Sex differences in muscle activity and motor variability in response to a non-fatiguing repetitive screwing task

Abstract

Background: Musculoskeletal disorders are more prevalent among women than among men, which may be explained by aspects of motor control, including neuromuscular requirements and motor variability. Using an exploratory approach, this study aimed to evaluate sex differences in neuromuscular responses and motor variability during a repetitive task performed on 3 days.Methods: Thirty women and 27 men performed the non-fatiguing, repetitive, 1-h screwing task. For neuromuscular responses, the mean and difference values of static, median, and peak percentile muscle activity levels (normalized to a reference voluntary contraction force) and, for motor variability, the mean and difference values of relative and absolute cycle-to-cycle variability across days were compared between both sexes for each muscle. A mixed-design analysis of variance was used to assess differences between both sexes.Results: The non-fatiguing character of the screwing task was confirmed by the absence of decreased force levels in maximal voluntary contractions performed before and after the task and by absence of electromyographic signs of muscle fatigue. The static and median muscle activity levels tended to be higher among women (on average 7.86 and 27.23 %RVE) than men (on average 6.04 and 26.66 %RVE). Relative motor variability of the flexor and biceps muscles and absolute motor variability of both upper arm muscles were lower in women (on average 0.79 and 29.70 %RVE) than in men (on average 0.89 and 37.55 %RVE). The median activity level of both upper arms muscles tended to decrease within days among women (on average -2.63 %RVE) but increase among men (on average + 1.19 %RVE). Absolute motor variability decreased within days among women (on average -5.32 to -0.34%RVE), whereas it tended to decrease less or increase within days among men (on average -1.21 to + 0.25 %RVE).Conclusion: Women showed higher levels of muscle activity and lower initial relative and absolute motor variability than males when performing the same occupational task, implying women may have a higher risk for developing disorders and point to both sexes using different intrinsic motor control strategies in task performance. Clearly, biological aspects alone cannot explain why women would be at higher risk for developing disorders than men. Therefore, a wider range of individual and environmental factors should be taken into account for optimizing work station designs and organizations by taking into account sex differences.

A Higher Serum Anion Gap Is Associated with the Risk of Progressing to Impaired Fasting Glucose and Diabetes

“…Individuals with elevated SAG, both men and women, had a high probability of suffering from IFG. Poorer compliance and management in men with diabetes, along with differences in the biological response to hyperglycemia and other risk factors between the sexes [ 20 – 22 ], may explain these findings. Obesity is a strong predictor of an increased risk for type 2 diabetes in adults [ 23 ] and probably plays a major role in the development of diabetes [ 24 , 25 ].…”

Which subject-related variables contribute to movement variability during a simulated repetitive and standardised occupational task? Recurrence quantification analysis of surface electromyographic signals

“…Two types can be distinguished. Metrics derived from linear measures, such as the standard deviation or coefficient of variation, inform of the variability magnitude (Luger et al 2020;Gaudez et al 2019;Pritchard et al 2019;Sedighi and Nussbaum 2017). They assume that variations between repetitions of a task are random and independent while these variations have deterministic properties (Caballero, Barbado and Moreno 2014).…”

“…The individual factors, such as subjectrelated characteristics, i.e. sex, age, height or body mass index (Luger et al 2020;Gaudez et al 2019;Müller et al 2013;Madeleine, Voigt, and Mathiassen 2008;Haddad et al 2008), their work experience on the job (Sedighi and Nussbaum 2017;Madeleine et al 2003), and such as the movements they make when performing the task (Gaudez et al 2019;Gilles et al 2019) all contribute to intrinsic movement variability (Gaudez, Gilles and Savin 2016). Movement variability is inherent to human motor control.…”

Sex-specific effects of localized muscle fatigue on upper body kinematics during a repetitive pointing task

“…This is believed to be a result of differences in anthropometry, strength, flexibility, and other factors of biological origin [ 19 – 21 ]. In addition, previous studies showed that females use different biomechanical techniques compared to males during repetitive tasks [ 19 – 22 ]. For instance, females demonstrated higher upper body muscle activity than males in a painting task [ 23 ].…”