Aerobic capacity (VO2max) has long been identified as one of the fundamental component of physical fitness and soldier's physical performance. Physically active people have higher VO2max values suggesting a relationship between VO2max and total daily energy expenditure (EE) in various military tasks as well.
PURPOSE: To assess whether fitness level affects energy expenditure during a 2-week military winter training period (WT).
METHODS: Voluntary 24 male conscripts (19.7 ± 0.3 yrs.) with varying VO2max (47 ± 6.7 ml/kg/min (range 30–58 ml/kg/min) were measured by a treadmill test until exhaustion. EE [kcal/d] was determined with the doubly labeled water (DLW) method. Body mass (BM), fat free mass (FFM) and fat percentage (F%) were measured by bioimpedance (InBody 720) after overnight fast in the beginning (wk0), after one week (wk1) and at the end of WT (wk2). The BM during WT (BMmean) was presented as an individual average of BM at wk0, wk1 and wk2. BM related EE (EEMET)[kcal/kg/h] was calculated as EE/ BMmean/24.
RESULTS: During WT EE was 3714 ± 395 kcal/day, EEMET 2.0 ± 0.3 kcal/kg/h, FFM increased (63.6 vs. 64.2 kg, p<0.05) and F% decreased (17.7 vs.16.9%, p<0.01), while BM did not change (77.6 vs. 77.2 kg, p=0.73). EEMET correlated positively with the VO2max (r=0.77, p<0.001) and BM change (r=0.77, p<0.001), negatively with wk0 BM (r=−0.85, p<0.001), F% (r=−0.73, p<0.001) and FFM (r=−0.58, p<0.01). However, total EE failed to correlate with the VO2max but correlated positively with the wk0 BM (r=0.41, p<0.05) and FFM (r=0.68, p<0.001).
The conscripts with higher VO2max seem interestingly to have higher EEMET during the 2-week winter training period. Furthermore, the favorable body composition (low F% and BM) was related to higher EEMET. In conclusion, the present findings may be explained by more intense participation and engagement for the military training of the conscripts with the higher work capacity due to better adaptation to working load during WT. Furthermore, the individuals with higher aerobic capacity may often have forced to perform more duties and physical activities during the military service than their poorer counterparts.