Cycling, Podcast, Science and Physiology, Training

Alexandra Coates, PhD | EP#375

 January 30, 2023

By  Bernardo Gonçalves


Alex Coates - That Triathlon Show

Alexandra Coates, PhD, is a postdoctoral fellow at the McMaster University in Canada. She is also a former elite short-course triathlete and triathlon coach.

In this episode you'll learn about:

  • Cardiac adaptations to endurance training
  • How important and rate-limiting are cardiac adaptations for endurance performance?
  • Stroke volume, VO2max, and what type of training to do to improve them?
  • Transferring scientific knowledge into practical application
  • What Alex would have done differently in her career knowing what she knows now

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Alexandra's background

03:04 -

  • I am a postdoctoral fellow at the University of McMaster in Hamilton, Ontario, Canada. 
  • I did my PhD in Guelph with Dr Jamie Burr, and I used to be an elite triathlete and a triathlon coach.
  • I was an elite ITU, Olympic distance triathlete.
  • I was on the national training team in the national training centre from the age of about 18 to 25. 
  • My best results, I went to under-23 worlds twice. I won elite nationals in 2015. 
  • I retired right before the Rio Olympics because I started my master's. 
  • I started coaching around the time when I retired because I needed the money. And I coach mostly age group or early-level developmental elite-type athletes. 
  • My last athlete was in December. So I recently retired from coaching. It was a good seven or eight years of coaching and now focus on research and science. 
  • I am interested in anything to do with overtraining or under, fueling or pushing too hard or ultra-endurance. So my master's research was on overreaching, and we did some cardiovascular and autonomic consequences of overreaching. 
  • I also did REDs work and iron deficiency work at that time.
  • And then, my PhD morphed into a more cardiac focus, and I looked at exercise-induced cardiac fatigue. 
  • My theory then was that exercise-induced cardiac fatigue might be driving some of these symptoms of underperformance with overreaching. I didn't fully answer that question, but I did do some work with ultramarathons and some exercise-induced cardiac fatigue studies throughout my PhD.  
  • And then now I'm switching into more of a performance focus with Dr Martin Gabala here at McMaster. (high-intensity intervals versus sprint intensity intervals). 

Heart Function during endurance exercise

07:30 -

  • The heart is responsible for pumping blood to the body. The right ventricle will pump your deoxygenated blood through pulmonary circulation to oxygenate that haemoglobin. 
  • Then the left ventricle is responsible for pumping the rest of that oxygenated blood to your body. 
  • The responsibility of the heart is to deliver that oxygenated blood while maintaining a given amount of pressure in the brain and essentially passing out. (regulated around maintaining blood pressure during exercise and delivery of oxygenated blood to the muscles)

Differences between the heart of an elite athlete and a regular person

08:36 -

  • One of the most significant physiological differences is that heart volume and the amount of blood the heart can pump out per beat. 
  • We have substantial increases in chamber size with an endurance athlete. The walls of an endurance athlete are thin relative to the ventricle size. (firm, but they're not thickened so that you would get them if you were a resistance athlete).
  • With a resistance or a concentric type adaptation to exercise, you get this wall thickening without that ventricular diameter.
  • Endurance athletes have a big internal diameter to pump out lots of blood. (volume overload)
  • The goal is to pump out more blood, more volume. 
  • With resistance athletes, it's a pressure overload. And so they have to work against these extremely high pressures. That's why they have this increase in muscle thickness. 

Stroke volume relation with volume and wall thickness

10:40 -

  • An adaptation that athletes have is much greater blood volume. So we have this increase in blood volume. Then we have this increase in heart size, where the heart accommodates this increased blood volume so you can pump more blood. 
  • There's also increased contractility, so the heart can pump harder.
  • There's also increased compliance. So the heart is better able to relax and fill. And that allows for even more blood to enter the heart during diastole. 
  • Let's assume someone starts an exercise program. In one session, you can have an increase in plasma volume.
  • It will increase your overall blood volume, increasing the VO2 max.
  •  You have this plasma volume expansion within 7-14 days of exercise. 
  • Within about 30 days, you'll have an increase in the haemoglobin, the oxygen-carrying capacity of the blood. 
  • Within weeks, you're going to see some of these increases in capillarity (more ability to deliver blood to the muscles)
  • You'll also see the increase in mitochondria at the muscles of the mitochondrial density and the mitochondrial content.
  • After months to years of training, you start to see these significant changes in cardiac adaptation.
  • The longest thing to change last will be your heart muscle. 
  • If you're doing strength training and trying to build muscle, it takes a long time—the same with heart tissue.

Cardiac adaptations as rate limiters for endurance performance

14:14 -

  • If we're talking about VO2 max, we tend to say there's a significant limitation to VO2 max. 
  • In well-trained individuals, the rate-limiting factor in VO2 max is heart and blood distribution-related. 
  • If you're less or trained, the rate limiter could be oxygen extraction at the muscle. (driven primarily by the mitochondria in the muscle) 
  • Elite athletes have tons of mitochondria and tons of these peripheral adaptations. And at that high level, we find that the muscle can take up more oxygen during maximal exercise than delivered. 
  • Assume you're doing single-leg kicking to failure.
  • More oxygen can be extracted during that type of exercise than if you're doing a full-body exercise. And the reason for that is because, of course, your body has to distribute the blood throughout your whole body during a whole-body exercise to maintain pressure and oxygen delivery to the brain. 
  • It comes down to the heart being able to pump more blood. 

Long-term athlete development to work on stroke volume

17:44 -

  • We will be limited by stroke volume, like, you know, throughout a lifetime of training. 
  • If you're trying to increase maximal cardiac output and maximal stroke volume, you have to train at that VO2 max.
  • You're training as close to VO2 max for as long as possible to stimulate just maximal blood being returned to the heart and pumped out of the heart. (high-intensity interval training)
  • So you're just maintaining VO2 max for as long as possible.
  • Elite cyclists saw an increase in VO2 max in these elite cyclists who had VO2 of 74 and made three sets of 13 times (30 seconds on and 15 seconds off), leading improvements in VO2 max from 73 or 74 to like 75 or 76.
  • Of course, you have to recover from it.
  • The rest of the training was pretty low-level. 
  • But prolonging that time of VO2 max will have the most potential for adaptation. 

Altitude training to increase haemoglobin and oxygen-carrying capacity of the blood

22:08 -

  • If we're thinking about the athlete as a whole, increasing oxygen-carrying capacity will improve your performance.
  • I did a presentation at our exercise physiology Canadian conference here this year.
  • And it was about getting the most out of the elite athlete. (focusing on that last 1% or the other 99%)
  • And to me, the other 99% is like getting your athlete to the start line healthy and ready to perform. And the 1% would be your interventions like altitude, heat, and supplements. 
  • With a proper altitude training protocol, the athlete might get a 1% to 2% improvement in performance. 
  • They can also have a negative performance if they come down and they're sick or get injured, have done enough high-intensity training, or did not recover properly from that high-intensity training. 
  • Some athletes might get that 1%, and others will do worse. 
  • If you've done everything you possibly can and the athletes are healthy and adapting well, that's when you focus on this little bit extra.

Low-intensity training and the cardiac system

24:48 -

  • High-level and elite endurance athletes train 20 to 35 hours a week. And so because of that volume, most of it is low intensity. (80% plus will be low intensity, and the other 20% will be medium and high intensity)
  • That's called. 
  • Training works with overload. You overload your system and recover from that. 
  • You can't do too much high-intensity overload because you'll get injured or sick.
  • You'll get some adaptation from low training, but you'll get more if you do high intensity and distribute that accordingly within a program. The trick is doing the most training you can while maintaining health, consistency and happiness.
  • One of the main principles of training is specificity. So if you're racing Ironman, low-intensity could work, but even elite athletes race at a high intensity. But if you're racing anything over eight hours, you don't ever have to do the hard stuff because you don't need to do it in the race.
  • But suppose you're racing anything that involves threshold and buffering capacity. 
  • You're going to have to do higher-intensity work. You can't do all your training in zone 2.
  • Assume athletes train 30 hours a week. I wonder if they were junior athletes and did a lot of high intensity throughout their junior year 23 careers and have those adaptations. Now, they're only maintaining those adaptations through low intensity. 
  • They do races with some high intensity, enough to keep them at that level.
  • If you have a beginner, doing low-intensity training will probably be hard for them.
  • Then they're going to plateau because they have yet to get those adaptations from high intensity. 

Cardiac fatigue and how it relates to overreaching


  •  So at the start, I was convinced that exercise-induced cardiac fatigue was one of the reasons why you would see underperformance from overreaching. 
  • Assume you had a three-week training camp; by the end of it, you're underperforming because you're so tired. 
  • My theory was that that could be cardiac. 
  • I started out doing cardiac fatigue research and did one study that looked at differences in cardiac fatigue following 25km, 50km, 80km and 160km of trail ultramarathon running. 
  • We were expecting to see more extended distance events with decreases in cardiac function. And we didn't see that, which went against the literature.
  • We found that the athletes that worked harder(25km type athletes) had more cardiac fatigue (decrease in injection fraction).
  • I'm not entirely sure if exercise-induced cardiac fatigue exists. 
  • There will be cases where you can overload the heart and the right ventricle. 
  • It has thinner walls and is more susceptible to these long bouts of exercise under high pressure. 
  • Therefore, it can dilate in a non-functional way, but it is pretty rare, not happening after just any given ultramarathon or any of the types of exercise that I studied. 
  • We've seen in the literature that exercise-induced cardiac fatigue are differences in the loading conditions around the heart. (you're dehydrated and have all this peripheral vasodilation after you exercise and so less blood is returning to the heart)
  • Then you'll also have this sustained heart rate elevation after you exercise. The heart's beating faster but pumping out less blood per beat. It may seem like the heart is working less well, but it's in different conditions.
  • So then I did a study where we did overreach athletes. So we caused an underperformance from overtraining in a three-week training block. And we have the cardiac data on that.

Inability to reach a maximum heart rate

35:11 -

  • We don't know what it's caused by at all. 
  • It's an autonomic suppression change but not one you would see at rest. 
  • If you overreach, it will not necessarily show up in your resting, waking heart rate or heart rate variability.
  • But it will show up during exercise.
  • Maximal heart rate will lower by about five to 10 beats. 
  • Above those intensities of about 70% will be down by about five to 10 beats. 
  • The big thing is HRV can't distinguish between your acute fatigue, which would be normal training fatigue, and the fatigue causing underperformance.
  • There's no threshold of heart rate variability, which tells you you are getting tired.
  • As you get more tired, your heart rate variability is going to look worse and worse.
  • You can use it as a general monitoring tool, like general fatigue levels.
  • It's useful when you're starting and want to see how things affect you.
  • Once you have that knowledge, you don't need the feedback. 

Additional topics on cardiac function

40:25 -

  • There is this idea that if you're doing ramp testing, your stroke volume will plateau at about 60 to 70% of your VO2 max. 
  • And that is certainly the case for a lot of people. But with super well-trained athletes, their stroke volume will continue to increase to more blood pumped out per beat until the maximum.
  •  The cause is the ability of the heart to relax and suck in more blood, pumping up more blood. (adaptations that would come from years of training)
  • It's so hard to measure cardiac output stroke volume during maximal exercise, so we don't have much data on it. It's this gradual adaptation that will occur over years of training.

Differences between men and women

43:20 -

  • Men will have much greater stroke volumes and cardiac outputs than women. (for the same body size). And also similarly, for blood volume, male athletes will have more significant blood volumes. 
  • Because of the pulmonary circulation, women have a greater chance of hypoxemia, meaning the blood is essentially pumped through the pulmonary circulation so fast that there's not enough time for all the oxygen to bind to the haemoglobin.
  • We use SMO2 and NIRS devices in my overreaching study.
  • We also use the NIRS to look at peripheral changes versus central changes.

Relevance of scientific knowledge to coaches and athletes

46:33 -

  • Sometimes coaches are ahead, sometimes scientists are ahead, and it can be very complimentary if the coaches and the scientists work together.
  • Sometimes we're doing these studies that do not apply to sports.
  • My work, in particular, has applications to athletes and coaches.
  • That dialogue can help raise the performance of athletes. (e.g. Kristian Blumenfeld)
  • It can be super relevant if you're willing to have that dialogue and explore what science has to offer. 

Applying scientific knowledge in coaching

49:21 -

  • Coaching is almost an art. 
  • Even with a science background, you do many things by how you feel the athlete is responding to the training.
  • My athletes do not come in and do VO2 max testing or lactate testing and stuff.
  • But I base my training on certain basic exercise physiology principles (health, consistency and recovery)
  • You can only get the most out of your training if you maintain that consistency and stay healthy.
  • Much of my coaching is avoiding overreaching, low energy availability and maintaining health. 
  • Where I pull a lot of the science in is that unless you are feeling good and adapting well to the training, you're either going down or plateauing. 
  • You need to have the energy through fuel and recovery, like from sessions, to push really hard sometimes.
  • Then you can get that volume in as a recovery session too. 

Examples of going against what is scientifically valid

52:07 -

  • My athletes, who are training only about seven to 10 hours a week, would not get dragged into this idea that we need to focus on low-intensity training.
  • I try to get them to consistently be able to train (hard for a few sessions a week, and then more moderate or easy for the other sessions)
  • It doesn't even have to ensure you're below lactate of 2mmol.
  • It just has to be low enough intensity that you're getting a stimulus, but you can recover from the high-intensity sessions.
  • There needs to be some overload, so there needs to be some high-intensity work. There also needs to be low intensity to provide that volume and complement the high-intensity work, and within the constraints of the athletes, you maximize what you can in those 10 hours.

Pitfalls to avoid when applying scientific knowledge in practical application

55:16 -

  • You have to be consistent. The low-intensity training has its benefits if you can stay consistent.
  • Find the amount or intensity of training that allows you to recover.
  • Don't do low carbohydrate training if you're a triathlete because you need to fuel for your sessions. 
  • What's happening is you're putting stress on your body and not allowing it to adapt to the training to the best of its abilities.
  • The recovery piece is the only part where you get faster.

Is there anything that Alexandra wish would have done differently as an athlete when she was racing?

57:15 -

  • We've realised how different the progression is between a female and a male athlete's development.
  • My trajectory was the same as all my peers: from 18 to 24, we needed to get faster because that happens with male development.
  • Female athletes in that 18 to 20-year gap gain body fat, which makes them slower and not have those same benefits of the testosterone that men get. 
  • Women through the 18 to 20-year-old age range get slower.
  • Coaches are trying to lose body fat, which will cause stress fractures and worsen everything. 
  • We were super injured and unhealthy by about 21 to 23 (stress fractures, everyone is dropping out of races). 
  • This is one of the cases where science was ahead of the coaching because we knew about the female athlete triad and low energy availability.
  • Female athletes have a different physiological trajectory than men, and don't expect female athletes to get faster because they probably won't. Have this long-term vision because these female athletes will probably peak closer to 30. 
  • In Canada, many female athletes got kicked out of our developmental group because they had gained weight and weren't performing. They were going through what happens naturally.

Three pieces of advice for endurance athletes

1:02:19 -

  • First, you can't be your best athlete if you don't have health. 
  • So that will come from nutrition and recovery and balancing your training with the rest of your life. 
  • The second one is because of that health; you get consistency. 
  • The third part becomes happiness; your training can have some results.
  • But after a period, you'll lose some of the joy, spark, or motivation.
  • You can be less trained, but if you're happy, motivated, and excited, you're going to do much better in races than if you're depressed and burnt out and just not loving it.

Rapid-fire questions

1:04:00 -

What's your favourite book or resource related to endurance sports?

Alex Hutchinson's book Endure. 

What is an important habit you've benefited from athletically, professionally or personally? 

Resilience and grit

And who's somebody that you look up to or that has inspired you? 

My PhD mentor Jamie Burr


Bernardo Gonçalves

Bernardo is a Portuguese elite cyclist and co-founder of SpeedEdge Performance, a company focused on optimising cycling and triathlon performance. He writes the shownotes for That Triathlon Show, and also produces social media content for each new episode.

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