Chronophotography finally allowed Marey to analyze the mechanics of how humans and the animals with which we share this planet propel themselves. In 1884 he initiated his analysis of human dynamics with ways that we jump.

1884 - Chronophotographie géométrique mécanisme du saut

Working with gymnasts from the military academy at Joinville, Marey marked their limbs, joints and head with silvered strips and buttons graphing their movements across the hangar noir. He employed his camera to trace the trajectory of the center of gravity in different kinds of jumps, and to show exactly what happens in each part of the body when the force of the landing is mitigated by the bending knees, or, oppositely, what happens when the knees remain stiff and all the force of the jump is carried through to the feet.

Marey often dynamographed his subjects as he chronophotographed them The men were fitted with dynamographic shoes whose heels (rather than toes) contained a small air capsule and spring which transmitted the pressure of their feet on the floor to a receiving tambour seen in the experiments.

1884 - Chronophotographie géométrique locomotion de l'homme, dynamomètre

The data Demenÿ and Marey compiled from these studies corroborated the earlier importance that Marey had assigned to the movement of the body's center of gravity: they showed that all muscular actions which alter the center of gravity of the body in such a manner as to raise it, augment the pressure on the ground, and all actions which lower the center of gravity diminish the pressure; bending the knees, in other words, lessens the effects of fatigue.