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Age related changes in surface myoelectric signals
R Merletti1, L R Lo Conte, C Cisari
1NeuroMuscular Research Center, Boston University.
Scandinavian Journal of Rehabilitation Medicine
|January 1, 1992
Summary
Elderly adults show smaller increases in muscle conduction velocity and myoelectric signal variables with voluntary contraction. However, their muscle function shows less decline during sustained contractions, suggesting age-related fiber changes.
Area of Science:
- * Neuromuscular Physiology
- * Geriatric Exercise Science
- * Biomedical Engineering
Background:
- * Aging impacts skeletal muscle function, affecting muscle fiber characteristics and neural control.
- * Muscle fiber conduction velocity (MCV) and myoelectric signal (MES) spectral variables are key indicators of muscle function.
- * Understanding age-related changes in these parameters is crucial for assessing muscle health in older adults.
Purpose of the Study:
- * To investigate age-related differences in MCV and MES spectral variables during voluntary and electrically stimulated contractions.
- * To compare neuromuscular responses between healthy elderly subjects and younger adults.
- * To explore the relationship between these physiological measures and underlying muscle fiber alterations.
Main Methods:
- * Studied 15 healthy elderly subjects (65-84 years) performing isometric voluntary contractions (20% and 80% MVC) and electrically elicited contractions.
- * Used tetanic electrical stimulation (20 Hz, 40 Hz) with varying amplitudes to induce fatigue.
- * Measured MCV and surface MES spectral variables, comparing results with data from younger adults (18-43 years).
Main Results:
- * Elderly subjects exhibited smaller increases in MCV and MES variables from 20% to 80% MVC compared to younger adults.
- * During sustained 80% MVC contractions, elderly subjects showed significantly less decline in MCV and MES variables.
- * No significant age-related differences were observed in MCV and MES variable decline during 40 Hz supramaximal stimulation.
Conclusions:
- * Findings suggest age-related decreases in fast-twitch muscle fiber number and size contribute to altered voluntary contraction responses.
- * Reduced decline during sustained contractions in elderly individuals may indicate compensatory mechanisms or fiber-type specific adaptations.
- * Further investigation is needed to explain the similar fatigue response under high-frequency electrical stimulation across age groups.