Hypobaric hypoxia (HH) affects the nervous system's ability to stabilize motor tasks, primarily through changes in neuromuscular activation. Previous studies have reported inconsistent findings regarding electromyographic responses under HH conditions, possibly due to a focus on individual muscle behaviors rather than inter-muscular coordination. This study aimed to determine the effects of HH on surface electromyography-based co-contraction indices (CCIs) during a repetitive upper extremity task and to evaluate the impact of acute (<3 hours) and prolonged (48 hours) exposure. A cross-sectional study was conducted at 3,600 m above sea level, involving 12 healthy adults (5 males, 7 females). Surface electromyographic activity of the biceps and triceps brachii muscles was recorded during a repetitive reaching-retrieving task. Two CCIs were calculated. A significant effect of HH exposure time was observed, with higher CCIs after 48 hours compared to acute exposure (F_1;44 = 4.172; p = 0.047, η²_p = 0.515). No significant interactions between task phases or movement durations were found. Exposure to HH for 48 hours significantly increases CCIs, suggesting compensatory neuromotor responses to HH. These findings highlight the utility of CCIs as markers of neuromuscular alterations during HH and provide insights into the strategies employed by the nervous system under extreme conditions. Future studies should explore these responses over longer periods and across diverse motor tasks.

Context: In human movement analysis, normalization of a surface electromyography signal is a crucial step; therefore, parameter selection for this procedure must be adequately justified. The aim of this research was to determine the variability of electromyography signals in eccentric hamstring contraction under different normalization parameters. Design: Cross-sectional study. Methods: Nine university rugby players (age 21.50 [3.61] y; body mass index 21.50 [4.95]) and no history of recent hamstring injury. Values from maximum voluntary isometric contraction protocol and task related (ie, Nordic hamstring exercise) were used for surface electromyography signal normalization. Intersubject and intrasubject variation coefficients were used for normalization method variability and for signal reproducibility, respectively. Results: Intrasubject variation coefficient value indicates acceptable reproducibility of surface electromyography (less than 12%) for all normalization procedures. Lower values of intersubject variation coefficient value were achieved for normalization procedures using task-related values. Conclusion: Parameters extracted from task execution provided less variability for surface electromyography amplitude normalization in eccentric hamstring muscle contractions.

Sex-related physiological responses to repetitive load-bearing work are of interest due to the limited available evidence and their relevance to occupational health. To investigate potential sex-related differences in selected physiological and perceptual variables during the performance of a repetitive upper-extremity task. A non-probabilistic sample of 20 young adults (10 men and 10 women) was recruited. Participants, in a standing position, performed repetitive work cycles every 2 seconds using their dominant upper limb with the elbow flexed at 90° elbow flexion, while handling loads equivalent to 10%, 20%, and 30% of their maximum voluntary isometric contraction. Local muscle oxygenation was monitored at 0, 10, and 20 minutes in the finger flexors and elbow flexors. Peripheral oxygen saturation, blood pressure, and perceived exertion were also assessed. No statistically significant differences were observed in muscle oxygen saturation; however, men showed slightly higher values. A significant sex difference in perceived exertion was identified only in the elbow flexors at 10% load at 10 minutes (p = 0.029). Blood pressure values were significantly higher in men, but only at minute 20 with the 10% and 20% loads. Physiological responses to repetitive work showed minimal sex-related differences. Local and global adaptations were similar, with only minor variations in perceived exertion. Future research should explore sex-related variability in samples representing the average working-age population and using alternative operational models.

Las personas mayores de 65 años constituirán la mayoría de la población mundial en corto plazo, pero en condiciones de vida precarias. Esto quiere decir que vivirán más años en peor condición de vulnerabilidad y fragilidad. Las sociedades y modelos de desarrollo no estarían preparados, generando altos costos personales, familiares y colectivos. En Chile la fragilidad sería altamente prevalente en esta población, impactando el desarrollo pleno de su vida. La sexualidad es uno de los aspectos que son invisibilizados y poco estudiados. Este trabajo realiza una aproximación crítica, a partir de la revisión y análisis de antecedentes de contexto, políticas públicas y legislación vigentes en Chile. En estos aspectos se evidencia atomización y orientación biomédica de las políticas públicas, colaborando en la comprensión de la relación fragilidad y sexualidad en personas mayores. Además, se revelan tareas de formación e investigación pendientes para la generación de políticas públicas para una vida activa y saludable.