Both
No, however, the solution to him running faster lies in improving his reactive/elastic ability specific to sprinting and, most likely, programming
I would speculate that the answer is yes; however, I wouldn’t recommend that all intensification of weights come to an end; however. While it will not play as much of a role in the training as someone who just doesn’t have the requisite strength, it may still be used in it’s place during max strength.
Example, Ben Johnson was freakishly strong but Charlie didn’t put the weights in perpetual cruise control. He just exercised caution via perform reps versus singles in the squat.
VJ- great indicator of power to weight ratio in a single explosive effort via hip/leg extension- though it is a complete pain in the ass to test properly (so easy to cheat) and the greater anti-gravitational challenge favors lighter athletes in terms of absolute results. This is also why heavier athletes have the advantage from the standpoint of relative results (ergo power index)
SLJ- another excellent test of power to weight ratio in a single explosive effort via hip/leg extension- easier to perform reliable testing; however, advantage goes to longer levered athletes and the dynamics of the jump pose a lesser anti-gravitational challenge. As a result, heavier athletes will tend to be more competitive in an absolute sense
Speed/quickness is a huge term- very ambiguous. Although by definition it is further in complexity than the single attempt jumps via its multi-directional nature and thus demands additional ability in terms of elasticity/reactivity that the single jumps do not
40yd- must have all of the above. Further dimensional complexity via relaxation component and the biodynamics of sprinting. While relaxation also applies to change of direction drills the speeds aren’t there to make it as much of a factor as it is in the sprint.
Morpho biomechanics play a huge rule with respect to success in every conceivable physical action.
From a dimensional complexity standpoint it becomes obvious why sprint training is the great challenge that it is.
By comparison, single effort jumps are a pedestrian training problem to solve.