Decreased Percent Body Fat but Not Body Mass is Associated with Better Performance on Combat Fitness Test in Male and Female Marines.

ABSTRACT: Pletcher, ER, Lovalekar, M, Coleman, LC, Beals, K, Nindl, BC, and Allison, KF. Decreased percent body fat but not body mass is associated with better performance on the Marine Corps Combat Fitness Test. J Strength Cond Res 37(4): 887-893, 2023-The military uses a variety of physical fitness tests to assess physical readiness. The Marine Corps designed the Combat Fitness Test (CFT) to emphasize functional fitness related to operational demands. The purpose of this study was to investigate the association between body mass (BM), fat free mass (FFM), and percent body fat (BF%) measured via air displacement plethysmography with CFT performance in male and female marines. Two-hundred 10 male (22.4 ± 2.6 years) and 84 female (22.6 ± 2.8 years) marines were grouped into quintiles according to BM (in kilograms), FFM (in kilograms), and BF%. Kruskal-Wallis test or 1-way analysis of variance were used to determine if significant differences in CFT total and component scores existed between the groups of subjects classified into quintiles of BM, FFM, and BF%. No significant differences in CFT scores were observed between BM quintile in either men or women. No significant differences in CFT scores were observed between FFM quintiles in men. Total CFT score ( p = 0.002), movement to contact (MTC; p = 0.014), maneuver under fire (MANUF; p = 0.008), and ammunition lift (AL; p = 0.014) were all significantly different among FFM quintiles in women. Total CFT score ( p = 0.007), MTC ( p = 0.001), and MANUF ( p = 0.022) were significantly different among BF% quintiles in men. Total CFT score ( p = 0.008), MTC ( p = 0.033), and AL ( p = 0.016) were significantly different among BF% quintiles in women. Male and female marines in the quintile with lowest BF% had better CFT scores than those in higher quintiles. Targeted physical training and nutrition considerations to optimize BF% may help improve military task performance.

Increases in Load Carriage Magnitude and Forced Marching Change Lower-Extremity Coordination in Physically Active, Recruit-Aged Women.

The objective was to examine the interactive effects of load magnitude and locomotion pattern on lower-extremity joint angles and intralimb coordination in recruit-aged women. Twelve women walked, ran, and forced marched at body weight and with loads of +25%, and +45% of body weight on an instrumented treadmill with infrared cameras. Joint angles were assessed in the sagittal plane. Intralimb coordination of the thigh-shank and shank-foot couple was assessed with continuous relative phase. Mean absolute relative phase (entire stride) and deviation phase (stance phase) were calculated from continuous relative phase. At heel strike, forced marching exhibited greater (P < .001) hip flexion, knee extension, and ankle plantar flexion compared with running. At mid-stance, knee flexion (P = .007) and ankle dorsiflexion (P = .04) increased with increased load magnitude for all locomotion patterns. Forced marching (P = .009) demonstrated a "stiff-legged" locomotion pattern compared with running, evidenced by the more in-phase mean absolute relative phase values. Running (P = .03) and walking (P = .003) had greater deviation phase than forced marching. Deviation phase increased for running (P = .03) and walking (P < .001) with increased load magnitude but not for forced marching. With loads of >25% of body weight, forced marching may increase risk of injury due to inhibited energy attenuation up the kinetic chain and lack of variability to disperse force across different supportive structures.

Compromised Dynamic Postural Stability Under Increased Load Carriage Magnitudes.

Warfighter performance may be compromised through the impact of load carriage on dynamic postural stability. Men and women may experience this impact to differing extents due to postural stability differences. Therefore, the authors investigated the effect of load magnitude on dynamic postural stability in men and women during a landing and stabilization task. Dynamic postural stability of 32 subjects (16 women) was assessed during the unilateral landing of submaximal jumps under 3 load conditions: +0%, +20%, and +30% body weight. Dynamic postural stability was measured using the dynamic postural stability index, which is calculated from ground reaction force data sampled at 1200 Hz. Two-way mixed-measures analysis of variance compared dynamic postural stability index scores between sexes and loads. Dynamic postural stability index scores were significantly affected by load (P = .001) but not by sex or by the sex by load interaction (P > .05). Dynamic postural stability index scores increased between the 0% (0.359 ± 0.041), 20% (0.396 ± 0.034), and 30% (0.420 ± 0.028) body weight conditions. Increased load negatively affects dynamic postural stability with similar performance decrements displayed by men and women. Men and women warfighters may experience similar performance decrements under load carriage conditions of similar relative magnitudes.

Energy Deficiency During Cold Weather Mountain Training in NSW SEAL Qualification Students.

Special operation forces participating in mountain warfare/cold weather (MWCW) training have higher energy demands, but adequate fueling is difficult to achieve. The purpose of the study was to determine energy expenditure relative to energy intake and examine fueling patterns during 3 days of MWCW training in Naval Special Warfare Sea, Air, Land (SEAL) Qualification Training (SQT) students. Ten SQT students (age: 23.3 ± 1.8 years, height: 182.3 ± 6.4 cm, and weight: 83.6 ± 4.5 kg) were fitted for heart rate and accelerometer monitors during MWCW training. Total daily energy expenditure was determined using a combination of direct observation and heart rate-VO2 regression. Total daily energy intake was collected using the Automated Self-Administered 24 (ASA24) assessment tool. Total daily energy expenditure for river crossing, alpine skills, and mountain patrol were 3,913 ± 293, 4,207 ± 400, and 5,457 ± 828 kcals, respectively. Reported total daily energy intakes were 2,854 ± 657 (river crossing) and 2,289 ± 680 kcals (mountain patrol), producing 1,044 ± 784 and 3,112 ± 1,420 kcal deficits, respectively. SQT students consumed 258 ± 95 g (3.1 ± 1.3 g·kg-1·day-1) of carbohydrates, 130 ± 55 g (1.6 ± 0.7 g·kg-1·day-1) of protein, and 113 ± 39 g (1.4 ± 0.5 g·kg-1·day-1) of fat. MWCW training evolutions elicited high total daily energy expenditure and inadequate energy intake, especially before and during active training sessions, which may lead to decreased work output, early onset fatigue, and increased risk of injury. Increasing total daily energy intake by providing fuel/fluids, primarily carbohydrates, during the planned breaks and "downtime" of each training evolution and focusing on provision of the balance of calories/macronutrients needed for a more complete and expedited recovery over dinner and evening snacks will help bridge the energy gap.

Force Sense of the Knee Not Affected by Fatiguing the Knee Extensors and Flexors.

CONTEXT: Knee injuries commonly occur in later stages of competition, indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, which, if negatively affected by fatigue, may result in less-effective neuromuscular control. OBJECTIVES: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. DESIGN: Quasi-experimental study design. PARTICIPANTS: 20 healthy and physically active women and men (age 23.4 ± 2.7 y, mass 69.5 ± 10.9 kg, height 169.7 ± 9.4 cm). INTERVENTIONS: Fatigue was induced during a protocol with 2 sets of 40 repetitions, and the last set was truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. MAIN OUTCOME MEASURES: FS of the hamstrings and quadriceps was tested on separate days before and after 3 sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS error). Electromyographic data of the tested musculature were collected to calculate and determine median frequency shift. T tests and Wilcoxon signed-rank tests were conducted to examine prefatigue and postfatigue FS error for flexion and extension. RESULTS: Despite verification of fatigue via torque-production decrement and shift in median frequency, no significant differences were observed in FS error for either knee flexion (pre 0.54 ± 2.28 N·m, post 0.47 ± 1.62 N·m) or extension (pre -0.28 ± 2.69 N·m, post -0.21 ± 1.78 N·m) prefatigue compared with the postfatigue condition. CONCLUSIONS: Although previous research has demonstrated that peripheral fatigue negatively affects threshold to detect passive motion (TTDPM), it did not affect FS as measured in this study. The peripheral-fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted.

Descriptive Epidemiology of Musculoskeletal Injuries During Marine Corps Recruit Training in Gender-Integrated and Male-Only Training Units.

INTRODUCTION: Musculoskeletal injuries (MSIs) occur frequently in military personnel. U.S. Marine Corps (USMC) recruits participate in an intense 13-week training program designed to transform civilians into basically trained Marines, during which they are susceptible to MSIs. Previous injury epidemiology research with USMC recruits was conducted in a non-gender-integrated training. Data for the current study were derived from a larger study, the USMC Gender-Integrated Recruit Training study, that was initiated to provide data-driven recommendations for gender integration during USMC recruit training. The purpose of the current analysis was to describe the unique profile of MSIs during USMC recruit training and compare MSIs between female and male recruits in gender-integrated training. MATERIALS AND METHODS: Medical record-reviewed MSI data were obtained for recruits in three models of USMC recruit training: two models of gender-integrated recruit training at Marine Corps Recruit Depot (MCRD) Parris Island-the older Series Track (ST) model and the newer Integrated Company (IC) model, and a Male-Only (MO) cohort at MCRD San Diego. Incidence, anatomic region and subregion, event at the time of MSI, MSI type and onset, and disposition following MSI were described for each model. Group comparisons were conducted using Fisher's exact tests or independent samples t tests, as appropriate. RESULTS: MSI data were available for 584 recruits (ST: 98 female recruits, 95 male recruits; IC: 85 female recruits, 106 male recruits; MO: 200 male recruits). The cumulative incidence of MSIs was significantly higher among female compared to male recruits in the ST (59.2% vs. 29.5%, P < .001) and in the IC (25.9% vs. 12.3%, P = .023) cohorts. The most frequent anatomic location for MSIs was the lower extremity (female recruits: ST: 76.5% of MSIs, IC: 88.6%; male recruits: ST: 81.1%, IC: 80.0%, MO: 83.8%). The most frequent body part affected was the hip among female recruits (ST: 26.5% of MSIs, IC: 37.1%). The most frequent body part affected by MSIs among the male recruits was the knee in the ST (32.4%) and IC (53.3%) cohorts and the lower leg (27.0%) in the MO cohort. A significantly greater percentage of female compared to male recruits sustained a hip MSI in the ST (23.5% vs. 2.1%, P < .001) and IC (12.9% vs. 0.0%, P < .001) cohorts. There was no significant difference in knee MSI incidence between sexes in the ST (P = .323) or IC (P = .757) cohorts. A large percentage of MSIs resulted in light duty (female recruits: ST: 69.4% of MSIs, IC: 74.3%; male recruits: ST: 64.9%, IC: 73.3%, MO: 94.6%). CONCLUSIONS: This was the first study to assess the burden of MSIs concurrently among female and male USMC recruits in gender-integrated training. MSIs, especially those affecting the lower extremity, continue to occur frequently in this population. Female recruits are more susceptible to MSIs during USMC recruit training compared to male recruits and are especially prone to hip MSIs. Future research should focus on identifying modifiable risk factors for MSIs in this population, with a focus on reducing lower-extremity MSIs in all recruits and hip MSIs in female recruits.

Design Considerations for a Multidisciplinary Approach to Provide Policy Recommendations on Gender-Integrated Recruit Training in the Marine Corps.

INTRODUCTION: Recruit training is designed to transform civilians into physically fit military service members, who embody their service's core values and possess military discipline and skills. At the time this research began, the U.S. Marine Corps (USMC) remained the only service that segregated recruits by gender at the lowest unit level (e.g., platoon) and employed gender-segregated drill instructor teams. USMC's Marine Corps Recruit Depots (MCRD) must comply with a 2020 Congressional Mandate to not segregate training by gender in Parris Island by 2025 and San Diego by 2028. In turn, USMC requested an independent scientific study to analyze current approaches to gender integration at recruit training to propose alternate models and other policy recommendations that increase gender integration while maintaining current USMC standards. The Marine Corps is currently evaluating alternate models and recommendations to optimize entry-level training. This article outlines considerations for choosing the optimal research study design, research methods, and types of data collected in a study intended to provide policy recommendations on gender-integrated recruit training for the USMC. MATERIALS AND METHODS: Research data were collected during visits to the MCRDs and selected recruit training locations for the Army, Air Force, Navy, and Coast Guard. Data collection on USMC recruits from three cohorts involved social science assessments (focus groups and surveys) and human performance testing (countermovement jumps and isometric mid-thigh pulls, sleep and activity wearables, and cortisol data) at multiple points in the training cycle. Data on recruits from the sister services were limited to social science assessments. Approximately 600 recruits between the two MCRDs and 160 recruits from the sister services participated in the study during a 7-month timeframe in 2021. The research team conducted extensive ethnographic observations of recruit training at all selected research sites and interviewed training cadre, drill instructors, and service leadership responsible for recruit training (∼90 interviews). Additionally, the research team interviewed 20 experts on gender integration or recruit training who possessed alternate viewpoints from the current USMC practice. RESULTS: The mixed methods study was designed to assess the current gender integration practices at recruit training across the services to generate alternative models of gender integration for USMC. The research team developed a set of multidisciplinary objectives and research questions serving as the foundation of the research study design and data collection process. The study was designed to collect qualitative, quantitative, and administrative data informed by social science and human performance disciplines. To ensure that all aspects and implications relevant to gender integration were considered, select data were collected across services and with stakeholders at all levels. CONCLUSIONS: This multidisciplinary research approach provided a comprehensive picture of the current USMC recruit training models. The research team captured multiple perspectives and data points for analysis through an expansive view on gender integration across all services, by interacting with participants at all levels of the institutions in varied ways. The information and data gathered enabled the research team to establish objective, data-driven alternate models, and recommendations for enhancing gender integration at recruit training for the USMC.

Increasing Gender Integration in U.S. Marine Corps Recruit Training: Policy Recommendations and Rationales From an Interdisciplinary Study.

INTRODUCTION: This article describes alternate models and policy recommendations created by an interdisciplinary team of researchers to increase gender integration at U.S. Marine Corps (USMC) recruit training. The USMC requested a study to analyze current approaches to gender integration at recruit training and provide alternate models that maximize integration, while continuing to train marines to established standards. USMC remains the only service that segregates recruits by gender at the lowest unit level (e.g., platoon) in recruit training and maintains gender-segregated drill instructor teams (i.e., same-gender teams train platoons of same-gender recruits). MATERIALS AND METHODS: A mixed-method, interdisciplinary approach was used to capture multiple perspectives and informed recommendations and alternate models for gender integration. The team studied select USMC, army, navy, air force, and coast guard recruit training locations, between June and November 2021. At each site, the team collected qualitative, quantitative, and administrative data as well as physical performance metrics and human performance outcomes. Study participants included recruits, drill instructors, training cadre, service leaders, and subject matter experts on gender integration in military services. Each alternate model was designed to maximize the feasibility of implementation within current USMC training conditions. RESULTS: The research team developed three alternate models and several policy recommendations. Alternate model 1 proposed a methodology for mixed-gender drill instructor teams within the Integrated Company model, USMC's current integrated training model. Alternate model 2 proposed an Integrated Company Plus model which increases the number and types of gender-integrated training events at or below the platoon level within the Integrated Company model. Alternate model 3 outlined an integrated platoon model where recruits fall out into integrated training platoons after their morning routine, with two options of varying integration based on USMC priorities for integration. The team also proposed a set of policy recommendations independent of the three alternate models to support current and future gender integration efforts at the Marine Corps Recruit Depots. CONCLUSIONS: Gender-integrated military training has been shown to positively alter perceptions and evaluations of women in military settings over detrimental aspects developed by gender-segregated training. The study team recommended USMC train recruits in the Integrated Company model with mixed-gender drill instructor teams (alternate model 1) and integrate more training events following the priority tiers outlined in the Integrated Company plus model (alternate model 2). The combined execution of these two alternate models would provide USMC recruits increased exposure to direct, sustained training from opposite-gender drill instructors and deliver intentional training opportunities for male and female recruits to work together and interact in meaningful ways. The integrated platoon model (alternate model 3) would offer USMC recruits the most direct exposure to training and working with members of the opposite gender, but it requires substantial changes to current logistics, accountability, and training procedures.

Load carriage changes tibiofemoral arthrokinematics during ambulatory tasks in recruit-aged women.

The introduction of women into U.S. military ground close combat roles requires research into sex-specific effects of military training and operational activities. Knee osteoarthritis is prevalent among military service members; its progression has been linked to occupational tasks such as load carriage. Analyzing tibiofemoral arthrokinematics during load carriage is important to understand potentially injurious motion and osteoarthritis progression. The study purpose was to identify effects of load carriage on knee arthrokinematics during walking and running in recruit-aged women. Twelve healthy recruit-aged women walked and ran while unloaded (bodyweight [BW]) and carrying additional + 25%BW and + 45%BW. Using dynamic biplane radiography and subject-specific bone models, tibiofemoral arthrokinematics, subchondral joint space and center of closest contact location between subchondral bone surfaces were analyzed over 0-30% stance (separate one-way repeated measures analysis of variance, load by locomotion). While walking, medial compartment contact location was 5% (~ 1.6 mm) more medial for BW than + 45%BW at foot strike (p = 0.03). While running, medial compartment contact location was 4% (~ 1.3 mm) more lateral during BW than + 25%BW at 30% stance (p = 0.04). Internal rotation was greater at + 45%BW compared to + 25%BW (p < 0.01) at 30% stance. Carried load affects tibiofemoral arthrokinematics in recruit-aged women. Prolonged load carriage could increase the risk of degenerative joint injury in physically active women.

Incidence and pattern of musculoskeletal injuries among women and men during Marine Corps training in sex-integrated units.

OBJECTIVES: The purpose of this analysis was to describe and compare the incidence and pattern of musculoskeletal injuries in women and men during the United States Marine Corps Ground Combat Element Integrated Task Force work-up and assessment phases in sex-integrated units. DESIGN: Descriptive cross-sectional study. METHODS: Certified athletic trainers and Navy corpsmen reported injury data for 302 Marines (women: 27.8%, men: 72.2%). Injury frequency, location, cause, type, and activity during injury were described. Fisher's exact tests were used to compare proportions of injured women and men. The cost of injuries was calculated using the Web-based Injury Statistics Query and Reporting System. RESULTS: A greater proportion of women (40.5%) sustained an injury compared with men (18.8%, p < 0.001). The lower extremity was the most frequent location for injury (women: 68% of injuries, men: 60%). The most frequent sub-location was the hip (24%) in women and foot/toes (26%) in men. Marching under load was the most common cause (women: 64%, men: 48%). Most injuries occurred during physical training (women: 78%, men: 66%), and were classified as pain/spasm/ache (women: 56%, men: 36%). The total lifetime cost of these injuries that occurred among 302 Marines was approximately $1.4 million U.S. dollars. CONCLUSIONS: The high risk of lower extremity injuries that occurred while marching under load during physical training, and the greater risk of injuries among women compared to men, indicates the need for further research to identify the components of combat Military Occupational Specialty specific training that could be modified to mitigate injuries.

Fight load index and body composition are most associated with combat fitness in female Marines.

Optimizing tactical fitness is important for combat readiness and injury prevention, especially as women have entered ground combat military occupational specialties. OBJECTIVES: To assess characteristics of male and female Marines by Combat Fitness Test (CFT) performance clusters. DESIGN: Cross-sectional study. METHODS: Anthropometric, body composition (BF%, fat and fat-free mass [FM and FFM], and Fight load index [FLI], physiological (maximal oxygen uptake, lactate threshold and anaerobic power/capacity), and musculoskeletal (isokinetic strength of the knee, shoulder, torso, and isometric strength of the ankle) assessments were obtained from 294 male (M) and female (F) Marines. Hierarchical cluster analysis classified Marines based on performance of two CFT events (sec): Maneuver Under Fire (MANUF) and Movement to Contact (MTC). Following tests for normality, one-way ANOVA or Kruskal Wallis tests, followed by Bonferroni post-hoc tests, assessed characteristics across clusters and sex (alpha=0.05). RESULTS: Two clusters (C) were determined: C1: N=66F, 16M and C2: N=18F, 194M, with C2 demonstrating better performance on the MANUF and MTC. C1F demonstrated significantly greater BF% and FLI than C1M, C2F, and C2M. C2M demonstrated significantly greater knee flexion strength than C1F and C2F, but C1M was only significantly greater than C1F. C2M demonstrated significantly greater ankle eversion and inversion strength than C1F. CONCLUSIONS: Women with increased BF%, increased FM and reduced FFM relative to a fighting load may have decreased performance in combat-related tasks. Training programs based on an individual Marine's baseline body composition and fitness characteristics can enhance combat fitness and force readiness.

Significantly Increased Odds of Reporting Previous Shoulder Injuries in Female Marines Based on Larger Magnitude Shoulder Rotator Bilateral Strength Differences.

BACKGROUND: Musculoskeletal injuries to the extremities are a primary concern for the United States (US) military. One possible injury risk factor in this population is side-to-side strength imbalance. PURPOSE: To examine the odds of reporting a previous shoulder injury in US Marine Corps Ground Combat Element Integrated Task Force volunteers based on side-to-side strength differences in isokinetic shoulder strength. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Male (n = 219) and female (n = 91) Marines were included in this analysis. Peak torque values from 5 shoulder internal/external rotation repetitions were averaged and normalized to body weight. The difference in side-to-side strength measurements was calculated as the absolute value of the limb difference divided by the mean peak torque of the dominant limb. Participants were placed into groups based on the magnitude of these differences: <10%, 10% to 20%, and >20%. Odds ratios (ORs) and 95% CIs were calculated. RESULTS: When separated by sex, 13.2% of men reported an injury, while 5.5% of women reported an injury. Female Marines with >20% internal rotation side-to-side strength differences demonstrated increased odds of reporting a previous shoulder injury compared with female Marines with <10% strength differences (OR, 15.4; 95% CI, 1.4-167.2; P = .03 ) and female Marines with 10% to 20% strength differences (OR, 13.9; 95% CI, 1.3-151.2; P = .04). No significant ORs were demonstrated in male Marines. CONCLUSION: Marines with larger magnitude internal rotation strength differences demonstrated increased odds of reporting a previous shoulder injury compared with those with lesser magnitude differences. Additionally, female sex appears to drastically affect the increased odds of reporting shoulder injuries (OR, 13.9-15.4) with larger magnitude differences (ie, >20%) compared with those with lesser magnitude differences (ie, <10% and 10%-20%). The retrospective cohort design of this study cannot delineate cause and effect but establishes a relationship between female Marines and greater odds of larger magnitude strength differences after returning from an injury.

Greater ankle strength, anaerobic and aerobic capacity, and agility predict Ground Combat Military Occupational School graduation in female Marines.

Women can serve in all military occupational specialties (MOS); however, musculoskeletal and physiological characteristics that predict successful completion of ground combat MOS schools by female Marines are unknown. OBJECTIVES: To determine which demographic, musculoskeletal, and physiological characteristics predict graduation from infantry and vehicle ground combat MOS schools in female Marines. DESIGN: Prospective cohort study. METHODS: Prior to MOS school, the following were assessed in 62 female Marines (22.0±3.0yrs, 163.9±5.8cm, 63.4±7.2kg): isokinetic shoulder, trunk, and knee and isometric ankle strength; body composition; anaerobic power (AP)/capacity (AC); maximal oxygen uptake (VO2max); and field-based fitness tests (broad jump, medicine ball throw, pro-agility). Both absolute and normalized (%body mass: %BM) values were utilized for strength, AP, AC, and VO2max. Select tests from each Marine's most recent Physical Fitness Test (PFT: abdominal crunches, 3-mile run time) and Combat Fitness Test (CFT: Maneuver Under Fire, Movement to Contact) were recorded. Participants were classified as graduated (N=46) or did not graduate (N=16). Simple logistic regression was performed to determine predictors of MOS school graduation. Statistical significance was set a priori at α=0.05. RESULTS: Absolute and normalized ankle inversion and eversion strength, normalized anaerobic capacity, absolute and normalized VO2max, right pro-agility, and PFT 3-mile run time significantly predicted MOS school graduation (p<0.05). CONCLUSIONS: Greater ankle strength, better agility, and greater anaerobic and aerobic capacity are important for successful completion of ground combat MOS school in female Marines. Prior to entering ground combat MOS school, it is recommended that female Marines should train to optimize these mobility-centric characteristics.

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.

Differential basal and exercise-induced IGF-I system responses to resistance vs. calisthenic-based military readiness training programs.

OBJECTIVE: The purpose of this study was to: 1) evaluate differential responses of the IGF-I system to either a calisthenic- or resistance exercise-based program and 2) determine if this chronic training altered the IGF-I system during an acute resistance exercise protocol. DESIGN: Thirty-two volunteers were randomly assigned into a resistance exercise-based training (RT) group (n=15, 27±5y, 174±6cm, 81±12kg) or a calisthenic-based training group (CT) (n=17, 29±5y, 179±8cm, 85±10kg) and all underwent 8weeks of exercise training (1.5h/d, 5d/wk). Basal blood was sampled pre- (Week 0), mid- (Week 4) and post-training (Week 8) and assayed for IGF-I system analytes. An acute resistance exercise protocol (AREP) was conducted preand post-training consisting of 6 sets of 10 repetitions in the squat with two minutes of rest in between sets and the IGF-I system analytes measured. A repeated measures ANOVA (p≤0.05) was used for statistical analysis. RESULTS: No interaction or within-subject effects were observed for basal total IGF-I, free IGF-I, or IGFBP-1. IGFBP-2 (pre; 578.6±295.7post-training; 14.3±1.9µg/mL; p=0.01). An interaction was observed for the RT group as IGFBP-3 increased from pre to mid (3462.4±216.4 vs. 3962.2±227.9ng/mL), but was not significant at the post-training time point (3770.3±228.7ng/mL). AREP caused all analytes except free IGF-I (40% decrease) to increase (17-27%; p=0.001) during exercise, returning to baseline concentration into recovery. CONCLUSION: Post-training, bioavailable IGF-I recovered more rapidly post-exercise. 8wks of chronic physical training resulted in increased basal IGFBP-2 and IGFBP-3, decreased ALS, increased pre-AREP free IGF-I and a more rapid free IGF-I recovery post-AREP. While total IGF-I was insensitive to chronic physical training, changes were observed with circulating IGFBPs and bioavailable IGF-I. To glean the most robust information on the effects of exercise training, studies must move beyond relying solely on total IGF-I measures and should consider IGFBPs and bioavailable IGF-I as these components of the circulating IGF-I system are essential determinants of IGF-I physiological action.

Musculoskeletal, biomechanical, and physiological gender differences in the US military.

UNLABELLED: The repeal of the Direct Ground Combat Assignment Rule has renewed focus on examining performance capabilities of female military personnel and their ability to occupy previously restricted military occupational specialties. Previous research has revealed female Soldiers suffer a greater proportion of musculoskeletal injuries compared to males, including a significantly higher proportion of lower extremity, knee, and overuse injuries. Potential differences may also exist in musculoskeletal, biomechanical, and physiological characteristics between male and female Soldiers requiring implementation of gender-specific training in order to mitigate injury risk and enhance performance. PURPOSE: To examine differences in musculoskeletal, biomechanical, and physiological characteristics in male and female Soldiers. METHODS: A total of 406 101st Airborne Division (Air Assault) Soldiers (348 male; 58 female) participated. Subjects underwent testing for flexibility, isokinetic and isometric strength (percent body weight), single-leg balance, lower body biomechanics during a stop jump and drop landing, body composition, anaerobic power/capacity, and aerobic capacity. Independent t tests assessed between-group comparisons. RESULTS: Women demonstrated significantly greater flexibility (P<.01-P<.001) and better balance (P≤.001) than men. Men demonstrated significantly greater strength (P≤.001), aerobic capacity (47.5±7.6 vs 40.3±5.4 ml/kg/min, P<.001), anaerobic power (13.3±2.1 vs 9.5±1.7 W/kg, P<.001), and anaerobic capacity (7.8±1.0 vs 6.1±0.8 W/kg, P<.001) and lower body fat (20.1±7.5 vs 26.7±5.7 (%BF), P<.001). Women demonstrated significantly greater hip flexion and knee valgus at initial contact during both the stop jump and drop landing tasks and greater knee flexion at initial contact during the drop landing task (P<.05-P<.001). CONCLUSIONS: Gender differences exist in biomechanical, musculoskeletal, and physiological characteristics. Sex-specific interventions may aid in improving such characteristics to optimize physical readiness and decrease the injury risk during gender-neutral training, and decreasing between-sex variability in performance characteristics may result in enhanced overall unit readiness. Identification of sex-specific differences in injury patterns and characteristics should facilitate adjustments in training in order for both sexes to meet the gender-neutral occupational demands for physically demanding military occupational specialties.

Exercise dose and insulin sensitivity: relevance for diabetes prevention.

PURPOSE: Exercise improves insulin resistance and is a first line for the prevention and treatment of type 2 diabetes. The extent, however, to which these responses are dose dependent is not known. The purpose of this study was to examine whether exercise dose was associated with improvements in insulin sensitivity after 4 months of exercise training in previously sedentary adults. METHODS: Fifty-five healthy volunteers participated in a 16-wk supervised endurance exercise intervention with a pre/postintervention design. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp, peak oxygen uptake by a graded exercise test, and body composition by dual-energy x-ray absorptiometry. The exercise intervention consisted of three to five sessions per week with a minimum of three sessions supervised. A ramped exercise prescription protocol was used to achieve 75% of peak HR for 45 min per session. Exercise dose, expressed as average kilocalories expended per week, was computed as the product of exercise intensity, duration and frequency. RESULTS: Improved insulin sensitivity was significantly related to exercise dose in a graded dose-response relationship. No evidence of threshold or maximal dose-response effect was observed. Age and gender did not influence this dose-response relationship. Exercise intensity was also significantly related to improvements in insulin sensitivity, whereas frequency was not. CONCLUSIONS: This study identifies a graded dose-response relationship between exercise dose and improvements in insulin sensitivity. The implication of this observation is of importance for the adaptation of exercise prescription in clinical situations.