Energy balance and physical demands during an 8-week arduous military training course.

This study assessed soldier's physical demands and energy balance during the Section Commanders' Battles Course (SCBC). Forty male soldiers were monitored during the 8-week tactics phase of the SCBC. Energy expenditure was measured using the doubly labeled water method. Cardiovascular strain (heart rate) and physical activity (using triaxial accelerometer) were also monitored. Average sized portions of meals were weighed, with all recipes and meals entered into a dietary analysis program to calculate the calorie content. Energy expenditure averaged 19.6 ± 1.8 MJ · d(-1) in weeks 2 to 3 and 21.3 ± 2.0 MJ · d(-1) in weeks 6 to 7. Soldiers lost 5.1 ± 2.6 kg body mass and body fat percent decreased from 23 ± 4% to 19 ± 5%. This average weight loss equates to an estimated energy deficit of 2.69 MJ · d(-1). The Army provided an estimated 14.0 ± 2.2 MJ · d(-1) in weeks 2 to 3 and 15.7 ± 2.2 MJ · d(-1) in weeks 6 to 7. Although this provision adheres to the minimum requirement of 13.8 MJ · d(-1) set by Army regulations, soldiers were in a theoretical 5.6 MJ · d(-1) energy deficit. The physical demands of SCBC were high, and soldiers were in energy deficit resulting in loss in body mass; primarily attributed to a loss in fat mass.

The effect of anatomical placement and trunk adiposity on the reliability and validity of triaxial accelerometer output during treadmill exercise.

BACKGROUND: Accelerometers are commonly used to quantify physical activity. There is no accordance regarding the most suitable attachment site. This study assessed the reliability and validity of accelerometer output (PAC) from 2 placements. METHODS: 26 females (age 20.4 ± 1.3 years, body mass 62.7 ± 6.8 kg) twice performed a 16-minute treadmill protocol comprising 4 stages (4, 5, 8, 10 km·hr(-1)) and oxygen uptake (VO2) was calculated. Participants wore an accelerometer at the hip and lower back. Skinfold thickness was measured at 8 sites. Reliability was assessed using coefficients of variation (CVintra). Interactions between placement, velocity and PAC (counts·5s(-1)) were assessed using analysis of covariance. PAC-VO2 associations were assessed using multiple regression. RESULTS: Hip and back placements returned similar reliability (CVintra = 3.0% and 2.8% respectively). Hip PAC were higher (P < .01) during walking with no differences observed during running. Indices of adiposity were related to hip PAC. Regression revealed hip and back PAC as significant predictors of VO2. Back PAC was the least variable. Hip skinfold thickness explained 15% additional variance in VO2 to PAC with reduced standard error. CONCLUSION: The lower back is a more suitable accelerometer placement for young, active females during treadmill exercise.

Injuries and injury risk factors among British army infantry soldiers during predeployment training.

PURPOSE: This prospective cohort study examined injuries and injury risk factors in 660 British Army infantry soldiers during a predeployment training cycle. METHODS: Soldiers completed a questionnaire concerning physical characteristics, occupational factors, lifestyle characteristics (including physical training time) and previous injury. Direct measurements included height, body mass, sit-ups, push-ups and run time. Electronic medical records were screened for injuries over a 1-year period before operational deployment. Backward-stepping Cox regression calculated HR and 95% CI to quantify independent injury risk factors. RESULTS: One or more injuries were experienced by 58.5% of soldiers. The new injury diagnosis rate was 88 injuries/100 person-years. Most injuries involved the lower body (71%), especially the lower back (14%), knee (19%) and ankle (15%). Activities associated with injury included sports (22%), physical training (30%) and military training/work (26%). Traumatic injuries accounted for 83% of all injury diagnoses. Independent risk factors for any injury were younger age (17-19 years (HR 1.0), 20-24 years (HR 0.71, 95% CI 0.55 to 0.93), 25-29 years (HR 0.89, 95% CI 0.66 to 1.19) and 30-43 years (HR 0.41, 95% CI 0.27 to 0.63), previous lower limb injury (yes/no HR 1.49, 95% CI 1.19 to 1.87) and previous lower back injury (yes/no HR 1.30, 95% CI 1.03 to 1.63). CONCLUSION: British infantry injury rates were lower than those reported for US infantry (range 101-223 injuries/100 soldier-years), and younger age and previous injury were identified as independent risk factors. Future efforts should target reducing the incidence of traumatic injuries, especially those related to physical training and/or sports.

Influence of hydration volume and ambient temperature on physiological responses while wearing CBRN protective clothing.

This study examined a low (L; 5 ml/kg per h) and high (H, 10 ml/kg per h) rate of fluid replacement in moderate (18°C) and hot (30°C) conditions on physiological responses while wearing personal protective equipment (PPE). PPE included the gas-tight suit (GTS), the powered respirator protective suit (PRPS) and the civil responder 1 (CR1). Relative to the moderate condition, physiological responses were greater in the hot condition. The percentage change in body mass was different (p < 0.05) between L and H in the hot (L vs. H, GTS: -0.83 vs. -0.38%; PRPS: -1.18 vs. -0.71%; CR1: -1.62 vs. -0.57%) and moderate conditions, although in GTS and CR1 body mass increased (L vs. H, GTS: -0.48 vs. 0.06%; PRPS: -0.66 vs. -0.11%; CR1: -0.18 vs. 0.67%). Fluid replacement strategies for PPE should be adjusted for environmental conditions in order to avoid >1% body mass loss and/or net body mass gain. STATEMENT OF RELEVANCE: Currently, the UK Emergency Services do not have specific evidence-based fluid replacement guidelines to follow when wearing chemical, biological, radiological and/or nuclear (CBRN) PPE. Although ad libitum fluid replacement is encouraged (when breathing apparatus permits), recommendations from evidence-based findings specific to different PPE and to different environmental conditions are lacking. This study provides novel evidence supporting the need to develop fluid replacement strategies during CBRN deployments in both moderate and hot environmental conditions for CBRN PPE.