The vertical excursion of the body visceral mass during vertical jumps is affected by specific respiratory maneuver.

Most of the inverse modeling of body dynamics in sports assumes that every segment is 'rigid' and moves 'as a whole', although we know that uncontrolled wobbling masses exist and in specific condition their motion should be optimized, both in engineering and biology. The visceral mass movement within the trunk segment potentially interferes with respiration and motion acts such as locomotion or jumping. The aim of this paper is to refine and expand a previously published methodology to estimate that relative motion by testing its ability to detect the reduced vertical viscera excursion within the trunk. In fact, a respiratory-assisted jumping strategy is expected to limit viscera motion stiffening the abdominal content of the bouncing body. Six subjects were analyzed, by using inverse dynamics incorporating wobbling masses, during repeated vertical jumps performed before and after a specific respiratory training period. The viscera excursion, which showed consistent intra-individual time courses, decreased by about 30% when the subjects had become familiarized with the trunk-stiffening maneuver. We conclude that: (1) present methodology proved to detect subtle visceral mass movement within the trunk during repetitive motor acts and, particularly, (2) a newly proposed respiratory maneuver/training devoted to stiffening the trunk segment can reduce viscera vertical displacement.