Exercise Physiology
yasamin yarahmadi
Abstract
The pathophysiology of heat stress occurs when the body's environmental and physiological responses exceed its ability to maintain homeostasis. When internal heat signals or external factors raise body temperature beyond a certain limit that the cooling mechanisms can effectively manage, the resulting ...
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The pathophysiology of heat stress occurs when the body's environmental and physiological responses exceed its ability to maintain homeostasis. When internal heat signals or external factors raise body temperature beyond a certain limit that the cooling mechanisms can effectively manage, the resulting increase in core temperature triggers response pathways that themselves induce physiological stress. The primary response mechanisms to heat stress include sweating, peripheral vasodilation, and shivering as thermogenic responses—all of which are activated by elevated temperatures and may seem counterproductive to the body's requirements, yet they operate through a neuromuscular and hormonal feedback system. Genetic factors influence individual heat tolerance; for instance, certain populations have variations in heat shock proteins (HSP70) and ion channels (TRPV1, RYR1) that enhance their heat response and tolerance. Additionally, individuals with higher relative VO2 max levels demonstrate greater heat tolerance, as those who are physically trained exhibit more sudomotor activity and effective evaporative cooling compared to untrained individuals. Furthermore, individuals who acclimatize to heat over time develop improved thresholds for heat stress, enabling them to better regulate internal and cardiovascular temperature stresses during exposure. This knowledge is crucial for populations at risk and in situations where physical exertion is required in hot conditions.
Exercise Physiology
yasamin yarahmadi; Morteza Tayebi
Abstract
Purpose: This study aimed to investigate the effect of PMS on aerobic, anaerobic, and cognitive performance in female combat athletes. Method: In this semi-experimental study with a repeated measures design, 20 female combat athletes (mean age: 24.5±2.1 years) were assessed during two phases of ...
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Purpose: This study aimed to investigate the effect of PMS on aerobic, anaerobic, and cognitive performance in female combat athletes. Method: In this semi-experimental study with a repeated measures design, 20 female combat athletes (mean age: 24.5±2.1 years) were assessed during two phases of their menstrual cycle: the PMS phase (7-10 days before menstruation) and the non-PMS phase (days 7-14 of the cycle). Aerobic performance was measured using the Bruce treadmill test, anaerobic performance was assessed by the Wingate test, and cognitive performance was evaluated through simple and choice reaction time tests. Statistical analyses were performed using paired t-tests and Pearson correlation (p<0.05). Results: The findings showed a significant reduction in VO₂ max (6.2%), time to exhaustion, and a significant increase in maximal heart rate and Rate of Perceived Exertion (RPE) during the PMS phase compared to the non-PMS phase (p<0.05). Anaerobic performance also declined, with a reduction in peak power (6.2%) and mean power (7.5%), an increase in fatigue index (16.2%), and lower blood lactate levels (p<0.01). Cognitive performance deteriorated during PMS, demonstrated by increased simple (16.7%) and choice (16.6%) reaction times, more errors, and decreased accuracy (p<0.01). Furthermore, there was a significant positive correlation between PMS symptom severity and VO₂ max reduction (r=0.72), as well as between blood lactate levels and reaction time (r=0.65) (p<0.01). Conclusion: PMS negatively affects aerobic, anaerobic, and cognitive performance in female combat athletes. These findings highlight the importance of considering the menstrual cycle phases in designing training and competition schedules for female athletes to optimize performance and prevent potential declines associated with PMS.
