The limits of human physiology

Examining the physiology of a former champion*

Last week we learned about the multi-year training demands of an elite bike racer. While there are tons of training plans available on the internet, last week’s post provides a big picture view of training load, and how an elite cyclist balances fitness and fatigue.

This week, we’ll talk about the physiological demands of world-class cycling.

Thanks to decades of awesome exercise research, we know that the physiological determinants of endurance performance can be categorized into three variables: maximal oxygen uptake, muscular efficiency, and lactate threshold.

Maximal oxygen uptake, or VO2max, is the ceiling: it’s where the heart can’t pump any more blood, and the muscles can’t produce any more energy with oxygen. Muscular efficiency is simply the amount of energy that goes towards muscular movement, like miles per gallon. Lastly, lactate threshold represents the max sustainable amount of power that your muscles can produce; your body can produce power just fine between lactate threshold and VO2max, but only for a few minutes.

One study from Austin Texas investigated those three variables in an elite cyclist. Like the study in last week’s post, this one followed the athlete for seven years. But instead of reporting training volumes, this paper gives us insight into the measured physiological values that a champion produces. These values are useful because they’re accurate, peer-reviewed numbers, not youtube estimates or hacked data.

The numbers are also valuable because they represent what lies just beyond the limits of human performance. That’s because unbeknownst to the authors, the subject of the study – our old friend Lance – was utilizing the most precise, world-class doping regimen at the time. And despite what you think about the athlete, the science behind the doping is fascinating stuff.

The last year of data collection in this study was 1999, the first of Lance’s seven consecutive Tour victories. Here’s a breakdown of the numbers:

  • VO2max of 85 ml/kg/min (the highest values ever reported are around 90)
  • Lactate threshold at 85% max
  • Muscular efficiency of 23%
  • Max sustainable power output of 400 watts, or 5.8 watts per kilogram

What made Lance so good, and where he was supremely genetically gifted, was his efficiency. Blood doping improves oxygen consumption, testosterone improves power and recovery, but efficiency is hard to manipulate with doping, as far as we know.

Based on studies like this and some extrapolating and predicting, many think the limit of human performance for each variable is 85 ml/kg/min VO2max, lactate threshold at 85% max, 23.5% efficiency, and a max sustainable power output of 6 watts per kilogram. It’s reasonable to believe an athlete could have one or two of those numbers, but it would have to be balanced. One could have a higher VO2max, but efficiency would be a little lower. Similarly, lactate threshold could be a bit higher, but then power output would be a little lower.

That doesn’t mean higher values aren’t impossible without doping, but it does raise some eyebrows. It’s also why the performance of Chris Froome, the current Tour leader, has come under such scrutiny now that we’ve seen his hacked power data.

Historically, every rider that’s had sustained power outputs between 6 – 6.5 watts per kilogram has been a dope-fueled super freak. In yesterday’s mountain stage, Froome produced approximately 6.2 watts per kilogram for 41 minutes. That’s unheard of in mortals, but not impossible.

Sorry if I ruined the Tour for you! It’s still fun to watch human-machine hybrids push the limits of nature.

Photo Credit: Georges Ménager/Flickr Creative Commons
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