Electromyographic amplitude versus torque relationships are different in young versus postmenopausal females and are related to muscle mass after controlling for bodyweight

Abstract

Purpose: To examine differences in the electromyographic vs torque (EMG-T) relationship, as well as muscle strength and indicators of muscle mass and quality between young versus postmenopausal females, and explore whether the potential differences in the EMG-T relationships could be explained by differences in muscle mass. Methods: Thirty young (age = 20.7 ± 2.8 y) and 30 postmenopausal (age = 56.3 ± 4.7 y) females completed maximal isometric strength testing (MVIT) and isometric ramp contractions at 40% and 70% MVIT, during which electromyographic signals were collected to quantify the slopes (Slope 40 ; Slope 70 ) and intercepts (Intercept 40 ; Intercept 70 ) of the EMG-T relationships. Muscle mass and quality measurements were also completed. Results: Postmenopausal females exhibited lower skeletal muscle mass (−2.3 ± 1.5 kg), fat free mass index (−1.1 ± 0.7 kg·m −2 ), MVIT (−17.1 ± 16.3 Nm), phase angle (−0.5 ± 0.0°), muscle cross sectional area (−5.5 ± 1.1 cm 2 ), muscle quality (−0.1±0.0 a.u), Slope 40 (−0.0003 ± 0.0002 mV·%MVIT −1 ), Slope 70 (−0.0003 ± 0.0002 mV·%MVIT −1 ), and had a higher echo intensity (+9.8 ± 2.8 a.u), Intercept 40 (+0.001 ± 0.001 mV), and Intercept 70 (+0.004 ± 0.003 mV) (p ≤ 0.001 – 0.04) than the young females. The EMG-T relationship variables were correlated with both muscle mass and quality after controlling for bodyweight. When controlling for muscle mass and bodyweight, group differences in the slopes of the EMG-T relationship and muscle strength were eliminated. Conclusion: Muscle mass and quality are primary contributors to the decrements in neuromuscular function observed in postmenopausal versus young females, and the preservation of muscle mass should be prioritized in the years leading up to, during, and immediately after menopause.

Metabolic and microvascular function assessed using near‐infrared spectroscopy with vascular occlusion in women: age differences and reliability

“…A Seca 514 medical body composition device (Seca, Hamburg, Germany) was used to assess participants’ body composition using multifrequency bioelectrical impedance analysis as previously described (Banks et al., 2021 ; Raeder et al., 2018 ). Participants were euhydrated and fasted for 10 h before body composition assessment.…”