Trampoline Transducer Vicon Calibration Jump Force Takeoff Landing Suspension system Gymnast
Trampolining is a sport entailing multiple somersaults and twists performed from an
elastic sprung bed. During the aerial phase gravity is the only external force acting on
the gymnast and since this acts through the gymnast's centre of mass, angular
momentum is conserved. As somersault and twist production are an essential part of
trampolining it is important to understand the mechanics for producing angular
momentum during the contact phase. Previous research has neglected important factors
such as the considerable mass of the bed and springs in the analysis of the contact
phase. Consequently the mechanics of the contact phase is not yet clear.
An experimental study is presented to determine the forces acting on the gymnast alone
and the forces acting on both the gymnast and the suspension system (bed and springs)
during the contact phase for plain jumps. Kinematic data was obtained using a three
dimensional motion analysis system and inverse dynamics was used to determine
vertical and horizontal forces. Kinetic data was recorded using four tri-axial force
transducers, mounted underneath the trampoline using custom designed brackets. Peak
vertical forces of 25 bodyweights were recorded during plain jumps at the centre of the
trampoline and peak horizontal forces up to 0.5 bodyweights were recorded in jumps
with approximately I m offorwards travel during the subsequent aerial phase.
A simulation model of the trampoline suspension system was developed comprising
thirty eight non-damped linear springs and fifteen point masses. The model was
evaluated using experimental data of an impactor (with known mass) dropped at centre
and off-centre locations on the trampoline from varying heights. Results showed the
trampoline behaves as a non-linear spring.
The study presents relationships between vertical force and vertical bed displacement
and horizontal force and horizontal bed displacement as well as the location of the mass
centre of the bed and springs as a function of the location of the bed centre. These
relationships may be used to model the behaviour of the bed and springs in the analysis
of the mechanics of the contact phase for trampolining skills entailing multiple
somersaults and twists.
A Master's Thesis. Submitted in partial fulfilment of the requirements for the award of Master of Philosophy of Loughborough University.