Conflicts in published research raised a series of questions on the precision of the measurements
used to differentiate between vertical jumps performed with and without pre-stretch. Procedures
outlined by previous researchers (eg. Komi and Bosco, 1978a; Bedi et al., 1987) were repeated
and extended. Force plate data were collected for a series of squat, counter movement and
rebound jumps. Individual subjects responded differently and no evidence could be found for an
optimal rebound dropping height.
Modal analysis of the force plate highlighted the need for improving its mounting. A frame was
designed to raise the resonant frequency of the plate and static and dynamic calibrations
revealed point of force application errors. 16 mm cinefilm was selected in preference to video
for the subsequent inverse dynamics analysis of rebound jumping.
French physiologist, Marey, observed that people appeared to jump higher following a rebound
than a counter movement. A 'Marey' style jumping exercise was used to examine different
takeoff and landing strategies. Variations in kinematic data filtering, body segment inertia
parameters and quasi-static analysis techniques on the resultant moment moments were
investigated. No differences in maximum jump height were found between counter movement
and rebound jump takeoffs. This apparent contraction to the findings in previous research was
accounted for by variations in the subjects' stretch heights at takeoff. A general proximal to
distal sequencing of muscle moment peaking was observed in both takeoff actions, but moments
peaked later in rebound takeoffs than when following counter movements. Larger peak
moments occurred during landings preceding coming to rest than during the landing phase of the
rebound jump. Quasi-statically determined muscle moments about the ankles and knees
matched closely with the inverse dynamics values, but joint and overall support moments were
consistently over estimated. Conflicts with selected published research findings were shown to
arise from a lack of measurement precision. Takeoff velocities were greater following counter
movements, but were insufficient to differentiate between jumping techniques. Rebounding was
found to increase leg extension.
Improvements in automatic measurement procedures combined with an enhanced understanding
of musculo-skeletal modelling were seen as a way of improving future knowledge of neuromuscular
coordination and power production in jumping.
Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.