Validity of heart rate derived core temperature estimation during simulated firefighting tasks.

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.

Prosthetic device and service satisfaction, quality of life, and functional performance in lower limb prosthesis clients.

OBJECTIVE: The aim of this study was to characterize the relationship between prosthetic device and service satisfaction, health-related quality of life (HRQOL), and functional movement in a diverse population of lower limb prosthesis users. METHODS: An online survey was conducted on individuals with lower limb amputation between September and October 2021. Sample validated questionnaires assessing demographic and clinical features, satisfaction, functional outcomes, and quality of life were analyzed using path analysis. RESULTS: Participants were 1736 individuals with lower limb amputation. Overall, 44% of participants reported dissatisfaction with prosthetic device, whereas 37% were dissatisfied with prosthetic service. Low functional mobility was reported by 58% of participants and 61% reported low HRQOL. Lower extremity functional status (ß = 0.55), HRQOL (ß = 0.08), Activities-specific Balance Scale (ß = 0.22), and modified fall efficacy scale (ß = -0.07) are significantly associated with prosthetic device satisfaction (P < 0.0005, R2 = 0.47). Satisfaction with provider service was significantly associated with lower extremity functional status (ß = 0.44) and balance confidence (ß = 0.18) (P < 0.0005, R2 = 0.34). CONCLUSION AND CLINICAL RELEVANCE: Civilians, veterans, and service members reported low functional mobility, low quality of life, and moderate levels of dissatisfaction with their lower extremity prosthetic device and provider service. Improvements in mobility, balance, quality of life, and fall efficacy may enhance device satisfaction. Functional mobility and balance improvements may increase ratings of provider service. This study provides feedback that may improve clinical decisions on lower limb prosthesis patient care.

Characterization of initial ankle-foot prosthesis prescription patterns in U.S. Service members following unilateral transtibial amputation.

Introduction: The purpose of this study was to explore relationships between patient-specific characteristics and initial ankle-foot prosthesis prescription patterns among U.S. Service members with unilateral transtibial limb loss. Methods: A retrospective review of health records identified 174 individuals with unilateral transtibial limb loss who received care at Walter Reed National Military Medical Center between 2001 and 2019. We examined patient-specific factors such as demographics, participant duty status at injury and amputation, amputation etiology, and timing between injury, amputation, and initial prescription. The type of first prescribed ankle-foot prosthesis was categorized as energy storing and return - nonarticulating, energy storing and return - articulating, or computer controlled. Results: Sex, amputation etiology, time from injury to initial prescription, and time from amputation to initial prescription differed by type of initial ankle-foot prosthesis prescription. Service members with shorter intervals between injury-initial prescription and amputation-initial prescription, and those injured by combat blast, were more likely to receive a non-articulating device. Incorporating sex, time from injury-initial prescription, time from amputation-initial prescription, and amputation etiology as predictors of prosthesis type, we were able to correctly classify 72% of all first prostheses prescribed. Discussion: Patient-specific characteristics such as sex, the time between injury-initial prescription, time from amputation-initial prescription and amputation etiology are essential characteristics that influence initial ankle-foot prosthesis prescription patterns in U.S. Service members.

Core and Whole-Body Vibration Exercise Improve Military Foot March Performance in Novice Trainees: A Randomized Controlled Trial.

INTRODUCTION: The purpose of the present study was to investigate core exercise training and whole-body vibration (WBV) as a training method to improve performance and recovery from an 8-km military foot march in novice trainees. MATERIALS AND METHODS: A 3 × 5 repeated measures randomized control trial was used to evaluate the effects of core exercise training and WBV on performance and recovery from an 8-km foot march. Thirty-nine participants were randomized into three groups: core exercise (Ex), WBV with core exercise (WBVEx), and control. Each participant completed two 8-km foot marches (FM1 and FM2) with a 35 pound rucksack, separated by 4 weeks. Participants in the Ex and WBVEx groups completed 3 weeks of core exercise training, three times per week in between FM1 and FM2. Performance time, creatine kinase (CK), and interleukin-6 (IL-6) were measured. The Auburn University Institutional Review Board approved all aspects of this study (protocol number: 19-211 MR 1907). RESULTS: Performance time (P < .001) and CK (P = .005) were significantly improved during FM2 as compared to FM1. The Ex (d = -0.295) and WBVEx (d = -0.645) treatments had a large effect on performance time. CK (P < .001) and IL-6 (P < .001) were significantly elevated at the completion of the foot march regardless of group. Only CK remained elevated for 2 days (P < .001) following the foot march. CONCLUSIONS: Core exercise training with or without WBV improved 8-km foot march performance time by 5-6 minutes. The improvements are likely because of an increase in trunk stability. Additionally, this study showed that completing two identical foot marches a month apart increases performance and improves recovery.

Impact of Two Types of Fitness Programs on Soldier Physical Fitness.

This study compared an expert supervised, fully resourced physical training (PT) program compared to a traditional physical training PT plan on Army Officer Candidate School (OSC) soldier fitness outcomes. This retrospective cohort study compared 228 OCS soldiers (179 male [26.74±3.78 years] and 49 female [26.55±4.18 years]) in two companies for 12 weeks. One company participated in a fully resourced PT program designed by fitness experts to improve overall fitness and mobility (TAP-C). One company participated in traditional physical training designed to excel on the Army combat fitness test (ACFT, includes deadlift, power throw, push up, sprint-drag-carry, core strength, run) developed and led by OCS soldiers with standard resources. We assessed performance on the ACFT events, and grip strength, standing broad jump, overhead squat, and 90/90 switch assessment. Analysis of covariance was used to compare main effects of company on ACFT measures, controlling for covariates of pretest score differences and sex. Results included a significant effect of group on ACFT performance (N=228), F(1, 223) = 12.8, p<0.001 and on performance of five of the six ACFT events: MDL, F(1, 223) = 5.44, p = 0.021; HRP, F(1, 223) = 11.67, p < 0.001; SDC, F(1, 223) = 20.06, p < 0.001; LTK, F(1, 223) = 16.95, p < 0.001; and 2MR, F(1, 223) = 23.76, p < 0.001. The traditional company performed significantly better on ACFT muscular, anerobic and aerobic endurance focused events; the TAP-C company performed significantly better on muscular strength/explosive power events and mobility assessments.

Anthropometrics Impact Army Combat Fitness Test Performance in Reserve Officer Training Corps Cadets.

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.

Whey Protein Supplementation Effects on Body Composition, Performance, and Blood Biomarkers During Army Initial Entry Training.

This study assesses if a lower dose of whey protein can provide similar benefits to those shown in previous work supplementing Army Initial Entry Training (IET) Soldiers with two servings of whey protein (WP) per day. Eighty-one soldiers consumed one WP or a calorie matched carbohydrate (CHO) serving/day during IET (WP: n = 39, height = 173 ± 8 cm, body mass = 76.8 ± 12.8 kg, age = 21 ± 3 years; CHO: n = 42, 175 ± 8 cm, 77.8 ± 15.3 kg, 23 ± 4 years). Physical performance (push-ups, sit-ups, and a two-mile run) was assessed during weeks two and eight. All other measures (dietary intake, body composition, blood biomarkers) at weeks one and nine. There was a significant group difference for fat mass (p = 0.044) as WP lost 2.1 ± 2.9 kg and had a moderate effect size (Cohen's d: -0.24), whereas the CHO group lost 0.9 ± 2.5 kg and had only a small effect size (d: -0.1). There was no significant group-by-time interaction on fat-free mass (p = 0.069). WP gained 1.2 ± 2.4 (d: 0.1) and CHO gained 0.1 ± 3 (d: 0) kg of FFM on average. There was a significant group by week 1-fat free mass interaction (p = 0.003) indicating individuals with higher initial fat-free mass benefitted more from WP. There were no group differences for push-up (p = 0.514), sit-up (p = 0.429) or run (p = 0.313) performance. For all biomarkers there was a significant effect of time as testosterone (p < 0.01), testosterone to cortisol ratio (p = 0.39), and IGF-1 (p < 0.01) increased across training and cortisol (p = 0.04) and IL-6 (p < 0.01) decreased. There were no differences in groups across IET for any of the biomarkers. We conclude one WP serving is beneficial for FM and for FFM in soldiers with high baseline FFM but may not significantly alter biomarker response or physical performance of IET soldiers who have high relative dietary protein intakes.

Systematic review and meta-analyses on the effects of whole-body vibration on bone health.

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.

Core and Whole Body Vibration Exercise Influences Muscle Sensitivity and Posture during a Military Foot March.

Military foot marches account for 17-22% of Army musculoskeletal injuries (MSI), with low back pain (LBP) being a common complaint. Core-exercise and whole-body vibration (WBV) have been shown to decrease LBP in patients with chronic low back MSI. This study investigated if WBV and/or core-exercise influenced LBP or posture associated with a military ruck march. A randomized control trial with three groups: (1) WBV and core-exercise (WBVEx); (2) core-exercise alone (Ex); and (3) control evaluated the effects of core-exercise and WBV on LBP during/after a two 8 K foot marches with a 35 lb rucksack. The intervention groups completed three weeks of core-exercise training with/without WBV. Outcome measurements included visual analog scale (VAS), algometer, posture and electromyography (EMG). LBP, pressure threshold, and posture were elevated throughout the foot march regardless of group. LBP remained elevated for 48 h post foot march (p = 0.044). WBVEx and Ex did not have a significant effect on LBP. WBVEx and Ex both decreased muscle sensitivity and increased trunk flexion (p < 0.001) during the second foot march (FM2). The 8 K foot marches significantly increased LBP. Core-exercise training with/without WBV decreases low back muscle sensitivity. WBV and core-exercise increases trunk flexion which may help improve performance and may influence LBP.

Musculoskeletal Injury in Reserve Officers' Training Corps: A Report From the Athletic Training Practice-Based Research Network.

BACKGROUND: Reserve Officers' Training Corps (ROTC) cadets must meet the same physical standards as active duty military servicemembers and undergo organized physical training (PT). ROTC participation, like all physical activity, can result in training-related musculoskeletal injury (MSKI), and of course, cadets could sustain MSKI outside of ROTC. However, MSKI incidence in ROTC programs is largely unknown. PURPOSE: To describe patient and injury demographics of MSKI in 5 universities' Army ROTC programs. STUDY DESIGN: Descriptive epidemiology study. METHODS: A retrospective chart review of electronic medical records was performed using the Athletic Training Practice-Based Research Network (AT-PBRN). Athletic trainers at 5 clinical practice sites within the AT-PBRN documented injury assessments via a web-based electronic medical record system. Medical records during the 2017-2018 and 2018-2019 academic years were used for analysis. Summary statistics were calculated for age, sex, height, body mass, military science year, training ability group, mechanism of injury, activity type associated with injury, anatomic location of injury, participation status, injury severity, and diagnosis. RESULTS: A total of 364 unique injuries were documented. Cadets in the most advanced fitness group (Alpha; n = 148/364) and in their third year of training (n = 97/364) presented with the most injuries. Injuries most commonly occurred during PT (n = 165/364). Insidious onset (n = 146/364) and noncontact (n = 115/364) mechanisms of injury were prevalent. The most frequent anatomic location of injury was the knee (n = 71/364) followed by the ankle (n = 57/364). General sprain/strain was the most frequent International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code reported (n = 34/364). CONCLUSION: The knee was the most frequent location of MSKI in ROTC participants, and most MSKIs had insidious onset. Cadets with higher injury frequency were high achieving (Alpha) and in a critical time point in ROTC (military science year 3). The majority of MSKIs can be attributed to ROTC training, with PT being the most frequent activity associated with injury. Civilian health care providers, from whom ROTC cadets will most likely seek medical attention, need to be aware of ROTC physical demands as well as the characteristics of training-related injuries.

Markers of Bone Health and Impact of Whey Protein Supplementation in Army Initial Entry Training Soldiers: A Double-Blind Placebo-Controlled Study.

Training civilians to be soldiers is a challenging task often resulting in musculoskeletal injuries, especially bone stress injuries. This study evaluated bone health biomarkers (P1NP/CTX) and whey protein or carbohydrate supplementations before and after Army initial entry training (IET). Ninety male IET soldiers participated in this placebo-controlled, double-blind study assessing carbohydrate and whey protein supplementations. Age and fat mass predicted bone formation when controlling for ethnicity, explaining 44% (p < 0.01) of bone formation variations. Age was the only significant predictor of bone resorption (p = 0.02) when controlling for run, fat, and ethnicity, and these factors together explained 32% of the variance in bone resorption during week one (p < 0.01). Vitamin D increased across training (p < 0.01). There was no group by time interaction for supplementation and bone formation (p = 0.75), resorption (p = 0.73), Vitamin D (p = 0.36), or calcium (p = 0.64), indicating no influence of a supplementation on bone biomarkers across training. Age, fitness, fat mass, and ethnicity were important predictors of bone metabolism. The bone resorption/formation ratio suggests IET soldiers are at risk of stress injuries. Male IET soldiers are mildly to moderately deficient in vitamin D and slightly deficient in calcium throughout training. Whey protein or carbohydrate supplementations did not affect the markers of bone metabolism.

Functional Performance of Firefighters After Exposure to Environmental Conditions and Exercise.

CONTEXT: Slips, trips, and falls are leading causes of musculoskeletal injuries in firefighters. Researchers have hypothesized that heat stress is the major contributing factor to these fireground injuries. OBJECTIVE: To examine the effect of environmental conditions, including hot and ambient temperatures, and exercise on functional and physiological outcome measures, including balance, rectal temperature, and perceived exertion. DESIGN: Randomized controlled clinical trial. SETTING: Laboratory environmental chamber. PATIENTS OR OTHER PARTICIPANTS: A total of 13 healthy, active career firefighters (age = 26 ± 6 years [range = 19-35 years], height = 178.61 ± 4.93 cm, mass = 86.56 ± 16.13 kg). INTERVENTION(S): Independent variables consisted of 3 conditions (exercise in heat [37.41°C], standing in heat [37.56°C], and exercise in ambient temperature [14.24°C]) and 3 data-collection times (preintervention, postintervention, and postrecovery). Each condition was separated from the others by at least 1 week and lasted a maximum of 40 minutes or until the participant reached volitional fatigue or a rectal temperature of 40.0°C. MAIN OUTCOME MEASURE(S): Firefighting-specific functional balance performance index, rectal temperature, and rating of perceived exertion. RESULTS: Exercise in the heat decreased functional balance, increased rectal temperature, and altered the perception of exertion compared with the other intervention conditions. CONCLUSIONS: A bout of exercise in a hot, humid environment increased rectal temperature in a similar way to that reported in the physically active population and negatively affected measures of functional balance. Rather than independently affecting balance, the factors of exercise and heat stress appeared to combine, leading to an increased likelihood of slips, trips, and falls.

Impact of Protein and Carbohydrate Supplementation on Musculoskeletal Injuries in Army Initial Entry Training Soldiers.

This project investigated whey protein and/or carbohydrate supplementation effects on musculoskeletal injury (MSI) outcomes. Four groups of Initial Entry Training soldiers consumed either: (1) one protein (38.6 g, 293 kcal); (2) one carbohydrate (63.4 g, 291 kcal); (3) two protein (77.2 g, 586 kcal); or (4) two carbohydrate servings/day (126.8 g, 582 kcal) after physical training and before bed, or before bed only. Odds Ratio, Chi-square and Wilcoxon ranked-sum test compared supplementation/no supplementation, number of servings, and protein/carbohydrate for MSI and limited/missed duty rates and limited/missed training days. Non-matched pairs group averages were compared to 2015/2016 historical data. Non-supplemented soldiers were approximately 5× more likely to sustain a MSI (χ2 = 58.48, p < 0.001) and 4× more likely to miss training (χ2 = 9.73, p = 0.003) compared to two servings. Non-supplemented soldiers missed five additional training days compared to two servings (W = 6059.5, p = 0.02). Soldiers consuming one serving were approximately 3× more likely to sustain a MSI than two servings (χ2 = 9.55, p = 0.002). There was no difference in limited/missed duty rates or limited/missed training days between consuming one or two servings. There was no difference between consuming one serving versus no supplementation or protein versus carbohydrate supplementation for any outcome variable. Soldiers consuming 2 servings/day of protein or carbohydrate had lower MSI rates, limited/missed duty rates, and limited/ missed training days compared to non-supplemented soldiers.

Effect of Whey Protein Supplementation on Physical Performance and Body Composition in Army Initial Entry Training Soldiers.

We investigated the effects of whey protein (WP) supplementation on body composition and physical performance in soldiers participating in Army Initial Entry Training (IET). Sixty-nine, male United States Army soldiers volunteered for supplementation with either twice daily whey protein (WP, 77 g/day protein, ~580 kcal/day; n = 34, age = 19 ± 1 year, height = 173 ± 6 cm, weight = 73.4 ± 12.7 kg) or energy-matched carbohydrate (CHO) drinks (CHO, 127 g/day carbohydrate, ~580 kcal/day; n = 35, age = 19 ± 1 year, height = 173 ± 5 cm, weight = 72.3 ± 10.9 kg) for eight weeks during IET. Physical performance was evaluated using the Army Physical Fitness Test during weeks two and eight. Body composition was assessed using 7-site skinfold assessment during weeks one and nine. Post-testing push-up performance averaged 7 repetitions higher in the WP compared to the CHO group (F = 10.1, p < 0.001) when controlling for baseline. There was a significant decrease in fat mass at post-training (F = 4.63, p = 0.04), but no significant change in run performance (F = 3.50, p = 0.065) or fat-free mass (F = 0.70, p = 0.41). Effect sizes for fat-free mass gains were large for both the WP (Cohen's d = 0.44) and CHO (Cohen's d = 0.42) groups. WP had a large effect on fat mass (FM) loss (Cohen's d = -0.67), while CHO had a medium effect (Cohen's d = -0.40). Twice daily supplementation with WP improved push-up performance and potentiated reductions in fat mass during IET training in comparison to CHO supplementation.

Local Pressure Application Effects on Neurological and Circulatory Function.

BACKGROUND: Pain and discomfort reported during sitting is a significant problem for aviators during prolonged missions. Previous work has determined that areas of local pressure exist during prolonged sitting in UH-60 seat systems; however, no work has examined the effects of this local pressure on measures of neurological and circulatory function. METHODS: A total of 30 healthy subjects completed the study in which focal pressure was applied in three conditions (no pressure, pressure to the ischial tuberosity, and pressure to the posterior thigh). We applied pressure using a purpose-built pressure application system allowing subjects to sit in a position mimicking the sitting position in a UH-60 Black Hawk helicopter and measurements were taken before, during, and after pressure application. We measured neurological function with the soleus Hoffmann reflex and sural nerve conduction velocity, and circulatory function with dynamic infrared thermography. RESULTS: We found a decrease in soleus Hoffmann reflex by 0.87 V and 0.52 V during pressure application at the posterior thigh and ischial tuberosity, respectively. No changes in nerve conduction velocity were found among the conditions during or after pressure application. Limb temperature increased 0.42-0.44°C during pressure application, but began to return to baseline once pressure was removed. DISCUSSION: This study examined the development of neurological and circulatory alterations due to local pressure application in an aviation specific functional position. These results may be used in the development of future interventions to mitigate the negative effects of localized pressure in military aviators.Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Local pressure application effects on neurological and circulatory function. Aerosp Med Hum Perform. 2018; 89(8):693-699.

Neck Kinematics and Electromyography While Wearing Head Supported Mass During Running.

BACKGROUND: Advanced combat helmets (ACH) coupled with night-vision goggles (NVG) are required for tactical athletes during training and service. Head and neck injuries due to head supported mass (HSM) are a common occurrence in military personnel. The current study aimed to investigate the effects of HSM on neck muscle fatigue that may lead to chronic stress and injury of the head and neck. METHODS: Subjects wore an ACH and were affixed with electromagnetic sensors to obtain kinematic data, as well as EMG electrodes to obtain muscle activations of bilateral sternocleidomastoid, upper trapezius, and paraspinal muscles while running on a treadmill. Subjects performed a 2-min warmup at a walking pace, a 5-min warmup jog, running at a pace equal to 90% maximum heart rate until absolute fatigue, and lastly a 2-min cooldown at a walking pace. Kinematic and EMG data were collected over each 2-min interval. Days later, the same subjects wore the same ACH in addition to the NVG and performed the same protocol as the first session. RESULTS: This study showed significant differences in muscle activation of the right upper trapezius [F(1,31) = 10.100] and both sternocleidomastoid [F(1,31) = 12.280] muscles from pre-fatigue to absolute fatigue. There were no significant differences noted in the kinematic variables. DISCUSSION: This study suggests that HSM can fatigue bilateral neck flexors and rotators, as well as fatigue the neck extensors and rotators on the contralateral side of the mounted NVG.Hanks MM, Sefton JM, Oliver GD. Neck kinematics and electromyography while wearing head supported mass during running. Aerosp Med Hum Perform. 2018; 89(1):9-13.

The Effect of Military Load Carriage on Postural Sway, Forward Trunk Lean, and Pelvic Girdle Motion.

Musculoskeletal injuries are a common occurrence in military service members. It is believed that the load carried by the service member impedes stability and alters back and pelvis kinematics, increasing their susceptibility to musculoskeletal injuries, specifically in the lower extremities. The purpose of this study was to examine the effects of two different loads on postural sway, forward trunk lean, and pelvic girdle motion in United States Army Cadets. Twenty male Army Reserve Officers' Training Corps Cadets participated in this study. Each participant performed the Modified Clinical Testing of Sensory Interaction (mCTSIB) Protocol and the Unilateral Stance (ULS) Protocol under three different rucksack load conditions (unloaded, 16.0 kg, and 20.5 kg loads). Mean postural sway velocity was recorded along with 2-D kinematics of the trunk in the sagittal plane and the pelvis in the frontal and sagittal planes. External loads of 16.0 kg (p < 0.001) and 20.5 kg (p ≤ 0.003) significantly increased mean sway velocity by 16% to 52% depending on stance and visual condition, but did not produce significant changes in trunk and pelvic kinematics.

Evaluation of 2 Heat-Mitigation Methods in Army Trainees.

CONTEXT: Heat injury is a significant threat to military trainees. Different methods of heat mitigation are in use across military units. Mist fans are 1 of several methods used in the hot and humid climate of Fort Benning, Georgia. OBJECTIVES: To determine if (1) the mist fan or the cooling towel effectively lowered participant core temperature in the humid environment found at Fort Benning and (2) the mist fan or the cooling towel presented additional physiologic or safety benefits or detriments when used in this environment. DESIGN: Randomized controlled clinical trial. SETTING: Laboratory environmental chamber. PATIENTS OR OTHER PARTICIPANTS: Thirty-five physically active men aged 19 to 35 years. INTERVENTION(S): (1) Mist fan, (2) commercial cooling towel, (3) passive-cooling (no intervention) control. All treatments lasted 20 minutes. Participants ran on a treadmill at 60% V̇o2max. MAIN OUTCOME MEASURE(S): Rectal core temperature, heart rate, thermal comfort, perceived temperature, perceived wetness, and blood pressure. RESULTS: Average core temperature increased during 20 minutes of cooling (F1,28 = 64.76, P < .001, ηp2 = 0.70), regardless of group (F1,28 = 3.41, P = .08, ηp2 = 0.11) or condition (F1,28 < 1.0). Core temperature, heart rate, and blood pressure did not differ among the 3 conditions. Perceived temperature during 20 minutes of cooling decreased (F1,30 = 141.19, P < .001, ηp2 = 0.83) regardless of group or condition. Perceived temperature was lower with the mist-fan treatment than with the control treatment (F1,15 = 7.38, P = .02, ηp2 = 0.32). The mist-fan group perceived themselves to be cooler even at elevated core temperatures. CONCLUSIONS: The mist fan and cooling towel were both ineffective at lowering core temperature. Core temperature continued to increase after exercise in all groups. The mist fan produced feelings of coolness while the core temperature remained elevated, possibly increasing the risk of heat illness.

Local Pressure Application Effects on Discomfort, Temperature, and Limb Oxygenation.

INTRODUCTION: Despite significant investment into the development and improvement of military helicopter seat systems, military aviators continue to report seat system related pain and discomfort during prolonged missions. METHODS: Using a factorial repeated measures design, 15 healthy subjects completed the study, in which focal pressure was applied to two locations on the sitting surfaces of the body (ischial tuberosity and middle of the posterior thigh). Pressure was applied using a purpose-built pressure application system allowing subjects to sit in a position mimicking the sitting position in the UH-60 Black Hawk helicopter. The researchers measured pain using the Category Partitioning Scale and McGill Pain Questionnaire and vascular function using dynamic infrared thermography in the lower leg and pulse oximetry at the great toe. Data were collected before and during a 10-min application of focal pressure applied to either the ischial tuberosity or middle of the posterior thigh and at two different pressure magnitudes (36 or 44 kPa). RESULTS: We found that during a 10-min pressure application, superficial skin temperature increased by 0.61°C, suggesting a decreased venous return during pressure application. We found that lower extremity blood oxygenation remained unchanged during pressure application. Subjects' reported pain increased during pressure application and was greater with 44 kPa of application compared to 36 kPa. DISCUSSION: These results support the hypothesis that locally high pressure creates symptoms of discomfort and paresthesia. Research examining the effects of local pressure application on physiological and neurological function is needed. Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Local pressure application effects on discomfort, temperature, and limb oxygenation. Aerosp Med Hum Perform. 2016; 87(8):697-703.