The Biomechanical and Biochemical Processes of Human Speed

The following is a short, quick overview of processes that are explained in far greater detail in the book:

Perhaps the easiest way to understand the biomechanical and biochemical processes responsible for the athletic dominance of people of West African descent is by visualizing two sprinters, one black and one white, at the starting line of a 100 meters race. They are the very best of athletes
and are similar in height, weight, age, experience, technical ability, motivation and determination. Any differences between them have been genetically determined.

As they walk slowly to the starting line, to the practiced eye, some physical differences are immediately evident. The black runner seems leaner and more muscular: the muscles in his legs, arms, back and shoulders are more visible, seem larger and more defined, and appear somehow closer to the surface of the skin. In fact, because of a denser network of muscle fibers and lower subcutaneous fat, they are. The white runner, you realize, has relatively shorter arms and legs and a longer torso; but his calves are larger and more muscular. You also notice, as they move around before the race begins, that the black athlete has, improbably, both narrower hips and larger, more muscular buttocks.

To the initiated, these visual clues are by themselves extremely compelling. The mechanical advantage of a longer and more efficient stride-the result of longer legs, narrower hips and lighter calves-and greater power-to-weight ratio-the result of more muscle and less fat-would probably, by itself, be sufficient to guarantee victory for the black athlete. But the biggest difference between these athletes is not externally visible.

Before the race even begins, the white athlete, in addition to his biomechanical disadvantage, will also be at a clear biochemical disadvantage because of one simple difference between themhow their bodies convert glucose into energy. Glucose is the major source for all cellular functions in the body, including muscle contraction. But the energy required for muscle contraction does not come directly from glucose itself but from a compound called adenosine triphosphate (ATP), which is produced by the breakdown of glucose.

The conversion of glucose to ATP occurs in two stages and by two different metabolic processes. The first stage, anaerobic metabolism- oxygen not required- is more than twice as fast as the second, but it is also less efficient, producing far less energy from each molecule of glucose. Only two of the 36 or 38 molecules of ATP produced by the breakdown of each glucose molecule are generated at this stage. The second stage, mitochondrion metabolism-oxygen required-is slow but extremely efficient. Almost all of the ATP molecules are created during this stage.

Both athletes will convert glucose to ATP by both processes but in different ratios. The black athlete will convert a greater percentage of his glucose stores to ATP during the first stage and the white athlete a greater percentage of his during the second. And it is this difference that is largely responsible for the greater athletic success of African Americans and others of West African descent.