ABSTRACT
Emerging questions in neuromuscular physiology revolve around whether males and females share similar neural control in diverse tasks across a broad range of intensities. In order to explore these features, high-density electromyography was used to record the myoelectrical activity of biceps brachii during trapezoidal isometric contractions at 35% and 70% of maximal voluntary force (MVF) on 11 male and 13 female participants. Identified motor units were then classified as lower-threshold (recruited at ≤30%MVF) and higher-threshold (recruited at >30%MVF). The discharge rate, interspike interval variability, recruitment and derecruitment thresholds, and estimates of neural drive to motor neurons were assessed. Female lower-threshold motor units showed higher neural drive (P < 0.001), accompanied by higher discharge rate at recruitment (P = 0.006), plateau (P = 0.001) and derecruitment (P = 0.001). On the other hand, male higher-threshold motor units showed greater neural drive (P = 0.04), accompanied by higher discharge rate at recruitment (P = 0.005), plateau (P = 0.04) and derecruitment (P = 0.01). Motor unit discharge rate normalised by the recruitment threshold was significantly higher in female lower-threshold motor units (P < 0.001), while no differences were observed in higher-threshold motor units. Recruitment and derecruitment thresholds are higher in males across all intensities (P < 0.01). However, males and females have similar activation and deactivation strategies, as evidenced by similar recruitment-to-derecruitment ratios (P > 0.05). This study encompasses a broad intensity range to analyse motor unit sex-related differences, highlighting higher neural drive and discharge rates in female lower-threshold motor units, elevated recruitment and derecruitment thresholds in males, and convergences in activation and deactivation strategies. HIGHLIGHTS: What is the central question of the study? Do male and female motor units behave similarly in low- and high-intensity contractions? What is the main finding and its importance? Female motor units show higher discharge rates in low-intensity tasks and lower discharge rates in high-intensity tasks, with no differences in recruitment behaviour. A broader inter-spike interval variability was also observed in females. These findings underline that there are sex-specific differences concern the firing strategies based on task intensity.
ABSTRACT
The 2019 Coronavirus (COVID-19) outbreak caused home confinement, as well as training and sport competitions withdrawals. The prolonged inactivity impact, and lack of in-person interactions among teammates-coaches, could negatively affect athletes. Total of 1508 self-selected Italian athletes, 338 children (aged 10.52 ± 1.31), 499 adolescents (aged 14.17 ± 1.13), and 671 adults (aged 27.59 ± 10.73), completed the Impact of Event Scale (IES-8, IES-15, and IES-R, respectively). Differences by gender, type of sport (individual vs. team), and competitive level (elite vs. amateur) were examined. One-way ANOVAs showed, in adults, significant differences between genders for perceived stress impact total score (TS; p = 0.017) and avoidance behavior, with higher scores in women (p = 0.045). Between individual and team sport, significant differences were found in TS (p = 0.038) and hyperarousal (p = 0.030), with higher results in individual. Adult elite athletes showed significantly higher scores in hyperarousal (p = 0.020) than amateurs. Significant differences were found between gender in adolescents for avoidance (p = 0.011), and between competitive levels in children, for intrusion (p = 0.020). These evidences may raise awareness on distress effects of COVID-19 lockdown among athletes and suggested applying specific well-being protocols during the activity resumption, considering gender, type of sport, and competitive level.
