Endurance Running and Persistence Hunting

 Introduction 

So why do we do it?  Why do we wake up (too) early, endure the snow, suffer through rain, recover only to induce more injury, sweat, hurt, and work to exhaustion?  Why do we run?  There are countless reasons, all of which are good.  Some people run to keep weight off.  Some runners do it to satisfy their competitive drive.  Some run to enjoy the outdoors, while others do it to achieve the endorphin-driven runner’s high.  There are countless reasons out there, and as a result, countless runners out there. Whatever your motive is, be proud that you have stuck with this challenging yet incredibly beneficial activity.  

However, whatever your personal rationale may be, research suggests that humans, as a species, run for much more profound reasons.  Our early ancestors did not run to burn off a Big Mac meal- they ran to hunt and they ran to survive.  They ran because millions of years of evolution resulted in humans who were perfectly adapted to do so.  Thus, when they ran, they were among the best.

Slow and Steady 

Rest assured, we are not fast.  According to a 2004 study published in Nature, elite human sprinters can run 10.2 m/s for about 15 s.  That is about 37km/h.  In highschool, I once ran a 100m sprint in 11.6 seconds (31km/h).  Not bad. 

According to that same 2004 study, horses and antelopes can sustain 15-20 m/s for minutes.  Traveling 54-72 km/h for minutes, not seconds.  That is the equivalent to running a 5.0 s 100m- and then about 30 more after that.  Sorry Usaine, you are slow, I am much slower, and humans as a species are just plain sluggish. 

While we lack the ability to run at high velocities, we excel at running slowly for a long time.  Not only do we excel over long distance, but we outclass our competitors when the conditions are harsh; hot and dry.  

Sweat
  
There are many adaptations that make us well equipped to endurance run.  One trait that gives us a significant adaptive advantage over other members of the animal kingdom is our ability to control our body temperature.  As we all know, humans sweat, which allows for heat dissipation via evapotranspiration.  We are also relatively hairless, which decreases heat retention.  

In the same 2004 article, the authors explain that we have an additional cooling mechanism built into the distribution of our blood vessels.  The authors note that an intricate cranial venous system supplies, “blood that has been cooled by sweating in the face and scalp to cool, via counter current heat exchange in the cavernous sinus, hot arterial blood in the internal carotid artery before it reaches the brain.”  In other words, we are adapted to cool down hot blood before it reaches our brain.  Our prey may have been fast, but we were the best at keeping a cool head.

Persistence Hunting 

  
So why would endurance running help our ancestors hunt?  Well, sprinting toward an antelope at the “blistering” speed of ~33 km/h would appear to be nothing more than a crawl to our prey.  As a result, rather than sprint toward the meal, our ancestors opted to jog.  

It is a somewhat humorous image- a predator casually moving toward its prey.  Picturing a hungry and aggressive cheetah, for example, leisurely trotting toward its quarry simply seems odd.  As peculiar as this strategy seems, this is exactly what our ancestors employed. 

Running slowly toward their target for long periods of time, our ancestors would utilize their advanced ability to endurance run to work their prey to exhaustion.  The targeted animal would run and then stop to pant in an attempt to stay cool, and then run again.  By contrast, the hunters possessed the ability to consistently and relentlessly pursue, partly because of their reduced hair and ability to sweat.  Eventually the animal would exhaust, overheat, and collapse.

Study

  
In a 2008 study published in the Journal of Human Evolution, Louis Liebenberg argues that persistence hunting was not only a viable option for hunters, but that it may have been widely utilized.  Some anthropologists have argued that persistence hunting was likely a rare and ineffective method to hunt.  This notion is reflected in low levels of documentation of this strategy.

Liebenberg, however, rebuts by stating, “The apparent scarcity of ethnographic records of persistence hunting does not imply that persistence hunting was rare, it could simply be that anthropologists who were able to observe persistence hunting were rare.” 

There seems to be some truth to this statement.  In Liebenberg’s article, he accounts his visit to the Kalahari Desert to observe a tribe who still employs this hunting strategy.  A member of the tribe, !Nate, initially informed Liebenberg that he could not run with them since “white men cannot do this.”  !Nate likely had good reason to be concerned.  An untrained anthropologist could potentially collapse before the prey, especially in 42 °C heat.  This shows that persistence hunting is undoubtedly difficult for the hunters, but slightly more difficult for the hunted. 

Liebenberg does admit that persistence hunting became less relevant after the invention of the bow-and-arrow and the domestication and use of dogs and horses for hunting.  Nevertheless, the evidence shows that persistence hunting may have been widely employed at one point, and is still used in some parts of the world today.

  
Closing

  
So why run?  It may be for a reason more trivial than survival.  However, for whatever reason you do chose to endurance run, you are utilizing a body which has been perfectly molded by evolution to do so.  

References 

Bramble, D.M., Lieberman, D.E. 2004.  Endurance running and the evolution of Homo. Nature. 423:345-352

Liebenberg, L. 2008. The relevance of persistence hunting to human evolution. Journal of Human Evolution 55:1156–1159 

Time to Exhaustion at VO2 Max- is it a reproducible measure for cyclists?

VO₂ max and Cycling Economy

VO₂ max is a benchmark of fitness that most endurance athletes are keenly aware of.  It is the measure of the maximum ability of an athlete’s body to transport and utilize oxygen, typically expressed in the units of ml/min/kg (volume of oxygen used, per minute, per kg of body weight).  So, very simply put, the more oxygen your body is using, and the lighter you are, the higher your VO₂ max is.  

Various sources have reported Lance Armstrong’s VO₂ max was approximately 85 ml/min/kg during his winning years, while the average 20 year old man’s is approximately 45 ml/min/kg.  The higher your VO₂ max, the better you will likely perform.  

So, why even hold races?  Why not just test everybody’s VO₂ max, and the highest wins?  While this measure of fitness is a great predictor of performance, it does not tell the entire story.  In cycling, factors such as nutrition, equipment, aerodynamics, drafting, and tactics come into play.  However, even if all of these influences are held constant, VO₂ max still does not predict who wins the race.  

Another very important factor, referred to as cycling economy, plays a critical role in predicting performance.  Cycling economy is essentially the measure of how efficiently one’s musculature utilizes the oxygen delivered to transfer power into the pedals.  It is one factor that will allow a cyclist with a lower VO₂ max to beat one with a higher VO₂ max.

Study

A  great test scientists use to predict performance in cyclists that takes into account both VO₂ max and cycling economy is to measure their time to exhaustion.  This involves the simple task of timing how long an athlete can last cycling while working at their VO₂ max.  In a 2011 study published in the Journal of Exercise Physiology, 17 competitive cyclists went through the time to exhaustion test to see if it is reproducible.  In other words, if you test your time to exhaustion on one day, will it be the same a week later?  This is what they found:

On the left of the graph (y-axis) we see the difference between the two trials, while the bottom (x-axis) shows the average of the two time to exhaustion trials for each athlete.  For 10 of the 17 athletes, their time to exhaustion increased when comparing the second trial to the first.  Of the 7 remaining athletes, there was very little difference between their first and second trials.  On average, the first time to exhaustion trial measured 223.2 ± 31.3 seconds, while the second trial measured 238.6 ± 33.5 seconds.  In other words, the athletes lasted longer at their VO2 max the second time around.

Discussion

So why is this?  This study was actually very well designed in that it measured other physiological factors that could explain this significant change including maximum heart rate, VO₂ max reached, and blood lactate levels.  Interestingly, all of these measures were constant between trials.

So if the riders were lasting longer, and it was not for physiological reasons, the authors propose that only leaves the rider’s psychology.  Essentially, the riders were able to last longer not because their bodies were better equipped to do so, but their minds were.

So is the time to exhaustion a reproducible test?  From a physiological standpoint it seems that all factors are reproducible.  However, due to psychological factors, it seems inevitable that an athlete will have the potential to improve without actually developing better fitness.

My Analysis

Firstly, keep in mind that this is just one study with a small sample size of only 17 riders.  In addition, the study only measured the time exhaustion on two separate occasions.  It would be interesting to know what impact more athletes and more trials would have on the results.  Maybe the times would then be more consistent.

On a side note, one part of this paper that I found very interesting was the influence of psychology on performance.  This article indirectly shows the importance of mental preparation and toughness during competition.  Getting faster without improving my fitness?  Sounds good to me!

Reference

Costa et. al., 2011. Reproducibility of Cycling Time to Exhaustion at VO₂ Max in Competitive Cyclists. Journal of Exercise Physiology.  14:28-34

The Beginning

Welcome!

The goal of this blog is to present and generate discussion about some of the newest research in health and athletic performance.  From nutrition and exercise, to injuries and equipment, all components of these issues will be addressed.  In many cases, I will test each topic out myself, and present what I experienced in conjunction with what the facts in the literature say.

If there is anything you specifically have an interest in and want to learn more about, do not hesitate to post on my blog!  So much research is being conducted worldwide on these topics- let's make use of it to become faster, stronger, and most importantly, as healthy as we can be!


Cheers!
Dr. Sean Delanghe