Muscle enhancement using closed-loop electrical stimulation: Volitional versus induced torque

Abstract In cases of partial deficiency of muscle activation capacity, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In this activation modality the shares of the volitional and induced torques within the overall h...

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Bibliographic Details
Published in:Journal of electromyography and kinesiology 2007-06, Vol.17 (3), p.275-284
Main Authors: Langzam, E, Nemirovsky, Y, Isakov, E, Mizrahi, J
Format: Article
Language:English
Subjects:
Adult
Algorithms
Electric Stimulation - methods
Electrical stimulation
Electromyography
Enhancement ratio
Female
Humans
Hybrid excitation
Leg - physiology
Male
Muscle Contraction - physiology
Muscle enhancement
Muscle, Skeletal - physiology
Physical Medicine and Rehabilitation
Recruitment, Neurophysiological - physiology
Tibialis Anterior
Torque
Volition - physiology
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Summary:Abstract In cases of partial deficiency of muscle activation capacity, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In this activation modality the shares of the volitional and induced torques within the overall hybrid torque are unknown. The purpose of this study was to suggest a computational approach to parcel out the volitional and stimulation induced components of joint torque generated during combined voluntary and electrical activation of the Tibialis Anterior muscle (TA). For this purpose, isometric contraction of the TA was studied on 5 healthy subjects, using an activation protocol involving ES alone, volitional activation alone and hybrid activation. Ankle torque and TA EMG were measured. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG filtering and on pre-measured calibration curves of volitional torque versus EMG. The results indicated that for a certain hybrid torque there is a linear decaying relationship between the induced torque and the volitional torque shares. Moreover, based on a defined enhancement ratio, the results indicate that within the range of stimulation intensities, there exist regions of increased facilitation, in which the stimulation efficiency is higher under combined compared to isolated conditions.
ISSN:1050-6411
1873-5711
DOI:10.1016/j.jelekin.2006.03.001