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.

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.

Introduction: Early increases in muscle strength following unilateral resistance training are typically accompanied by strength gains in the contralateral untrained muscles, a phenomenon known as cross-education. However, the specific motor unit adaptations responsible for this gain transfer remain poorly understood. To address this gap, we recorded myoelectrical activity from the biceps brachii using high-density electromyography.Methods: Nine participants performed 8-week unilateral resistance training and were compared to nine control individuals who did no intervention. Discharge characteristics of longitudinally tracked motor units were assessed during maximal voluntary contractions and isometric ramp contractions at 35% and 70% of the maximal voluntary force (MVF) at baseline (T0), 4 weeks (T1), and 8 weeks (T2) post-intervention.Results: MVF increased by 7% in untrained muscles at T1 and 10% at T2 (p < 0.05). These gains were accompanied by significant decreases in motor unit recruitment thresholds (p < 0.01) and higher net discharge rate (i.e., gain in discharge rate from recruitment to peak) following intervention (p < 0.05). Trained muscles presented greater MVF (+11%, T1; +19%, T2) with similar motor unit adaptations, including a lower recruitment threshold (p < 0.01) and a higher net discharge rate (p < 0.01).Discussion: Our findings indicate that higher strength in untrained muscles is associated with a higher net discharge rate, implying a greater spinal motoneuron output to muscles. The present results underscore the role of motor unit adaptations in the transfer of strength gains to non-trained muscles, offering novel insights into the neural mechanisms underlying cross-education.

Neural determinants explaining the asymmetrical force and skill observed in limb dominance still need to be comprehensively investigated. To address this gap, we recorded myoelectrical activity from biceps brachii using high-density surface electromyography in twenty participants, identifying the maximal voluntary force (MVF) and performing isometric ramp contractions at 35% and 70%MVF and sustained contractions at 10%MVF. Motor unit discharge characteristics were assessed during ramp contractions, the proportion of common synaptic input to motoneurons was calculated with coherence analysis, and the firing rate hysteresis (∆F) was used to estimate spinal motoneuron intrinsic properties. The dominant limbs presented a greater MVF compared to the non-dominant side (+ 9%, p = 0.001), with similar relative recruitment and derecruitment thresholds of motor units (p > 0.05). The discharge rate was significantly higher on the dominant side (p < 0.001), along with a greater proportion of common synaptic input (+ 14%, p = 0.002). No significant differences were observed in the ∆F (p > 0.05). Our findings suggest that greater strength on the dominant side is associated with higher neural drive to muscles due to a greater proportion of common synaptic inputs rather than differences in motoneuron intrinsic properties. These results underscore neural asymmetries at the motor unit level, corresponding to different mechanical outputs underlying limb dominance.