Quantification of physiological and mental workloads of faster and slower finishers of a long-distance military training activity.

Background: Long-distance runs with equipment are practised in military training establishments to develop physical stamina and prepare for battles. A study was planned to quantify and compare the physiological and mental workloads of the early and late finishers of a military endurance run through the jungle terrain of north-eastern India in hot and humid conditions.

Methods: Twenty-five soldiers of the Indian Army completed a 15 km run through a rural and jungle track with 6.5 kg of equipment. Twelve participants who finished the race before 130 min were categorised as 'early finishers', and 13 were categorised as 'late finishers' who finished the race after 130 min. Physiological parameters, viz., heart rate (HR), breathing rate (BR), estimated core temperature (ECT), peak acceleration (PAC), and physiological intensity (PHYI) and mechanical intensity (MECHI) were recorded using BioHarness V.3 (Zephyr Technologies, USA) and NASA Task Load Index scores were obtained to assess mental workload. Mann-Whitney U test was applied to assess the level of significance at a p value of <0.05.

Results: HR, ECT and PAC were significantly higher (167.9 and 156.0 beats/min, 39.0℃ and 38.4℃, and 1.1 and 1.0 g, respectively) for the first group compared with the second group. The second group expressed higher BR and subjective responses ('total scores' were 76.5 and 82.5, respectively) than the first. The PHYI was significantly higher (from 7.2 to 6.3) for the first group, whereas the MECHI was similar in both groups.

Conclusion: The successful completion by the first group can be attributed to their motivation to continue heavy work in an adverse environment, and their ability to negotiate with natural obstacles was reflected through controlled subjective responses. Adoption of a possible safe and stable approach to the same task might have led the second group to take a longer duration, exert higher mental effort and demand lower physiological cost.