Perceived fatigue and associated physiological responses during long-distance pedestrian movement in low-pressure hypoxic environments

The hypoxic environment at high altitudes poses significant physiological challenges and safety risks during long-distance evacuations in tunnel fires. However, the underlying response patterns linking pedestrian fatigue and physiological indicators under such conditions remain insufficiently explored. To address this gap, an individual 1 km constant-speed treadmill experiment was conducted in Lhasa (altitude: 3655 m), representing different movement intensities. 30 healthy subjects who had lived in Lhasa for more than six months participated in the experiment. Physiological parameters, including heart rate, blood oxygen saturation, respiratory rate, and blood pressure, were monitored and analyzed together with perceived fatigue ratings. Results indicated that the 4 km/h task represented a low-intensity movement condition, with physiological parameters stabilizing after brief cardiopulmonary adjustment and perceived fatigue remaining low for most participants. In contrast, the 6 km/h task induced considerable physiological stress, with 57% of participants reaching the perceived-fatigue threshold. Participants reaching the perceived-fatigue threshold exhibited greater physiological strain, while females exhibited greater fluctuations in heart rate and blood oxygen saturation than males. Notably, 20% of female participants reached the perceived-fatigue threshold after 0.2 km at 6 km/h. Furthermore, a perceived-fatigue model was developed based on physiological indicators, incorporating distance, gender and body mass index as influencing factors. The findings provide controlled experimental evidence for evaluating perceived fatigue and associated physiological responses during long-distance movement under low-pressure hypoxic conditions, and may support future fatigue-related evacuation modeling and risk assessment for high-altitude tunnel scenarios.