Study Finds Cold and Mental Fatigue Shape Endurance Performance

Performance in endurance sports such as distance running, cycling, and cross-country skiing depends on many variables, including environmental temperature and mental state. Cooler conditions of around 10°C (50°F) may enhance endurance in certain situations. However, extreme cold can impair muscle and nerve function, leading to slower performance. These responses are linked to the Sympathetic Adrenal-Medullary (SAM) system, a pathway that helps regulate stress reactions. Mental fatigue is another factor, often caused by psychological pressure, which can lower motivation and increase tiredness. In warm environments, such fatigue appears connected to the Hypothalamic-Pituitary-Adrenal (HPA) axis, another stress-regulating system that influences exercise capacity.

Until recently, the combined role of cold exposure and mental fatigue in endurance performance was not well understood. To examine this, Daiki Imai and colleagues at Osaka Metropolitan University’s Research Center for Urban Health and Sports carried out a study with nine healthy young men. Participants were exposed to whole-body cooling while performing Stroop color-word tasks designed to induce mental fatigue. The researchers then analyzed endurance exercise capacity, with attention to perceived fatigue and physiological stress responses. 

Overall, group-level performance showed no significant differences across conditions. Yet when individual data were examined, important patterns emerged. Participants who reported higher levels of subjective fatigue demonstrated a measurable decline in endurance ability. The analysis also revealed that the SAM system, rather than the HPA axis, was more strongly associated with increased fatigue under these circumstances.

Professor Imai, first author of the study published in the European Journal of Applied Physiology, explained the relevance of the findings: “The results of this study provide a scientific basis for effective conditioning strategies for winter sports and work in cold environments. Going forward, we will establish specific methods to minimize the effects of cold stress and mental fatigue. Further, we will investigate the characteristics of individuals who are susceptible to these effects.”