Since you linked the German version of the Japanese documentary that people were keen to get a translation of, I thought I’d summarise the main points made in this video about Powell’s biomechanics.
First, they compare his initial couple of steps to those of Gay and reach the following conclusions:
a) Gay steps from side to side, whereas Asafa’s feet go straight forward.
b) Gay’s footplant only involves the balls of his feet whereas Asafa’s involves his mid-foot.
c) Gay’s foot contact is shorter than Powell’s (Gay spends 0.86s on the ground during his first 6 steps and Powell 0.99).
[The problem with all of this is that Gay is running in spikes from a three-point start and Powell in sneakers and from blocks.]
They then go to Japan for some biomechanical analysis and find that Powell’s longer foot contacts allow him to generate much more forward drive. His first step accelerates him to 10.5m/s compared to 9.4m/s for Asahara (a Japanese 10.02s sprinter, generally considered to be a good starter).
[Again, Powell is running in sneakers and Asahara in spikes.]
They then do MRI scans and find that Powell has a massive psoas major that is twice as big as that of Asahara. They conclude that this enables him to recover his legs very quickly, thus allowing for his fast start and good knee lift.
Asahara states that he could never run like Powell because he doesn’t have the necessary power.
They then analyse video footage of Gay’s and Powell’s best race (9.84 and 9.74 respectively) to look at their biomechanics at maximum speed. They find that Gay reaches top speed at 70m and Powell at 60m. At top speed, Gay’s stride rate is 4.9 strides per second and his stride length 2.42m. For Powell it’s 4.96 and 2.60, meaning he’s better at both. At 40m, btw., Gay’s stride rate is still higher than that of Powell whose long strides during the acceleration phase result in a slower stride rate in the early stages of the race.
To figure out how he can achieve such superior stride rate and frequency, they determine the force needed to stretch his tendons (they are getting him to contract his quads, so I guess they are looking at the patella tendon) by 1cm. The average person needs 43kg of force to do this. For Asahara it’s 59kg and for Powell 114kg. They thus conclude that his superior tendon stiffness allows him to have both, a very high stride rate and a great stride length.
They then talk about Osaka and conclude that he lost this race because he lost control over his body resulting in co-contraction of agonists and antagonists in his legs. Co-contraction is usually prevented by spinal reflexes and involvement of the brain messes this up. This is why his maximum stride length in this race was only 2.40m.
They also show some interesting footage of him in bed the night before the final. He nervously plays with the light switch of his bedside lamp and repeatedly tells his roommate that he’s going to win the gold.
Towards the end, they show some footage of Asafa refusing to follow his coach’s instructions and complaining about having to train too hard.
Then they show the hill Powell used to run on as a child and some footage of him attending church.
Finally, Asafa talks about the immense pressure he is under to keep his family and country happy.
Hope this is of some help,
Robin.