Veronique Hauschild

Physical training, fitness, and injuries: lessons learned from military studies

Injuries are the leading cause of medical encounters across the U.S. military services resulting in more than 2.0 million clinic visits per year. Almost 50% of military service members experience an injury each year and half of those injuries are caused by physical training (PT), exercise, or sports. To prevent a problem as large and complex as injuries in the military requires a systematic approach. Several key questions must be answered to effectively address a problem such as injuries: (1) how big is the problem? (2) what are the causes and risk factors for the problem? (3) do modifiable risk factors for the problem exist? and (4) what works to prevent the problem? The article discusses leading causes of injuries for U.S. Army populations. It then explores key risk factors for exercise and training-related injuries: (1) the amounts of training, (2) types of training activities, (3) participants level of fitness, and (4) personal health risk behaviors. The article concludes with a review of prevention strategies illustrating interventions that have been shown to be effective, and others that are not effective. The data presented suggest that PT and exercise cause injuries and that modifications of training are most likely to prevent the problem.

Fitness tests and occupational tasks of military interest: a systematic review of correlations

Physically demanding occupations (ie, military, firefighter, law enforcement) often use fitness tests for job selection or retention. Despite numerous individual studies, the relationship of these tests to job performance is not always clear. This review examined the relationship by aggregating previously reported correlations between different fitness tests and common occupational tasks. Search criteria were applied to PUBMED, EBSCO, EMBASE and military sources; scoring yielded 27 original studies providing 533 Pearson correlation coefficients (r) between fitness tests and 12 common physical job task categories. Fitness tests were grouped into predominant health-related fitness components and body regions: cardiorespiratory endurance (CRe); upper body, lower body and trunk muscular strength and muscular endurance (UBs, LBs, TRs, UBe, LBe, TRe) and flexibility (FLX). Meta-analyses provided pooled rs between each fitness component and task category. The CRe tests had the strongest pooled correlations with most tasks (eight pooled r values 0.80–0.52). Next were LBs (six pooled r values >0.50) and UBe (four pooled r values >0.50). UBs and LBe correlated strongly to three tasks. TRs, TRe and FLX did not strongly correlate to tasks. Employers can maximise the relevancy of assessing workforce health by using fitness tests with strong correlations between fitness components and job performance, especially those that are also indicators for injury risk. Potentially useful field-expedient tests include timed-runs (CRe), jump tests (LBs) and push-ups (UBe). Impacts of gender and physiological characteristics (eg, lean body mass) should be considered in future study and when implementing tests.

Risk Factors for Injury Associated with Low, Moderate, and High Mileage Road Marching in a U.S. Army Infantry Brigade

OBJECTIVESnRoad marching is an important physical training activity that prepares soldiers for a common occupational task. Continued exploration of risk factors for road marching-related injuries is needed. This analysis has assessed the association between modifiable characteristics of physical training and injury risk.nnnMETHODSnInjuries in the previous 6 months were captured by survey from 831 U.S. Army infantry soldiers. Road marching-related injuries were reported as those attributed to road marching on foot for specified distances while carrying equipment. Frequencies, means, and relative risk ratios (RR) for road marching-related injury with 95% confidence intervals (CI) were calculated. Adjusted odds ratios (OR) and 95% CI were calculated for leading risk factors using multivariable logistic regression.nnnDESIGNnRetrospective cohort study.nnnRESULTSnHalf (50%) of reported injuries were attributed to road marching or running. When miles of exposure were considered, injury risk during road marching was higher than during running (RRroad marching/running=1.8, 95% CI: 1.38-2.37). A higher product of road marching distance and weight worn (pound-miles per month) resulted in greater injury risk (RR≥1473 pound-miles/<1472=1.92, 95% CI: 1.17-2.41). Road marching-related injuries were associated with carrying a load >25% of ones body weight (OR>25%/1-20%=2.09, 95% CI: 1.08-4.05), having high occupational lifting demands (OR50-100+lbs/25-50lbs=3.43, 95% CI: 1.50-7.85), road marching ≥5 times per month (OR≥5 times/4 times=2.11, 95% CI: 1.14-3.91), and running <4 miles per week during personal physical training (OR0/≥10 miles/week=3.56, 95% CI: 1.49-8.54, OR1-4/≥10 miles/week=4.14, 95% CI: 1.85-9.25).nnnCONCLUSIONSnIdeally, attempts should be made to decrease the percentage of body weight carried to reduce road marching-related injuries. Since this is not always operationally feasible, reducing the cumulative overloading from both physical training and occupational tasks may help prevent injury.

Regarding the Bulzacchelli et al. Article on Injury During U.S. Army Basic Combat Training.

Regarding the Bulzacchelli et al. Article on Injury During U.S. Army Basic Combat Training Bulzacchelli et al. performed a systematic review to determine the level of evidence for 23 potential risk factors for injuries during Army basic combat training (BCT), including gender and physical fitness. They concluded that evidence was limited, mixed, or insufficient for all but age, smoking, and low physical activity prior to basic training. We feel their methodology dismissed or ignored substantial relevant evidence, and the conclusions do not reflect familiarity with existing data. As a result, readers are erroneously led to believe little is known about two of the most important and consistent injury risk factors among Army trainees: gender and aerobic fitness. The credibility of a systematic review depends largely on the thoroughness of the search for relevant studies. The authors searched only a single database, thus excluding many publically available military reports readily obtainable through the Defense Technical Information Center. For instance, a report by Knapik and colleagues identified 14 studies indicating an association between slower run times and higher risk of injuries during military recruit or cadet training. Six of these were Army BCT studies. That same report identified 18 studies (ten BCT) showing female recruits experienced significantly higher injury rates than male recruits. As a result of the overly narrow criteria used to score, include, and synthesize studies, Bulzacchelli et al. also failed to capture and adequately assess the breadth of evidence. In addition to multivariate analyses, attention should be given to the consistency of data across studies, indications of dose response, stratified analyses, and other aspects of study design. The authors identified four studies of seven populations (four male, three female) where aerobic fitness measured by run times was assessed. These studies consistently indicated slower runners had higher injury risk (Table 1). Furthermore, the authors failed to recognize that run times, step-tests, and VO2max (maximum oxygen uptake) 3 all measure the same component of fitness: weight-bearing aerobic fitness. Therefore, they failed to incorporate two of the studies they had scored as being of medium quality

Musculoskeletal training injury prevention in the U.S. Army: Evolution of the science and the public health approach

Injuries cause more morbidity among soldiers in the U.S. Army than any other health condition. Over two-thirds of U.S. soldiers injuries occur gradually from cumulative micro-traumatic damage to the musculoskeletal system as a result of physical training activities. Paradoxically, the very physical training activities required to improve soldier performance also result in injury. Determining the amounts and types of physical training that maximize performance while minimizing injuries requires scientific evidence. This evidence must be incorporated into a framework that ensures scientific gaps are addressed and prevention efforts are evaluated. The five-step public health approach has proven to be an effective construct for Army public health to organize and build an injury prevention program. Steps include: 1) surveillance to define the magnitude of the problem, 2) research and field investigations to identify causes and risk factors, 3) intervention trials and systematic reviews to determine what works to address leading risk factors, 4) program and policy implementation to execute prevention, and 5) program evaluation to assess effectiveness. Dissemination is also needed to ensure availability of scientific lessons learned. Although the steps may not be conducted in order, the capability to perform each step is necessary to sustain a successful program and make progress toward injury control and prevention. As with many U.S. public health successes (e.g., seatbelts, smoking cessation), the full process can take decades. As described in this paper, the U.S. Army uses the public health approach to assure that, as the science evolves, it is translated into effective prevention.

Associations of age, aerobic fitness, and body mass index with injury in an operational Army brigade

OBJECTIVESnTo investigate the effects of age, aerobic fitness, and body mass index (BMI) on injury risk in operational Army soldiers.nnnDESIGNnRetrospective cohort study.nnnMETHODSnMale soldiers from an operational Army brigade were administered electronic surveys regarding personal characteristics, physical fitness, and injuries occurring over the last 12 months. Injury risks were stratified by age, 2-mile run time, and BMI. Analyses included descriptive incidence, a Mantel-Haenszel χ2 test to determine trends, a multivariable logistic regression to determine factors associated with injury, and a one-way analysis of variance (ANOVA).nnnRESULTSnForty-seventy percent of 1099 respondents reported at least one injury. A linear trend showed that as age, 2-mile run time, and BMI increased, so did injury risk (p<0.01). When controlling for BMI, the most significant independent injury risk factors were older age (odd ratio (OR) 30years-35years/≤24years=1.25, 95%CI: 1.08-2.32), (OR≥36years/≤24years=2.05, 95%CI: 1.36-3.10), and slow run times (OR≥15.9min/≤13.9min=1.91, 95%CI: 1.28-2.85). An ANOVA showed that both run times and BMI increased with age.nnnCONCLUSIONSnThe stratified analysis and the multivariable logistic regression suggested that older age and poor aerobic fitness are stronger predictors of injury than BMI.

Impact of physical fitness and body composition on injury risk among active young adults: A study of Army trainees

OBJECTIVESnTo determine the combined effects of physical fitness and body composition on risk of training-related musculoskeletal injuries among Army trainees.nnnDESIGNnRetrospective cohort study.nnnMETHODSnRosters of soldiers entering Army basic combat training (BCT) from 2010 to 2012 were linked with data from multiple sources for age, sex, physical fitness (heights, weights (mass), body mass index (BMI), 2 mile run times, push-ups), and medical injury diagnoses. Analyses included descriptive means and standard deviations, comparative t-tests, risks of injury, and relative risks (RR) and 95% confidence intervals (CI). Fitness and BMI were divided into quintiles (groups of 20%) and stratified for chi-square (χ2) comparisons and to determine trends.nnnRESULTSnData were obtained for 143,398 men and 41,727 women. As run times became slower, injury risks increased steadily (men=9.8-24.3%, women=26.5-56.0%; χ2 trends (p<0.00001)). For both genders, the relationship of BMI to injury risk was bimodal, with the lowest risk in the average BMI group (middle quintile). Injury risks were highest in the slowest groups with lowest BMIs (male trainees=26.5%; female trainees=63.1%). Compared to lowest risk group (average BMI with fastest run-times), RRs were significant (male trainees=8.5%; RR 3.1, CI: 2.8-3.4; female trainees=24.6%; RR 2.6, CI: 2.3-2.8). Trainees with the lowest BMIs exhibited highest injury risks for both genders and across all fitness levels.nnnCONCLUSIONSnWhile the most aerobically fit Army trainees experience lower risk of training-related injury, at any given aerobic fitness level those with the lowest BMIs are at highest risk. This has implications for recruitment and retention fitness standards.