Hand and torso pre-cooling does not enhance subsequent high-intensity cycling or cognitive performance in heat

The purpose of this study was to compare the separate and combined effects of two practical cooling methods (hand and torso) used prior to exercise on subsequent high-intensity cycling performance in heat. Ten trained male cyclists (V̇O2peak: 65.7 ± 10.7 ml.kg−1.min−1) performed four experimental trials (randomised within-subjects design) involving 30-min of pre-cooling (20-min seated; PRE-COOL, 10 min warm-up; PRE-COOL+WUP), while using a: (1) hand-cooling glove (CG); (2) cooling jacket (CJ); (3) both CG and CJ (CG+J); or (4) no-cooling (NC) control, followed by a cycling race simulation protocol (all performed in 35.0 ± 0.6°C and 56.6 ± 4.5% RH). During the 30-min of pre-cooling, no reductions in core (Tc) or mean skin temperature (Tsk) occurred; however, Tsk remained lower in the CJ and CG+J trials compared to NC and CG (p = 0.002–0.040, d= 0.55–1.01). Thermal sensation ratings also indicated that participants felt “hotter” during NC compared to all other trials during both PRE-COOL and PRE-COOL+WUP (p = 0.001–0.015, d= 1.0–2.19), plus the early stages of exercise (sets 1–2; p = 0.005–0.050, d= 0.56–1.22). Following cooling, no differences were found for absolute Tc and Tsk responses between trials over the entire exercise protocol (p > 0.05). Exercise and cognitive (working memory) performance also did not differ between trials (p = 0.843); however, cognitive performance improved over time in all trials (p < 0.001). In summary, pre-cooling (20-min seated and 10-min warm-up) in heat did not improve subsequent high-intensity cycling performance, cognitive responses and associated thermoregulatory strain (Tc and Tsk) compared to control

Beyond change scores: Employing an improved statistical approach to analyze the impact of entry fitness on physical performance during British Army basic training in men and women

AbstractThe aim was to use a robust statistical approach to examine whether physical fitness at entry influences performance changes between men and women undertaking British Army basic training (BT). Performance of 2 km run, seated medicine ball throw (MBT) and isometric mid‐thigh pull (MTP) were assessed at entry and completion of Standard Entry (SE), Junior Entry‐Short (JE‐Short), and Junior Entry‐Long (JE‐Long) training for 2350 (272 women) recruits. Performance change was analyzed with entry performance as a covariate (ANCOVA), with an additional interaction term allowing different slopes for courses and genders (p &lt; 0.05). Overall, BT courses saw average improvements in 2 km run performance (SE: −6.8% [−0.62 min], JE‐Short: −4.6% [−0.43 min], JE‐Long: −7.7% [−0.70 min]; all p &lt; 0.001) and MBT (1.0–8.8% [0.04–0.34 m]; all p &lt; 0.05) and MTP (4.5–26.9% [6.5–28.8 kg]; all p &lt; 0.001). Regression models indicate an expected form of “regression to the mean” whereby test performance change was negatively associated with entry fitness in each course (those with low baseline fitness exhibit larger training improvements; all interaction effects: p &lt; 0.001, &gt; 0.006), particularly for women. However, when matched for entry fitness, men displayed considerable improvements in all tests, relative to women. Training courses were effective in developing recruit physical fitness, whereby the level of improvement is, in large part, dependent on entry fitness. Factors including age, physical maturity, course length, and physical training, could also contribute to the variability in training response between genders and should be considered when analyzing and/or developing physical fitness in these cohorts for future success of military job‐task performance

Development of an evidence-based swimming representative military task to assess swimming competency in the British Army

Background: There is a requirement for British Army personnel to operate in/around water. Assessing role-related swimming/water competence will support personnel to conduct their job-roles safely and effectively. Objective: To undertake a Job-Task Analysis (JTA) of British Army personnel when working in/around water and use this information to develop a Swimming Representative Military Task (RMT) to assess swimming/water competence. Methods: Workshops, surveys, and observations were used to conduct a JTA, which identified and described job-tasks conducted by British Army personnel in/around water. Ergonomic analysis of these job-tasks identified seven water-based physical actions, which were considered fundamental for all personnel to be competent in performing. These seven actions guided design of a Swimming RMT, which was subsequently conducted twice by 103 serving personnel (89 men, 11 women) and once by 65 recruits (49 men, 16 women). Results: The RMT comprised of entering the water in combat fatigues and webbing, removing webbing, swimming 50 m, and staying afloat for up to 10 minutes. During RMT trials, in trial 1, 85% of serving personnel and 74% of recruits successfully completed the RMT, which increased to 93% in serving personnel for trial 2. Across trials 1 and 2, all three timed RMT elements showed moderate-high correlational reliability (ICC range: 0.462-0.791). On average, serving personnel were quicker to complete the 50 m swim phase compared to recruits (91±24 s vs. 100±26 s; U = 2575.0, rb = -0.192, p = 0.039). Conclusions: The JTA-informed Swimming RMT provides an assessment of the minimum role-related swimming/water competence standard for British Army personnel

Field Validation Of The Heat Strain Decision Aid During Military Load Carriage

Objectives: We aimed to determine the agreement between actual and predicted core body temperature, using the Heat Strain Decision Aid (HSDA), in non-Ground Close Combat (GCC) personnel wearing multi terrain pattern clothing during two stages of load carriage in temperate conditions. Design: Cross-sectional. Methods: Sixty participants (men = 49, women = 11, age 31 ± 8 years; height 171.1 ± 9.0 cm; body mass 78.1 ± 11.5 kg) completed two stages of load carriage, of increasing metabolic rate, as part of the development of new British Army physical employment standards (PES). An ingestible gastrointestinal sensor was used to measure core temperature. Testing was completed in wet bulb globe temperature conditions; 1.2-12.6°C. Predictive accuracy and precision were analysed using individual and group mean inputs. Assessments were evaluated by bias, limits of agreement (LoA), mean absolute error (MAE), and root mean square error (RMSE). Accuracy was evaluated using a prediction bias of ± 0.27°C and by comparing predictions to the standard deviation of the actual core temperature. Results: Modelling individual predictions provided an acceptable level of accuracy based on bias criterion; where the total of all trials bias ± LoA was 0.08 ± 0.82°C. Predicted values were in close agreement with the actual data: MAE 0.37°C and RMSE 0.46°C for the collective data. Modelling using group mean inputs were less accurate than using individual inputs, but within the mean observed. Conclusion: The HSDA acceptably predicts core temperature during load carriage to the new British Army non-GCC PES, in temperate conditions

The neural correspondences associated with sleep deprivation in waking cognitive performance of military clearance divers

The aim of the present study was to investigate the effects of reduced sleep duration on Electroencephalogram (EEG) activity during cognitive performance tasks in Military Clearance Diver trainees, using a novel dry-electrode EEG system

External workload and cognitive performance of a tactical military scenario-based field exercise

Introduction: Military personnel must manage a multitude of competing physiological and cognitive stressors whilst maintaining high levels of performance. Quantifying the external workload and cognitive demands of tactical military field exercises closely simulating operational environments, will provide a better understanding of stressors placed on personnel to inform evidence-based interventions. Methods: Thirty-one soldiers completing a dismounted 48-hr tactical field exercise, participated in the study. External workload was quantified using a wrist-worn tri-axial accelerometer, with cognitive function (Go-/No-Go, N-back, Psychomotor Vigilance Task [PVT]) and subjective workload ratings (NASA-TLX) assessed pre-, mid- and post-exercise. Physical activity was described using Euclidian Norm Minus One (mg), with Moderate Vigorous Physical Activity (MVPA) and Sedentary Light Physical Activity (SLPA) as ≥ or <113 mg, respectively. Changes in general cognitive performance (total accuracy-speed trade-off (ASTO) % change) and function outcome variables (overall mean reaction time, ASTO and number of correct and missed responses) were calculated for each assessment from pre-, to mid- and post-exercise. Results: For the exercise duration (50:12 ± 02:06 hh:mm) participants spent more time completing SLPA compared to MVPA (1932±234 vs 1074±194 min; p<0.001), equating to 33% of the time spent completing MVPA. Overall cognitive performance decreased over the exercise (pre-to-post: -249). However, the largest decrement was observed pre-to-mid (-168). Perceived mental demand associated with the cognitive assessments significantly increased over the duration of the exercise (pre-: 33; mid-: 38 and post-: 51; χ2F(2) = 26.7, p = <0.001, W = 0.477) which could suggest that participants were able to attenuate a further declines in cognitive performance by investing more effort/ mental resources when completing assessments. Conclusion: The study successfully quantified the physical activity, and subsequent impact on cognitive function, in soldiers completing a 48-hr tactical field exercise. Further research is needed to better understand how physiological stressors interact with cognitive function during military operations