Q - Power

Indoor Rowing Team

VO2max (2 of 2)

(Above) A marathon world record time of 2:03:58.2 was set in Berlin on 28th September 2008 by Haile Gebrselassie. It would be broken by Patrick Makau in September 2011, again in Berlin, in a time of 2:03:38.

(Below) They do not come much bigger than Lucas Mueller who rows in the 6 seat of the 2011 World Champion German men's eight. At 208cm (6'10"), he is 14cm (5½") taller than the next tallest person in the crew.

Consider a top-end elite marathon runner. He weighs 56kg and has an astonishingly high relative VO2max of 86ml/kg. He is also Ethiopian (and is not a hypothetical athlete), but that does not matter for present purposes. His absolute VO2max is therefore 4,816ml/min.

So for a rower, he is just about able to make the last seat in the 2nd VIII of a rather average boat club. On the erg he will not quite make it to a 6:50 2k... but what would happen if we scaled him up (just pretend we could). Just imagine what would happen if he weighed 70% more, i.e. 95.2kg, being a good size for an elite rower. Well then wouldn't his VO2max be 1.7 x 4,816ml, being 8,187ml?

No, it would not. The way oxygen travels around the body involves it passing across membranes (the surfaces of the lungs, the surfaces of the cells, the surfaces of the mitochondria within them). As a person gets proportionately bigger, their surfaces increase as a squared function of height, whilst their mass increases as a cubic function. This means that surface area increases by the percentage increase in mass to the power of 2/3. So if our elite runner were 1.7 times heavier, his absolute VO2max would increase by 1.7^2/3, being just over a 42% increase, taking it to 6,860ml. However since his weight has shot up, his relative VO2max is now only 72ml/kg (i.e. 6860/95.2). So as a runner, he was better off smaller. 

However here is an interesting observation. For his 70% increase in weight, if he was on the water he would only need 1.7^2/9 more power, being 12.5%. An extra 42% of available oxygen against an increase in the oxygen bill of only 12.5%. Looks like being bigger works if you float!

The result is broadly similar (although actually different) on the erg. You don't have to worry about displacement at all, but at higher rates you have to consider the energy used sliding back and forth (on the water, the boat does most of the sliding underneath you in the opposite direction to you). You are still much better off bigger.

So there we have it, the reason why water rowers are 6'4", 95kg, and by all accounts getting bigger, and the reason why marathon runners are typically small (although in both sports long legs help for mechanical reasons). It is all because 2/9 is smaller than 2/3.

<<  <  [1] [2] 

Website Builder