Today we revisit a topic that seems to run like carousel, popping up once every few months on the site - how much faster can human beings run? How close to a "ceiling" in performance are we?
The latest discussion is inspired by a few articles, and a recent round-table discussion between some of the all-time greats of 800m running, and the new world record holder, David Rudisha. For those who haven't heard, Rudisha was appropriately named the IAAF Male Athlete of the Year for his two world records in 2010.
But preceding that announcement was a panel discussion between Alberto Juantorena, Sebastian Coe, Wilson Kipketer And Rudisha in Monaco. To watch the discussion and read some commentary on it, check out Letsrun.com here.
One of the topics that came up was how much faster the record would still go. Rudisha came agonizingly close (1/100th of a second) to dipping under 1:41.00, so it's safe to assume that barrier is in reach. But how much lower? Here are three quotes attributed to those legends:
"This record belongs to the future - 1:41.01." and "You never know the limit of a human being." - Alberto Juantorena
"I don't think we're anywhere near them (the limits of the event) ..." - Seb Coe
"In 800 it is possible to run under 1:40. It is still coming." - Wilson Kipketer
Then, an interesting piece by the Guardian discussed the same issues around whether we are near the limits, with the conclusion that it will take many years before we know the answer to this question. I will point out that saying this is not quite the same thing as saying that we are not near the limit, but rather that we just do not know where it is. There is a ceiling somewhere above us, but we don't know when we will hit our head! You can read that piece here.
The physiological basis for "limits"
In trying to evaluate these arguments, I think it's important to understand a little bit about the physiological basis for why there may be a limit to performance. And here, the most important thing to recognize is that we don't fully know what that basis might be. It certainly varies by event, and is more complex than I want to go into now, but those keen for more might consider reading our series on Fatigue and Performance
For example, in 100m sprinting, some limits are the metabolic changes in the muscle, which affect its force-producing capacity, combined with mechanical factors such as muscle-tendon elasticity, ability to apply force to the ground, the force and torque on joints, and limits to how quickly neural signals can reach the muscle from the brain.
Some really interesting work by a colleague at my university has confirmed that the rate of force production and muscle relaxation drops over time during maximal exercise, even when the electrical signal to activate the muscle doesn't change. In other words, there is a drop in the force that the muscle can produce, and that's why even events as short as 10 seconds show signs of pacing - if you go too hard early, you fall away at the end. But, the peripheral factors, like acidosis in the muscle, depletion of ATP, accumulation of calcium and phosphate are only part of the problem, and the Guardian article talks more of the mechanics of sprinting, which affect the force production on the ground.
As you move up in distance, other factors play more of a role. The rate of energy supply becomes a factor in middle-distance events, oxygen availability is a potential limiter (though whether it is to skeletel muscle or to the brain (more likely) is a debate). So too, chemical changes such as a drop in pH may be regulated or responsible for a decline in performance. Then, as you reach marathon distances, fuel availability becomes important (hitting the wall being the obvious sign of not getting this right), and the ability to burn fat to preserve glycogen is part of the elite athlete make-up. Heat storage is another limiting factor, because fatigue occurs when the body temperature reaches what has been called a critical level of hyperthermia.
The point is that performances are not limited by one thing only, but rather a complex interaction between all the physiological systems, whose weighting depends on the type of event, and the external conditions for the event on the day.
Those interested in a more academic discussion of the topic might consider the following review articles:
Distribution of cycling power output: Impact and mechanisms
Physiological regulation of pacing strategies (and hence exercise performance)
Model for performance regulation by the brain
Applying this to performance limits
In any event, you may be wondering what this has to with a debate over whether an athlete can run under 1:40 for 800m, sub 9.40s for 100m, or break the 2-hour barrier in the marathon?
Well, in my view, knowing that performance is limited by physiological changes in the muscle, lungs, heart, brain, body temperature, there is an obvious "barrier" that cannot be broken without causing harm to the athlete. We cannot simply head out and run or cycle ourselves to the limit - our brain controls the degree of muscle activation so that we are protected against, quite literally, exercising ourselves to death. So the brain will, for example, detect the rate of heat storage early on and then reduce the exercise workrate through adjustments in muscle activation, the result of which is a slowing in pace, but also a drop in heat storage and avoidance of that limiting body temperature. The same presumably happens with oxygen availability, glucose supply (probably both to the brain), blood flow, cardiac output, osmolality - any number of "homeostats" that have to be defended in order for us to survive
This is the reason, incidentally, that it is possible to predict the maximal sustainable power output by a cyclist during a mountain climb in the Tour de France. We did this in July during the Tour, to some criticism, but I'm confident in saying that the physiological basis is sound, and so too is the prediction that power outputs of 6.1 W/kg to 6.3 W/kg represent a maximal power output that is possible given human physiology.
In other words, exercise performance is limited by a capacity in oxygen delivery, a capacity in heat storage and body temperature, a capacity in the rate of ATP supply, a capacity in the total energy availability. Short of finding a human being who exceeds everything we know of physiology, or finding that individual who possesses the maximal combination of every single physiological attribute (this individual doesn't exist except in theory), the records will not "leap" forward, they will inch forward incrementally, and I do believe that we are quite close to the limit, when world records will become more and more infrequent, and eventually no longer be broken, unless we start measuring down to the nearest thousandth of a second.
The sub-2 hour marathon as an example
Let's look at the sub-2 hour marathon as an example. This came up last week again, when Ed Coyle suggested that he was "confident" it could happen and predicted a 1:58 as the limit. It won't be in my lifetime, that's for sure, but I'll get onto that shortly.
READ ON...
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