Bruce H. Jones

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes

One hundred thirty-eight female collegiate athletes, par ticipating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was meas ured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or compe tition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extrem ity injuries in female collegiate athletes.

Intrinsic risk factors for exercise-related injuries among male and female army trainees

Physical training-related injuries are common among army recruits and other vigorously active populations, but little is known about their causation. To identify intrinsic risk factors, we prospectively measured 391 army trainees. For 8 weeks of basic training, 124 men and 186 women (79.3%) were studied. They answered questionnaires on past activities and sports participa tion, and were measured for height, weight, and body fat percentage; 71 % of the subjects took an initial army physical training test. Women had a significantly higher incidence of time-loss injuries than men, 44.6% com pared with 29.0%. During training, more time-loss in juries occurred among the 50% of the men who were slower on the mile run, 29.0% versus 0.0%. Slower women were likewise at greater risk than faster ones, 38.2% versus 18.5%. Men with histories of inactivity and with higher body mass index were at greater injury risk than other men, as were the shortest women. We conclude that female gender and low aerobic fitness measured by run times are risk factors for training injuries in army trainees, and that other factors such as prior activity levels and stature may affect men and women differently.

Epidemiology of injuries associated with physical training among young men in the army

It is widely acknowledged that musculoskeletal injuries occur as a result of vigorous physical activity and exercise, but little quantitative documentation exists on the incidence of or risk factors for these injuries. This study was conducted to assess the incidence, types, and risk factors for training-related injuries among young men undergoing Army infantry basic training. Prior to training we evaluated 303 men (median age 19 yr), utilizing questionnaires and measurements of physical fitness. Subjects were followed over 12 wk of training. Physical training was documented on a daily basis, and injuries were ascertained by review of medical records for every trainee. We performed univariate and multivariate analyses of the data. Cumulative incidence of subjects with one or more lower extremity training-related injury was 37% (80% of all injuries). The most common injuries were muscle strains, sprains, and overuse knee conditions. A number of risk factors were identified, including: older age, smoking, previous injury (sprained ankles), low levels of previous occupational and physical activity, low frequency of running before entry into the Army, flexibility (both high and low), low physical fitness on entry, and unit training (high running mileage).

Physical training and exercise-related injuries. Surveillance, research and injury prevention in military populations.

Athletes and soldiers must both develop and maintain high levels of physical fitness for the physically demanding tasks they perform; however, the routine physical activity necessary to achieve and sustain fitness can result in training-related injuries. This article reviews data from a systematic injury control programme developed by the US Army. Injury control requires 5 major steps: (i) surveillance to determine the size of the injury problem; (ii) studies to determine causes and risk factors for these injuries; (iii) studies to ascertain whether proposed interventions actually reduce injuries; (iv) implementation of effective interventions; and (v) monitoring to see whether interventions retain their effectiveness.Medical surveillance data from the US Army indicate that unintentional (accidental) injuries cause about 50% of deaths, 50% of disabilities, 30% of hospitalisations and 40 to 60% of outpatient visits. Epidemiological surveys show that the cumulative incidence of injuries (requiring an outpatient visit) in the 8 weeks of US Army basic training is about 25% for men and 55% for women; incidence rates for operational infantry, special forces and ranger units are about 10 to 12 injuries/100 soldier-months. Of the limited-duty days accrued by trainees and infantry soldiers who were treated in outpatient clinics, 80 to 90% were the result of training-related injuries.US Army studies document a number of potentially modifiable risk factors for these injuries, which include high amounts of running, low levels of physical fitness, high and low levels of flexibility, sedentary lifestyle and tobacco use, amongst others. Studies directed at interventions showed that limiting running distance can reduce the risk for stress fractures, that the use of ankle braces can reduce the likelihood of ankle sprains during airborne operations and that the use of shock-absorbing insoles does not reduce stress fractures during training.The US Army continues to develop a comprehensive injury prevention programme encompassing surveillance, research, programme implementation and monitoring. The findings from this programme, and the general principles of injury control therein, have a wide application in civilian sports and exercise programmes.

Exercise, Training and Injuries

SummaryAlthough exercise results in a number of well documented physical fitness and health benefits, accruing such benefits entails a risk of exercise-related injuries. Musculoskeletal injuries occur frequently among fitness programme participants, runners, athletes, military recruits and others who engage in routine vigorous exercise. The same parameters of exercise (intensity, duration and frequency) that determine the positive fitness and health effects of physical training also appear to influence the risk of injuries. Studies of runners and other physically active groups have consistently demonstrated that greater duration and frequency of exercise are associated with higher risks of injury. However, the sports medicine literature shows little association between exercise intensity and injuries, a finding which may be misleading. The strongest and most consistent association reported exists between greater total amounts of exercise and higher risks of injury. This is not surprising, since the total amount of exercise is the product of the intensity, duration and frequency of exercise. Recent military research confirms the finding that higher volumes of running are associated with higher rates of injury. Furthermore, the study of army recruits suggests that greater amounts of exercise not only result in greater risks of injury, but in some instances may also impart no additional increase in fitness, a finding consistent with an earlier study of civilian runners. Several military studies also demonstrate that those recruits who have been more physically active in the past are less likely to be injured during basic training. These military studies also document a number of other factors, such as older age, smoking, sedentary jobs and lifestyle, high or low flexibility and high arches of the feet, which may contribute to or modify the risks for exercise-related injuries.In conclusion, the present review suggests that, for activities such as running, specific parameters of exercise may contribute to the overall risk of injuries in rough proportion to their contribution to the total amount of activity performed. Also, better knowledge of the effects of the parameters of training and other factors on the risks of exercise-related injuries is necessary to make more judicious choices about how to best achieve the benefits of exercise and to prevent injuries.

Musculoskeletal injuries: Description of an under-recognized injury problem among military personnel

INTRODUCTION Although injuries are recognized as a leading health problem in the military, the size of the problem is underestimated when only acute traumatic injuries are considered. Injury-related musculoskeletal conditions are common in this young, active population. Many of these involve physical damage caused by micro-trauma (overuse) in recreation, sports, training, and job performance. The purpose of this analysis was to determine the incidence of injury-related musculoskeletal conditions in the military services (2006) and describe a standardized format in which to categorize and report them. METHODS The subset of musculoskeletal diagnoses found to be injury-related in previous military investigations was identified. Musculoskeletal injuries among nondeployed, active duty service members in 2006 were identified from military medical surveillance data. A matrix was used to report and categorize these conditions by injury type and body region. RESULTS There were 743,547 injury-related musculoskeletal conditions in 2006 (outpatient and inpatient, combined), including primary and nonprimary diagnoses. In the matrix, 82% of injury-related musculoskeletal conditions were classified as inflammation/pain (overuse), followed by joint derangements (15%) and stress fractures (2%). The knee/lower leg (22%), lumbar spine (20%), and ankle/foot (13%) were leading body region categories. CONCLUSIONS When assessing the magnitude of the injury problem in the military services, injury-related musculoskeletal conditions should be included. When these injuries are combined with acute traumatic injuries, there are almost 1.6 million injury-related medical encounters each year. The matrix provides a standardized format to categorize these injuries, make comparisons over time, and focus prevention efforts on leading injury types and/or body regions.

High injury rates among female army trainees: a function of gender?

BACKGROUND Studies suggest that women are at greater risk than men for sports and training injuries. This study investigated the association between gender and risk of exercise-related injuries among Army basic trainees while controlling for physical fitness and demographics. METHODS Eight hundred and sixty-one trainees were followed during their 8-week basic training course. Demographic characteristics, body composition, and physical fitness were measured at the beginning of training. Physical fitness measures were taken again at the end of training. Multivariate logistic regression analysis was used to evaluate the association between gender and risk of injury while controlling for potential confounders. RESULTS Women experienced twice as many injuries as men (relative risk [RR] = 2.1, 1.78-2.5) and experienced serious time-loss injuries almost 2.5 times more often than men (RR = 2.4, 1. 92-3.05). Women entered training at significantly lower levels of physical fitness than men, but made much greater improvements in fitness over the training period.In multivariate analyses, where demographics, body composition, and initial physical fitness were controlled, female gender was no longer a significant predictor of injuries (RR = 1.14, 0.48-2.72). Physical fitness, particularly aerobic fitness, remained significant. CONCLUSIONS The key risk factor for training injuries appears to be physical fitness, particularly cardiovascular fitness. The significant improvement in endurance attained by women suggests that women enter training less physically fit relative to their own fitness potential, as well as to men. Remedial training for less fit soldiers is likely to reduce injuries and decrease the gender differential in risk of injuries.

Lower limb morphology and risk of overuse injury among male infantry trainees.

The effect of anatomic variation on the risk of overuse injuries has not been adequately evaluated. To determine the association of several common anatomic characteristics (genu varum, genu valgum, genu recurvatum, and lower limb length differences) with risk of overuse injury, we made prospective morphologic measurements of young men prior to beginning 12 week of Army infantry training. The training included frequent running, marching, calisthenics, and other vigorous activities. Lower extremity anatomic landmarks were high-lighted, and front- and side-view photographic slides were taken of the 294 study volunteers. The slides were compute digitized, and the following measures calculated: pelvic width to knee width ratio (to assess genu valgum/varum), quadriceps angle (Q-angle), knee angle at full extension, and lower limb length differences. The cumulative incidence of lower limb overuse injury was 30%. Relative risk of (RR) of overuse injury was significantly higher among participants with the most valgus knees (RR = 1.9). Those with Q-angle of more than 15 degrees had significantly increased risk specifically for stress fractures (RR = 5.4). Anatomic characteristics were associated with several other types of injuries, including pain and nonacute muscle strain due to overuse. This pilot study provides evidence that some lower limb morphologic characteristics may place individuals at increased risk of overuse injuries.

Cigarette smoking and exercise-related injuries among young men and women.

BACKGROUND We evaluate whether a recent history of cigarette smoking is a risk factor for exercise-related injuries sustained during Army basic training, controlling for factors such as demographic, physical fitness, and health variables. METHODS We conducted an observational cohort study in 1087 male and 915 female Army recruits undergoing 8-week basic military training. Data were collected from questionnaires, anthropometric measurements, physical fitness tests, company training logs, and medical records of all clinic visits. RESULTS During the 8-week training period, 33% of men and 50% of women had at least one clinic visit for injury, including 14% of men and 25% of women who lost more than 5 days of training due to injury. Recruits who reported smoking at least one cigarette in the month prior to beginning basic training (which was conducted in a smoke-free environment) had significantly higher injury rates during training than those who did not report smoking (40% versus 29% for men, and 56% versus 46% for women). The relationship with smoking history was present most strongly for overuse injuries (32% versus 24% in men and 51% versus 40% in women). Multiple logistic regression analyses controlling for all other factors consistently showed adjusted odds ratios of about 1.5 for injury rate in those with a history of smoking compared to those without. CONCLUSIONS The association of history of cigarette smoking with injury occurrence was consistent throughout the analyses, with very little confounding by other factors. The detrimental effects of smoking on injuries appears to persist at least several weeks after cessation of smoking.

Prevention of Physical Training-Related Injuries: Recommendations for the Military and Other Active Populations Based on Expedited Systematic Reviews

BACKGROUND The Military Training Task Force of the Defense Safety Oversight Council chartered a Joint Services Physical Training Injury Prevention Working Group to: (1) establish the evidence base for making recommendations to prevent injuries; (2) prioritize the recommendations for prevention programs and policies; and (3) substantiate the need for further research and evaluation on interventions and programs likely to reduce physical training-related injuries. EVIDENCE ACQUISITION A work group was formed to identify, evaluate, and assess the level of scientific evidence for various physical training-related injury prevention strategies through an expedited systematic review process. Of 40 physical training-related injury prevention strategies identified, education, leader support, and surveillance were determined to be essential elements of a successful injury prevention program and not independent interventions. As a result of the expedited systematic reviews, one more essential element (research) was added for a total of four. Six strategies were not reviewed. The remaining 31 interventions were categorized into three levels representing the strength of recommendation: (1) recommended; (2) not recommended; and (3) insufficient evidence to recommend or not recommend. EVIDENCE SYNTHESIS Education, leadership support, injury surveillance, and research were determined to be critical components of any successful injury prevention program. Six interventions (i.e., prevent overtraining, agility-like training, mouthguards, semirigid ankle braces, nutrient replacement, and synthetic socks) had strong enough evidence to become working group recommendations for implementation in the military services. Two interventions (i.e., back braces and pre-exercise administration of anti-inflammatory medication) were not recommended due to evidence of ineffectiveness or harm, 23 lacked sufficient scientific evidence to support recommendations for all military services at this time, and six were not evaluated. CONCLUSIONS Six interventions should be implemented in all four military services immediately to reduce physical training-related injuries. Two strategies should be discouraged by all leaders at all levels. Of particular note, 23 popular physical training-related injury prevention strategies need further scientific investigation, review, and group consensus before they can be recommended to the military services or similar civilian populations. The expedited systematic process of evaluating interventions enabled the working group to build consensus around those injury prevention strategies that had enough scientific evidence to support a recommendation.