From a muscular engagement point of view the start is a well-timed and powerful contraction of the posterior chain. The posterior chain is the series of muscles that have overlapping insertion points, forming a chain link like structure. These muscles include the lower to middle back (erector spinae), glutes, hamstrings and the calves can even be considered a part of the posterior chain. This group of muscles has an extremely high potential for power production through the entire start motion and thus can translate to a very fast start when recruited and trained correctly.
When body position on the block and form throughout the motion are both correct, there will be a snap from the hips directing the body forward, followed by a finishing push from the calves. While this motion is very powerful, it is not a motion that is natural when thinking about “jumping” off the blocks. It is a different motion than a vertical jump and thus recruits different muscles. This needs to be taken into account and in the coming articles we will talk about how to train these muscles and the motion.