The Boundaries of Size and Speed

I do like to day dream. If you slip far enough away anything is possible. I find myself on occasion dreaming of being a genetic endurance freak with the ability to leave my competition gasping for air while I ride away into the distance. Unfortunately, no such luck occurred at my conception and I am left to only dream. Amazingly though such people do exist. Hard work and a little dash of super DNA rounds out the top 10 at most of the grand tours. But yet even beyond these supreme endurance athletes are a small group of actual genetic freaks. The images above, well in particular the rather large whippet dog and the bull of all bulls actually suffer from a disorder where the hormone that regulates muscle mass is not present. This mysterious hormone called Myostatin is produced in skeletal muscle and then circulates around the body to regulate muscle mass. In ordinary individuals no matter how many hours they spend in the gym eventually they reach a level where their muscle mass plateaus. In the case of a genetically modified mouse or a naturally occurring dog there is no Myostatin present to regulate muscle mass so it continues to grow even without any major stimulus. In human cases there are reports of young children with super human strength and a six pack to die for, but yet I am not overly certain of the life span of these fortunate or possibly unfortunate individuals. My day dreams slightly stray from the realms of huge muscles but rather dwell on a VO2max somewhere in the theoretical realms of the spawn of Lance Armstrong (no introduction needed) crossed with Chrissy Wellington (3 x Ironman world champion who goes as fast as most of the guys). So.... what does regulate our ability to uptake and utilize oxygen? Are there individuals who are unknowingly sitting on the couch with the potential to hold 800W for a 40km Time Trial, Possibly? We believe that this potential is partially regulated by the fact that the larger the muscle cross sectional area the further oxygen has to diffuse from the circulation to the center of the muscle and this process is ultimately dictated by the laws of physics. There are of course alternative ways to achieve superhuman performance. Doping is probably the most common and simplest of these forms of performance enhancement. If only they sold EPO at the supermarket, but yet I suppose then everyone would be on it and we would be back at square one again. All in all scientists are still yet to accurately define what exactly limits the boundaries of human adaptation, at the moment I believe the majority of it lies in our minds!!