Gender differences in skeletal muscle fatigability are related to contraction type and EMG spectral compression

Abstract

The purposes of this study were 1) to evaluate gender differences in back extensor endurance capacity during isometric and isotonic muscular contractions, 2) to determine the relation between absolute load and endurance time, and 3) to compare men [n = 10, age 22.4 +/- 0.69 (SE) yr] and women (n = 10, age 21.7 +/- 1.07 yr) in terms of neuromuscular activation patterns and median frequency (MF) shifts in the electromyogram (EMG) power spectrum of the lumbar and hip extensor muscles during fatiguing submaximal isometric trunk extension exercise. Subjects performed isotonic and isometric trunk extension exercise to muscular failure at 50% of maximum voluntary contraction force. Women exhibited a longer endurance time than men during the isometric task (146.0 +/- 10.9 vs. 105.4 +/- 7.9 s), but there was no difference in endurance performance during the isotonic exercise (24.3 +/- 3.4 vs. 24.0 +/- 2.8 repetitions). Absolute load was significantly related to isometric endurance time in the pooled sample (R(2) = 0.34) but not when men and women were analyzed separately (R(2) = 0.05 and 0.04, respectively). EMG data showed no differences in neuromuscular activation patterns; however, gender differences in MF shifts were observed. Women demonstrated a similar fatigability in the biceps femoris and lumbar extensors, whereas in men, the fatigability was more pronounced in the lumbar musculature than in the biceps femoris. Additionally, the MF of the lumbar extensors demonstrated a greater association with endurance time in men than in women (R(2) = 0.45 vs. 0.19). These findings suggest that gender differences in muscle fatigue are influenced by muscle contraction type and frequency shifts in the EMG signal but not by alterations in the synergistic activation patterns.

Muscle Maintenance by Volitional Contraction against Applied Electrical Stimulation

“…The choice may be arguable but seems appropriate as physiological research confirms an association between muscle fatigue and shifts in firing rates towards lower values [7,[12][13][14][15][16][17][18][19][20]. Moreover, regression analyses between the MF and MPF slopes with time were capable of detecting differential responses in the fiber types: with slow twitch fibers showing more resistance to fatigue than the fast twitch fibers [26,27].…”

“…Evaluation of muscle fatigue: EMG power spectral frequency analysis was used to evaluate skeletal muscle endurance [12][13][14][15][16][17][18][19][20]. The median frequency (MF) and the mean power frequency (MPF)…”

Quebec Research on Work-related Musculoskeletal Disorders

“…Some biological sex differences are well established. For example, studies have shown that men have a greater ratio of type II (fast) to type I (fatigue-resistant) muscle fibres (Mannion et al, 1997(Mannion et al, , 1998Staron et al, 2000), possibly explaining male-female differences in fatigability (Clark et al, 2003). Generally, we stress the importance of considering that gender, sex, social class, age and ethno-cultural group membership interact in various ways with WMSDs determinants (Habib and Messing, 2012;Lederer, Rivard and Mechakra-Tahiri, 2012;Premji et al, 2010;Seifert et al, 2007).…”

Effects of Volume Training on Strength and Endurance of Back Muscles: A Randomized Controlled Trial

“…A load cell (SF01, EMG system of Brazil Ltda. ), with a capacity of 0-200 kgf, was attached to the Roman chair with a chain and to a nylon torso harness, equipped with a ring at the mid-sternal region to measure the maximum strength of the back extensors (in Newtons: N) 21 . The participants performed three maximal voluntary isometric contractions (MVIC) of the back extensors in a horizontal position (Figure 2 (A)), with a three minute rest between trials.…”