Running Economy: Neuromuscular and Joint Stiffness Contributions in Trained Runners

Int J Sports Physiol Perform. 2018 May 29;1-22. doi: 10.1123/ijspp.2018-0151. Online ahead of print.

Abstract

It is debated whether running biomechanics make good predictors of running economy, with little known information about the neuromuscular and joint stiffness contributions to economical running gait.

Purpose: The aim of this study was to understand the relationship between certain neuromuscular and spatiotemporal biomechanical factors associated with running economy.

Methods: Thirty trained runners performed a 6-minute constant-speed running set at 3.3 m∙s-1, where oxygen consumption was assessed. Overground running trials were also performed at 3.3 m∙s-1 to assess kinematics, kinetics and muscle activity. Spatiotemporal gait variables, joint stiffness, pre-activation and stance phase muscle activity (gluteus medius; rectus femoris (RF); biceps femoris(BF); peroneus longus (PL); tibialis anterior (TA); gastrocnemius lateralis and medius (LG and MG) were variables of specific interest and thus determined. Additionally, pre-activation and ground contact of agonist:antagonist co-activation were calculated.

Results: More economical runners presented with short ground contact times (r=0.639, p<0.001) and greater strides frequencies (r=-0.630, p<0.001). Lower ankle and greater knee stiffness were associated with lower oxygen consumption (r=0.527, p=0.007 & r=0.384, p=0.043, respectively). Only LG:TA co-activation during stance were associated with lower oxygen cost of transport (r=0.672, p<0.0001).

Conclusions: Greater muscle pre-activation and bi-articular muscle activity during stance were associated with more economical runners. Consequently, trained runners who exhibit greater neuromuscular activation prior to and during ground contact, in turn optimise spatiotemporal variables and joint stiffness, will be the most economical runners.

Keywords: electromyography; gait; oxygen cost of transport; running performance.