool tidbits in no particular order, with my random commentary
- horses that exercise and train in cool temperatures still have improved physiological responses when exercised in hot conditions (so something is better than nothing.....), but the greatest acclimatization results from training in hot conditions. 

- In human studies heat acclimation starts to occur within 3-5 days of regular exposure to and exercise in the heat (I noticed the same thing).  Most adaptations are complete within a 14 day period.  Thank goodness since most of my sessions will be concentrated in the first 14 days of the 21 day period before Tevis because of going to Disneyland this weekend and beginning of next week (YES!!!!!).  So gives me an excuse to let both of us take it easy that week before Tevis after I come back.  We will do 1 or 2 heat sessions, but for the most part I will be relaxing and resting, knowing we did the hard part of heat conditioning in the previous 2 weeks.

- The most notable changes of heat acclimation are increase in plasma volume (oooohhhhh.....because an older horse has a decrease in plasma volume and this is one reason cited for their higher HR and core temps in the heat.......I’m actually combating Farley’s older age by doing heat training!!!!!!!), a decrease in heart rate and core temps during exercise, an increase in sweating rate, and initiation of sweating at a lower body temperature (other references I found put this at ~1*C), and an increase in blood flow to capillary beds of the skin.  In general the cardio adaptations are complete within the first week of acclimation, whereas alterations in sweating responses require 10-14 days of repeated heat exposure (I did not go back to the original reference to find out what their definition of “repeated” was). Even though all this was in reference to human conditioning, Hinchcliff goes on to say that in horses there is evidence that similar changes occur.

- Sweat dripping from the horse’s body is “wasted” sweat.  It means that the amount of sweat being produced is in excess of what can be used for evaporative cooling, and evaporative cooling is how sweat cools. Sweating rates increase during exercise after acclimization.....however it abates FASTER after exercise is done, so the overall sweat losses were LOWER in acclimated horses. In this particular study that is cited, calculated sweat ion losses were 26% lower after acclimation, which was mostly due to the 10% decrease in mean sweat sodium concentration.

Here is a really interesting table from Hinchcliff that summarizes the concept (click to make larger): 

- how long does heat conditioning stick? So far everything for horses and runners I’ve found refers to conditioning for the heat “21 days prior to the event” without any reference that you could say....get that heat training out of the way a few weeks earlier. However, Hinchcliff cites some human studies that report the “rate of decay” (LOL) as one to “several” weeks.  In physically fit people, there is a slower rate of decay of the heat adaptations.  HOWEVER (and this is why I probably couldn’t find anything) no one has looked at the time course of decay in horses.  *sad eyes*.

Recommendations?  I can’t possibly list them all, but here are the highlights
1.  Horse should have a high level of “event-specific” fitness and be given adequate time to acclimate to exercise in the hotter conditions.

2. Clip

3. During the acclimatization process (14-21 days): minimal exercise during week 1, with initially only light exercise during the heat of the day with harder workouts performed during cooler periods.  Gradual increase in duration and intensity of exercise performed in the heat., including some exercise performed at the intensity required of the horse during competition (which in endurance isn’t as hard to do, but the duration is something that is sometimes hard to mimic in training)

4. Start monitoring the horse's “clinical data” 1-2 weeks prior to travel to a hotter climate so you have a good baseline during the initial days of training in the hot conditions (most of these recommendations assume that you will be taking your horse to the hotter competition area, not trying to acclimate your horse at home with blankets etc). Measure water and feed intake. Record heart rate, respiratory, rectal temps before and after training sessions.  Intensity of work effort can be estimated by heart rate monitor use.  Daily weighing is useful for estimation of fluid loss. 

5. Rectal temps were cited as being particularly important, especially post-exercise, because this is the best way to detect heat illness.  Apparently there is a lag of in rectal temperatures post exercise, especially after heavy exercise in hot and humid conditions, so measuring temps 5-10 minutes post exercise is important (by sheer luck I got this one right!).

6. The normal lecture on hydration and elyte/salt supplementation.

7. A high fat diet (8-10% on total diet basis) may “reduce the heat generated by colonic fermentation when compared to a more traditional diet that is higher in roughage”. Mmmm......no specific studies that actually quantify changes from manipulating the diet ==> heat work.  So very theoretical at this point.

Let's end with a few thoughts from my data.  

I'm finally getting temps in the 101 range post session (up to 25 minutes of work, saddled with a rump rug even in temps over 100*F). At the 10 minute mark post exercise, body temps are declining. After some more research on rectal temps ....apparently a horse’s body temperature can reach 105-106*F during endurance rides performed under moderate climate conditions.....so my work in the 101 range is probably OK.  If I take temps during Tevis, I’ll probably be completely freaked out by how high the temps are in competition and laugh at myself ever being worried about 101-102.  From what I’m reading, severe hyperthermia is considered temps above 42*C, which is about 108*F.  Temps 101.5*F and below are considered normal in the horse, according to the AAEP.

I finally have enough data that I’m looking at averages - average temperature increase from start to end of session, from start to 10 min post session, and from the end of the session to 10min post session (after cooling).  Because the horse’s temperature isn’t as closely regulated to a very narrow range (aka humans), assuming my start temp is in the normal range, I think looking at the degree drop and rise will be more informational than the absolute temperatures.  I’m still looking at pulses as absolute numbers, because I care more about the cut off of 60 and 50 than I do the “average”, and the pulses change much faster than temperatures.  I would rather know that she recovered to 56 in 5min and to 48 in 10min than that she dropped an average of 20 beats in 5 minutes (which is meaningless since getting an accurate pulse right after the work out that represents her HR during the end of the work out is impossible - it immediately starts dropping, even as I try to count it, and it varies during the work out depending on whether she’s spooking at the scary side of the arena etc.).

This will probably be my last significant post on heat training and it's effects!  I'll do one more post either right before or after Tevis on the whole 3 weeks of heat conditioning data I have on Farley and any interesting trends, but I think I've "exhausted" (as in heat exhausted....hahaha I crack myself up....) what I can find easily on this subject during my lunch breaks. 

If anyone finds out any heat related horsey stuff that I've missed, I would LOVE to hear from you in the comments!  Especially about latherin and why it decreases in fit horses?  Maybe it's biochemically expensive and since fit horses don't need it as much it decreases?

Ring bone!

If you are enjoying these biology posts, I have a recommendation for you.  I recently acquired a new textbook "Equine Exercise Physiology" by Hinchcliff and it's fabulous!!!!!!  Unfortunately it's pricey and your library may or may not own it....but if you do enough leg work on the internet, you *might* be able to find a pdf version for free.  I didn't use the book specifically for this post, but I just read the chapters on tendons and ligaments and was very impressed, as they clearly explained the biology and current research without dumbing it down and gave specific training advice at the end of chapters. A huge point was made about how much adaptation and conditioning can really be done to different musculoskeletal tissues and their conclusion is that how a horse conditions is highly dependent on the work and conditioning that they did as yearlings and younger - ie being able to run around on pasture. The last paragraph of the tendon/ligament chapter gave me chills:


"After skeletal maturity, training will have no effect on tendon adaptation and therefore training should be directed at muscular, respiratory, and cardiovascu- lar fitness rather than the tendon."

Instant sense of humility about any horse I've ever conditioned and took too much credit for their success or failure.  Likely the fruits of my labor were sown well before the horse was even a thought in my brain.

But once again I find myself getting off topic!

Today's post is based on a reader question.

Ring bone is a term used for osteoarthritis (OA) of the 3 lower joints of the horse's leg.  The bones are P1, P2, P3 (also called the proximal, middle, and distal phalanx among other names.  The Distal phalanx/P3 is also called the coffin bone) and depending on which bones are involved you may hear the ringbone referred to as "high" or "low.

Picture Credits: Figure 23-21 Hoof cartilage attached to palmar process of distal phalanx. 1, 2, 3, Proximal, middle, and distal phalanges; 4, hoof cartilage.
(Dyce et al. Textbook of Veterinary Anatomy, 4th Edition. W.B. Saunders Company, 122009.)



Osteoarthritis is new bone is deposited (note that the "extra" stuff in the picture above is cartilage and is normal) around (periarticular) or in the joints (articular). 

Here are some examples of ring bone (random pics from a google image search)

Nasty eh? 

Now we get to the REALLY fun part.  :).  The WHY and the HOW.  

In veterinary medicine there is a classification scheme called DAMNIT-V which classifies diseases according to categories like Degenerative, vascular, toxicity, etc.  Working within this scheme does 2 things.  When vets are considering possible diagnoses for a case (differential diagnosis, or DDx) using this acronomyn to think of possibilities from each category makes it less likely we will miss something. 

The chart below is from dvm360.com (a website I regularly go to if I need vet concepts explained in simple language) that shows the DAMNIT-V (V = vascular and is sometimes not included) categories along with some examples.

So for a lame horse, there are many categories (and diseases) to consider.  Is it inflammatory (osteoarthritis)?  Trauma, mechanical, neoplasia (cancer), developmental (OCD)?

Based on signalment (age, breed, sex etc.), presentation, history etc. would make some diseases more likely than others.  Diagnostics will further narrow it down. 

Now let's assume that indeed we have a case of osteoarthritis, which is a disorder whose mechanism of injury is inflammation. 

Even at this simple first step (naming the disease and DAMNIT-V category) there is some controversy.  Many of the internet resources list osteoarthritis (OA) as a degenerative disorder and even refer to it as "Degenerative Joint Disorder" (DJD).  What I was taught in school is that OA, being a productive bony disorder whose basis is in inflammation, it is technically incorrect to refer to it as degenerative disorder and we were asked not to use DJD in describing it.  Having not been in the real world clinics, I'm not sure what the general consensus is on this, so I will stick to what I was taught in class, and what is used in my favorite pathology book (Pathologic Basis of Veterinary Disease, 5th Ed, Zachary).  So, for the basis of this discussion OA = inflammation.

It gets confusing because although OA occurred because of inflammation, as a joint disease it is classified as a noninflammatory joint disease.  Inflammatory joint diseases are things like rheumatoid arthritis (which belongs in the immune-mediated DAMNIT-V category).

So, to summarize: Although OA is an inflammatory disorder, end stage OA is not an inflammatory joint disease.  

Whew.  Moving on.

Risk Factors for Developing OA
Zachary mentions that the number one risk factor for a human to develop OA is age (however this disease is NOT considered an inevitable consequence of aging) and most cases in humans are "primary", meaning that there is no identifiable cause. 

An example of a primary arthritis is me living to a ripe old age of.....I don't know.....30?  [I kid, I kid :)] and being told I now have arthritis and when I ask why, they say "it might be the running, or the riding, or the fact you broke your arm, or that fall down the stairs, or your bones line up funny or [insert your pet theory]......or a combination of living and that person next door who is your exact age and did the exactly the same things doesn't have arthritis....so we really don't know.

In animals most cases of arthritis seem to be secondary (ie - they have arthritis because of some other disease/injury/cause).  (On a slightly related topic, the important predisposing factor - ie "primary" cause - for arthritis in animals is osteochondrosis - OCD). 

Many different things can cause inflammation that lead to OA over time.  Note that many of these factors are not specific to "ring bone" development but to OA development anywhere in the skeleton.

Here are some specific causes that I found among my sources: 

-Traumatic injury - Wire injury to the pastern area that irritates/pisses off the periosteum of the bone.  One concept pounded in my brain during this particular subject at school is that the periosteum has one response to being pissed off - make lots and lots of new bone.

-Abnormalities in conformation - long sloping pasterns, upright pasterns, long toe low heel, pigeon toed, splay foot.  Conformation flaws can lead to excess strain or instability in one joint, causing inflammation.

-Joint instability (extra bone is deposited around joints that are instable in an attempt to stabalize it)

Joint surfaces that are incongruant

Inflammation of the synovium 

Excessive joint strain because of a single misstep, or a repetitive overstrain leading to joint inflammation


An article at the Thehorse.com (which tends to be overall reliable source of information) cites "age, work, and concussive forces" as the three things that make a horse the most susceptible to ring bone. The article is citing Jeff Thomason, PhD, a specialist in equine biomechanics and anatomy at the Ontario Veterinary College at the University of Guelph and he goes on to say that ring bone tends to occur in older horses worked on hard surfaces much of their lives and acknowledges the horses at the most risk are those with long toes and low heels, and probably those horses with upright pasterns or high heels.

The original question that spawned this post was whether or not trotting over hard surfaces (like hard packed roads) was a risk factor in developing ring bone. I hope you are beginning to appreciate the difficulty in answering that question.  First is the issue of "causality" which is proving something caused something else, especially when temporally separated as far apart as the work the horse might have performed, and the development of OA. 

I'm not sure that the factors of "age, work, concussive forces" are very helpful when trying to tease out the cause of ring bone and make decisions in our training.  Especially if the root cause is poor lower leg conformation.  Age and work on poor conformation, especially over hard surfaces where more concussive force must be dispersed on an already poor structure is a plausible explanation, but doesn't tell us whether a middle aged horse that has good conformation worked over moderately hard surfaces (like hard packed dirt roads) will later develop ring bone.   

What's my opinion? 

Especially because other than possible association between poor conformation = potential joint instability/abnormal concussion absorption = inflammation = OA development, I'm not sold on increased concussive forces = OA. 

Leaving aside traumatic injuries, it seems to me that the bulk of the evidence points to joint instability or other structural joint issues as the catalyst for this issue, and adding concussive forces, age, work etc. exacerbate the issue. 

So, when I'm thinking about preventing ring bone and OA in general in my horses, I'll spend more time looking and considering conformation than obsessing over the exact footing that I'm working over. 

I think good structure and biomechanics + common sense/moderation of all footing types goes a long way to preventing these sorts of injuries.  Too much of anything isn't good.  All sand training isn't any better than all hardpacked dirt training.  Doing all my training at a trot and never walking or cantering isn't ideal either. 

For a number of years my only available "every day" conditioning surface was extremely hard packed dirt road next to a canal, with some asphalt pavement interspersed.  So, I did a lot of arena work to change up the footing.  And a couple times a month I trailered out to an area that had a mix of different footing types.

Everything in moderation.

It's also important to realize that a carriage horse being worked at a trot/jog over pavement is very different from what we are asking our endurance horses to do, even if our main conditioning trails are packed dirt roads and gravel. Ring bone and side bone is often cited as a "carriage horse" disease, even though it occurs in other breeds and disciplines. 

In summary, ring bone and hard surfaces aren't something I spend too much time obsessing about in my horses.  I have a horse with good leg conformation, who is not a draft breed, who I try to work over a variety of surfaces, and chances are a career ending injury will be something other than OA development in the lower limbs.  And even if ring bone is a significant factor in her life later on, it won't necessarily be due to the ground we conditioned on - it's more likely to be because of a pastern trauma injury (of which she has at least 2 healed scars, one which is much worse than the other) which are beyond my control, or because of an overtraining issue, or a "bad step" cause.  And I'm equally as likely to injury her on ground that is too soft.  In the herd of standardbreds that I work with for civil war reenacting, there are some horses that have ring bone and some horses that don't.  The horses all have a similar background and are managed in a very large pasture.  While there is a wide variety of ages, much of the population is in it's teens, with a substantial proportion in their 20's or beyond.  Some have it, some don't.  Some are symptomatic, some aren't. Like many of the conditions that develop later in life, I think that we do not have the formula figured out for what exactly causes it, and while some of the risk factors might be known, there are a ton of confounding factors and there are other conditions that warrent our attention and perhaps our efforts at prevention.  As with so many disorders and injuries, paying attention to conformation and structure can prevent so many issues!


OK - I think we've got the point: a wide range of factors that encompass everything from genetics and conformation to injury from overtraining/overstrain or "one bad step" can cause inflammation ==> OA.   

But how does the inflammation lead to all that bone formation? 

Inflammation is the short term protective response of the body to an insult or injury.  The "hallmarks" of inflammation are "rubor, calor, tumor, and functio laesa".  Yes, I actually had to memorize that for a test.  In simple english that translates to "redness, heat, swelling, and loss of function". All of these things happen because of the innate immune system that has cells that respond to the insult/injury, and release cytokines/chemokines that are tiny molecules that act as chemical gradients to attract other "inflammatory" cells, and act on various biological entities such as  cells, membranes, bone marrow etc to cause all the local and systemic effects that we associate with "inflammation". 

Acute inflammation is necessary and useful!  This process that has us icing, taking NSAIDs, and elevating our poor sprained ankle are actually initiating the healing and repair process. However, an inflammation process that gets "too big" or goes on "too long" can cause excessive tissue damage.  The inflammatory process can be a bit like the "shotgun" approach of the body to deal with something, rather than a finely honed needle.  It's an incredibly beautiful system that does an unbelievable job against a wide variety of insults.....but it's also imperfect since it does have to deal with such a wide variety.  

I'm purposefully glossing over much of the fine detail associated with the inflammatory response since it is a topic that really needs its own post if we are going to discuss, but in summary, all those little cytokines and chemokines are not only initiated the repair and healing process of the damaged tissue, they also affect the healthy tissues around the injury to some degree. And if that healthy tissue happens to be the perisoteum or bone, or the soft tissues intimately associated with the joint......that can lead to the instability, changes in the articular surface and everything else we have been discussing!

Ugh.  Having spent WAY more time on this post than I should have today, it's back into the lab to play with my bacteria and restreak plates!

Biology for Endurance Riders and their Horses

Biology for Endurance

I have a question for you, my Dear Reader. Over the years I’ve done a number of posts about biology concepts that I thought were interesting and relevant to endurance. I firmly believe that if you understand the underlying biological concept, you as a rider and manager of your horse can think through the methods and products out there and make an informed decision on what you want to use and try.

Mugwumps posted something very interesting recently on “trainer brain”.  Basically, she was about to share with a client something she had recently discovered about her client’s horse that was going to FIX an issue and totally revolutionized some of her training thoughts and methods..........and the client was all like “that’s great. I love that you fix the horse and I trust you to do it, and I’m happy that you are going to do it, and while I love horses, I want to ride and enjoy my horses”.  The client enjoyed riding horses and being with the horse etc.....but didn’t particularly care about the nuts and bolts of how to train and thinking through all the training “stuff” and the “method behind the madness”. 

I had to laugh when I read the post because I immediately saw that I have “vet brain”.  It isn’t enough for me to know what is wrong and what I have to do to fix it.  I have to know the HOW and the WHY behind it.  In fact, I barely care about the WHAT unless I know the WHY AND HOW.  And yes, I completely get that there are a substantial portion of my readers, that while they love endurance, love conditioning, and love their horses.......do not particularly care about the biology and magic behind what they are doing.  In fact, that might be one of the reasons I’m not sure I can do clinical medicine for any length of time, because so many clients are just going to want to know the what and the fix....and I find that so unfulfilling.  :(

I think that a larger proportion of endurance riders care about the WHY and HOW than the equestrian population at large, but I don’t fool myself that all of you are quite as obsessed as I am.........but my hope is that in these “essential biology concepts for endurance riders” posts that there is a tidbit or two for everyone to enjoy matter how much or little you care about the WHY and the HOW.

As a complete side note, I am curious where my readers fall on the spectrum.....Do you care a lot of HOW/WHY?  Somewhat?  Not usually at all? Post in the comments.....

But, somehow we have wandered off the subject of the post!  I had a question for my Readers and it was NOT whether you particularly cared about biology......In fact, on further reflection I may want to remain in blissful ignorance of the particular answer...
 
Someday I want to redo those biology concept posts, update with necessary with current references, and put them into one place where it is easy to find and reference the information. While that project probably won’t happen for a while, I am wondering whether there are any biological mysteries that I haven’t covered and that you are curious about? 

Here’s some of the topics I’ve covered in the past in various detail, along with some questions that I’ve been asked that are in the draft pile. 

Heat Conditioning (Metabolics)

Hydration (Nutrition)

Antioxidants, including vit E and Selenium (Nutrition)

Hay, oil, and all that other “stuff” (Nutrition)

Fascinating muscle and joint factoids (Musculoskeletal)

Tendon conditioning and repair (Musculoskeletal)

Bone conditioning, repair, and fractures (Musculoskeletal)

The hoof - structure, growth, and function (Dermatology)

What’s up with the grey horses (Oncology)

Magic spleens (Hematology)

Are arabs really better at this endurance thing (Genetics)

NSAIDs (Pharmacology)

Balance and soundness - Design of the back and response to pressure (biomechanics)

Lyme disease (Infectious disease)

Rabies (Infectious Disease)

West Nile (Infectious Disease)

Testing the Test (Diagnostics)

Stress response - running out the stress

 The Immune system - an introduction

Filling: what is it, what does it mean, and how does wrapping help? (Inflammatory/Immunology)

Locomotion: jumping, weight carried, and other size dependent biomechanics.

Heat Conditioning Week 1

For the last week I’ve been doing a heat conditioning on Farley, and arguably on myself since I’m the one wandering about the arena at the same time. Since unfortunately I have not perfected the art of sitting in the bleachers under an umbrella and yelling “trot!” and having Farley proceed at a nice working trot around the arena. 

The point is......I’m ready to share with you my first week’s worth of data and some of my commentary! 

First some definitions and notes:

1. Because the start of my experiment also coincided with the start of a heat wave, I decided that in temps over 100 degrees, Farley could run around bare. I might change that in the future, but I was worried about putting a sheet or saddle on her and forcing her to run around in such extreme heat conditions, especially because we had never done it before. In the end, only one day was cool enough (under 100 degrees during our session) that I “covered her up” for our session. Instead of a sheet, I chose the heaviest, biggest saddle I own and added a rump rug. I think that duplicates the conditions that I’m conditioning for better than a cotton sheet. 

2. The Heat Index shown on the table was calculated from the National Weather Service using temperature and relative humidity.  Yes, our weather in the past week was that miserable.  We set a record for the number of days over 105*F in a row....Weather data was recorded at the time of the workout.

3. The “Start” parameters were taken in her paddock, in a flysheet, before leading her out.  The “end” parameters are taken in the arena immediately after stopping the work out.  I took Pulse first, then temperature since her heart rate drops faster than the rectal temperature. “Post” recordings was after walking over to the shade and hose and putting water on her and scraping.  Takes me about 5 min after finishing workout to take the end parameters and then walk her over to the cooing area.  Another 5 min of cooling, for a total of ~10 min post workout the “post” readings were taken. Cooling = in shade with cold hose water applied. 

Here’s the raw data: (some columns hidden for clarity) - click to make it larger

My observations and thoughts:

How many times? I was able to do 4 sessions with Farley during the first week. Day 1 on Week 2 is exactly one week after I started this process.


Starting Temperatures: Only on the first day the starting temperature elevated over 100*F.  As time progressed, her starting temperature DROPPED each day, even though the heat index (and weather temperature, not shown) was INCREASING each day.

Body temperatures over 101*: I only saw body temperatures over 101*F twice - once on the first day after cooling, and on the last day, at the end of the workout.  However, on that last day, the body temperature dropped back below 101 at the end of the cooling period.

Body Temperatures observations: Only on the first day (which was also the first day of the heat wave) did her body temperature continue to significantly rise from the end of the session, even after cooling.  In general, body temperature remains elevated after a session, even after pulse rapidly drops.

How long for Body Temp to reach starting temps? It would be interesting to see how long it took for her temperature to return to prior session levels, but I haven’t had that much time on my hands!!!!!

Respiration? I could not reliably take respiration counts so they are not included.  Only on day one did respiration stay elevated at the post cooling stage (not inverted, but still visibly elevated). 

Starting Condition: For all the sessions during week 1 Farley was absolutely drenched in sweat just standing in her pasture (do you blame her?  I’m sweating just thinking about how hot it was....).  At the end of the work out, she had visible wet gooey sweat on most of her body.  On July 6th (first workout of the second week), which is the only day so far that has NOT been in the triple digits, she was dry in her paddock with some residual dried salt on her neck.  Her body temp was also the lowest it had been so far. On this day after 15 minutes of a working trot saddled with a full rump rug, I stopped the work out intending to end it at that point (since I wasn’t sure how working her in a saddle and rug would affect her, even in the cooler temperatures).....but she was still absolutely dry, with only some dark damp areas under her girth.  So, I sent her out for another 5 minutes at a more extended/active trot (and she cantered some) to try and get some more heat.

Sweat Composition: The sweat on her body on week 2 day 1 session was different - more like water, less gooey and drippy.  I’m not sure if this means that the actual composition of the sweat is different or something different. 

Tired? At no point was Farley “tired” after any of the sessions. She was spooking at the scary side of the arena, offering extended trots and canters, although what we were working at, and what I asked for was a “working” trot pace.

Did I get any benefit of heat conditioning yet? I think that the results in the first 3 days of week 1 clearly show active heat conditioning.  All three sessions were 10 minutes and had increasing temperatures/heat indexes.  However all 3 days show a progressively lower body temperatures and pulses before, during, and after work. It was based on these numbers that I increased the duration of the next session to 15 minutes.

Rectal Temp thoughts: I’m not sure what exact numbers I should be targeting for rectal temperatures.  I’m more familiar with pulses and I’m very comfortable with the fact that the heart rates are not excessively high during the workout, and are coming down very quickly.  I don’t have the experience with rectal temps.  Preliminary research of studies that looked at horses and heat seem to work with 40*C (104*F) and 101*F.  ie, they will exercise horses until a rectal temperature of 104*F is reached, and then cool to 101*F or below.  I dont’ think I need to reach body temperatures as high as 104 to see benefits of heat conditioning and I would rather error on the side of NOT excessively stressing my horse two weeks before Tevis, so I think working in the 101-102*F range is probably appropriate, as long as I see temperatures come down to 101 or below after cooling.  

Heart rate thoughts: I think one thing that I’m missing is the actual rate of heart rate drop after the session. How many minutes did it take for her HR to drop below 60?  Below 50?  I think for now the 1 min and 10 min mark that I’m getting readings is sufficient.  The extra time and effort in getting more readings wouldn’t gain me enough additional information and if this protocol gets complicated and time intensive enough, I’m not as likely to get out and get ‘er done.  Know thyself......

I also think that I might need to ask for more effort or a longer time.  I don’t think her pulse is elevated enough during the sessions.  Making sure I keep her moving consistently at a working trot is important.  She’s not even near distress or even tired and I have enough body temperature data to back up my decisions so I’m more comfortable asking her to keep on motoring on.  I was super conservative this week since I was trying something new, and I intend to continue to be conservative, but I’m starting to have some confidence in the protocol and the results.

Using water to cool the horse thoughts: Besides using objective data to measure a horse’s response to heat and work, the other really interesting piece of this is seeing what really makes a difference in cooling a horse.  Shade is SO IMPORTANT.  Water and sponging and scraping is nice....but especially if I didn’t have shade for my horse, I think I would probably error on the side of putting less water on the horse overall and just focus on small key areas like over the jugular, flank, chest and girth.  I’m noticing the excess water left in the coat on places like the back and rump, even though I tried to scrape it off as best I can, seems to really impede the horse’s ability to continue to cool down once you’ve stopped actively putting water on the horse.  More water ALWAYS remains in the coat than you would like. The chest, neck, girth, flank areas are already wet because of the sweat, and they are in “shady” places on the horse, so I think water left in these areas post sponging/hosing in these areas isn’t quite as critical.  I’ve been hosing Farley completely off after the sessions because that’s what I usually do after a ride at home that I have a hose handy....but I rarely if EVER do this at a ride.  I had never analyzed or really thought about it before, but I think I was on the right track.  There’s probably a reason that horses sweat on their “shady” parts before their big expansive “sunny” parts - and I think I’ll use as my rule of thumb to not sponge Farley at a ride in areas that aren’t already damp/wet with sweat. 

Plan for Next week: I got 4 sessions in last week and I’m planning on 4-5 sessions for week 2.  I think this is about right.  I think doing something TOO consistently gets me in trouble - letting days off happen because of sheer laziness or because life gets in the way is a good thing.  I tend to error on the side of too much when I design a protocol or program much rather than not enough, and taking days off as they come lets my horse recover if what I’m doing is on the side of “too much”.  It also reminds me of what my horse looks like after some time off which is a very good thing!  A tired horse can “sneak up” on you!  Another rider who is doing a similar program is averaging ~3-4 days heat conditioning and then 1 day off, so I’m in the same ball park.

I’ll report back in another week.

Any comments?  Is anyone doing this and tracking the results?  Anything I’m missing from the data so far?


If someone has some time on their hands....I would love to see some data on how long heat conditioning “sticks”.  I know that to gain it takes 14-21 days of doing something in the heat.  But once you’ve done this type of work, how long can you hold onto it? 

So far in my experience heat conditioning for my body doesn’t seem to hold from summer to summer.  I spent one summer in on the coast working, and when I would make trips into the valley it was HOT and I felt like a wilting flower.  Even though they were temps I would normally have been fine with when I lived in the valley. However, if I screw up and get too hot and go into heat exhaustion (happened to me once a long time ago), then I seem to suffer the consequences of reduced heat tolerance for about 2 years.  So if I do good it doesn't last, but if I screw up it does?  Doesn’t seem very fair.........

Alright folks, time for me to head out and do week 2 day 2 session and gather some more data for next week!

Fractures

I had a reader request on fractures - specifically spiral fractures - and what could cause one.  Randomly falling?  Does there have to be stress cracks or similar present?

Of course, having recently completed a week of orthopedics, and already a bit in awe of bone and its awesome-ness (see my my "bone is cool" post), I may have gotten a bit excited about the subject and probably went way beyond what 99% of my readers really want to know about the subject. 

So here's a warning - this post is for the geeks that want to know the why behind the obvious.  I'm going to save the rest of you some time. The obvious is this: if you overload bone it breaks.

Feel free to skim this and pick and chose what stuff you want to understand and what stuff you just want to plunk a few "gee whiz" facts out of.  :)  My hope is that there is something interesting for everyone here, not that you are able to pass a nit picky multi-guess test on the subject........

****Necessary disclaimer for any nosy vet school administrators that come across this post....all pictures and text are either generated by me, or were honestly stolen off of google, which BTW seems to be where all the professors get their pics for lectures anyways.  I haven't deliberately lifted any images or pictures from the vet school that didn't show up on the first couple pages of a google search.

Shall we begin?

First off, bone responds to stress and loading forces very similarly to any other solid object in this world (except it can adapt and get stronger in addition to just saying *bad word*  and breaking).  In explaining how and why a bone breaks, first we need know how a bone responds to loads.

Wolf's Law: Basically says that if loading on the bone increases, the bone will remodel itself and in order to resist the forces acting on it. ie, bone will become thicker and "stronger" when you increase the demand on it, like during weight bearing exercise.  The converse is true too - if loading of the bone decreases, the bone remodels itself and less bone is present and the bone is "weaker" because less force is acting on it.

Wolf's law is the whole premise behind "conditioning" bone.  Conditioning for endurance rides is all about not creating too many stress fractures (that can weaken the overall bone and eventually cause a "pathologic fracture", we will talk more about stress fractures later in the both).  Eventually the little bone eaters (osteoclasts) will come along and remove the damaged bone that has cracks in it, and the the little bone makers (osteoblasts) come along and deposit more bone in its place.  Voila!  Bone has adapted and become stronger. 

Once you've reached a certain level of conditioning, it's all about keeping a certain activity level on the bone so that the body doesn't think that all that extra bone isn't needed and start letting the bone eaters eat more bone than the bone makers are depositing.

I went into quite a bit of detail of how bone conditions and repairs itself in my "Bone is Cool" post so please refer to that if you want more information (and ask questions if you have any!!!). So...we are going to move onto the actual bio mechanics of bone.  Let your inner engineer rejoice!

More ways to visualize/understand how bone biomechanics:
Let's say you take a bone (a long bone for the purposes of our visualization).  Now you add a "load" that bends that bone........At a certain amount of load, if you remove the load, the bone will return back to it's original shape right? It is at this load/energy that the bone is elastic.

An example of a type of load that a long bone might be "elastic" is walking around under normal body weight.  As I take a step, 130 pounds of load is applied to my leg bone and the leg bone flexes just a little. When I pick up my foot, the bone returns to it's original shape.

If you increase the load enough, the bone still bends....but doesn't quite return to it's original shape when the load is removed - there is micro damage!!!!!  The bone didn't break or "fail" but it suffered some damage as a result of the load.  This is called the plastic region.

The point between the elastic and the plastic region is called the "yield point".  The point beyond the plastic region (where the bone still stays whole, but has some micro damage) is where the bone breaks is the "failure point".

In summary: at lighter loads the bone will change shape, but be able to return to original shape when the load is removed.  At heavier loads the bone will change shape and while it won't break, can't fully return to the original shape.  At a certain point, the bone cannot handle the load and it will break or fail.  The "loads/weight" can also be thought of as "energy" being applied to the bone.  Lower energies = elastic, higher energies = plastic.  At a high enough energy applied to the bone, the bone breaks.

The big picture - let's put together the pieces and add a couple more!:
When a force is applied to a bone, how it reacts is based on the load (we've already talked about load and how it relates to elastic and plastic and failure points) AND based on the geometry of the bone's cross section. 

I'm going to start with the summary point because I think you will be able to follow the "why" better if you have the big picture first.

1. Force/energy/work is applied to the bone.

2. It bent or otherwise displaced and changed shape.

3. And then, because the force wasn't too great, the bone returned to it's original shape, either with or without stress fractures.

4. Because of Wolf's Law, bone was deposited in a way to make the bone stronger and resist the load.

5. The next time the same load was applied, the bone didn't bend or displace/change shape as much!

6. Over time, the bone remodels to resist the load (ie - bending or torsion forces) and more and more energy is required to change to cause displacement/change of shape when applying a load to a bone.

Of course, this assumes you don't overload and break the bone (or cause so many stress cracks that you end up with a pathologic fracture - we will discuss later.....)

Take a look at the picture above.  Ignore the captions and just focus on the fact that these are all cross sections of femur's (femurs are the big "thigh" bones").  Do you notice the different shapes of the cross sections?  the cross section is different because in each case different forces (or lack of forces) are acting on the bone and the bone is responding according to Wolf's law.

How a bone bends under a load, and how well it resists torsion is related to it's cross sectional area and how the bone is distributed around it's neutral axis.
*"bend" and "torsion" are types of forces that occur when a load is placed on a bone 
*for the real geeks out there, I'm now going to talk about polar and and area moment of inertia without actually mentioning those terms.......

Here are 2 important concepts: 
1. The further the material is from the neutral axis, the better the bone is at resisting bending and torsion.

2. The larger the bone's x-section is, the better the bone is at resisting bending and torsion.


Our bones aren't perfectly round.   How did the bone get distributed around the neutral axis assymmetrically?  By Wolf's Law!  Because the areas of the bone that experienced stressed got stronger and thicker and bigger!!!!!!!

Looking at the femur cross sections above, can you see that more bone is deposited on some sides than others?  That means that the bone is more adapted to resisting bending forces in that particular direction. The stress we place on our bones during movement and exercise does not build up bone equally in all directions.  It builds up bone in the specific areas of the bone that experience stress during that particular activity.  

This is why you can have a horse that has really solid conditioned bones that can pound out the trot down hill with minimal bone damage even though there is a tremendous force being applied to the bones.....but if that horse falls and the bone bends in a direction it's not used to, or is started in a different sport, it only takes a relatively small amount of force to break that bone - perhaps in the case of a fall, only the body weight of the animal.

The very last physics concept I will bore you with!!!!!!! VISCOELASTICITY
The last thing you need to understand about bones before we get into types of fractures and how they occur is viscoelasticity.

I still don't understand this concept more than superficially.

The basic premise is this - How the bone responds to force/work/energy depends on the amount of that force/work/energy......but ALSO how FAST you load the bone.    The bone can absorb more energy if you load it fast, than if you load it slowly.

The amount of ENERGY that the bone has absorbed will affect what the fracture looks like. 

For example, this is a "low energy" fracture.  The bone absorbed less energy before shattering, perhaps loaded "slowly".

These are "high energy" fractures.  These bones absorbed much more energy before shattering, and thus were perhaps "rapidly" loaded.

Types of fractures
Beyond the rate of loading, you can tell what forces were acting on the bone, by looking at the fracture type.

Here are the different forces that can act on a bone:

The bone is strongest in compression, followed by tension, and is weakest in shear force.

A fracture because of compression will result in an oblique fracture - this is because the bone will shear along the line of the greatest tension - which happens to be 45 degrees to the long axis (the shear plane).


What about a fracture because of tension?  That will result in a transverse fracture



Bending and torsion forces generate fractures that are a combination of oblique and transverse fractures, because the bending and torsion forces generate a combination of compression and tension on the bone.

Bending is a combination of tension on side of the bone and compression on the other -  the bone initially fails along the tension side (because the bone is stronger against compression forces) and starts to crack transversely.  This is the "plane of maximum tension".  The fracture continues along the shear planes (shear plane of bone is 45 degrees) on the compression side.

The result is a "butterfly" fragment of bone on the compression side of the bone. 

Torsion forces create spiral fractures:

You can see that the fracture, although it "spirals" around the bone, still follows the basic "tension" and "shear" planes of the bones, creating transverse and 45 degree oblique breaks!

If you can't picture a bone subject to a torsion force....imagine this scenario......
- A horse falls on a downslope and because of a rock or other trail debris, the foot remains stationary.  The horse is off balance, and instead of falling straight over the leg, the body twists around with the leg still in place.  Voila!  Torsion applied and a spiral fracture result.

In real life, fractures are caused by a combination of forces - for example torsion with a bit of bending thrown in, so you might see a spiral fracture with a butterfly fragment. And remember, the speed of the loading and the energy absorbed also matters! 


Stress Fractures
We are going to briefly talk about stress fractures since I think it is a more relevant form of "bone pathology" to most horse owners than a catastrophic fracture. 

"stress risers" = the fancy term that includes small/stress fractures as well as other defects in a material - in this case BONE.

According to Wikipedia (the BEST, most trusty source as well all know....no I'm not being serious), a stress riser occurs in an area of an object (like a bone....) where stress is concentrated. Why would stress be concentrated in one spot?

An object (like a bone....) is strongest when the force/energy/load being applied to it is distributed over the entire thing......a micro crack/defect/contaminant (ie a "stress riser") in the object concentrates the force/energy load and reduces the area that the force is distributed over within the object.

Because the force is concentrated in a smaller area within the object, eventually the material that the object is made of fails and the result is a small fracture.  Which we can call a "stress fracture".  Get enough stress fractures (whether they occurred through few reps of a high load - such as working the bone in the plastic region -  or lots of reps of a low load) and they will decrease bone strength exponentially.

If the defect (fracture or other defect in the bone) makes up 10% of the bone's diameter, the bone experiences a less than 5% reduction in strength.

If the defect makes up 20% of the bone's diameter, the bone will decrease in strength by 34%.

Note the lack of a linear relationship.  Small fractures and other defects in the bone are NO BUENO.  Too many stress fractures = bone strength loss = pathologic fracture

If this section on stress fractures is your biggest interest in this post, I would encourage you to go back and read my other bone post.

Here is an excerpt from that post (italics are my additions in this post):

"Stress creates tiny stress fractures (these are the stress risers we just discussed, a better word for these are micro cracks since they are the precursors to stress fractures) in the bone.  This is a normal and lets the body know that it needs to send little bone eater cells to take out the stress fracture, and then send in the bone builder cells to rebuild the bone.  You can't make bone stronger until it's replaced...and to replace bone, you have to remove the bone that is present, a little bit at a time, while rebuilding."

...tiny little cracks (occur) because the bone is under an increased load, which are being replaced by stronger bone.  These tiny little stress cracks are perfectly normal and not a concern unless..........
You overload the bone to the point where the bone building process can't keep up with the amount of bone being compromised by the micro cracks.  The bone eater cells are frantically eating up bone to get ride of the cracks and the bone builder cells are working furiously to put bone back into place - but they can only do it so fast. 

Resorption (bone eaters) takes days to weeks, formation (bone builders) takes 3 months. During the gap between resorption and formation is a period of time that the bone is potentially weaker. 

The build up of micro cracks can lead to a stress fracture.  Stress fractures can lead to a complete fractures, like the perforation of a stamp.  FYI - this is considered a "pathological fracture" as opposed to a acute or traumatic fracture, since the cause of the fracture wasn't necessarily due to your decision to gallop down a stretch of load - the fracture was due to an underlying cause of overtraining and a build up of micro damage and stress fractures.  BOOM.  Broken leg, dead horse.  BAD.   "

J.J. Kruzic, D.K. Kim, K.J. Koester, R.O. Ritchie, Indentation techniques for evaluating the fracture toughness of biomaterials and hard tissues, Journal of the Mechanical Behavior of Biomedical Materials, Volume 2, Issue 4, August 2009, Pages 384-395, ISSN 1751-6161, http://dx.doi.org/10.1016/j.jmbbm.2008.10.008. (http://www.sciencedirect.com/science/article/pii/S1751616108001021)

 The above pictures is from an unrelated experiment but do a good job showing micro cracks and stress fractures.

Some other good images (the holes are normal, the crack is not)

(above = abnormal)

(above = normal, for your reference)

 Any questions? :)

Ketch-up post

A quick post to catch up on the happenings, and then we will resume with our regularly scheduled programming soon.

It's still really really really hot here.  Like over 110 hot. 

• I've decided that when it's over 100 degrees, Farley does her heat conditioning without a sheet or blanket. 
• I've decided that when it's near or over 110, me and Farley will probably do something different for our heat training than standing in the arena free lunging.  Because insisting on keeping to our plan of a working trot under those conditions just sounds stupid.  Doing it earlier in the day when it's still *just* a 100?  Smarter.  Going for an early morning leadline run on those days? Even smarter
• The cooler motor went out last night.  And the hottest weather is still to come this week.  Basically, running the cooler (swamp cooler) all day because it's over 105 will cause the motor to get REALLY hot and not work any more.  And on a Sunday evening they will decide SCREW YOU.  Fingers crossed for a replacement motor today and easy install.  I had to pawn my bird off with my boyfriend's mom who has air conditioning, or the bird on the menu tonight would not have been chicken, but a decidedly different species indeed. 

Heat conditioning....

• Is going well.  I'll a full update for you in another 2 weeks or so - what I did, how I did it, and what the numbers look like.  A couple of interesting observations already: I can walk out to my horse in the middle of the afternoon who is just standing in her pen in the sun drenched in sweat, take a rectal temperature and it will be completely normal or slightly below normal.  That's how well she's regulating her temperature at rest.  Wow!  So a horse that looks hot in pasture may or may not actually be in distress.  The rectal temperatures before, just after, and post cooling are interesting too - I may take temps throughout tevis at vet checks to get more information of how hot does she get and how does it fluctuate during a ride?  I think that taking a temp may be just as helpful as heart rates for how understanding how hot she's getting, whether I'm doing a good job of cooling, and how heat stressed she is.  
• And on the subject of Tevis......  On a facebook group I belong too, some one was asking about a local ride and what we thought of it etc.....so I brought up my 2012 Camp Far west story on the blog, which was my first ride (I did the LD) since Feb 2011. When rereading the post, it does NOT sound like a rider who would be doing Tevis 10 months later.  I promise to come clean after Tevis and with the benefit of hindsight, post everything like the number of actual conditioning rides and miles I have on her to prepare her for Tevis, and anything else that I haven't been posting here out of sheer embarrassment.  :3. (here's the camp far west story if you want a refresher)

And now's that time where I share with you some of the best links and articles I've come across recently, just in case you need yet more reasons to waste time reading stuff on the internet :)

• The 4 minute work out Based on the information I read in that 20 min book (did a review on it but now can't find the blog link) I started during interval training in very short sessions rather than my traditional easy and long run (with some tempo runs thrown in) mileage program base that I've been doing since I was a teenager.  It netted me some surprising PR's (the sort of PR's at distances like 10+ mile races that are just as astounding as the fact that Farley completed 3 50's this spring....) so I've become a bit of believer of this idea of less is more in running.  I've never run so fast for so far, and remained injury free before.  Another link you might be interested in is: The rise of the minimalist workout
• On a related subject, here's a link to an article: "Longer runs are easier".

And for those of you that want horse specific information, here's something all endurance riders should consider: Trotting speed matters when diagnosing subtle lameness (even on the flat and straight - think vet checks)

Lastly, I have a blog recommendation.  I haven't come across a blog that was completely new to me, from a person that wasn't already connected in some way, for quite some time.  She's training to ride her first Tevis this year, and I encourage you to check it out:

• http://www.enduranceriding.me/

Heat and heat conditioning

Please someone explain to me why I can write posts for this blog day after day after day for a paltry $5/month (that’s what I make on Google ads), but I can’t even think of a good subject, let along actually START my Ride and Tie Vet Student scholarship worth $1,000. 

*Sigh*

In the comments yesterday Crysta (author of the blog Go Diego Go) brought up heat conditioning, which was a tangental point to the discussion of multidays versus doing the mileage in one chunk and the effect of hot afternoons versus rest. 

As it’s no less than 105 degrees here until we get a break of temps in the 90’s for fourth of July, I think now is an excellent time to talk about heat and heat conditioning. 

The heat of the afternoon, even with appropriate heat conditioning, takes the toll on a horse and rider (which is why I think a one day 100 in the summer may be easier physiologically than the same mileage over 36 hours - see previous post on the subject). 

The cumulative heat load that builds up over a hot afternoon has to be dissipated whether or not the horse and rider is conditioned for the heat or not.  The heat conditioned team can do so “better” and has less of a risk of ending up in distress......but energy and physiological resources still have to be “spent” to keep the body cool. 

There is a neutral operating temperature range for all species where no extra energy has to be spent to maintain body temperature (shivering, sweating etc.). The animal’s metabolic rate within this temperature zone is steady and the same as the resting metabolic rate - ie no extra energy expended.  Above and below this temperature range the metabolic rate rises as various physiological mechanisms “kick in” to either cool or warm the animal.  I think it’s natural to think about the calories or energy expended to keep ourselves warm when we fall below the thermal neutral zone (TNZ), however metabolic rate and energy expended increases when we go above the TNZ too! 

***It is important to keep in mind that this “neutral zone” is in a NON-exercising animal.  

A naked human TNZ is 28-30 degrees C, while a clothed one 22-25 degrees C.  One resource I have states the TNZ for humans as 33-35 degrees C (but whether this with clothing or in the birthday suit I'm not sure?).

For those of you (like me) that are a bit C-->F challenged:
22*C = 71.6*F
25*C = 77*F
28*C = 82.4*F
30*C = 86*F
33*C = 91.4*F
35*C = 95*F

For the sake of this discussion I’m going to assume that we are all wearing clothing and let’s call the human TNZ where we can maintain body temperature without expending energy as 80*F. 

The equine TNZ is much lower than humans. Depending on the time of year (thus coat) and body condition, most of my sources peg the equine TNZ as 30-50*F for a horse in temperate climates. 

In both the human and the horse the TNZ drops when you add exercising.......The physiologic structures that are propelling the horse down the trail and the rider up and down in the saddle, such as muscles, are generating heat.  The environment has to be that much colder to compensate for the increase in body heat, OR some sort of physiologic mechanism needs to kick in to actively disperse that extra heat. 

Depending on the coolness of the ride, the rider *might* be in their TNZ (if the ride is 60*F, that might be the right temperature for an exercising endurance rider to stay within the thermal neutral zone).

However, it can safely be assumed that when doing endurance rides, the horse is absolutely expending energy to stay cool and maintain a normal core temperature.  If you consider that at least for those of us in California’s central valley, we are regularly doing summer rides where the temps are in the mid 90’s or higher in the afternoon - that is a LOT of energy expended by the horse to cooling mechanisms during the ride.

No wonder I feel beat and the horse looks tired after a hot ride!

Some of the mechanisms a horse employs as they compete in temperatures above their thermal neutral zone are:

-blood vessel dilation

-increased respiration - accounts for about 25% of heat dissipation in the horse

-increased heart rate

-increased blood flow to skin (which transports heat from body core to the skin, which it unloads into the environment - a process greatly accelerated by animals with a sweating mechanism), and sweating (as an interesting side note.......Did you know that camels sweat?  And that marsupials and rodents don’t sweat but moisten their bodies by salivating and licking themselves?????????) In a concept that comes up over and over in biology, as the body size of an animal increases, the relative amount of surface area decreases.........which makes horses relatively inefficient at dissipating large amounts of heat through the skin....which is also the single most important way for a horse to dissipate heat!!!!!  Evaporation through sweating accounts for about 65% of heat dissipation in the horse.

- As FYI points since these aren’t strictly a physiologic changes, but they are all ways to dissipate heat....wind is your friend  :)  Have a hot horse that you have sponged and scooped?  But the air is just sitting there and not helping you out and now you have a rather wet, coolish horse but want to get cooler?  Generate some wind!  And put your horse in the shade.  And let him drink water. And periodic short walks to help muscles pull heat out of deeper tissues. 

All of these mechanisms “cost” something in physiological currency.  You don’t get anything free in this world..........In summary: If you are at an endurance ride, your horse is spending energy to keep cool. The hotter the ride or the time of day, the bigger that energy expenditure is.  This is a biological fact that has nothing to do with how much “heat conditioning” you have.  This is the cost of staying alive and moving forward in the heat.

So, if hot weather is going to cost my horse energy no matter what, what IS the point of heat conditioning? 

Heat conditioning allows you (and your horse) to actually function and perform in hot conditions instead of dying.  In some cases heat conditioning will reduce the physiologic “cost” of the cooling mechanisms, and in other cases it will just make them more available/effective/active.

How can you heat condition or function in the heat better?

General conditioning - just having muscles that are more fit will impact “heat conditioning”.  Fit muscles generate less heat to achieve the perform the same level of “work”.  Less heat generated is less heat that needs to be dissipated. Conditioning also expands capillary beds which improves the flow of blood to the skin and muscles which will make the horse more efficient at dumping the heat outside the body to the environment.

Live somewhere hot.  This sounds contrite, but it’s true.  I’ve grown up my entire life in an area where triple digits for weeks on end is not abnormal.  I’ve never had air conditioning, worked outside, and don’t notice hot temps unless it’s a really high humidity (50+) or it’s over 115*F or so.

Wear long sleeves and sweat shirts all the time.  Especially if you are working inside with an airconditioner.

Drive with the windows up and no air conditioning.  (If Tess is with me I have to make an exception - in that case I’m in a heavy jacket while I drive).

Don’t get sunburnt - I find that how much heat I can handle for how long takes a dramatic downward turn if I allow myself to get sunburnt.

Walk in the shade, run in the sun.  This actually works.  Try it!

Exercise in the middle of the day.  I do all my runs and rides at noon until the weather starts to hit triple digits.  Since I’ve started doing this, I haven’t had any problems with the heat.

My horse wears a fly blanket.  I don’t think that it makes her any hotter than without it (she’s not any more sweaty under it).  But if it does?  *shrug* I consider that a fringe benefit.

Exercise in clothes that make you sweat - live in the bay area and running in the afternoon only gives you a high of 75*F?  Where a sweat shirt and pants. 

Run high intensity intervals- this is how even in cooler weather I raise my core temp and practice living with sweat dripping down my armpits and having my respiration up really high.

Don’t clip for training.....and then +/- clip for competition if necessary

Lose weight

Get younger: From a article in the Equine Veterinary Journal Supplement: “Ageing compromises the ability to handle the combined demand of exercise and thermoregulation in part due to decreased absolute pre-exercise PV.”  Or in plain english, as you age your plasma volume (PV) decreases and the decrease in PV is to blame for why old horses reached a core temperature of 40*C faster during exercise and had a greater HR when they reached this temperature.

How long will it take to “heat condition”?

TheHorse.com says that most horses will need at least 3 weeks in a warmer climate to allow their bodies to adapt.

As this post is taking WAY more time than it should (HOURS!!!!) I’m not going to try and find any more sources on this.  Three weeks feels about right.  Two-three weeks is about how long it takes me acclimate to really hot weather and be active in it.  2-3 weeks is about how long it takes for a physiologic system to do some major shifting in metabolic pathways, gene upregulation etc.  2-3 weeks is how long it takes for vegetables not to taste bitter to me after I cut out all refined sugar in my diet.  2-3 weeks seems to be the magic number for a body to adapt, so that sounds entirely reasonable to me.........

Although, after reviewing this post, maybe this wasn’t a complete waste of my time?  Maybe I could rework this subject as my Ride n Tie Scholarship submission? 

References: here is a partial list of my references - I originally had them within the post, but it started to get a bit messy.

http://sky.scnu.edu.cn/life/class/ecology/chapter/Chapter4.htm

http://library.williams.edu/theses/pdf.php?id=403

faculty.washington.edu/brengelm/neut_zone/pg1.html

AAEP

http://www.ncbi.nlm.nih.gov/pubmed/21059010

Thehorse.com

Multidays

It's Thursday and I'm still really really, deep-in-my-bones tired.

Soreness is mostly gone except for a few twinges in my quads and some residual stiffness in my neck, but there's some healing going on someplace because I'm the sort of tired that only occurs when the body is diverting massive resources to something other maintenance activities.

I have 2 jobs - yesterday I went in to put in some hours with the department that is mostly sit down computer work.  Today I got brave and actually waltzed in the door of my more active lab job.  And....was begging for mercy mere hours later.  I spent the entire morning fantasizing about sneaking into my homeroom that was just a building away and taking a nap on the couch for my entire.lunch......mmm.......

It's a bit strange because Ive spent my time over the last couple days both more hyped up than I've been a long time (over Tevis and prepping for it, and all the blog posts I want to write, and a scholarship RnT essay that I haven't started) and yet really really sedentary. The dichonomy between what my mind is doing and what my body is doing doesn't feel....right.

In summary, I feel like I did 100 miles last weekend. 

I've been giving some thought to whether it's harder for a horse to do the mileage all in one chunk (ie 100 miles in 24 hours) or as a multiday (2 50's over 48 hours). 

As a rider, I feel about the same whether I do a one or two day 100 - mileage is mileage when it comes to my riding.

What about the horse?  

Historically I would have automatically said that riding a multiday was easier on the horse.  After all, isn't that what I've practiced and preached over the years?  That the intermediate step before moving up a distance is to ride a series of low mileage multidays? 

But now I'm not sure. 

Advantage of riding 2 50's: the horse can catch up on hydration and eating over the 12 hour break

Disadvantage of riding 2 50's: You are riding through 2 afternoons, not just one.

IMO during an endurance ride, heat is you and your horse's enemy #1.  If you ride 100 miles over 2 days, you are doing twice as many miles in the heat of the day, than if you continued on and ride the "second 50" in the evening and into the early morning hours.   The ability of a horse to "perk" up after the sun falls in a 100 is remarkably like the "perkiness" I feel on my horse at the start of day 2 of a multiday. 

It's hard to make any hard and fast rules.  What if it isn't a hot ride?  Then does the 12 hour break make up for riding during 2 afternoons?  Is it possible for a horse that has been a poor eater and drinker in the first 50 miles "catch up" in a 12 hour break and finish the 2nd 50 strong the next day?  Can you do that in a 100 utilizing 1 hour holds? 

What are the actual physiologic differences in a horse asked to do 100 miles over a 24 hour period, and horse asked to go 100 miles over a 36 hour period (in 2 12 hour periods with a 12 hour rest period between) over similar terrain in similar weather at a similar pace?

I don't know.  But I'm inclined to say that in general mileage is mileage is mileage.  And whether you are splitting that mileage up over 2 or 3 days rather than doing it in one big chunk....the miles are still miles.  With one caveat that I'll get to shortly.

I think that this miles are miles are miles has 2 important implications.

Firstly, why is it that we will do 2 or 3 50's in a weekend, yet, not do 2 or 3 consecutive weekends of one day 50's (leave the trailering consideration out of it)?  One seems entirely reasonable, the other a recipe for overriding your horse.

Secondly, I think we are less likely to give a horse the rest before and after a multiday as compared to a 100. Because we have a perception that the 100 is harder on the horse. 

So, if miles are miles are miles......why do 100's have a greater pull rate than 50's and people riding consecutive 50's? 

First, we are going to assume that the 50's and the 100's we are comparing are comparable - in fact, let's assume for the sake of this discussion that the 50's ride the same 50 mile loop on each day, and that the 100 is 2 loops of the same 50 mile trail.  So, the 100 mile horses are not riding trail they haven't seen during the day, the horses on both rides are doing the same mileage and the same terrain.  And now, let's assume that you have decent weather.  Moderately hot in the afternoon, and cooling off in the evening/wee hours of the morning to long sleeve tshirt weather (can you tell that I'm in California?).

If we ran this experiment, I predict that 2 things would happen.

1. The pull rate on the 100 would be greater than the pull rate at the end of the 2 consecutive 50's. 
2. The actual dehydration and other physiologic parameters of all the horses in both events as measured at the 36 hour mark after the initial start would be identical, (or possibly the horses on the 24 hour 100 would be slightly improved over the horses on the 50....).

If the physical ramifications are the same for both, why the greater pull rate on the 100?  I think it has more to do with the mental aspect of the game than the physical. I get stupid at the end of a long 100 that is taking me much of my 24 hours to complete.  I'm not necessarily any more sore or stiff or tired after a 100 versus a 2 days, but trying to work through sleep deprivation at the end of a long 100 is the WORST.  It's really really hard to make good decisions, and it's really really hard to keep doing the "little" things that make sure you don't have problems later in the ride.  Riding 2 50's basically gives you (IMO) exactly the same physical "workout" without having to deal with the mental stuff.

I know I need 8-9 hours of sleep a night.  I have no idea what my horse needs - but whatever it is, just like me they aren't getting it on a 100.  And just like the rider, I think that mental "tiredness" and "stupidity" of the horse after a long day with no sleep plays a bigger role in the pulls than any true physical unreadiness, assuming that same horse can do the same 100 miles over 2 days at a multiday. 

IMO a 100 mile rider and 100 mile horse aren't necessarily a fitter team than those doing back to back 50's, but they ARE dealing with a mental component that just isn't present during a multiday (and yes, I think there are people and horses are that better at dealing with this than others).

So......if you want to do 100's and you feel stuck at the 50 mile mark, consider doing back to back 50's over similar terrain in similar weather as the 100 you want to do. Obviously if your goal is Tevis, don't do 2 50's in the bay area, or in the high desert in December and expect success and smooth sailing for a 100 held in July in the Seirra Nevadas. But assuming that you and your horse get through those comparable 50's in good physical shape, recognize that your biggest obstacle for riding a 100 at that point is mental.  Physically, as long as you gave you and your horse the appropriate rest after those 50's, you should be ready to go.

Obviously, this is all a guess on my part.  Educated guessing from someone with too much time on their hands and a commute that allows them to be inside their head too much....but guesses all the same.  (I welcome your comments and thoughts!)

My next post will address moving up in distance (I've done an LD.  Now what?) so I don't want to venture too far down the lane of moving up distances and when the right time is to move up a distance....but a couple more thoughts on multidays

- Because I'm starting to feel like mileage is mileage is mileage.....If I wanted to do an intermediate distance between a 50 and a 100 miles before diving into 100 miles over 2 days, I would do a 50 and an LD back to back before doing 2 50's.  (as a side note, I would do the 50 the day before the LD, not the other way around - that allows me to ride my horse in the cool of the morning, the heat of the afternoon, and then the cool of the morning again.  Instead of doing 2 cools and ending on a hot, which is not how a 100 is going to go!)

- I think that doing LD mulidays do NOT give you the same benefit of moving up to 50's as doing multiday 50's does for moving up to 100's.  Because most of the LD mileage is done before the heat of the day, you have to consider that you just did 50 or 60 miles in the best part of the day when it was cool, and zero mileage in the heat of the day.  (In contrast, doing 2 50's as 100 mile prep means that you will be doing MORE mileage in the sun than you will for your 100, which may offset the 12 hour break in helping prepare you for the step up in ride distance).  Even doing 3 or 4 LD's in a row isn't a guarantee that you are preparing your horse well for the step up in distance - The break is too long between ride starts (18 hours), all mileage is done in the cool of the day.  This is one reason why I think the step up from an LD to a 50 is in some ways tougher than the step up from a 50 to a 100. 

Responsible horse owners

Yesterday I decided that responsible horse owners don't sit at home and write blog posts all day when there is a trailer to unpack.  Responsible horse owners don't watch whole seasons of supernatural episodes on the couch when horse hooves need trimming.  Responsible horse owners absolutely don't take covert naps when their horse needs turn out (I don't worry about turn out except for the first 7 or 10 days post ride.  In which case I'll do it, or I pay someone else to do it.  Lessons learned from Tevis 2010....).

So.  I compromised.  And Farley and I went on a bareback, in-a-halter, I-might-have-been-in-a-helmet, but-definitely-I-was-bare-foot ride. 

I closed my eyes, raised my hands in the air, and BREATHED. 

I looked like a demented hippie doing yoga.  On horse back. At 2pm in the afternoon.  On the most humid day I've ever experienced in CA.  

Farley walked some, trotted some, but mostly just walked. 

For 20 minutes I focused on nothing else but breathing and being centered and balanced and straight.  Which is surprisingly hard to do with your hands in front of you on the reins. 

So I didn't use the reins. 

I knotted the reins in her hair so she wouldn't get caught up in them if they shifted to the side and decided that the worst that would happen is that I would slide off her back into the soft dirt if she did something stupid.  Which being bareback isn't that far. 

I still love riding bareback.  Even as an adult, knowing that I no longer bounce as well as I used to.  Even after getting quality instruction in the saddle and KNOWING how to use the tack to my advantage, NOTHING quite soothes my soul as well as going bareback.  Because sometimes being a responsible horse owner is being able to put away the shoulds and oughts and embracing what is right for that moment.