On sustained levels of energy expenditure

I have recently stumbled upon an article on prolonged endurance events and the limits on energy expenditure. (C. Thurber et al., Extreme events reveal an alimentary limit on sustained maximal human energy expenditure, Science Advances, vol. 5, no. 6, (2019) eaaw0341). I found it particularly interesting and I decided to give here a short summary of its findings. 

The champions of prolonged effort are migrating birds. Several studies have been devoted to the measure of the energy expenditure during their long treks, the consensus being that migrating birds can sustain energy budgets of the order of 5 times their basal metabolic rate. So the natural question is where do humans stand in this. 

Clearly humans can produce energy at rates much high than the basal metabolic one, provided the efforts are of short duration. There are however events which require weeks' or even months' long efforts. The article that inspired this post was based on a study of the energy expenditure of a group of athletes who ran six marathons a week for five months as part of the Race Across the USA, from west to east coast, a race of almost 5000 kms. The findings are summarised in the figure below.

While for short-duration events the athletes can expend an energy in multiples of the basal metabolic rate, once the duration of the event increases the energy expenditure starts falling rapidly levelling off for events of very long duration. The authors of the article infer an asymptotic value of 2.5 times the basal metabolic rate. The explanation of this limit is not quite clear. One possible source of this limitation is a long-term fatigue of the cardio-vascular system as well as of the organs involved in waste excretion. The authors of the article argue that the limitation is due to the digestive process. Energy intake implicates the alimentary system and the latter poses limits to the maximum energy uptake. Once the energy demand exceeds the maximum rate, the body starts drawing on its reserves leading to a non-sustainable situation. 

One interesting finding of the study of Thurber et al. was that towards the end of the race the athletes were burning per day fewer calories than what could be expected based on the distance run. While a part of this reduction could be attributed to a reduction in non-exercise activity it appears that a reduction of non-muscular physiological activity was also in play. According to the authors this energy expenditure reduction was essential in allowing the athletes to complete the race.

This is a remarkable finding since it adds support to the constrained energy expenditure model. Put in a nutshell, the additive energy expenditure model posits a linear increase of the total energy expenditure in response to physical activity. The constrained model on the other hand suggest a subtler relation. The body adapts to an increase of physical activity by reducing the energy spent on other physiological tasks, leading to a total energy expenditure which levels off at high activity loads. Energy balance models focusing solely on the effect of physical activity on total energy expenditure may provide a biased measure of the latter. In particular additive total energy expenditure approaches will tend to overestimate the effect of physical activity at higher activity levels. 

I find it really funny that a study on ultra-marathoners yields results which could provide insights on weight control strategies, but, after all, physical activity is a continuum ranging from that of the week-end jogger to the one of cross-continent runners.

An interesting article by P.J. Vazel

The regular readers of this blog will have certainly noticed that the writings of P.J. Vazel are a source of inspiration for me. I was closely following his blog when it was still regularly updated. Unfortunately the blog is now essentially dead although all the articles published there are still available. (Well, not all. There is one noteworthy exception, but more on this later). While P.J. Vazel is not blogging anymore he is still quite active on twitter and from time to time I am visiting his page which is always interesting from a technical point of view. While I appreciate the writings of P.J. Vazel I was recently somewhat disappointed when I discovered that he is one of the champions of Semenya. According to him the testosterone-based DSD rules of the IAAF are sexist based not on science but on a misogynical approach.

I recently listened to an interview of P.J. Vazel at Radio Canada where he defended these positions. (If you understand french you can listen to this short interview entitled "Athlètes hyperandrogènes : un règlement sans fondement scientifique". And you can enjoy the scrumptious french-canadian accent of the interviewing journalist S. Bureau). I must admit that having discovered that pro-Semenya attitude of P.J. Vazel I have lost a part of my admiration for him.

Anyhow, the main topic in this post has nothing to do with hyper-androgenic women. (And in fact I hate going back to this subject repeatedly). Here I will deal with a study of P.J. Vazel on the evolution of the sprinting top speed based on measures spanning a century. 

The ancient runners are not bad but I prefer the ones of my blog's logo

Vazel did a great job of compilation and analysis and he explains in a very pedagogical way the flaws in every measurement. In the graphic below I summarise his findings plotting the evolution of the sprinting top speed over the years. I split on purpose the data into two groups. Those before 1970 are somehow less credible since they are not based on fully automatic measurements. It's only with the advent of high-speed cameras and precision electronic time-keeping that the measures of top speed can be seriously taken. (I have thus decided to discard the more than dubious 11.66 m/s on R. Metcalfe in 1932 and replace it by the more credible 10.97 m/s of E. Tolan).

Some points are remarkable in this graphic. The 1962 peak of 12.04 m/s is due to none other than the great Bob Hayes. Although the value seems almost too good to be true I do not put it beyond Hayes' exceptional talent. The speed surge around 2010 is, of course, due to the other great sprinter, U. Bolt. 

If you are interested in the subject I urge you to read the study of Vazel: it is clearly written and moreover it is in english (so, if you can read this post you can read Vazel's). There are some nice historical photos also, including this great photo of B. Hayes. 

Just have a look at the track: it looks like a sand-beach to me. Can you imagine the conditions under which Hayes was running the 100 m in 10 s flat?

An the beginning of this post I mentioned the one article that has disappeared from Vazel's blog. (Fortunately I had saved it in pdf form while it was available). It has to do, you guessed it, with hyper-androgenic women. It was a matter-of-fact, quite objective and very informative article. At the time I could not explain its disappearance. Now I do. 

Women's decathlon revisited

The regular readers of this blog have certainly noticed my love for combined events. And the king among them is the decathlon. For me the decathlon is something magical and I have trouble understanding why women are confined to the watered-down version that constitutes the heptathlon. If we are vying for a complete parity between men and women in sports then it is high time to make the decathlon the official combined event for women. Unless we do this we will not have real combined events specialists but just girls who excel in one or two disciplines and can put together a decent heptathlon. I am fully aware that there exist (or have existed) many great heptathletes among women and I have a great admiration for most of them. But somehow I feel that they are not on par with the great male decathletes.

I had started to believe that women's decathlon was dead and buried but then I stumbled upon the site of Women's Decathlon Association. They have done a great statistical work compiling an extended list of all performances over 5000 points as well as the top individual performances for each event. Here is the list of the ten best women's decathlons of all times: 

Unfortunately the most recent entry goes back to 2006. Let's hope that the situation will improve in the future. And here is the list of the best performances per event. 

The current world record holder A. Skujyte has the lion's share with three  best performances but it is interesting to notice that, just like in heptathlon, B. Spotakova holds the best javelin performance. A minor surprise is the S. Dragila, a 6999 points decathlete and 4.83 pole vaulter does not hold the best pole vault performance (but, to be fair, when she competed in the decathlon, where she jumped 4.10 m, her pole vault best was 4.40 m).

US decathlon record holder Jordan Gray

But, what is more important, they are organising a decathlon championship. They started in 2018, even before the association was officially created, and they did it again this year.  On this occasion J. Gray established a new US record, just shy of 8000 points, moving to the third place overall in women's decathlon. Here are the full results.

Women's decathlon has been in limbo practically since its introduction, back in 2004. I was hoping that with the introduction of women's pole vault, moving from heptathlon to decathlon would have been a mere formality. And I was not alone in this line of thought.

You may remember Becca Gillespy Peter, the woman behind Pole Vault Power, from my post on pole vault

Becca Gillespy Peter

For her the obvious step after pole vault was the decathlon. In her own words

“I wanted to do decathlon when I was in high school, but girls pole vault was brand new. Senior year was the first year we had pole vault in our state. ‘Decathlon is the next thing,’ I thought at the time. ‘It’s not here yet, but it’ll be here soon”.

Well, a decade and a half later, the women’s decathlon has yet to arrive. And she continues

“I don’t want to bash the heptathlon, which is an amazing event,” she says. “But it is less demanding than the decathlon, which is widely seen as finding the world’s best all-round athlete. What kind of message does that send to women and girls? In effect, they are being told they can’t be the world’s greatest athlete, that they can’t do as many events as men. And that isn’t right”.

Olympic and World pole vault champion, S. Dragila is categorical. 

"The heptathlon is really too easy for elite women. You find someone who’s fast and powerful, they dominate the heptathlon. I think there just needs to be another technical event in there to set the field apart".

Dragila's decathlon record was never homologated as a national one. And the same is true for the record of J. Stary going back to 1980.

So, where does the resistance to women's decathlon come from? The only criticism which I find perfectly justified is the one concerning the order of events. Permuting first and second day field events with respect to the men's decathlon is not such a good idea. For L. Gramantik, the coach of D. Warner, 

“Reversing the order of the events for women is a terrible sequence considering the physical challenge of the events, where day one would be predominantly technical, followed by speed power on day two”.

And then there is the resistance of the heptathletes themselves. For them the decathlon would mean having to learn two more technical events (discus and pole-vault) and risk being less succesful than in the heptathlon.

Becca Gillespy Peter, for her part, says she is sympathetic to these concerns 

“If there is ever going to be a switch to the women’s decathlon, you need at least eight years – or two Olympic cycles – to implement it as it is unfair to destroy the career of a current elite heptathlete”.

Are we going to see a women's decathlon in the 2028, Los Angeles, Olympics? I am not very optimistic about this, but the fact that there exist a US-centric action in favour of this discipline allows a sliver of hope.