Effect of Cold vs Temperate Conditions on Physical Performance During Extended Mountain Warfare Training at Moderate Altitude.

Introduction: The purpose of this study was to investigate the effect of environmental conditions on body composition, upper body power, and lower body power throughout a ∼4-week military mountain training exercise. We hypothesized that countermovement jump and ballistic push-up performance would decrease as a result of extended mountain field training and that winter (cold) conditions would result in greater decrements compared to fall (temperate) conditions. We also expected to observe a strong positive correlation between changes in performance and changes in skeletal muscle mass. Finally, we expected acute changes in performance upon altitude exposure.

Materials And Methods: A total of 111 U.S. Infantry Marines (110 M; 1 F) provided written informed consent to participate in this study according to a protocol approved by the Naval Health Research Center. There were 54 participants in the fall cohort and 57 in the winter cohort. Maximum effort countermovement jump and ballistic push-up performance were assessed at different timepoints: (1) baseline at the sea level, (2) before training at ∼2100 m, (3) midpoint of training at ∼2100 m, (4) end of training at ∼2100 m, and (5) after 3 to 4 weeks of recovery at the sea level. The fall cohort trained at moderate temperatures (average day/night, 20°C/3°C), whereas the winter cohort trained under snowy winter conditions (7°C/-14°C).

Results: The results suggested that seasonal conditions did not significantly affect changes in body composition or physical performance. Furthermore, no acute effects of altitude on physical performance were detected. Training exercise did, however, cause performance decrements in countermovement jump height, countermovement jump peak power, and ballistic push-up height. Repeated measure correlation analyses suggested that there was a weak positive correlation between the decrease in skeletal muscle mass and the decrease in countermovement jump peak power throughout the training.

Conclusions: The results of our study suggest that explosive movements are negatively affected by extended military training, seemingly independent of environmental training conditions or temperature. Planning and execution of military training should account for the likelihood that warfighter physical power will decline and may not return to pretraining levels within the month following the training event. It may also be advised to consider targeted exercises to aid in recovery of muscular strength and power. Future work should consider additional factors that likely influenced the decrease in physical performance that occurs during extended military training, such as nutrition, sleep, and psychological and cognitive stresses.