Is baseline aerobic fitness associated with illness and attrition rate in military training?

BMI and Physical Activity, Military-Aged U.S. Population 2015-2020

INTRODUCTION

Obesity and physical inactivity are considered possible U.S. national security threats because of their impact on military recruitment. The objectives of this study were to estimate the prevalence of (1) BMI eligibility for military entrance, (2) adequate physical activity participation among the BMI-eligible population, and (3) combined BMI eligibility and adequate physical activity.

METHODS

This cross-sectional study of nonpregnant, military-aged civilians (aged 17-42 years) used objectively measured weight and height data and self-reported aerobic physical activity data from the 2015-2020 National Health and Nutrition Examination Survey. BMI eligibility was defined as 19.0-27.5 kg/m², per Department of Defense regulation. Adequate physical activity for entering initial military training was defined as ≥300 minutes/week of equivalent moderate-intensity aerobic physical activity from all domains, approximating U.S. Army guidance. Participants meeting both definitions were further classified as eligible and active. Analyses were conducted in 2021-2022.

RESULTS

Of military-aged participants (unweighted n=5,964), 47.3% were eligible by BMI. Among BMI-eligible participants, 72.5% reported adequate physical activity. Taken together, 34.3% were both eligible and active. The prevalence of eligible and active status was higher among males, persons who were younger and non-Hispanic White, college graduates, and those with higher family income than among their counterparts.

CONCLUSIONS

Among the military-aged U.S. population, slightly under half were eligible to enter the military on the basis of their BMI, and only 1 in 3 met BMI eligibility and were adequately physically active. Equitable promotion of healthy weight achievement and physical activity participation may improve military preparedness.

Development and Validation of a Dynamically Updated Prediction Model for Attrition From Marine Recruit Training

ABSTRACT

Dijksma, I, Hof, MHP, Lucas, C, and Stuiver, MM. Development and validation of a dynamically updated prediction model for attrition from Marine recruit training. J Strength Cond Res 36(9): 2523-2529, 2022-Whether fresh Marine recruits thrive and complete military training programs, or fail to complete, is dependent on numerous interwoven variables. This study aimed to derive a prediction model for dynamically updated estimation of conditional dropout probabilities for Marine recruit training. We undertook a landmarking analysis in a Cox proportional hazard model using longitudinal data from 744 recruits from existing databases of the Marine Training Center in the Netherlands. The model provides personalized estimates of dropout from Marine recruit training given a recruit's baseline characteristics and time-varying mental and physical health status, using 21 predictors. We defined nonoverlapping landmarks at each week and developed a supermodel by stacking the landmark data sets. The final supermodel contained all but one a priori selected baseline variables and time-varying health status to predict the hazard of attrition from Marine recruit training for each landmark as comprehensive as possible. The discriminative ability (c-index) of the prediction model was 0.78, 0.75, and 0.73 in week one, week 4 and week 12, respectively. We used 10-fold cross-validation to train and evaluate the model. We conclude that this prediction model may help to identify recruits at an increased risk of attrition from training throughout the Marine recruit training and warrants further validation and updates for other military settings.

Predicting how health behaviours contribute to the development of diseases within a military population in the Hungarian Defence Forces

INTRODUCTION

Recent legislative amendments in Hungary have resulted in the possibility for early retirement being abolished in the Hungarian Defence Forces. The retirement age for professional soldiers has also increased to 65 years, thereby greatly increasing the average length of military service. This necessitates greater attention to the health and care of service personnel due to the increase of chronic non-communicable diseases with age. The aim of this research was to identify how health behaviours might potentially contribute to diseases in the Hungarian Defence Forces.

METHODS

All members of the Hungarian Defence Forces undergoing health screenings between 2011 and 2015 were assessed. Health variables analysed were derived from the health screening data sheet which is collected from every member of the Hungarian Defence Forces undergoing a health screening since 2009. Items recorded were connected to health behaviour (physical activity, nutrition, smoking), subjective well-being (psychosomatic backache, fatigue and quality of waking up to describe the quality of sleep), sociodemographic data (age, gender) and the mental toughness quotient (MTQ). A logistic regression model was utilised to predict how health behaviour may affect the development of disease.

RESULTS

Factors most associated with the development of disease included psychosomatic backache (P<0.000), age (P<0.001), frequency of undertaking sports (P<0.05), quality of sleeping and waking up (P<0.05) and the assessment of gender differences (P<0.05).

CONCLUSIONS

Extension of the length of active service will result in an increased burden of disease for members of the Hungarian Defence Forces. This includes both physical and psychological morbidity that could potentially be obstacles for service personnel to perform their military duties. Health behaviours such as psychosomatic backache, the frequency of performing sports and sleep quality may predict the development of disease and should be explored in health screening consultations.

Preseason Aerobic Fitness Predicts In-Season Injury and Illness in Female Youth Athletes

Background:

Although preseason aerobic fitness has been suggested as a modifiable risk factor for injury in adult athletes, the relationship between aerobic fitness, injury, and illness in youth athletes is unknown.

Purpose:

To determine whether preseason aerobic fitness predicts in-season injury and illness risk in female adolescent soccer players.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

Fifty-four female adolescent soccer players underwent preseason evaluation to determine years of experience, body mass index (BMI), maximal aerobic capacity (VO_2max), and time to exhaustion (T_max) during cycle ergometer testing. All injuries and illnesses during the subsequent 20-week season were recorded. Variables were compared between individuals with and without a self-reported injury and individuals with and without a self-reported illness. Separate Poisson regression models were developed to predict number of injuries and illnesses for each individual by use of age, years of experience, BMI, VO_2max, and T_max.

Results:

Twenty-eight injuries and 38 illnesses in 23 individuals were recorded during the season. Although not a statistically significant finding, individuals who reported an in-season injury had lower VO_2max than those who did not (54.9 ± 7.3 vs 58.3 ± 8.5 mL/kg/min, P = .13). Individuals who reported an illness had significantly lower VO_2max than those who did not (54.5 ± 9.9 vs 58.8 ± 6.2 mL/kg/min, P = .014). With the Poisson regression models, VO_2max was a significant predictor of both injury (odds ratio [OR], 0.95; P = .046) and illness (OR, 0.94; P = .009), while no significant relationships were identified between injury or illness and age, years of experience, T_max, or BMI (all P > .05).

Conclusion:

Among adolescent female soccer players, greater preseason aerobic fitness is associated with a reduced risk of in-season injury and illness. Off-season intervention to promote aerobic fitness may help reduce the risk of lost time during the season due to injury and illness.