Young men utilise limited neuromuscular preparation to regulate post-impact knee mechanics during step landing

- We investigated changes in pre-impact preparation during repeated step landing trials.
- We examined the link between pre-impact preparation and post-impact knee mechanics.
- Individuals spontaneously altered preparation, which varied between individuals.
- Preparation ranged on a continuum to regulate post-impact knee mechanics.
- The implications of different strategies on knee loading warrants further study.

PurposeThe neuromuscular mechanisms determining the mechanical behaviour of the knee during landing impact remain poorly understood. It was hypothesised that neuromuscular preparation is subject-specific and ranges along a continuum from passive to active.MethodsA group of healthy men (N = 12) stepped-down from a knee-high platform for 60 consecutive trials. Surface EMG of the quadriceps and hamstrings was used to determine pre-impact onset timing, activation amplitude and cocontraction for each trial. Partial least squares regression was used to associate pre-impact preparation with post-impact knee stiffness and coordination.ResultsThe group analysis revealed few significant changes in pre-impact preparation across trial blocks. Single-subject analyses revealed changes in muscle activity that varied in size and direction between individuals. Further, the association between pre-impact preparation and post-impact knee mechanics was subject-specific and ranged along a continuum of strategies.ConclusionThe findings suggest that neuromuscular preparation during step landing is subject-specific and its association to post-impact knee mechanics occurs along a continuum, ranging from passive to active control strategies. Further work should examine the implications of these strategies on the distribution of knee forces in vivo.