U.S. Air Force recruit injury and health study

Abstract

Objectives: To assess the types, rates, and risks of injury for male and female USAF recruits.

Design: Outpatient visits for female (5250) and male recruits (8656) were collected and analyzed for rate of injury, types of injuries, and risk of injury throughout a 6-week training period.

Results: One third of female recruits and one sixth of male recruits were injured at least once during recruit training. The overall rate for injuries in women and men was 63.0 and 27.8 per 1000 person-weeks, respectively. The adjusted relative risk for women versus men for all injuries was 2.22, and was consistent (1.67 to 3.27) across injury sites. Despite declining absolute rates of injury by week (106.1–13.4 for women and 53.7–13.2 for men), relative risk of injury for women versus men remained fairly constant throughout each training week. The relative risk for injury serious enough to result in medical hold was 1.69 for women vis-a-vis men. Approximately half of all medical discharges for women and men were for injuries.

Conclusions: Female recruits were injured twice as often as male recruits, and were 1.5 times more likely to be removed from their training cohort for injury. Relative risk for injuries to specific body areas remained fairly consistent, indicating that no gender-specific injuries were occurring. Further efforts to determine the cause of injuries should be undertaken, and interventions aimed at reducing the disparate risk of injuries in women should be developed and evaluated.

Introduction

Each year, over 35,000 young men and women undergo 6 weeks of basic military training (BMT) at Lackland Air Force Base, Texas, soon after enlisting in the U.S. Air Force (USAF). As no medical surveillance system was in place prior to the study period, anecdotal evidence from USAF BMT training staff and medical personnel indicated that female recruits were experiencing higher rates of injury, illness, and attrition than male recruits. A review of the literature revealed that there are few studies on the injury rates of military recruits, and none on USAF recruits undergoing BMT. However, women have been consistently shown to have higher rates of injury and illness and to use health care services more than men, regardless of being in training, in garrison, deployed, or in civilian life.1, 2, 3, 4, 5, 6, 7, 8, 9 Of the training-related studies, Jones et al.2 found that the cumulative risk of injury of the 8-week Army basic training cycle is about 50% for women and 25% for men. The authors noted that training-related injuries were the number one cause of morbidity and limited duty due to medical restrictions in Army recruit training. They also found that female trainees suffered nearly twice as many training-related injuries as men. Shaffer et al.10 found injury incidence rates of 37% for female Navy recruits, 44% for female Marine Corps recruits, and 62% for female Marine Corps officer candidates during their respective training schools, but did not have male data for comparison. However, another study of male Marine Corps recruits by Almeida et al.11 found an injury incidence rate per trainee-months to be half that of women (0.57 versus 1.08).

Of note, several studies have shown a correlation between low levels of physical fitness, especially endurance performance, and increased risk of training-related injury.2, 3, 4, 9, 11, 12, 13, 14, 15, 16 Kowal3 found that injury was correlated with lack of conditioning, greater body weight and body fat, and limited leg strength. Jones et al.4 found that low aerobic fitness and female gender are risk factors for training injuries in Army trainees, but suggested that other factors, such as prior activity levels and stature, might affect men and women differently. Burke and Dyer15 suggest that the relationships shown in data between some physical fitness measures and injury are not strong and, in some cases, are hard to interpret, as in the Army’s “Run, Dodge, and Jump” test. However, data do show on some measures, such as sit-ups and heart rate response, that there is a greater likelihood that the less fit individual will sustain some sort of injury during training than will a more fit colleague.

This article represents a portion of a larger study, the USAF Female Recruit Morbidity Study,17 the primary purpose of which was to assess and compare injuries and illnesses among female USAF recruits and a matched cohort of male recruits. This article will address only the injury portion of that study. Its primary objectives were to:

• Assess the types, rates, and risks of injuries.

• Identify the week of training and source of injuries.

• Compare rates of injury of female and male recruits.

• Identify gender-specific injuries.

Specific hypotheses of interest included:

• Female recruits have higher rates of injury than male recruits.

• Specific injuries are significantly associated with week of training.

• Female recruits have gender-specific injuries.

• Female recruits have higher rates of recycling and attrition than male recruits.

It was hoped that the analysis of this data would suggest modifications to the training protocol that might reduce injuries and decrease attrition and recycle rates, thus reducing training costs while producing a healthier airman for the USAF.