Inflammatory and Oxidant Responses to Arduous Military Training: Associations with Stress, Sleep, and Performance.

BACKGROUND: Arduous military training frequently consists of prolonged physical activity, sleep disturbance, and stress that increases musculoskeletal injury risk and performance decrements. Inflammatory and oxidative stress responses have been reported in response to arduous training, but with inconsistencies across markers and with under-representation of women. The purpose of the current report was to measure circulating inflammation and oxidative stress responses to military training and to correlate biomarkers with subjective measures of stress and sleep quality as well as military fitness test performance. METHODS: Candidates undergoing the 10-week Marine Corps Officer Candidate School (OCS; 101 men; 62 women) were monitored, with demographic and questionnaire data collected, and blood drawn before and after OCS. Blood was analyzed for six markers of inflammation and three markers of oxidative stress. Associations between biomarkers and questionnaire and fitness test performance were tested. RESULTS: All measured inflammatory markers as well as plasma antioxidant capacity were elevated following OCS. The inflammatory increase was higher in women for several markers. Sleep disturbance and stress perception were associated with IL-6, IL-10 and CRP concentrations, suggesting that low sleep disturbance and stress perception were associated with low inflammatory load. Additionally, those with the highest inflammation at each time point performed worse on fitness tests than those with low inflammation. CONCLUSIONS: Following arduous military training, the circulating environment in a significant portion of officer candidates resembled chronic low-grade inflammation. This circulating inflammatory environment appeared worse with poor sleep, high stress perception, and poor fitness test performance, with utility observed for CRP, IL-6, and IL-10 as biomarkers of these responses. Since inflammation may contribute to musculoskeletal injury and performance decrements, minimizing chronic inflammation during military training should be explored.

Physiological characteristics predictive of passing military physical employment standard tasks for ground close combat occupations in men and women.

Challenges for some women meeting the physical employment standards (PES) for ground close combat (GCC) roles stem from physical fitness and anthropometric characteristics. The purpose of this study was to identify the modifiable and nonmodifiable characteristics predictive of passing GCC-based PES tasks and determine the modifiable characteristics suitable to overcome nonmodifiable limitations. 107 adults (46 women) underwent multiday testing assessing regional and total lean mass (LM), percent body fat (BF%), aerobic capacity (V̇O2peak), strength, power, and PES performance. Predictors with p-value <0.200 were included in stepwise logistic regression analysis or binary logistic regression when outcomes among sexes were insufficient. Relative and absolute arm LM (OR: 4.617-8.522, p < 0.05), leg LM (OR: 2.463, p < 0.05), and upper body power (OR: 2.061, p < 0.05) predicted medicine ball chest throw success. Relative and absolute arm LM (OR: 3.734-11.694, p < 0.05), absolute trunk LM (OR: 2.576, p < 0.05), and leg LM (OR: 2.088, p < 0.05) predicted casualty drag success. Upper body power (OR: 3.910, p < 0.05), absolute trunk LM (OR: 2.387, p < 0.05), leg LM (OR: 2.290, p < 0.05), and total LM (OR: 1.830, p < 0.05) predicted maximum single lift success. Relative and absolute arm LM (OR: 3.488-7.377, p < 0.05), leg LM (OR: 1.965, p < 0.05), and upper body power (OR: 1.957, p < 0.05) predicted water can carry success. %BF (OR: 0.814, p = 0.007), V̇O2peak (OR: 1.160, p = 0.031), and lower body strength (OR: 1.059, p < 0.001) predicted repeated lift and carry success. V̇O2peak (OR: 1.540, p < 0.001) predicted 2-km ruck march success. Modifiable characteristics were the strongest predictors for GCC-based PES task success to warrant their improvement for enhancing PES performance for women.

Allostatic Load Is Associated with Overuse Musculoskeletal Injury during US Marine Corps Officer Candidates School.

INTRODUCTION: Overuse musculoskeletal injuries (MSKIs) remain a significant medical challenge in military personnel undergoing military training courses; a further understanding of the biological process leading to overuse MSKI development and biological signatures for injury risk are warranted. The purpose of this study was to determine the association between overuse MSKI occurrence and physiological characteristics of allostatic load (AL) characterized as maladaptive biological responses to chronic stress measured by wearable devices in US Marine Corps officer candidates during a 10-week training course. METHODS: Devices recorded energy expenditure (EE), daytime heart rate (HR), sleeping HR, and sleep architecture (time and percent of deep, light, REM sleep, awake time, total sleep). Flux was calculated as the raw or absolute difference in the average value for that day or night and the day or night beforehand. Linear mixed-effect model analysis accounting for cardiorespiratory fitness assessed the association between overuse MSKI occurrence and device metrics (α = 0.05). RESULTS: Sixty-nine participants (23 females) were included. Twenty-one participants (eight females) sustained an overuse MSKI. Overuse MSKI occurrence in male participants was positively associated with daytime HR (ß = 5.316, p = 0.008), sleeping HR (ß = 2.708, p = 0.032), relative EE (ß = 8.968, p = 0.001), absolute flux in relative EE (ß = 2.994, p = 0.002), absolute EE (ß = 626.830, p = 0.001), and absolute flux in absolute EE (ß = 204.062, p = 0.004). Overuse MSKI occurrence in female participants was positively associated with relative EE (ß = 5.955, p = 0.026), deep sleep time (ß = 0.664, p < 0.001), %deep sleep (ß = 12.564, p < 0.001) and negatively associated with absolute flux in sleeping HR (ß = -0.660, p = 0.009). CONCLUSIONS: Overuse MSKI occurrences were associated with physiological characteristics of AL including chronically elevated HR and EE and greater time in restorative sleep stages, which may serve as biological signatures for overuse MSKI risk.

Hormonal contraception and medical readiness for female service members.

Many female military service members choose to use hormonal contraception to prevent pregnancy and/or to control or suppress menses. Hormonal contraception, which comes in many different forms based on dose, estrogen/progestin type, and route of administration (oral, vaginal, transdermal, implant, intrauterine device, injectable), may cause side effects, some of which can influence military medical readiness, or the health status necessary to perform assigned missions. This expert review summarizes the evidence around common military-relevant side effects of hormonal contraception that could impact readiness, including effects on weight and body composition, bone health, psychological health, and physical performance, and serves as a tool for uniformed and civilian clinicians counseling female service members about hormonal contraception. Current evidence suggests some hormonal contraception can lead to weight and fat gain, may modulate susceptibility to mood or mental health disorders, and could impact bone mineral density and stress fracture risk; more research is needed on physical performance effects. Clinicians must be familiar with readiness considerations of each type of hormonal contraception to provide comprehensive patient education and allow for optimal shared decision-making about hormonal contraception use among female Service members. Considering the relative lack of data on the effects of nonoral hormonal contraception routes on readiness outcomes and the growing interest in long-acting reversible contraceptives among female service members, future research should continue to investigate effects of all hormonal contraception methods available to service members.

Skeletal muscle adaptations to high-intensity, low-volume concurrent resistance and interval training in recreationally active men and women.

This study compared the structural and cellular skeletal muscle factors underpinning adaptations in maximal strength, power, aerobic capacity, and lean body mass to a 12-week concurrent resistance and interval training program in men and women. Recreationally active women and men completed three training sessions per week consisting of high-intensity, low-volume resistance training followed by interval training performed using a variety upper and lower body exercises representative of military occupational tasks. Pre- and post-training vastus lateralis muscle biopsies were analyzed for changes in muscle fiber type, cross-sectional area, capillarization, and mitochondrial biogenesis marker content. Changes in maximal strength, aerobic capacity, and lean body mass (LBM) were also assessed. Training elicited hypertrophy of type I (12.9%; p = 0.016) and type IIa (12.7%; p = 0.007) muscle fibers in men only. In both sexes, training decreased type IIx fiber expression (1.9%; p = 0.046) and increased total PGC-1α (29.7%, p < 0.001) and citrate synthase (11.0%; p < 0.014) content, but had no effect on COX IV content or muscle capillarization. In both sexes, training increased maximal strength and LBM but not aerobic capacity. The concurrent training program was effective at increasing strength and LBM but not at improving aerobic capacity or skeletal muscle adaptations underpinning aerobic performance.

Effects of Prune (Dried Plum) Supplementation on Cardiometabolic Health in Postmenopausal Women: An Ancillary Analysis of a 12-Month Randomized Controlled Trial, The Prune Study.

BACKGROUND: Estrogen withdrawal during menopause is associated with an unfavorable cardiometabolic profile. Prunes (dried plums) represent an emerging functional food and have been previously demonstrated to improve bone health. However, our understanding of the effects of daily prune intake on cardiometabolic risk factors in postmenopausal women is limited. OBJECTIVES: We conducted an ancillary investigation of a randomized controlled trial (RCT), The Prune Study, to evaluate the effect of 12-mo prune supplementation on cardiometabolic health markers in postmenopausal women. METHODS: The Prune Study was a single-center, parallel-design, 12-mo RCT in which postmenopausal women were allocated to no-prune control, 50 g/d prune, or 100 g/d prune groups. Blood was collected at baseline, 6 mo, and 12 mo/post to measure markers of glycemic control and blood lipids. Body composition was assessed at baseline, 6 mo, and 12 mo/post using dual-energy X-ray absorptiometry. Linear mixed-effects models were used to evaluate the effect of time, treatment, and their interaction on cardiometabolic health markers, all quantified as exploratory outcomes. RESULTS: A total of 183 postmenopausal women (mean age, 62.1 ± 4.9 y) completed the entire 12-mo RCT: control (n = 70), 50 g/d prune (n = 67), and 100 g/d prune (n = 46). Prune supplementation at 50 g/d or 100 g/d did not alter markers of glycemic control and blood lipids after 12 mo compared with the control group (all P > 0.05). Furthermore, gynoid percent fat and visceral adipose tissue (VAT) indices did not significantly differ in women consuming 50 g/d or 100 g/d prunes compared with the control group after 12 mo of intervention. However, android total mass increased by 3.19% ± 5.5% from baseline in the control group, whereas the 100 g/d prune group experienced 0.02% ± 5.6% decrease in android total mass from baseline (P < 0.01). CONCLUSIONS: Prune supplementation at 50 g/d or 100 g/d for 12 mo does not improve glycemic control and may prevent adverse changes in central adiposity in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT02822378.

Prunes preserve cortical density and estimated strength of the tibia in a 12-month randomized controlled trial in postmenopausal women: The Prune Study.

Non-pharmacological therapies, such as whole-food interventions, are gaining interest as potential approaches to prevent and/or treat low bone mineral density (BMD) in postmenopausal women. Previously, prune consumption preserved two-dimensional BMD at the total hip. Here we demonstrate that prune consumption preserved three-dimensional BMD and estimated strength at the tibia. PURPOSE: Dietary consumption of prunes has favorable impacts on areal bone mineral density (aBMD); however, more research is necessary to understand the influence on volumetric BMD (vBMD), bone geometry, and estimated bone strength. METHODS: This investigation was a single center, parallel arm 12-month randomized controlled trial (RCT; NCT02822378) to evaluate the effects of 50 g and 100 g of prunes vs. a Control group on vBMD, bone geometry, and estimated strength of the radius and tibia via peripheral quantitative computed tomography (pQCT) in postmenopausal women. Women (age 62.1 ± 5.0yrs) were randomized into Control (n = 78), 50 g Prune (n = 79), or 100 g Prune (n = 78) groups. General linear mixed effects (LME) modeling was used to assess changes over time and percent change from baseline was compared between groups. RESULTS: The most notable effects were observed at the 14% diaphyseal tibia in the Pooled (50 g + 100 g) Prune group, in which group × time interactions were observed for cortical vBMD (p = 0.012) and estimated bone strength (SSI; p = 0.024); all of which decreased in the Control vs. no change in the Pooled Prune group from baseline to 12 months/post. CONCLUSION: Prune consumption for 12 months preserved cortical bone structure and estimated bone strength at the weight-bearing tibia in postmenopausal women.

Effect of acute resistance exercise on bone turnover in young adults before and after concurrent resistance and interval training.

Weight-bearing physical activity can stimulate bone adaptation. This investigation explored the effect of an acute bout of resistance exercise before and after resistance+interval training on circulating biomarkers of bone metabolism and muscle-bone crosstalk. Healthy young male and female participants (n = 21 male, 28 ± 4 years; n = 17 female, 27 ± 5 years) performed a 6 × 10 squat test (75% 1RM) before and after a 12-week resistance+interval training program. Before and after completion of the training program, blood samples were collected at rest, immediately postexercise, and 2 h postexercise. Blood samples were analyzed for ßCTX, P1NP, sclerostin, osteocalcin, IGF-1, and irisin. Significant effects of acute exercise (main effect of time) were observed as increases in concentrations of IGF-1, irisin, osteocalcin, and P1NP from rest to postexercise. A sex*time interaction indicated a greater decline in ßCTX concentration from rest to 2 h postexercise and a greater increase in sclerostin concentration from rest to immediately postexercise in male compared with female participants. Sex differences (main effect of sex) were also observed for irisin and P1NP concentrations. In summary, changes in concentrations of biochemical markers of bone metabolism and muscle-bone crosstalk were observed in males and females after an acute bout of resistance exercise and following 12 weeks of resistance+interval training.