Electromyographic Threshold and Microvascular Reactivity for Assessment of Muscle Fatigue in Elderly Women [1

Abstract

INTRODUCTION: To analyze muscle fatigue in elderly women using two non-invasive methods, surface electromyography and laser-Doppler flowmetry. METHODS: The sample consisted of 60 sedentary elderly women of 65 to 85 years of age, all enrolled at the Open University for the Elderly (UAMA). The women in the intervention group (n=30) participated in a strength-training program, while the women in the control group (n=30) did not. The intervention group performed a strength-training program involving two sessions a week for sixteen weeks. The muscle fatigue evaluation was conducted through electromyographic fatigue threshold (EMGFT), also using the simultaneous evaluation of the results of electromyographic activity and 30-second chair stand test (CST) and flowmetric assessment of microvascular reactivity by laser-Doppler flowmeter. RESULTS: Muscle performance was improved in the intervention group, with a significant increase in muscle strength when the 30-second CST baseline values were compared with those registered following the intervention (9.63±1.90 repetitions/30 seconds versus 15.16±3.23 repetitions/30 seconds, respectively; P<.001). In addition, there was a statistically significant reduction in peripheral muscle fatigue according to the fatigue index, an improvement in neuromotor efficacy and an increase in EMGFT. The microvascular reactivity data obtained showed significant gains in the hyperemic area in the intervention group compared to the control group. CONCLUSION/IMPLICATIONS: The EMGFT protocol used to analyze the variables from the electromyographic signal and the PORH protocol used to evaluate microcirculation by laser-Doppler flowmetry can be applied to study muscle fatigue in the elderly.