Systematic reduction of leg muscle activity throughout a standard assessment of running footwear

Journal of Sport and Health ScienceVolume 11, Issue 3, May 2022, Pages 309-318Journal of Sport and Health ScienceHighlights•

We analyzed leg muscle activity during 5 running bouts at a predetermined speed.

Over time, muscle activity decreased by up to 50% before reaching a steady state.

The main reduction in activity occurred during the first 1.5 km of the protocol.

The adaptation process may represent the development of a more economical running style.

Future running shoe testing protocols should include at least 1.5 km of warm-up.

AbstractPurpose

This study aimed to investigate whether there is a systematic change of leg muscle activity, as quantified by surface electromyography (EMG), throughout a standard running footwear assessment protocol at a predetermined running speed.

Methods

Thirty-one physically active adults (15 females and 16 males) completed 5 testing rounds consisting of overground running trials at a speed of 3.5 m/s. The level of muscle activity from 6 major leg muscles was recorded using surface EMG. The variables assessed were the EMG total intensity as a function of time and the cumulative EMG overall intensity. Systematic effects of the chronological testing round (independent variable) on the normalized EMG overall intensity (dependent variable) were examined using Friedman analysis of variates and post hoc pairwise Wilcoxon signed-rank tests (α = 0.05).

Results

There was a systematic reduction in overall EMG intensity for all 6 muscles over the time course of the running protocol (p < 0.001) until the fourth testing round when EMG intensities reached a steady state. The one exception was the biceps femoris muscle, which showed a significant reduction of EMG intensity during the stance phase (p < 0.001) but not the swing phase (p = 0.16).

Conclusion

While running at a predetermined speed, the neuromuscular system undergoes an adaptation process characterized by a progressive reduction in the activity level of major leg muscles. This process may represent an optimization strategy of the neuromuscular system towards a more energetically efficient running style. Future running protocols should include a familiarization period of at least 7 min or 600 strides of running at the predetermined speed.

Keywords

Muscle co-contraction

Running familiarization

Running footwear

Running shoes

Surface electromyography

© 2021 Published by Elsevier B.V. on behalf of Shanghai University of Sport.

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