Utility of preinduction tests as predictors of attrition in infantry recruits: a prospective study.

INTRODUCTION: Infantry recruit attrition wastes resources and can affect combat readiness. The purpose of this study was to examine the utility of preinduction tests as a predictor of attrition among conscripts in the first year of infantry training. METHODS: 303 infantry conscripted recruits participated in a prospective study. Before their service, recruits received health profile and Quality Group Scores (QGSs). Recruits were screened at induction using questionnaires, by functional movement screening (FMS) and by upper and lower quarter Y-balance, dynamic and anthropometric tests. They were followed for musculoskeletal injuries and attrition during the first year of training. RESULTS: 165/303 (54.5%) recruits were diagnosed with musculoskeletal injury or pain during the first year of their training. 15.2% did not complete their first year of service as combatants and 5.9% were discharged. On multivariable binary stepwise logistic regression analysis for attrition, protective factors were higher QGSs (OR 0.78, 95% CI 0.69 to 0.89) and recruits diagnosed with musculoskeletal injuries or pain (OR 0.20, 95% CI 0.09 to 0.48). Pain in the balance test performed at the beginning of training was a risk factor (OR 3.31, 95% CI 1.44 to 7.61). These factors explained only 15.4% of the variance in attrition. CONCLUSIONS: FMS was not a significant predictor of infantry attrition. Measuring the three variables found to be associated with infantry attrition would seem to be valuable when the number of infantry candidates greatly exceeds the number of infantry positions. Transferring infantry attriters to non-combatant roles and not discharging them is a way to manage the problem of attrition.

Sex Differences in Human Thermoregulation: Relevance for 2020 and Beyond.

The participation of women in physically strenuous athletic and occupational tasks has increased substantially in the past decade. Female sex steroids have influences on thermoregulatory processes that could impact physical performance in the heat. Here, we summarize and evaluate the current literature regarding sex differences in thermoregulation and provide recommendations for heat-illness risk-mitigation strategies.

Physical and psychological stressors linked with stress fractures in recruit training.

This study aimed to measure ambulation in infantry army basic training, and to evaluate if covering more distance can explain stress fractures in a stressor-stress model. Forty-four male combat recruits (18.7 ± 0.7 years) participated in a 6-month rigorous high intensity combat training program. Baseline data included anthropometric measurements, VO(2)max, and psychological questionnaires. Actual distance covered was measured using a pedometer over an 11-week training period. Psychological questionnaires were repeated after 2 months. Sixteen recruits were diagnosed with stress fractures by imaging (SFi = 36.4%). Statistical analysis included comparing measured variables between SFi and those without stress fractures (NSF). The recruits covered 796 ± 157 km, twofold the distance planned of 378 km (P < 0.001). The SFi group covered a distance 16.4% greater than that of the NSF group (866 ± 136 and 744 ± 161 km, respectively, P < 0.01), and also demonstrated greater psychological stress. These data reveal the importance of adherence to or enforcement of military training programs. In the light of these data, the Israeli Defense Forces program needs reappraisal. A stressor-stress response might explain the susceptibility of certain recruits for injury. Using advanced technology, monitoring ambulation may prevent stress fracture development by limiting subjects exceeding a certain level. Psychological profile may also play a role in predicting stress fracture development.

Female recruits sustaining stress fractures during military basic training demonstrate differential concentrations of circulating IGF-I system components: a preliminary study.

OBJECTIVE: Stress fracture injuries sustained during military basic combat training (BT) are a significant problem and occur at a higher rate in female recruits than male recruits. Insulin-like growth factor-I (IGF-I) is an easily measured biomarker that is involved in bone formation and positively correlated with bone mineral density, especially in women. This study examined the response of the IGF-I system between female soldiers that sustained a stress fracture (SFX, n=13) during BT and female soldiers who did not (NSFX, n=49). DESIGN: Female soldiers (n=62, 18.8 ± 0.6 yr) from 2 companies of a gender-integrated combat battalion in the Israeli Defense Forces participated in this study. Height, weight and blood draws were taken upon entry to BT (preBT) and after a four-month BT program (postBT). Stress fractures were diagnosed by bone scan. Serum was analyzed for total IGF-I, free IGF-I, IGF binding proteins (IGFBP)1-6, BAP, calcium, CTx, IL1ß, IL6, PINP, PTH, TNFα, TRAP, and 25(OH)D. Statistical differences between SFX and NSFX groups and time points were assessed by RM ANOVA with Fisher post-hoc (p≤0.05). RESULTS: The SFX group was significantly taller and had lower BMI than NSFX (p≤0.05). Serum concentrations of total IGF-I, bioavailable IGF-I, other bone biomarkers, and cytokines were not significantly different between SFX and NSFX preBT. Serum IGFBP-2 and IGFBP-5 were significantly higher in the SFX compared to the NSFX preBT (p≤0.05). In both groups, total IGF-I increased pre to postBT (p≤0.05). Additionally, a significant difference was observed in the bioavailable IGF-I response pre to postBT for both groups. The SFX group demonstrated a significant decrease in bioavailable IGF-I pre to postBT (preBT: 0.58 ± 0.58 ng/mL; postBT 0.39 ± 0.48; p≤0.05) whereas the NSFX group demonstrated a significant increase in bioavailable IGF-I pre to postBT (preBT: 0.53 ± 0.37 ng/mL; postBT: 0.63 ± 0.45; p≤0.05). CONCLUSIONS: Our study demonstrated that serum IGF-I changes during basic training and that women sustaining stress fractures during BT significantly decreased bioavailable IGF-I, whereas their uninjured counter parts increased bioavailable IGF-I. These results suggest that stress fracture susceptibility may be related to differential IGF-I system concentrations and response to physical training.

Effect of a personal ambient ventilation system on physiological strain during heat stress wearing a ballistic vest.

The present study was conducted in order to evaluate whether physiological strain is alleviated by a new personal cooling system (CS) consisting of a layered vest and integrated blower that generate a flow of air. Twelve male volunteers were exposed to climatic conditions of 40 degrees C, 40%RH (40/40), and 35 degrees C, 60%RH (35/60) during a 115 min exercise routine, followed by 70 min resting recovery, while wearing a battle dress uniform (BDU) and a ballistic vest, with (COOL) or without (NOCOOL) CS. The CS was able to attenuate the physiological strain levels during exercise, when compared to identical exposures without the CS. Temperature elevation, (DeltaT (re)) after 100 min of exercise, was lower by 0.26 +/- 0.20 and 0.34 +/- 0.21 degrees C in 40/40 and 35/60, respectively, (p < 0.05). Mean skin temperature (T(sk)) was lower by 0.9 +/- 0.4 and 0.6 +/- 0.5 degrees C for 40/40 and 35/60, respectively. Heart rate (HR) was not significantly different for COOL versus NOCOOL for 40/40. At 35/60, HR was lower by 10 beats per min (bpm) (p < 0.05). Physiological strain index (PSI) was 9 and 21% lower for the 40/40 and 35/60, respectively, for COOL versus NOCOOL (p < 0.05). Heat storage (S) rates were 19 and 24% lower and sweat rates were 21 and 25% lower for the 40/40 and 35/60, respectively, for COOL versus NOCOOL (p < 0.05). However, the CS was not effective in alleviating physiological strain during resting recovery with no difference in T (re) cooling rate, S, or HR drop rate between groups over resting recovery periods. The CS tested in this study was found to be an effective tool for lowering physiological strain while exercising but not during resting recovery. Therefore, the CS should be further developed in order to achieve greater attenuation of the thermal strain during exercise and improve effectiveness during rest. Overall, it has the potential to be useful for both military and sports personnel.