Biomechanics of impacts Flashcards
What is the definition of an impact
A collision between two objects where the relative velocity is non-zero
On which two variables does the effect of an impact depend
magnitude of the impact
duration over which the impact is applied
Using inverse dynamics, what three variables are required to calculate joint moments
Knowledge of the force acting at distal joints, calculated from GRF
segment kinematics e,g angular velocities
intertia parameters e.g segment shape and COM location
What three assumptions are made when using inverse dynamics to calculate joint moments
all joints are ball and socket or hinge
segment doesnt change shape during impact
centre of mass doesnt move during impact
state two ways in which the use of Vicon to quantify soft tissue movement can be made more valid
minimal marker mass so that they move when soft tissue moves
lots of markers (150+) to give a good representation of the whole segment
What can be calculated by looking at the change in shape of the calf during an impact and why is calculating this important
moments of intertia
showed that there was around a 30% difference in moments of intertia during the impact which could increase injury risk at certain times
Define a moment of intertia
the bodies tendency to resist angular acceleration
Generally, what two factors do inverse dynamics not account for in their calculations
that soft tissue moves
that soft tissue dissapates energy
what two qualities of an impact can increase the likelyhood of a running related injury
magnitude of the force applied
increased speed at which the force is applied
what is the limitation of most of the studies on running related injuries and GRF
they’re retrospective studies so you can’t be sure that that pattern of GRF was present before the injury was sustained
What were the main findings published by Davis et al. (2016)
Greater VIP, VILR and VALR in injured vs non-injured runners
in a prospective study so better design
Potential for gait retraining to reduce injury risk
Summarise the findings of Leiberman et al 2010
large initial peak ion GRF trace was present in RFS but not in FFS
FFS had a much lower peak impact force
removing shoes from habitually shod RFS caused a large increase in the rate of loading
what were the future directions suggested by Leiberman et al in their 2010 paper
controlled prospective study to see if those who do not rear foot strike have reduced injury rates
Explain why there was a difference in the % decrease in force achieved when dropping a shot put onto a rugby shoulder pad, measured by the force plate and by Tekscan
tekscan sample rate = 250 Hz
force plate = 2000Hz
impact peaks occur v quickly so lower sampling rate likely to miss the impact peak
Explain why a regression equation was required when doing the in vivo shoulder pad testing
to upscale the changes in impacts measured by Tekscan because it was likely to underestimate the impacts due to its low sampling rate
