Marilyn A. Sharp

Temporal Changes in the Physical Fitness of US Army Recruits

This article defines physical fitness and then reviews the literature on temporal trends in the physical fitness of new US Army recruits. Nineteen papers were found that met the review criteria and had published recruit fitness data from 1975 to 2003. The limited data on recruit muscle strength suggested an increase from 1978 to 1998 (20-year period). Data on push-ups and sit-ups suggested no change in muscular endurance between 1984 and 2003 (19-year period). Limited data suggested that maximal oxygen uptake (V̇O2max) [mL/kg/min] of male recruits did not change from 1975 to 1998 (23-year period), while there was some indication of a small increase in female recruit V̇O2max in the same period. On the other hand, slower times on 1-mile (1.6km) and 2-mile (3.2km) runs indicate declines in aerobic performance from 1987 to 2003 (16-year period). The apparent discrepancy between the V̇O2max and endurance running data may indicate that recruits are not as proficient at applying their aerobic capability to performance tasks, such as timed runs, possibly because of factors such as increased bodyweight, reduced experience with running, lower motivation and/or environmental factors. Recruit height, weight and body mass index have progressively increased between 1978 and 2003 (25-year period). Both the body fat and fat-free mass of male recruits increased from 1978 to 1998 (20-year period); however, body composition data on female recruits did not show a consistent trend. In this same time period, the literature contained little data on youth physical activity but there was some suggestion that caloric consumption increased. This article indicates that temporal trends in recruit fitness differ depending on the fitness component measured. The very limited comparable data on civilian populations showed trends similar to the recruit data.

Comparison of the physical fitness of men and women entering the U.S. Army: 1978-1998.

PURPOSE To compare the physical fitness levels of recruits entering the U.S. Army in 1998 to those entering in 1978 and 1983. METHODS In 1998, 182 men and 168 women were tested before beginning basic training at Fort Jackson, SC. The measurements were 1) skin-fold estimation of percent body fat (%BF); 2) maximum oxygen uptake by treadmill running (VO2max); and 3) upper-body (UB), lower-body (LB), and upright pulling (UP) isometric strength. These data were compared to data from basic trainees at Fort Jackson in 1978 (skin folds, VO2max, UB, and LB) and 1983 (skin folds and UP). RESULTS Body weight (BW) of 1998 recruits was greater (P < 0.05) than 1978 recruits (men, 12%; women, 6%) and 1983 recruits (men, 8%; women, 7%). %BF of 1998 recruits was greater (P < 0.05) than 1978 recruits (men, 15%; women, 5%) and 1983 recruits (men, 15%; women, 17%). The 1998 men had more fat-free mass (FFM) (P < 0.05) than men in 1978 (8%) or 1983 (5%), whereas 1998 women were only different from those measured in 1978 (4%, P < 0.05). The VO2max of men (50.6 +/- 6.2 mL x kg(-1) x min(-1)) was equivalent to men in 1978, whereas that of women (39.7 +/- 5.2 mL x kg(-1) x min(-1)) was 6% greater (P < 0.05). The 1998 recruits were stronger (P < 0.05) on all measures of muscle strength than recruits measured in 1978 (men, UB = 16%, LB = 12%; women, UB = 18%, LB = 6%) and 1983 (men, UP = 7%; women, UP = 6%). CONCLUSION The aerobic capacity, muscle strength, and FFM of 1998 recruits is comparable to or greater than that of 1978 and 1983 recruits; however, 1998 recruits tended to have more BW and a greater %BF.

Effects of two different eight - week training programs on military physical performance

Various physical demands are placed on soldiers, whose effectiveness and survivability depend on their combat-specific physical fitness. Because sport training programs involving weight-based training have proven effective, this study examined the value of such a program for short-term military training using combat-relevant tests. A male weight-based training (WBT) group (n = 15; mean ± SD: 27.0 ± 4.7 years, 173.8 ± 5.8 cm, 80.9 ± 12.7 kg) performed full-body weight-based training workouts, 3.2-km runs, interval training, agility training, and progressively loaded 8-km backpack hikes. A male Army Standardized Physical Training (SPT) group (n = 17; mean ± SD: 29.0 ± 4.6 years, 179.7 ± 8.2 cm, 84.5 ± 10.4 kg) followed the new Army Standardized Physical Training program of stretching, varied calisthenics, movement drills, sprint intervals, shuttle running, and distance runs. Both groups exercised for 1.5 hours a day, 5 days a week for 8 weeks. The following training-induced changes were statistically significant (P < 0.05) for both training groups: 3.2-km run or walk with 32-kg load (minutes), 24.5 ± 3.2 to 21.0 ± 2.8 (SPT) and 24.9 ± 2.8 to 21.1 ± 2.2 (WBT); 400-m run with 18-kg load (seconds), 94.5 ± 14.2 to 84.4 ± 11.9 (SPT) and 100.1 ± 16.1 to 84.0 ± 8.4 (WBT); obstacle course with 18-kg load (seconds), 73.3 ± 10.1 to 61.6 ± 7.7 (SPT) and 66.8 ± 10.0 to 60.1 ± 8.7 (WBT); 5 30-m sprints to prone (seconds), 63.5 ± 4.8 to 59.8 ± 4.1 (SPT) and 60.4 ± 4.2 to 58.9 ± 2.7 (WBT); and 80-kg casualty rescue from 50 m (seconds), 65.8 ± 40.0 to 42.1 ± 9.9 (SPT) and 57.6 ± 22.0 to 44.2 ± 8.8 (WBT). Of these tests, only the obstacle course showed significant difference in improvement between the two training groups. Thus, for short-term (i.e., 8-week) training of relatively untrained men, the Armys new Standardized Physical Training program and a weight-based training experimental program can produce similar, significant, and meaningful improvements in military physical performance. Further research would be needed to determine whether weight-based training provides an advantage over a longer training period.

Prediction of Simulated Battlefield Physical Performance from Field-Expedient Tests

Predictive models of battlefield physical performance can benefit the military. To develop models, 32 physically trained men (mean +/- SD: 28.0 +/- 4.7 years, 82.1 +/- 11.3 kg, 176.3 +/- 7.5 cm) underwent (1) anthropometric measures: height and body mass; (2) fitness tests: push-ups, sit-ups, 3.2-km run, vertical jump, horizontal jump; (3) simulated battlefield physical performance in fighting load: five 30-m sprints prone to prone, 400-m run, obstacle course, and casualty recovery. Although greater body mass was positively associated with better casualty recovery performance, it showed trends toward poorer performance on all the other fitness and military performance tests. Regression equations well predicted the simulated battlefield performance from the anthropometric measures and physical fitness tests (r = 0.77-0.82). The vertical jump entered all four prediction equations and the horizontal jump entered one of them. The equations, using input from easy to administer tests, effectively predict simulated battlefield physical performance.

Physical Fitness and Body Composition After a 9-Month Deployment to Afghanistan

PURPOSE To examine change in physical fitness and body composition after a military deployment to Afghanistan. METHODS One hundred and ten infantry soldiers were measured before and after a 9-month deployment to Afghanistan for Operation Enduring Freedom. Measurements included treadmill peak oxygen uptake (peak VO2), lifting strength, medicine ball put, vertical jump, and body composition estimated via dual-energy x-ray absorptiometry (percent body fat, absolute body fat, fat-free mass, bone mineral content, and bone mineral density). RESULTS There were significant decreases (P < 0.01) in peak VO2 (-4.5%), medicine ball put (-4.9%), body mass (-1.9%), and fat-free mass (-3.5%), whereas percent body fat increased from 17.7% to 19.6%. Lifting strength and vertical jump performance did not change predeployment to postdeployment. CONCLUSIONS Nine months deployment to Afghanistan negatively affected aerobic capacity, upper body power, and body composition. The predeployment to postdeployment changes were not large and unlikely to present a major health or fitness concern. If deployments continue to be extended and time between deployments decreased, the effects may be magnified and further study warranted.

Risk factors for musculoskeletal injuries for soldiers deployed to Afghanistan.

PURPOSE This study determined injury incidence and examined the association between musculoskeletal injuries and potential intrinsic and extrinsic risk factors. METHODS This retrospective cohort study involved a survey of 593 volunteers from two battalions of a Stryker Brigade Combat Team upon completion of a 12-mo deployment to Afghanistan. The survey included questions on physical characteristics, work duties, equipment worn, fitness training, and injuries experienced during the deployment. RESULTS Of the surveyed soldiers, 45% sustained an injury during the deployment. Total injuries resulted in 5049 d of limited duty, an average of 8.5 d per injury. The body regions with the largest numbers of injuries were the low back (17.4%), knee (12.7%), and shoulder (10.0%). The majority (65%) of injuries occurred while working. The most frequent activities soldiers reported as the cause of injury were lifting and carrying (9.8%), dismounted patrolling (9.6%), and physical training (8.0%). Older age, higher enlisted rank, female sex, months deployed, more time spent standing, longer strength training sessions, heaviest load worn, and heavier or more frequent lifting tasks were all associated with injury. DISCUSSION Tasks requiring physical energy expenditure such as load carriage, lifting, or standing resulted in an increased risk of musculoskeletal injury in this study. Lifting/carrying, dismounted patrols, and physical training were associated with 26% of musculoskeletal injuries. The weight of loads carried and lifting may be exceeding the work capacity of the soldiers, resulting in injury. These injuries in turn limit available work days for military units, reducing combat power.

Physiological Employment Standards III: physiological challenges and consequences encountered during international military deployments

Modern international military deployments in austere environments (i.e., Iraq and Afghanistan) place considerable physiological demands on soldiers. Significant physiological challenges exist: maintenance of physical fitness and body composition, rigors of external load carriage, environmental extremes (heat, cold, and altitude), medical illnesses, musculoskeletal injuries, traumatic brain injuries, post-traumatic stress disorder, and environmental exposure hazards (i.e., burn pits, vehicle exhaust, etc.). To date there is very little published research and no comprehensive reviews on the physiological effects of deployments. The purpose of this paper is to overview what is currently known from the literature related mainly to current military conflicts with regard to the challenges and consequences from deployments. Summary findings include: (1) aerobic capacity declines while muscle strength, power and muscular endurance appear to be maintained, (2) load carriage continues to tax the physical capacities of the Soldier, (3) musculoskeletal injuries comprise the highest proportion of all injury categories, (4) environmental insults occur from both terrestrial extremes and pollutant exposure, and (5) post-deployment concerns linger for traumatic brain injury and post-traumatic stress disorder. A full understanding of these responses will assist in identifying the most effective risk mitigation strategies to ensure deployment readiness and to assist in establishment of military employment standards.

Effect of a 13-Month Deployment to Iraq on Physical Fitness and Body Composition

This investigation evaluated the effects of a 13-month deployment to Iraq on body composition and selected fitness measures. Seventy-three combat arms soldiers were measured pre- and postdeployment. Body composition was assessed by dual X-ray absorptiometry (DXA). Strength was measured by single repetition maximum (1-RM) lifts on bench press and squat. Power was assessed by a bench throw and squat jump. Aerobic endurance was evaluated with a timed 2-mile run. Exercise and injury history were assessed by questionnaire. Upper and lower body strength improved by 7% and 8%, respectively (p < 0.001). Upper body power increased 9% (p < 0.001) and lean mass increased 3% (p < 0.05). In contrast, aerobic performance declined 13% (p < 0.001) and fat mass increased 9% (p < 0.05). Fewer soldiers participated in aerobic exercise or sports during deployment (p < 0.001). Unit commanders should be aware of potential fitness and body composition changes during deployment and develop physical training programs to enhance fitness following deployment.

Injury Rates and Injury Risk Factors among U.S. Army Wheel Vehicle Mechanics

This study describes injury rates, injury diagnoses, anatomical locations of injuries, limited duty days, and activities associated with injuries in a sample of Army mechanics. Medical records of 518 male and 43 female Army mechanics were screened for injuries during 1 year at a large U.S. Army installation. Weight, height, age, and ethnicity were also extracted from the medical records. Body mass index was calculated as weight/height2. Overall injury rates for men and women were 124 and 156 injuries/100 person-years, respectively, with a rate of 127 injuries/100 person-years for all soldiers combined. Women had higher overuse injury rates while men had higher traumatic injury rates. Limited duty days for men and women were 2,076 and 1,966 days/100 person-years, respectively. The lower back, knee, ankle, foot, and shoulder involved 61% of the injuries. Activities associated with injury included (in order of incidence) physical training, mechanical work, sports, airborne-related activities, road marching, garrison/home activities, and chronic conditions. Among the men, elevated injury risk was associated with higher body weight and higher body mass index. It may be possible to prevent many injuries by implementation of evidenced-based interventions currently available in the literature.

Maximal aerobic capacity for repetitive lifting: comparison with three standard exercise testing modes

SummaryA multi-stage, repetitive lifting maximal oxygen uptake (