Physiological monitoring of movement and manoeuvrability during a military skiing exercise.

Introduction: Military forces receive training in various high-altitude warfare techniques to safeguard border regions and lives. Skiing is one of such practices where research evidences are limited. Therefore, a study was conducted to continuously monitor the physiological status of soldiers during military skiing practice to quantify the actual demands.

Methods: 11 Indian soldiers skied a distance of 8 km while carrying 18 kg of military equipment. Physiological status and heart rate variability (HRV) were continuously recorded throughout the exercise. The participants completed the event in about 3 hours. The icy track consisted of about 50% upward slopes, 40% downward slopes and only 10% of flat surface. The full data set was divided into four phases (45 min each), to understand the degree of changes in physiological, and autonomic responses with progress in time and intensity. Repeated measures analysis of variance was used to examine the degree of significance between the phases.

Results: Physiological factors including HR rose consistently from the first to the fourth phase, increasing from 116 to 150 beats/min. The peak acceleration was maintained within 0.4-0.6 g and ground speed varied from 0 to 14.8 km/hour, respectively. The time domain parameters decreased steadily from pre-exercise to the first half of the event, then slightly increased at the beginning of the second half before decreasing again during the final part. The low frequency increased during the first half and remained low until the end of the second half, while the high frequency exhibited an exactly opposite pattern.

Conclusion: The HRV data indicated parasympathetic withdrawal and sympathetic activation in first half, primarily due to the uphill climb. The third phase featured with the flatter surface, which increased the speed and led to partial parasympathetic activation. The final incline caused a rise in physiological responses and sympathetic dominance. Persistent cold, exposure to hypoxia and job requirements ensured that the physiological variables remained at a 'moderately' high level.