[quote]This paper adopts the view that humans are limited in how fast they can run by how much force they can apply within the muscle contraction times.
I keep reading this everywhere.
Am I right in saying Usain isn’t applying more force than a Linford Christie or Ben Johnson since he isn’t even close to there strength levels?.
If so, what gives?. Greater elasticity?.
Carl Lewis (rarely lifted) Vs Linford Christie (700lb + squat).
Well, Linford must be applying greater force?. But not in the same league as Carl?.[/quote]
Re Linford squatting 700 lbs: this demonstrates that he could produce force in around 400 milliseconds. Usain/Carl can produce more force than Linford in 100 milliseconds (a time scale repesenting ground contact time plus a bit of preactivation time) though not anywhere near 700 lbs. To be more precise Usain/Carl would produce their appropriate levels of force in less than 100 milliseconds (maybe close to 70 milliseconds); at this point the force would peak – the muscle fiber would need to relax after this. Most of the motor units (groups of muscle fibers composed of slow and fast twitch fibers) that Linford trained(and strengthened) during the squat would not be recruited in top speed sprinting – an alternating one legged movement; therefore Linford risked great injury, increase in overall weight, and energy that could have been utilised elsewhere for little if any gain in force produced in less than 100 milliseconds. At world record speed one needs to produce about 1400N (roughly 142 kilograms including bodyweight) from each leg at an angle of about 5 degrees off vertical (forward) in less than 100 milliseconds. In contrast Linford was squatting 199 kilograms (including bodyweight) on each leg in 400 milliseconds which is only an extra 57 kilograms. This underlines the true requirement in sprinting; it is not to produce overall force necessarily but to recruit the strongest motor units that can reach peak contraction in 70 milliseconds approximately. These motor units would comprise almost exclusively of fast twitch fibres. Such motor units already exist – imagine isolating those units and increasing the force producing capacity of them exclusively. To summarise, Usain or Carl could recruit these motor units and coordinate their recruitment better than Linford; perhaps Usain and his Jamaican colleagues have a training movement than facilitates the recruitment of such motor units and strengthening of these motor units exclusively. However it is my belief that such a training movement only has a small effect in the form with which they perform it; there are many more effective and significant training movements that can be devised.