Perception of muscle strength with and without biofeedback during swallowing and fist-clenching tasks

Abstract

This study investigated the accuracy of the proprioceptive system in swallowing as compared with fist clenching. The role of surface electromyography (SEMG) biofeedback in replicating motor strength was also evaluated. The study was completed in two phase. Phase 1 participants (n = 50) were aged 20–30 years; phase 2 involved participants(n= 50) aged over 50 years. SEMG activity was measured during performance of maximal and graded (half) strength swallowing and fist-clenching tasks. Subjects performed each task eight consecutive times, under three conditions: (1) with biofeedback; (2) without biofeedback; and (3) without feedback following a delay. A portable SEMG biofeedback device recorded the strength and timing of muscular activity and represented the information in analogue waveform on a computer screen. Under biofeedback conditions, subjects were instructed to observe the SEMG waveform to determine their maximal peak SEMG amplitudes. Data were collected from the final five of eight consecutive attempts of each task and a measure of variance calculated. Results demonstrated greater variation in strength of muscle contraction for swallowing attempts than for fist-clenching tasks, in younger participants only. This effect was only statistically significant for full-strength conditions regardless of feedback. In the older age group, variation was higher in the ‘with feedback’ condition; this was not evident in the younger group. For both age groups, graded strength responses were more varied than maximal strength responses. It is postulated that these results indicate that the proprioceptive system of unimpaired subjects may respond differently to SEMG biofeedback than that of participants with an impaired system who require SEMG biofeedback to compensate for a proprioceptive loss. Inferences and applications to the dysphagic population are discussed.