"We now see a lot of athletes, especially the Jamaicans, doing hurdle drills to strengthen the hip flexion. These hip flexion drills enhance the soleus muscle (lower calf), and studies show a strong correlation between the size of the soleus muscle and sprinting performance. A strong soleus muscle can play a significant role in acceleration over the first 10 meters, when the sprinter is at his slowest.
Research suggests that if a sprinter is 10 percent taller, then he would have a 10 percent shorter ground contact time, which would allow him to run 10 percent faster. However, the limiting factor with a taller sprinter is the energy it takes to bring the legs forward because of the longer limbs. If we can get the tallest sprinters to strengthen their hip flexors and the shorter sprinters to contract their muscles faster, then we should be able to see times around 9.27 seconds. Having said that, I doubt we'd really get past 9.2, because the loading involved at those speeds would force us to have super heavy bones, but then of course the weight becomes a negative factor." - Jeremy Richmond