Sex-specific reliability and multidimensional stability of responses to tests assessing neuromuscular function

Area of Science:

• Neuromuscular Physiology
• Exercise Science
• Biomedical Engineering

Background:

• Understanding sex-specific differences in neuromuscular function is crucial for tailored training and rehabilitation.
• Previous research has explored reliability in muscle fatigue but often lacks sex-specific analysis.
• Surface electromyography (sEMG) and electrical stimulation are key tools for assessing neuromuscular responses.

Purpose of the Study:

• To estimate sex-specific effects on the test-retest reliability of peripheral and central neuromuscular measures.
• To analyze reliability during brief and sustained isometric maximal voluntary contractions (MVC) of ankle plantar flexors.
• To compare reliability between sexes using linear and nonlinear sEMG signal analysis.

Main Methods:

• 10 men and 10 women performed five identical trials of brief (5s) and sustained (2min) isometric MVC with superimposed electrical stimulation.
• Surface electromyography (sEMG), dynamometry, and electrical stimulation were used to measure neuromuscular function.
• Test-retest reliability was assessed using intraclass correlation coefficients (ICCs) and analysis of variance.

Main Results:

• Women exhibited greater central and peripheral fatigability than men during sustained MVC.
• Reliability for central activation ratio was lower in women compared to men for both brief and sustained MVC.
• Despite sex differences in fatigue, all measured neuromuscular indices demonstrated meaningful test-retest reliability (p<0.05) across trials for both sexes.

Conclusions:

• Female participants showed significantly greater central and peripheral fatigue after sustained plantar flexor MVC.
• Acceptable agreement was found between dynamometry, electrical stimulation, and sEMG measurements over time for both sexes.
• The findings highlight important sex-specific considerations for neuromuscular fatigue assessment and reliability.