INTRODUCTION:
Ankle plantar flexors substantially contribute to propulsion in human walking, and their relative contributions may be affected by the type of footwear used. In this study, we aimed to examine plantar flexor fine-wire electromyography (wEMG) activity in different footwear types and barefoot walking. We further examined the effect of walking speed on the relative activity of ankle plantar flexors.
METHODS:
Nine healthy people volunteered to this study (five males) with two sessions. In session 1, participants were familiarized to the study protocol. In session 2, electrical activity of flexor hallucis longus (FHL), soleus (SOL), medial and lateral gastrocnemius (MG and LG) muscles were measured with wEMG during eight overground walking tasks: preferred speed walking with shoes, barefoot and with flip-flops; with shoes: 30% slower and faster than preferred speed walking with shoes, and maximum walking speed; walking barefoot and with flip-flops at the same speed as preferred speed walking with shoes (matched speed). Then they performed maximal isometric plantar flexion contractions and maximal big toe flexions superimposed on ankle plantar flexion (MVICs) in an isokinetic dynamometer for wEMG normalization. Root mean square activity was calculated in the push-off phase of individual step cycles based on ground reaction force data. The relative contribution of each muscle to propulsion was calculated as: (mean RMS value %MVIC of the given muscle / mean RMS value %MVIC of all muscles) * 100. Cohen’s d±90% confidence intervals were calculated to define the magnitude of differences.
RESULTS:
In all muscles, wEMG activity increased with speed. With increasing speed the relative contribution to propulsion increased in FHL (from 19 to 22%), did not change in SOL (32%), decreased in MG (from 32 to 25%) and increased in LG (from 18 to 21%). There were no differences between preferred and matched barefoot walking speed or wEMG activity level (d range = 0.06-0.17). wEMG activity for all muscles was lower during matched barefoot walking than preferred speed walking with shoes (7-10% MVIC, d range=0.31-0.47). Flip-flop data are under analysis.
CONCLUSION:
We found that relative wEMG activity of the examined muscles was affected by speed and absence or presence of shoes. During barefoot walking, wEMG activity of plantar flexor muscles was lower than during shod walking at the same speed, which presumably means that shod walking limits the contribution of intrinsic foot muscles to propulsion, which should be further examined.
REFERENCES:
1 Murley GS, Menz HB, Landorf KB. (2014). Gait & Posture, 39(4), 1080-5.
2 Goldmann JP, Potthast W, Brüggemann GP. (2013). Footwear Sci, 5 (1): 19-25.
3 Franklin et al., Gait & Posture. 60: 1-5, 2018.
CONTACT:
annamaria.a.peter@jyu.fi
2018.
23rd Annual Congress of the ECSS - European College of Sports Medicine, Dublin, Ireland, 4-7 July 2018