EMG-Analysis of Resisted and Assisted Dorsiflexion During Gait Transition

EMG-analysisofresisted and assisted dorsiflexion during gait transition

P. Malcolm, V. Segers, I. Van Caekenberghe, D. De Clercq

Department of Movement and Sport Sciences, GhentUniversity,

e-mail:

Introduction:Various studies indicate that the ankle musculature plays an important role in the walk-to-run-transition (WRT). Recently Segers and co-workers found a loweredWRT-speed after inducing local muscular fatigue in the TA by means of a fatigue protocol. The purpose of the present study was to validate the results of Segers et al by means of an experimental manipulation that would act on the ankle specifically around the heel contact phase during the actual WRT acceleration.

Methods:The TA muscular effort was altered by means of a pair of ankle-foot-exoskeletons powered by McKibben pneumatic muscles. 8 female subjects performed 5 WRT’s in 3 experimental conditions:

In the resist condition the pneumatic musclesproduced TA-resisting plantarflexion torque

In the assist condition the pneumatic muscles produced TA-assisting dorsiflexion torque

In the control condition the subjects wore the exoskeleton without the pneumatic muscles.

Results and discussion:We found the lowest WRT-speed in the resist condition, an intermediate WRT-speed in the control condition and the highest WRT-speed in the assist condition (table 1). This indicates an inverse relationship between TA-muscular effort and WRT-speed.

In most subjects and conditionsa rising-descending pattern with an apex was observed in the evolution of the integrated EMG of the TA during the activation burst around heel contact (figure 1). This pattern resembles Hreljac’s definition of a trigger reaching a critical level with the exception that WRT occurred on average 4 steps after the critical level was reached instead of immediately after.There were significant high correlations between the walking speed corresponding with the apex and the WRT-speed which indicates that the apex and the WRT-are closely linked in time (table1).

fig 1: evolution of iEMG of the TA during the activity burst

in the 10 heel contacts preceding gait transition

Conclusion:The pattern that was found in the EMG of the TAcould be interpreted as a trigger reaching a critical level causing the WRT-to happen at a specific speed.These results further emphasise the role of the dorsiflexors in the WRT.

References:

Segers V, Lenoir M, Aerts P, De Clercq D.Gait & Posture. 2007; 25: 639-647

Hreljac A. Med Sci Sports Exerc. 1993; 25:1158-1162

Acknowledgements:

The author wishes to thank Technische Orthopedie BelgiëNV ( and FestoNV ( for their technical support.