18/12/2023
Good, solid advice from one of the champion sprint mushers/Professor of Clinical Nutrition...
Heat Tolerance
with Dr. Arleigh Reynolds
Arleigh graduated from Cornell University and was on the faculty at Cornell University. He worked for Nestlé Purina Pro Plan as a senior nutritional scientist from 1998 through 2023. Arleigh is now on the faculty at University of Alaska, Fairbanks since 2014.
In his world of sled dogs, Arleigh went on to be a three time world champion in sprint mushing. He's one of six mushers in the history to win a Triple Crown, winning the open North American, the Fur Rendezvous, and the Tok Race of Champions.
Arleigh is a professor of clinical nutrition. He's a diplomat to the American College of Veterinary internal medicine. He's a director of the center of One Health Research at University of Alaska, Fairbanks.
https://www.uaf.edu/.../steeri.../reynolds-arleigh/index.php
*Temps are in Fahrenheit
ACCLIMATION
You talked a little bit about acclimating to warmer temperatures. Can you expand upon that? I mean, how long, in your opinion, does it take? I mean, and I remember you telling me that 32°F in a sled dog is dangerously warm.
"It is. So our first races of the year would often be in Montana Creek, which is below the Alaska range. We would often leave home at 40 below and arrive down there at 40 above. That's an 80 deg shift from what the dogs are used to. And a lot of teams would look like dish rags and really have overheating issues. So what we found to help, but what helped us, was we had a dog barn. So when it was 40 below out, our dogs would be living inside when it was 55 or 60, and just living inside like that, we go down there and win those races going away, and our dogs would handle the heat really really well. I never had problems with that. But I also selected for heat tolerance in my dogs, I would take the young ones when they're puppies and yearlings and run them in 50 deg weather for their last run of the year, slowly and not with a lot of you know weight in the sled or anything. The dogs that came back wagging their tails and looking good, those are the ones that stayed in our kennel, the dogs that looked like they were hot, they became limited class dogs. So we did a lot of selection for that, so the reason I bring that up is there's a lot to heat tolerance. There is certainly a genetic component. Keeping their body condition on the thin side is huge. And exercising them in the conditions, the temperature and humidity that you're going to experience, and then monitoring them so you know, you can read them and know when they're getting into trouble, those are, I think your best weapons, and then, you know, like I was talking before, washing off that foam from the back of their mouth so that their cooling apparatus works well. And I always keep a thermometer with me, and I always keep something to cool the dogs off with, so that if they do get in trouble you can get them out of trouble quickly.
Where you run into trouble with overheating is when the body temperature stays elevated for a prolonged period of time."
CONDITIONING
VO₂max, what is it and why is it important?
"VO₂max is the maximum amount of oxygen that a dog can metabolise per unit of body weight per unit of time, and really what it is is a measure of the size of the dog's engine, the bigger the engine the more power output the more they can do, the reason it's important is if we can take a dog from an un-trained to a trained state they can exercise at a greater intensity for a longer period of time without getting tired, that's the bottom line, they don't build up as much lactic acid, they don't get as hot and they're able to do more work if we can increase that VO₂max. Two ways we can do that... one is by conditioning and the other is the way we feed them.
An off the street dog that's not exercising might have a VO₂max of around 100mL/kg, we can get them up to 240 (highest measured in a human athlete being around 90mL/kg) by the way we train them and feed them, we can have a huge impact.
Dogs are about 3x the VO₂max of the very best human.
The real secret to developing VO₂max in terms of diet is feeding higher fat diets, they don't have to be all fat but higher fat. We were able to increase VO₂max by almost 50% by the way we fed the dogs once we got them to the peak of training, so we were taking them from 120-240.
VO₂max affects endurance factor but it also affects power, because when you can do the same amount of work by just using oxygen without having to generate lactic acid you can do that work longer, for example... when we look at energy look at a glucose molecule, a sugar molecule, as an example if it's fully burned in oxygen you get 36ATPs out of it (the energy currency the cell uses for energy), you take that same glucose molecule and instead of burning it in oxygen you do it anaerobically and generate lactic acid you get 2ATPs, so you will run through your glucose stores 18x faster if you're going anaerobic than if you're staying aerobic, and higher VO₂max allows you to stay aerobic longer at higher power outputs, at higher exercise intensities."
What are indicators? we don't have the ability to measure VO₂max, what will we see?
"When you're working your dogs what are the indices of fatigue?... Wide mouth open breathing, their tail-set, their enthusiasm, whether they're shaking or not when they get back from a workout, those types of things will give you a good indication of how exhausted the dog is, and one of the things that's related to this ofcourse is heat stress, and that's a big issue as you come into events in warm weather and this is highly related to that, a dog that's staying aerobic is going to be able to tolerate higher temperatures better than one that goes anaerobic for one thing, and then they're going to recover faster too."
How do we tell the difference between Heat problems and Fatigue?
"There's one simple answer to that... take the dog's temperature. One of the things I've always tried to do with my guys 'cause dogs are individuals and we were running teams of 16/18 dogs at a time so you gotta be able to read each one of those dogs and what they're telling you, one of the things I would always do in the summer time when we were exercising is take the dog's temperature so I could get an idea of what temperature correlated with what behaviour for individual dogs, and that was really helpful and that's something somebody can do and get an idea of how hot, you'd be surprised I think when you take those dog's temperatures how hot some of those dogs are getting, we had dogs that would sometimes come back from a summer workout with temperatures of 108/109 Fahrenheit, the key was that they would drop down below 104 in less than a minute, if they're staying above 104/105 for any period of time that's when you really gotta be carefull. One of the things I learn't that really helped me a lot in terms of heat tolerance for helping the dogs you wanna acclimate them to warm weather but you don't wanna get them so hot that they get hurt, certainly exercising in warm weather helps, having access to allow them to cool off like swimming and stuff like that helps.
One of the things we found with our dogs is when they get really warm they pant really hard and they get this white foamy saliva that kinda coats their mouth and back of their throat, that's a real problem because dogs as predators they don't sweat like we do, the way that their cooling mechanism is designed is they pant so that they can keep their brain cool, there's a blood vessel plexus in the back of their throat that acts like a radiator in a car and when they pant they're moving air over that thing and the evaporation of the moisture cools the blood that's going to their brain and keeps their brain from overheating even though their body's getting pretty warm so that they can continue to chase prey, it's just an adaptation, but here's the problem... when they get all that white foam there it insulates that radiator and it doesn't work very well, so one of the things we taught our dogs to do was to drink out of a sq**rt bottle, not so much 'cause we were trying to give them so much water but we were trying to rinse that stuff off the back of their throat so their cooling mechanism would be more efficient and they wouldn't have to pant as hard to stay cool, it really made a big difference."
The difference between long slow distance and high intensity training?
"In terms of improving VO₂max the best way to do that is with long slow distance training, and you're also gonna way decrease their risk of injury and you're also gonna reduce the risk of a heat stress by doing that. The Norwegians actually figured this out a long time ago, they do what they call polarized training where they spend like 80-90% of their training at long slow distance and just like 10% at speed or interval type training and by doing that they decreased injury, they decreased fatigue and they really improved the benefits of the training.
It takes 8-12 weeks to get them in really good condition, we put the dogs on the wheel for 2hrs at a time 3x a week and get them pretty fit and that's really how we could bolster their VO₂max and then we could maintain that VO₂max by doing that once every 7-10 days, the low intensity type training that maintains VO₂max, you can maintain it by hitting it once every 7-10 days."
"You think you can't take time away from what you're doing because you think it's gonna put you back but actually by taking a little time out to condition, your training is gonna improve and the dog's performance is gonna improve because the dog's not gonna get as hot, they're not gonna get as tired, they're not gonna worry about how hard they're breathing, they're gonna be able to focus on what it is you want them to do because they're in great shape... and they run cooler like that, they eat better, they drink better, because when dogs get dehydrated or overheated they don't wanna do either one of those things, so it helps their overall performance. "
FASTING
"The dogs with the best endurance were the ones that were fed 24hrs ahead of time, there's several reasons for that... one is that whenever you eat you secrete Insulin and Insulin is a hormone that actually inhibits your ability to mobilise and use fat for energy, and most dogs have 50-100 times more energy stored in fat than they do in the stored form of carbohydrate which is glycogen so you wanna be able to optimize that energy source and that Insulin stays elevated for about 4hrs, so for atleast 4hrs after a dog eats you've impaired their access to their most important fuel source, their largest fuel tank. Another problem with eating is that there's a certain amount of heat that is generated in the process of digestion and absorption, we call it Specific Dynamic Action of heat, diving marine mammals actually use that to keep themselves warm, but that heat especially in a dog that might have some issues with heat tolerance 'cause they're exercising in warm weather they're gonna start 1 or 2 or 3 degrees (Fahrenheit) warmer at the beginning of exercise which means they're gonna overheat more rapidly. You also have the blood flow to the gut that has to digest and absorb that food, and if you're trying to work you're taking that blood away from the muscles and that can either make the dog sick to the stomach if they're working so hard sometimes they may actually vomit, but it does rob the muscles from some of the blood that they need to do their work.
You wanna optimize that fat utilisation but here's the thing... they're always gonna need some carbohydrates but if we can supply half of the energy they're burning as fat that means they aren't burning half carbohydrates and that carbohydrate store which is 1/50th the size of the fat store lasts longer, so they can exercise for a longer period of time."
Let's talk about HYDRATION.
"Single most important nutrient, man... Water."
What kind of advice might you give in preparation for running tomorrow that is going to help dogs deal with heat and stay hydrated?
"Yeah, that's a great question. And of course, staying hydrated is a challenge when it's really warm and when it's really cold. Those are the two big times when it's hard to stay hydrated. A lot of this is how we train the dogs to eat and drink before we ever get to the race. We would try to maintain the same routine in terms of watering, especially for at least a couple of weeks before, like going to the Fur Rendezvous, so that the dogs were drinking at the same time every day. And we would bait the water, as you know, with just a little bit of food. So it's not really giving them much calories, but it makes it like a tasty soup. So they would drink what we gave them. Part of that was because if we leave water out, it freezes. But a bigger part of that was when we're on the road, we want them to drink so we know when they drank, so we know when we can air them and when we can exercise them so that they're on a schedule that works for the event. We don't want our dogs running with a full bladder that's just not comfortable or even worse, water in their stomach. Right? That's even worse.
And I would see guys in our arena doing that, watering the dogs right before a race, man, that is crazy. And every time I've seen people do that, the dogs end up throwing up in our arena.
So a typical schedule for us, if we had a noon race, we'd get up at 7:30 in the morning, air the dogs about 8:00, we'd water them, go in and have breakfast, come out about an hour and a half later and air them again. So now you're looking at what, 930. Then we drive to the race site and air them one more time before we actually raced. And that would give them all the opportunity that they needed to get all of the water out of their system.
But keep in mind, when you give a dog water, okay, it's in their stomach. They have to absorb it mostly from their intestine, and then they transport it. Some of it will get taken up into organs, but a lot of it gets urinated out. And that's actually one of the really beautiful things about using a little bit of glycerol, is that glycerol will pull some of that water into muscle cells and hold on to it so that when the dog starts exercising, they actually burn that glycerol for a fuel and liberate that water right within the muscle cell so it doesn't have to go through the stomach, through the intestines, through the blood to get there. It's there, and they'll run one to two degrees cooler when you do something like that. We've measured this. To me, it's a game changer.
– "Incredible Athletic Dogs" with Dr. Arleigh Reynolds DVM, PhD, D.A.V.D. June 2021
https://m.youtube.com/watch?v=4v7PlfHpJ38
WATER
"In terms of the water, watering is super important, I mean it's the most important nutrient, and as you know, we work really hard to keep the dogs hydrated. For us, water loss is tremendous because it's not just dogs don't sweat, but it's not just urinary water loss, which goes up really high when you're feeding a lot of food, but it's because they got to handle the metabolic waste. But it's also when you breathe out in a very warm or very cold environment, you lose a ton of moisture every breath. Like our dogs, when the temperature goes below zero, their water loss from respiratory water loss will actually exceed their urinary water loss. Every breath they breathe in is 0% humidity, every breath they breathe out is 100% saturated and lost to their body because it freezes, right, so I just bring that point up in that water is very important. So we would have strategies like water loading with 1% glycerol in the morning before the races and then regular water through the rest of the day. I think it's some areas where you have to be really careful right after exercise. You don't wanna over water the dogs because that can lead to them over consuming it and either vomiting or, god forbid, leading to like bloat or torsion. So I would always limit them to like, half a pint or so right after exercise, and then let's give them access to smaller amounts after that. And so I think that's really important. To get to your point about drinking too much, there are some dogs that have just this thing where they feel that they have to finish the bucket if it's a bucket of water, that can lead to problems, because when they drink that much water and I've seen this, a couple of guys do this by overwatering their sled dogs, too. Your kidneys filter many times your total blood volume every day, and they resorb like 97% of that, and they're able to do that because they have this countercurrent exchange of salts. So the filtrate goes in at the same concentration as blood. And because the salt concentrations get higher and higher the further it goes into the kidney, it pulls more and more water out. So you're able to concentrate the urine quite a bit more concentrated than what your blood is. If you wash those salts out of that gradient, you can't concentrate your urine, all of a sudden you're in trouble because you're not just urinating out what you drank, you're losing, every time your blood gets filtered, which is happening all day, you're not able to concentrate that urine, and you lose so much, you actually dehydrate yourself by over watering. Sounds paradoxical, but it's true."
BODY CONDITION SCORE
"Look at their body condition score, don't let them get heavier than a four. When you're looking at them, you wanna be able to see that last rib or two when they take a deep breath, when you run your hand over their spine, you wanna feel the spinous process. It shouldn't be sticking up like a picket fence, but you can tell they're there, and I think one of the best places is where the wings of ilium, the hip bones that come up along the spine, you want that flesh to be level there or slightly concave, you don't want it to be really concave and have those little spinous process on the sacrum sticking up, but you don't want them rounded between them, that's one of the best places to check for the dogs... if they get obese before they're a year old, they're much more likely to be obese later in life. And that's gonna cause problems with... and things like overheating too. A dog that's even one body condition score too high is carrying a significant amount of extra fat, which turns into insulation, which might be fine when you're doing cold water stuff, but most of your Nationals, at least on the ones in June, can be pretty warm. So we wanna stay away from being too heavy."
– "From The Cradle To A Champion: An In-depth Guide to Performance Pediatric Nutrition" with Dr. Arleigh Reynolds DVM, PhD, D.A.C.V.N. April 2023
https://m.youtube.com/watch?si=XZPtJM71NpYhcj1f
HYDRATION
"I think the best thing you can do is let them have access to water all the time. The one time I limit access to water is right after exercise, so they don't drink too much and then either throw up or have the risk of getting a torsion. I mean, that was one of the other big advantages of us having this indoor kennel, is that the dogs had access to water all night, and they hydrated so much better. So what we do, because at 20-30 below, you can't just leave water out, right? It turns to a brick pretty fast. So we mix some dog food to make kind of a light soup. We call it baiting the water, and we warm it up, and then we give them just under a quart, like in the morning. And then a couple of hours later, we'll train and they'll drink that right up. They'll drink the whole thing up because it's flavored, okay? But that's adapting to the situation we have because we can't leave water out. It'll freeze.
The ideal situation is let them drink when they can. And I'll tell you something else that we learned, I think is interesting. So when we feed our dogs, so typical day, we get up, water them, give them a couple of hours, then we turn them loose, train them, come back, give them a little bit of water after the run, and then we'll feed them, say, an hour, 2 hours after the run, when they're allowed to drink as much as they want throughout the day. So the largest water intake we see is about an hour and a half to 2 hours after they eat. They drink more water than they do after a run or in the morning watering. And part of that is because the act of digesting food, you're taking these long molecules and breaking them into their component parts, and each of those parts has to be hydrated. So it takes a fair amount of water to do that. And then, of course, processing that food and then excreting the wastes also take water, but they'll drink significantly more water. And I think a lot of us don't either realize that or know that. And so I think that can actually be a hydration drain on the dog if they don't have water during that period of time."
– Sporting Dog Talk Podcast: Canine Conditioning and how it affects all Working Dogs. Feb 2021
https://open.spotify.com/episode/6sERiqBwlDUUNPHRmewmjq
HYDRATION, ELECTROLYTES, GLYCEROL
One of the things that I've done in the past is I've used different things for water baiting. But what about chicken broth? Just a little bit of chicken broth added to the water. What does the salt in chicken broth do? Should I stay away from salt?
"No, I think as long as you're keeping the salt concentration fairly low, then you're going to be fine. Would you rather eat no salt chicken soup or chicken soup that had a little salt in it? Salt is one of the greatest palatability enhancers that we have. But the thing where you want to be a little bit careful is if you add too much salt, then it can actually lead to the dogs then having to urinate more because it has to get rid of that salt and pull more water with it, and you can actually lessen their hydration status. So a little salt is really good. Too much salt is not so good.
And no, that's a great point you bring up when we're looking at electrolyte formulas for dogs. Dogs don't sweat like people do. The only place they can sweat is in between the pads of their feet. So it's not how they cool themselves off. So I don't really tend to use electrolytes unless the dog has diarrhea, and if that dog has diarrhea, then I will add some electrolytes in there. If you do want to use electrolyte solution just because it's palatable, what I do is cut it in about half with water, so that you don't run into that problem we just described with there being too much salt there that can actually inhibit their hydration rather than help it. So it's fine if you want to use, there are some really nice canine electrolyte solutions out there, but I always add a bit more water than they say just to make sure that the salt concentration isn't too high and they're still palatable at that level.
So there's another thing that we've developed, and I learned about this actually from science that was done on deepwater divers, and then later on on elite cyclists that were cycling in really warm weather. And that is, if you're really concerned about the dog's hydration status, say you're working some dogs in really warm, humid weather, and you know that they're not probably going to be able to drink for a few hours while they're out there, and you don't want them to get dehydrated, because you're going to do several runs, maybe within a day or over several days, we use once a day in the morning before, I'm not sure what time of day you guys are running, but let's say again that an hour and a half to 2 hours before you run, we'll actually add 1% glycerol or glycerin to the water, and so to make that simple, that's 10ml or ten CCs per quart or liter of water. And what that does is that's a normal component of fat, but you're taking it as just the glycerol, that glycerol crosses almost every cell membrane in the body, but particularly, it goes into the muscles, and then it pulls water with it and holds onto that water. And then when the dog starts exercising, it actually burns that glycerol as a fuel, and that releases that water already there in the muscle.
So it's better than giving them oral water or IV water even, because they don't have to drink it and absorb it and have it transported. It's already there. And what we found in our dogs, for us, a warm day running would be anything above 20 degrees. And when you're starting hitting 40 degrees, and we've had world championships where it was in the 40s and 50s, and that's really a heat stress for our dogs. And what we find under those conditions is that the dogs will run one to two degrees Fahrenheit cooler when they've been pre-treated like this, and they'll maintain their hydration status better over those three days than dogs that are given the same amount of water without this stuff in it. And they recover better, they eat better, they drink better because they maintain their hydration.
Maintaining hydration is really key to maintaining performance, particularly over multiple bouts of performance. That's what we do, and it works. I've been doing that for... shoot, we started it in the 90s. I've never had an issue with a dog having any trouble with that. But like anything else, I always recommend that folks try stuff in training before they take it to a competition, just so they're comfortable with it. They know how it works. They know what their dogs look like when they're doing it. And this is completely legal. It's not a drug. It's not the World Anti Doping association, which is the folks that monitor drugging for human and canine athletes, that is not on their list of banned substances because it's a normal component of fat. The one thing I would caution people, though, is that you want to give it with water, and I keep it right at that 1% solution. You don't want to go higher than that."
Dr. Arleigh Reynolds has dedicated his life to studying the ultimate athlete. No one on this planet has a greater understanding on how to fuel and condition ...
