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Purpose: To assess physiological metrics during the use of a commercially available bilateral active ankle exoskeleton during a challenging military-relevant task and if use of the exoskeleton during this task influences: metabolic load, physiological measures or rate of perceived exertion., Methods: Nine healthy volunteers (5M, 4F) completed this randomized cross-over design trial, with a baseline visit and two randomized test sessions (with/without the exoskeleton). Variables included impact on time to exhaustion during walking on a treadmill at varying speeds and gradients (0-15%) at 26.7°C, 50% humidity with a loaded rucksack (30% body weight). The primary outcome measure was change in metabolic cost with/without the exoskeleton (O2 consumption, metabolic equivalents); secondary outcomes were change in heart rate and perceived exertion between conditions., Results: Participants averaged 22.4 ± 4.5 years old, 173.7 ± 7.4 cm tall, weighed 80.9 ± 13.9 kg, and VO2max of 43.8 ± 10.6 mL/kg/min. Total kcals did not differ between conditions (with/without exoskeleton; t = 0.98; p = 0.357). Kcals/min were significantly lower (1.06 kcals/min) with the exoskeleton (t = 3.94; p = 0.004). Average oxygen consumption (VO2) was significantly lower (2.36 mL/kg/min) with the exoskeleton (t = 2.81; p = 0.023), and peak VO2 was 3.33 mL/kg/min lower with the exoskeleton (t = 2.37; p = 0.045). Peak and Average METS were also lower with the exoskeleton by 0.98 (t = 2.61; p = 0.031) and 1.23 (t = 2.39; p = 0.044) respectively., Conclusions: Results suggest a powered ankle exoskeleton may decrease energy consumption during military relevant tasks when conducted in a laboratory environment. There may also be physiological benefits such as reduced core temperate and heart rate. Replication of this work in the field environment is warranted., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Sefton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

We sought to examine how resistance training (RT) status in young healthy individuals, either well resistance trained (T, n=10) or untrained (UT, n=11), affected molecular markers with leg immobilization followed by recovery RT. All participants underwent two weeks of left leg immobilization via a locking leg brace. Afterwards, all participants underwent eight weeks (3 d/week) of knee extensor focused progressive RT. Vastus lateralis (VL) ultrasound-derived thickness and muscle cross-sectional area were measured at baseline (PRE), immediately after disuse (MID), and after RT (POST) with VL muscle biopsies also being collected at these time points. Both groups presented lower ultrasound derived VL size metrics at MID versus PRE (p<0.001), and values increased in both groups from MID to POST (p<0.05); however, VL size increased from PRE to POST in UT only (p<0.001). Mean and type II myofiber cross-sectional area values were greater at PRE and POST versus MID (p<0.05), with T being greater than UT throughout (P<0.012). In both groups, satellite cell number was not affected by leg immobilization but increased in response to RT (p<0.014), with T being greater than UT throughout (p=0.004). Total RNA (ribosome content) decreased (p=0.010) from PRE to MID, while total RNA and certain endoplasmic reticulum stress proteins increased from MID to POST regardless of training status. Immobilization-induced muscle atrophy and recovery RT hypertrophy outcomes are similar between UT and T participants, and the lack of molecular signature differences between groups supports these findings. However, results are limited to younger adults undergoing non-complicated disuse.

We aimed to determine how a bout of resistance or aerobic exercise impacts physiological responses and performance during firefighting occupational tasks. Thirty-two non-firefighters completed two baseline assessments and three trials: resistance exercise (RE), aerobic exercise (AE), or a rested control (CON). Trials were followed by an occupational task assessment (OTA; four rounds of 10 deadlifts (38.6-61.4 kg) and 0.24-km 40lb-sandbag carry) in an environmental chamber (35 °C/50% humidity) while wearing standard municipal firefighter gear. Time to complete by condition was not statistically different (CON: 18.9 ± 4.4, AE: 20.0 ± 3.6, RE: 20.2 ± 5.0 min; p = 0.16). During the OTA average heart rate (CON: 149 ± 16, AE: 166 ± 12, RE: 160 ± 13 bpm; p < 0.01), estimated core temperature (CON: 37.6 ± 0.4, AE: 38.7 ± 0.3, RE: 38.4 ± 0.5 °C; p < 0.01), and skin temperature (CON: 36.3 ± 0.5, AE: 37.5 ± 0.6, RE: 36.9 ± 0.9 °C; p < 0.01) were elevated following AE and RE compared to CON, and higher following AE compared to RE. Our findings suggest job performance may not be impacted, although physiological stress during the tasks may be elevated, following on-shift exercise, and more prominently following aerobic exercise., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Consent to participate: Informed consent was obtained from all individual participants included in the study. Ethical approval: The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of Auburn University (protocol code #22–149 MR 2205, 05/05/2022)., (© 2024. The Author(s).)

Purpose: Acute exercise can transiently enhance cognitive flexibility. The cognitive demand of firefighters makes it relevant to understand if on-shift exercise could produce similar improvements in cognitive performance during subsequent occupational tasks. Metrics of heart rate variability (HRV), such as time- and frequency-domain outcomes, may shed light upon the influence exercise has on cognition, as they discern information related to cardiac autonomic (sympathetic/parasympathetic) function. We aimed to determine if acute resistance and aerobic exercise impact cognitive flexibility during occupational tasks and its relation to HRV., Methods: 32 participants completed a baseline Wisconsin Card Sorting Task (WCST) and three experimental trials: resistance exercise (RE), aerobic exercise (AE), or a rested control (CON). An occupational task assessment (OTA) including four rounds of 10 deadlifts and a 0.15-mile sandbag carry in an environmental chamber (35 °C/50% humidity) was completed after each trial. The second round was followed by the WCST. Repeated measures ANOVAs were used to analyze differences by condition., Results: For the WCST, total, perseverative, and non-perseverative errors did not differ (ps > 0.39). Time-domain HRV metrics were not different (ps > 0.05). All frequency-domain metrics, other than low-frequency power, were not different (ps > 0.24). Low-frequency power was lower based on condition (p = 0.03). Post hoc analysis showed low-frequency power was lower following AE compared to RE and CON., Conclusion: Results suggest an acute bout of on-shift aerobic or resistance exercise may not impact cognitive flexibility during subsequent simulated occupational tasks, despite depressed metrics of heart rate variability following aerobic exercise., Competing Interests: Declarations Ethical approval Approval was obtained from the ethics committee of XX University (protocol code #22-479 AR 2211) and all study procedures adhere to the tenets of the Declaration of Helsinki. Conflict of interest The authors report no conflicts of interest., (© 2024. The Author(s).)

Physical fitness is mandatory for public safety officers. Police officers experience elevated levels of cardiovascular disease and associated risks making fitness a peak concern. Officers often have more marked fitness level decreases with aging compared to the general population. This cross-sectional study investigated the cardiovascular health, muscular strength/endurance, and mobility of officers in a medium-sized police department (N = 83); (4 females, 79 males), age (36.82 ± 10 years), height (179.02 ± 7.7 cm), body mass (95.1 ± 16.29 kg) compared to American College of Sports Medicine (ACSM) guidelines. The findings revealed that police officers begin their careers with above average strength but demonstrate greater declines with age than the general population. Officers also demonstrated cardiovascular fitness below ACSM standards and significant decreases with aging compared to the general population. Body fat percentages ( p = 0.003) and BMI ( p = 0.028) surpassed recommendations, with higher than normal increases with age. Maximum vertical jump decreased as officers age ( p = 0.004). These findings support the implementation of a targeted physical fitness regimen and the resources for a program designed to improve current health and fitness, reduce the greater than expected decreases with aging, and aim to optimize occupational performance and the safeguarding of the lifelong health and well-being of officers.

Introduction: Fitness is a vital component in military success. The Army is in the process of implementing a new assessment for soldier fitness, the Army Combat Fitness Test (ACFT). Success on the assessment is a major factor in job assignments and promotional opportunities. This generates questions related to modifiable (i.e., fitness and body composition) and non-modifiable (i.e., limb length and testing equipment) factors impacting performance. Currently, anthropometrics differences in ACFT performance have not been investigated. Thus, this study aimed to assess the impact of anthropometrics on ACFT performance in Reserve Officer Training Corps Cadets., Materials and Methods: Anthropometric measures and ACFT scores were collected from Reserve Officer Training Corps cadets (n = 105, age: 20.4 ± 2.4 years, body mass index: 25.0 ± 2.8 kg/m2, and M/F = 84/21). All ACFT events were evaluated by certified graders. Measurement locations were based on established anthropometric assessment standards and previous research (hand, lower arm, upper arm, upper leg, lower leg, and torso lengths). The study was approved by the Auburn University Institutional Review Board (protocol code #21-410)., Results: There were weak correlations between hand length and three-repetition maximum deadlift [0.393; P ≤ .001], standing power throw [0.399; P ≤ .001], sprint-drag-carry [-0.315; P = .002], and ACFT score [0.212; P = .035]. The lower leg had weak correlations with standing power throw [0.249; P = .013], sprint-drag-carry [-0.215; P = .033], and ACFT score [0.213; P = .034]. Hand and lower leg length impacted individual event performances when comparing shortest and longest limb lengths [all P values <.05]., Conclusions: Hand and lower leg length significantly impact ACFT performance. These results present practical information to individuals responsible for developing protocols and scoring for the ACFT. Reassessment of events and the equipment utilized are warranted to assure that event performance is not hindered by a non-modifiable factor that is not representative of fitness or occupational demands. Future work should investigate how different trap-bar and kettlebell handle sizes, as well as medicine ball sizes, impact performance on the ACFT., (© The Association of Military Surgeons of the United States 2022. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Rectal core temperature monitoring can help fire services mitigate heat injury but can be invasive and impractical. EQ02 + LifeMonitor provides a non-invasive estimation of core temperature. Therefore, the primary purpose of this study was to determine the validity of the EQ02 + LifeMonitor compared to the gold standard rectal thermometer core temperature assessment, as well as the potential influence of turnout gear on the estimated and physiological strain experienced during these activities. Thirteen participants completed simulated firefighting tasks with and without turnout gear, involving four rounds of a 5-min walk on a treadmill at 2.8 mph/2.5% grade and 20 deadlifts over 5 min in an environmental chamber set to 40.6 °C; 50% humidity. During each trial participants wore both an EQ02 + LifeMonitor and DataTherm II rectal thermometer. The results from the devices were statistically equivalent (p < 0.001), yet there was a statistically significant difference in the value (~ 0.1 °C; p < 0.001). There was a significant effect of devices [p < 0.001] and time [p < 0.001], but no interaction effect [p = 0.70] on core temperature drift. Estimated core temperature was marginally different from that measured via the DataTherm II. The EQ02 on average overestimated core temperature. Heart rate, rating of perceived exertion, and area under the curve of core temperature were significantly elevated due to turnout gear [ps < 0.025], but not core temperature skin temperature, or ventilatory rate [ps > 0.372]. These results suggest the EQ02 + LifeMonitor may be a viable, non-invasive alternative for assessing core temperature compared to rectal temperature monitoring, especially during rigorous, intermittent activities. Turnout gear does however increase heart rate, cumulative core temperature, and perceived exertion. Additionally, the validity of the estimated core temperature is not impacted by the use turnout gear. This is likely due to significant changes in heart rate, which allowed the heart-rate derived estimate of core temperature to remain consistent with changes in DataTherm II rectal temperatures., (© 2023. The Author(s).)

We sought to determine the skeletal muscle genome-wide DNA methylation and mRNA responses to one bout of lower load (LL) versus higher load (HL) resistance exercise. Trained college-aged males ( n = 11, 23 ± 4 years old, 4 ± 3 years self-reported training) performed LL or HL bouts to failure separated by one week. The HL bout (i.e., 80 Fail) consisted of four sets of back squats and four sets of leg extensions to failure using 80% of participants estimated one-repetition maximum (i.e., est. 1-RM). The LL bout (i.e., 30 Fail) implemented the same paradigm with 30% of est. 1-RM. Vastus lateralis muscle biopsies were collected before, 3 h, and 6 h after each bout. Muscle DNA and RNA were batch-isolated and analyzed using the 850k Illumina MethylationEPIC array and Clariom S mRNA microarray, respectively. Performed repetitions were significantly greater during the 30 Fail versus 80 Fail ( p < 0.001), although total training volume (sets × reps × load) was not significantly different between bouts ( p = 0.571). Regardless of bout, more CpG site methylation changes were observed at 3 h versus 6 h post exercise (239,951 versus 12,419, respectively; p < 0.01), and nuclear global ten-eleven translocation (TET) activity, but not global DNA methyltransferase activity, increased 3 h and 6 h following exercise regardless of bout. The percentage of genes significantly altered at the mRNA level that demonstrated opposite DNA methylation patterns was greater 3 h versus 6 h following exercise (~75% versus ~15%, respectively). Moreover, high percentages of genes that were up- or downregulated 6 h following exercise also demonstrated significantly inversed DNA methylation patterns across one or more CpG sites 3 h following exercise (65% and 82%, respectively). While 30 Fail decreased DNA methylation across various promoter regions versus 80 Fail, transcriptome-wide mRNA and bioinformatics indicated that gene expression signatures were largely similar between bouts. Bioinformatics overlay of DNA methylation and mRNA expression data indicated that genes related to "Focal adhesion," "MAPK signaling," and "PI3K-Akt signaling" were significantly affected at the 3 h and 6 h time points, and again this was regardless of bout. In conclusion, extensive molecular profiling suggests that post-exercise alterations in the skeletal muscle DNA methylome and mRNA transcriptome elicited by LL and HL training bouts to failure are largely similar, and this could be related to equal volumes performed between bouts.

Objective: To determine whole body vibration influence on human bone density and bone biomarkers., Methods: We identified studies in Medline, Web of Science, Cumulative Index of Nursing and Allied Health, SPORTDiscus, Embase and Cochrane from inception to November 2021. Human randomized controlled trials involving commercially available whole body vibration platforms were included. Outcomes included bone density mean difference and serum concentrations of biomarkers (Procollagen type 1 N-terminal Propeptides, Osteocalcin, Bone specific alkaline phosphatase, and C-terminal Telopeptide of type 1 collagen). Random effects model (Hedges' g effect-size metric and 95% confidence-intervals) compared whole body vibration effect on bone density and bone biomarkers. Moderator analyses assessed health status, age, menopausal status, vibration type, vibration frequency, and study duration influence., Results: Meta-analysis of 30 studies revealed bone density improvement after whole body vibration (Hedges' g = 0.11; p = 0.05; 95% CI = 0.00, 0.22). Whole body vibration improved bone density in healthy (Hedges' g = 0.10; p = 0.01; 95% CI = 0.02, 0.17) and postmenopausal women (Hedges' g = 0.09; p = 0.02; 95% CI = 0.01, 0.18). Bone density also increased following side-alternating whole body vibration intervention (Hedges' g = 0.21; p = 0.02; 95% CI = 0.04, 0.37). Whole body vibration had no significant effect on either bone formation biomarkers (Hedges' g = 0.22; p = 0.01; 95% CI = 0.05, 0.40) or bone resorption biomarkers (Hedges' g = 0.03; p = 0.74; 95% CI = -0.17, 0.23)., Conclusion: Whole body vibration may be clinically useful as non-pharmacological/adjunct therapy to mitigate osteoporosis risk in healthy postmenopausal females. Additional studies are needed to determine the underlying mechanisms., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)