Occupational Experience Effects on Physiological and Perceptual Responses of Common Soldiering Tasks.

ABSTRACT: Cohen BS, Redmond JE, Haven CC, Foulis SA, Canino MC, Frykman PN, Sharp MA. Occupational Experience Effects on Physiological and Perceptual Responses of Common Soldiering Tasks. J Strength Cond Res 37(4): 894-901, 2023-This study measured the impact of occupational experience (i.e., time spent deployed, in military service, and in job and task performance frequency in training, deployment, and study practice) on the physiological (heart rate [HR] and oxygen consumption [VO 2 ]) and perceptual (rate of perceived exertion [RPE]) responses to performance of critical physically demanding tasks (CPDTs). Five CPDTs (road march, build a fighting position, move under fire, evacuate a casualty, and drag a casualty to safety), common to all soldiers, were performed by 237 active duty soldiers. Linear regression models examined the association between measures of experience and physiological and perceptual performance responses to task demands. The level of significance was adjusted for multiple comparisons and set at ρ ≤ 0.0125 for this study. Significant and notable effect sizes included the impact of time spent deployed on the physiological measures of the road march (PostHR F = 24.84, p < 0.0001, ß=-9.65), sandbag fill (PostHR F = 8.26, p = 0.005, ß = -2.83), and sandbag carry (MeanHR F = 7.51, p = 0.007, ß = -1.12; PostHR F = 7.35, p = 0.007, ß = -0.87). For the road march task, there was a nearly 10 bpm decrease in postperformance HR for every year spent deployed. Road march, sandbag fill, and sandbag carry tasks PostHRs were also notably negatively associated with the experience measures of time in their MOS (job and time in military service but not for other physiological and perceptual responses, including VO 2 and RPE. Frequency of task performance in training, deployment, and study practice was not meaningfully associated with experience. The results suggest that increasing task familiarization through on-the-job occupational operational experience may result in greater proficiency and reduced physiological effort.

Modeling the Metabolic Costs of Heavy Military Backpacking.

INTRODUCTION: Existing predictive equations underestimate the metabolic costs of heavy military load carriage. Metabolic costs are specific to each type of military equipment, and backpack loads often impose the most sustained burden on the dismounted warfighter. PURPOSE: This study aimed to develop and validate an equation for estimating metabolic rates during heavy backpacking for the US Army Load Carriage Decision Aid (LCDA), an integrated software mission planning tool. METHODS: Thirty healthy, active military-age adults (3 women, 27 men; age, 25 ± 7 yr; height, 1.74 ± 0.07 m; body mass, 77 ± 15 kg) walked for 6-21 min while carrying backpacks loaded up to 66% body mass at speeds between 0.45 and 1.97 m·s-1. A new predictive model, the LCDA backpacking equation, was developed on metabolic rate data calculated from indirect calorimetry. Model estimation performance was evaluated internally by k-fold cross-validation and externally against seven historical reference data sets. We tested if the 90% confidence interval of the mean paired difference was within equivalence limits equal to 10% of the measured metabolic rate. Estimation accuracy and level of agreement were also evaluated by the bias and concordance correlation coefficient (CCC), respectively. RESULTS: Estimates from the LCDA backpacking equation were statistically equivalent (P < 0.01) to metabolic rates measured in the current study (bias, -0.01 ± 0.62 W·kg-1; CCC, 0.965) and from the seven independent data sets (bias, -0.08 ± 0.59 W·kg-1; CCC, 0.926). CONCLUSIONS: The newly derived LCDA backpacking equation provides close estimates of steady-state metabolic energy expenditure during heavy load carriage. These advances enable further optimization of thermal-work strain monitoring, sports nutrition, and hydration strategies.

Comparison of Different Variants of the U.S. Army Occupational Physical Assessment Test.

INTRODUCTION: The U.S. Army Occupational Physical Assessment Test (OPAT) is a pre-enlistment physical employment screening assessment developed to place recruits and soldiers into Military Occupational Specialties (MOSs) based on their physical capabilities in order to optimize performance and limit injury. The OPAT consists of the seated power throw (SPT), strength deadlift (SDL), standing long jump, and interval aerobic run. During the scientific validation of the OPAT, two variants of the SPT and two variants of the SDL were used. Although the OPAT was validated using both variants for each test, U.S. Army scientists and policymakers have received queries regarding how these variants compare to each other. Therefore, the purpose of this study was to compare different variants of the SPT and SDL. MATERIALS AND METHODS: Thirty-two participants (14 male and 18 female) between the ages of 18 and 42 years visited the laboratory on one occasion and performed two variants of the SPT (seated on the ground [the current OPAT standard] versus seated in a chair with a 35 cm seat height) and two variants of the SDL (using a hex-bar [the current OPAT standard] versus using paired dumbbells). Testing order for the different variants was randomized. The protocol was approved by the U.S. Army Medical Research and Development Command Institutional Review Board. RESULTS: Performing the SPT from a chair significantly (P < .05) increased performance when compared to performing the SPT from the ground (5.4 ± 1.3 m versus 5.0 ± 1.4 m, respectively). Values for the two SPT variants were correlated (tau = 0.90). Performing the SDL using the hex-bar significantly increased the maximal weight lifted when compared to performing the SDL using paired dumbbells (86.9 ± 18.4 kg versus 83.1 ± 18.0 kg, respectively). Values for the two SDL variants were correlated (tau = 0.83). CONCLUSIONS: Performing different variants of the SPT and SDL influenced the resulting score. Although these findings do not alter the administration or scoring of the OPAT, they do provide a valuable reference in the event of future inquiries regarding the development of the OPAT.

Predicting Soldier Task Performance From Physical Fitness Tests: Reliability and Construct Validity of a Soldier Task Test Battery.

ABSTRACT: Spiering, BA, Walker, LA, Larcom, K, Frykman, PN, Allison, SC, and Sharp, MA. Predicting soldier task performance from physical fitness tests: reliability and construct validity of a soldier task test battery. J Strength Cond Res 35(10): 2749-2755, 2021-The purpose of this study was to determine the reliability and construct validity of a battery of tests designed to assess soldier task performance. In the first part of the study (designed to assess test-retest reliability), 33 enlisted soldiers (31 men, 2 women; 23 ± 3 years; 1.75 ± 0.08 m; and 81.4 ± 12.8 kg) completed a 4-event "soldier task test battery" (STTB) on 4 occasions, each separated by at least 1 week. The STTB consisted of the following tests, in order: (a) 30-m grenade throw for accuracy; (b) running long jump while wearing a 20.5-kg load; (c) 1 repetition maximum box lift; and (d) 3.2-km load carriage time trial while wearing a 33-kg load. In the second part of the study (designed to assess construct validity), 41 male soldiers (22 ± 3 years; 1.75 ± 0.08 m; and 81.4 ± 12.9 kg) completed the STTB and a series of physical fitness tests. The physical fitness tests included measurements of body composition, muscular strength, muscular power, muscular endurance, and cardiovascular endurance. Overall performance on the STTB (reflected by the sum of z-scores across individual tests) demonstrated an intraclass correlation coefficient of 0.95 and was correlated to lean mass, V˙o2peak, and measures of muscular strength and power. Lean body mass and standing long jump predicted performance on the STTB (R2 = 0.41). In conclusion, this STTB can reliably assess performance of soldiering tasks. The relationships between the STTB and physical fitness tests can be used to develop training programs to prepare soldiers to perform physically demanding tasks.

Spatiotemporal and Kinematic Comparisons Between Anthropometrically Paired Male and Female Soldiers While Walking With Heavy Loads.

INTRODUCTION: Limited work comparing the effect of heavier carried loads (greater than 30 kg) between men and women has attributed observed differences to sex with the possibility that anthropometric differences may have contributed to those discrepancies. With the recent decision permitting women to enter Combat Arms roles, knowledge of sex-based differences in gait response to load carriage is more operationally relevant, as military loads are absolute and not relative to body weight. The purpose of this study was to describe differences in gait parameters at light to heavy loads between anthropometrically similar male and female soldiers. MATERIALS AND METHODS: Eight female and 8 male soldiers, frequency-matched (1-to-1) on height (±0.54 cm) and mass (±0.52 kg), walked at 1.34 m∙s-1 for 10-min bouts on a level treadmill while unloaded (BM) and then carrying randomized vest-borne loads of 15, 35, and 55 kg. Spatiotemporal and kinematic data were collected for 30 s after 5 min. Two-way repeated measures analyses of variance were conducted to compare the gait parameter variables between sexes at each load. RESULTS: As load increased, overall, the percent double support increased, step frequency increased, stride length decreased, hip and ankle range of motion (ROM) increased, and vertical center of mass (COM) displacement increased. Sex-based significant differences were observed in knee ROM and mediolateral COM displacement. Among the male participants, knee ROM increased significantly for all loads greater than BM. For mediolateral COM displacement, male remained constant as load increased, whereas female values decreased between BM and 35 kg. CONCLUSIONS: Spatiotemporal and kinematic differences in gait parameters were primarily because of increases in load magnitude. The observed sex-related differences with increasing loads suggest that women may require a more stable gait to support the additional load carried.

Relationship of Anthropometric Measures on Female Trainees' and Active Duty Soldiers' Performance of Common Soldiering Tasks.

INTRODUCTION: This study compared the relationship between height (HT), body mass (BM), and body mass index (BMI) of female trainees and active duty female soldiers and their performance on simulated common soldiering tasks (CSTs) with high physical demands. METHODS: Female trainees (n = 133) and soldiers (n = 229) completed the following CSTs: sandbag carry, move under fire, casualty drag, casualty evacuation, and road march. Quartiles were created among HT, BM, and BMI by which task performance was compared using ANOVAs with Tukey post hoc comparisons. RESULTS: For both trainees and soldiers, HT, BM, and BMI were positively associated with improved road march, casualty drag, casualty evacuation, and sandbag carry performance. On the move under fire task, only soldier HT was positively associated with improved performance. CONCLUSION: Female trainees and soldiers who are taller and heavier with a higher BMI may demonstrate better performance on CSTs required of all soldiers. In addition to task-specific training, performance of CSTs may be enhanced in tasks requiring strength and power by recruiting and retaining taller and heavier females with a higher BMIs. Allowances should be considered for soldiers and trainees who can successfully perform soldiering tasks with high physical demands despite less desirable anthropometric measurements.

U.S. Army Physical Demands Study: Differences in Physical Fitness and Occupational Task Performance Between Trainees and Active Duty Soldiers.

Canino, MC, Foulis, SA, Zambraski, EJ, Cohen, BS, Redmond, JE, Hauret, KG, Frykman, PN, and Sharp, MA. U.S. Army Physical Demands Study: Differences in physical fitness and occupational task performance between trainees and active duty soldiers. J Strength Cond Res 33(7): 1864-1870, 2019-U.S. Army initial entry training (IET) is designed to prepare trainees for the military environment and subsequent training, including specific programs to increase physical fitness to perform job-specific tasks to the minimal acceptable performance standard (MAPS). The aim of this study was to compare physical fitness and occupational task performance of trainees at the end of IET to that of active duty soldiers. One hundred seventy-nine male combat arms trainees at the end of IET and 337 male combat arms active duty soldiers performed a sandbag carry (SBC), casualty drag (CD), and move under direct fire (MUF). Physical fitness was assessed using Army Physical Fitness Test scores. A questionnaire was administered to determine frequency of task performance. Active duty soldiers compared with trainees were older (p < 0.01) and performed more push-ups (p < 0.01) and sit-ups (p < 0.01). Trainees performed the 2-mile run faster (p < 0.01). Ninety-four percent of trainees and 99% of active duty soldiers performed the 3 tasks to the MAPSs. Active duty soldiers performed significantly faster on both the SBC (p < 0.01) and CD (p < 0.01) and reported a higher task frequency on the SBC (p = 0.03) and CD (p < 0.01). No difference in MUF performance (p = 0.16) and task frequency (p = 0.13) was detected. Initial entry training seems to provide sufficient physical training as most trainees were able to meet the MAPSs; however, performance differences were still apparent between trainees and active duty soldiers. Additional practice performing the physically demanding tasks may help maximize performance on the physically demanding job requirements.

Functional physical training improves women's military occupational performance.

The U.S. Armed Forces have recently approved full integration of women into combat roles. Physical fitness demands for executing Military Occupational Specialties (MOS) are substantial; thus lifting and load carriage capability improvements are desirable. OBJECTIVES: To determine if a specially-designed physical conditioning program could lessen the gap between the performance of male and female Soldiers in lifting and load carriage and thereby enable women to meet the requirements of most, if not all, Army MOSs. METHODS: Forty women participated in a 24-week physical training program, which included resistance training, long-distance running, backpacking, and specialized drills. Pre- and post-tests of occupational and physical performance measures were conducted before and after training. Repeated measures analysis of variance were used to determine statistically significant differences among the pre-, mid- and posttests. RESULTS: Women increased maximal occupational lifting strength 12-20 kg, added 9-34 repetitions in lifting endurance, increased 0.23 m in jumping performance, added 46 repetitions in local muscular endurance, and decreased load carriage for time by 3.7-8.6 min. Women scored within 82-94% of untrained male scores for aerobic capacity and muscular endurance after training. CONCLUSION: Women's ability to perform physically-demanding military occupational tasks was significantly improved following 6 months of concurrent training, with emphasis on load carriage and lifting. The percentage of women that qualified for current "heavy" and "very heavy" MOSs was initially 24%, but increased to 78% after training. A resistance training program of 6+ months can adequately prepare women for "heavy" to "very heavy" MOS's.

U.S. Army Physical Demands Study: Development of the Occupational Physical Assessment Test for Combat Arms soldiers.

OBJECTIVES: The United States Army sought to create a legally defensible, scientifically validated physical pre-employment screening test. The purpose of this study was to identify a single combination of predictor tests that would predict physical performance on all of the criterion measure task simulations relevant to the Combat Arms military occupational specialties. DESIGN: Concurrent validation. METHODS: Data from 838 (608 males, 230 females) soldiers who completed both the criterion measure task simulations of a military occupational specialty and up to 14 predictor tests were used in the development of the test batteries. Stepwise regressions were used to identify test batteries that significantly predicted performance on the criterion measure task simulations of the military occupational specialties. RESULTS: Three test batteries were developed based on different subsets of the predictor tests: Test Battery 1 consisted of the medicine ball put, squat lift, beep test, standing long jump, and arm ergometer (adjusted R2=0.80-0.85, p<0.01); Test Battery 2 consisted of the medicine ball put, squat lift, beep test, and standing long jump (adjusted R2=0.79-0.80, p<0.01); and Test Battery 3 consisted of the standing long jump, 1-minute push-ups, 1-minute sit-ups, 300m sprint, and Illinois agility test (adjusted R2=0.55-0.71, p<0.01). CONCLUSIONS: Test Battery 2 was selected as the Army's Occupational Physical Assessment Test. It was highly predictive of performance of the Combat Arms military occupational specialties, required no complex equipment, and covered a range of physical fitness domains.

U.S. Army Physical Demands Study: Reliability of Simulations of Physically Demanding Tasks Performed by Combat Arms Soldiers.

Foulis, SA, Redmond, JE, Frykman, PN, Warr, BJ, Zambraski, EJ, and Sharp, MA. U.S. Army physical demands study: reliability of simulations of physically demanding tasks performed by combat arms soldiers. J Strength Cond Res 31(12): 3245-3252, 2017-Recently, the U.S. Army has mandated that soldiers must successfully complete the physically demanding tasks of their job to graduate from their Initial Military Training. Evaluating individual soldiers in the field is difficult; however, simulations of these tasks may aid in the assessment of soldiers' abilities. The purpose of this study was to determine the reliability of simulated physical soldiering tasks relevant to combat arms soldiers. Three cohorts of ∼50 soldiers repeated a subset of 8 simulated tasks 4 times over 2 weeks. Simulations included: sandbag carry, casualty drag, and casualty evacuation from a vehicle turret, move under direct fire, stow ammunition on a tank, load the main gun of a tank, transferring ammunition with a field artillery supply vehicle, and a 4-mile foot march. Reliability was assessed using intraclass correlation coefficients (ICCs), standard errors of measurement (SEMs), and 95% limits of agreement. Performance of the casualty drag and foot march did not improve across trials (p > 0.05), whereas improvements, suggestive of learning effects, were observed on the remaining 6 tasks (p ≤ 0.05). The ICCs ranged from 0.76 to 0.96, and the SEMs ranged from 3 to 16% of the mean. These 8 simulated tasks show high reliability. Given proper practice, they are suitable for evaluating the ability of Combat Arms Soldiers to complete the physical requirements of their jobs.

Characterization of Foot-Strike Patterns: Lack of an Association With Injuries or Performance in Soldiers.

OBJECTIVES: Characterize the distribution of foot-strike (FS) patterns in U.S. Army Soldiers and determine if FS patterns are related to self-reported running injuries and performance. METHODS: 341 male Soldiers from a U.S. Army Combined Arms Battalion ran at their training pace for 100 meters, and FSs were recorded in the sagittal plane. Participants also completed a survey related to training habits, injury history, and run times. Two researchers classified FS patterns as heel strike (HS) or nonheel strike (NHS, combination of midfoot strike and forefoot strike patterns). Two clinicians classified the musculoskeletal injuries as acute or overuse. The relationship of FS type with two-mile run time and running-related injury was analyzed (p ≤ 0.05). RESULTS: The Soldiers predominately landed with an HS (87%) and only 13% were characterized as NHS. Running-related injury was similar between HS (50.3%) and NHS (55.6%) patterns (p = 0.51). There was no difference (p = 0.14) between overuse injury rates between an HS pattern (31.8%) and an NHS pattern (31.0%). Two-mile run times were also similar, with both groups averaging 14:48 minutes. CONCLUSION: Soldiers were mostly heel strikers (87%) in this U.S. Army Combined Arms Battalion. Neither FS pattern was advantageous for increased performance or decreased incidence of running-related injury.

Lower extremity biomechanical changes associated with symmetrical torso loading during simulated marching.

The dose-response relationship between biomechanical variables and the magnitude of external loads is unclear. The use of different load distributions (e.g., pack types) may confound results because of changes in torso center of mass. Therefore, we examined the relationship between load magnitude and sagittal plane lower extremity mechanics of Soldiers walking with two symmetrically distributed loads. Fourteen Soldiers marched on a force-sensing treadmill at 1.34 m/s for 10 minutes with no load (BW_00) and while wearing vest-borne loads of 15 kg (BW_15) and 55 kg (BW_55). The effects of the loads on sagittal plane joint angles and moments were compared using 1-way repeated measures analyses of variance. Compared with BW_00, knee extension moment increased with the 15- and the 55-kg loads (both p < 0.003), confirming previously reported load-related biomechanical responses. Knee moment increases during early stance appeared to be the primary means by which the lower extremity counteracted BW_15 during early stance; in contrast, hip extensors and ankle dorsiflexors appeared to be the primary muscular efforts responsible for propulsion during late stance. Findings elucidated the effects of load magnitude on lower extremity mechanics without postural changes that result from pack-related shifts in torso center of mass.

Lower extremity mechanics during marching at three different cadences for 60 minutes.

During group marches, soldiers must walk in step with one another at the same imposed cadence. The literature suggests that shorter trainees may be more susceptible to injury due to overstriding that can occur when taller recruits dictate marching cadence. This study assessed the effects of fixed cadence simulated marching at cadences above and below preferred step rate (PSR) on lower extremity joint mechanics in individuals who were unaccustomed to marching. During three separate visits, 13 volunteers walked with a 20 kg load on a force-sensing treadmill at self-selected PSR, PSR+15% (shorter strides), and PSR-15% (longer strides) at 1.3 m/s for 60 min. Two-way RM ANOVAs (cadence by time) were performed during the stance phase. Ranges of motion and anteroposterior ground reaction force increased significantly as cadence decreased (P < .03). Knee extension moment increased slightly when step rate decreased from PSR+15% (shortest strides, 0.85 ± 0.2 N m/kg) to PSR (0.87 ± 0.3 N m/kg, 3% increase); however, this increase was substantially greater (20% increase) when cadence was decreased from PSR to PSR-15% (longest strides, 1.09 ± 0.3 N m/kg). Our results indicate that overstriding during fixed-cadence marching is a factor that can substantially increase mechanical stress on lower extremity joints.

A history of low back pain affects pelvis and trunk mechanics during a sustained lift/lower task.

This study compared three-dimensional trunk and pelvis range of motion (ROM) during a sustained asymmetric box lift/lower task between a group with a history of low back pain (HBP, n = 9) and a group with no history of low back pain (NBP, n = 9). Participants lifted an 11-kg box for 10 min at 12 cycles/min from ankle height in front to shelves 45 deg off-centre at waist height. Kinematic data were collected at the beginning (min1), middle (min5) and end of the bout (min9). Two-way analyses of variance were performed for all variables. Pelvis and trunk transverse ROM were similar at min1. By min9, HBP group did not change (31.9 ± 9 deg); however, ROM decreased in NBP group (21.6 ± 6 deg, p < 0.05). Therefore, despite no current pain, the HBP group demonstrated protective lifting mechanics compared to controls. Also discussed are implications for studying lifting paradigms at sub-maximal effort over longer periods of time. PRACTITIONER SUMMARY: Differences between groups over time demonstrate residual consequences of low back pain (LBP) in a manual materials handling scenario. Individuals with a history of LBP (pain free for 6 months) demonstrated more conservative lifting mechanics towards the end of the bout compared to controls with no history of LBP.

Marksmanship deficits caused by an exhaustive whole-body lifting task with and without torso-borne loads.

Studies of exhaustive exercise on marksmanship are inconclusive and have not measured trigger pull latencies (LAT) nor considered impact of added torso loads. This study examined the impact of exhaustive whole-body exercise and torso loading on accuracy, precision, and latency during a marksmanship test. Twelve men lifted a 20.5-kg box on to a 1.55-m high shelf until they could not maintain a 12 lifts·min⁻¹ pace. Within 25 seconds of ending the lifting task, the subjects started a 10-minute rifle marksmanship test (8 shots·min⁻¹). During lifting and shooting, the subjects wore 2 different loads: NOLOAD = boots, uniform, and helmet (5.9 kg) and LOAD = a torso-borne load (29.9 kg) + NOLOAD. With the LOAD, the subjects were only able to work for 69% as long, perform 31% as many lifts, or do 38% as much total work compared with the NOLOAD condition. Despite performing less total external work during LOAD, the heart rate (HR) was more than 25% higher than NOLOAD. Measures of accuracy and precision improved and stabilized after minute 3. Overall, LAT increased (p < 0.025) for LOAD (mean ± SE, 2,522 ± 81 milliseconds), compared with NOLOAD (2,240 ± 121). During 0-4 minutes, LAT for LOAD was 14% greater than for NOLOAD (p < 0.05); from 4 to 10 minutes, LAT did not differ. Exhaustive whole-body exercise transiently degraded accuracy regardless of load. In the LOAD condition, LAT was immediately increased and sustained for 10 minutes; in the NOLOAD condition, LAT increased gradually. Although load did not decrease accuracy, it increased the time to engage targets, which can impact fighting effectiveness and survivability.

Hypohydration reduces vertical ground reaction impulse but not jump height.

This study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (approximately 4% body mass) does not improve jump height. Measures of functional performance from a force platform were determined for 15 healthy and active males when euhydrated (EUH), hypohydrated (HYP) and hypohydrated while wearing a weighted vest (HYP(v)) adjusted to precisely match water mass losses. HYP produced a significant loss of body mass [-3.2 +/- 0.5 kg (-3.8 +/- 0.6%); P < 0.05], but body mass in HYP(v) was not different from EUH. There were no differences in absolute or relative peak force or power among trials. Jump height was not different between EUH (0.380 +/- 0.048 m) and HYP (0.384 +/- 0.050 m), but was 4% lower (P < 0.05) in HYP(v) (0.365 +/- 0.52 m) than EUH due to a lower jump velocity between HYP(v) and EUH only (P < 0.05). However, vertical ground reaction impulse (VGRI) was reduced in both HYP and HYP(v) (2-3%) compared with EUH (P < 0.05). In conclusion, this study demonstrates the failure to improve jump height when HYP can be explained by offsetting reductions in both VGRI and body mass.

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.

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 Army's 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.

Physiological consequences of U.S. Army Ranger training.

PURPOSE: Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones. METHODS: In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal.d, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 +/- 4.4 y; 176.1 +/- 7.8 cm; 78.4 +/- 8.7 kg; 14.7 +/- 4.2% body fat) before and after the course. RESULTS: Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass. CONCLUSION: Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (>or=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.