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.

The 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 < 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 < 0.001) and MBT (1.0-8.8% [0.04-0.34 m]; all p < 0.05) and MTP (4.5-26.9% [6.5-28.8 kg]; all p < 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 < 0.001, η p 2 $$ {\eta}_{\mathrm{p}}^2 $$ > 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.

Cognitive, Psychophysiological, and Perceptual Responses to a Repeated Military-Specific Load Carriage Treadmill Simulation.

BACKGROUND: Dismounted military operations require soldiers to complete cognitive tasks whilst undertaking demanding and repeated physical taskings. OBJECTIVE: To assess the effects of repeated fast load carriage bouts on cognitive performance, perceptual responses, and psychophysiological markers. METHODS: Twelve civilian males (age, 28 ± 8 y; stature, 186 ± 6 cm; body mass 84.3 ± 11.1 kg; V̇O2max, 51.5 ± 6.4 mL·kg-1·min-1) completed three ∼65-min bouts of a Fast Load Carriage Protocol (FLCP), each interspersed with a 65-min recovery period, carrying a representative combat load of 25 kg. During each FLCP, cognitive function was assessed using a Shoot/Don't-Shoot Task (SDST) and a Military-Specific Auditory N-Back Task (MSANT), along with subjective ratings. Additional psychophysiological markers (heart rate variability, salivary cortisol, and dehydroepiandrosterone-sulfate concentrations) were also measured. RESULTS: A main effect of bout on MSANT combined score metric (p < .001, Kendall's W = 69.084) and for time on the accuracy-speed trade-off parameter of the SDST (p = .025, Ñ 2 = .024) was evident. These likely changes in cognitive performance were coupled with subjective data indicating that participants perceived that they increased their mental effort to maintain cognitive performance (bout: p < .001, Ñ 2 = .045; time: p < .001, Ñ 2 = .232). Changes in HRV and salivary markers were also evident, likely tracking increased stress. CONCLUSION: Despite the increase in physiological and psychological stress, cognitive performance was largely maintained; purportedly a result of increased mental effort. APPLICATION: Given the likely increase in dual-task interference in the field environment compared with the laboratory, military commanders should seek approaches to manage cognitive load where possible, to maintain soldier performance.

Association between external training loads and injury incidence during 44 weeks of military training.

Military training is physically arduous and associated with high injury incidence. Unlike in high-performance sport, the interaction between training load and injury has not been extensively researched in military personnel. Sixty-three (43 men, 20 women; age 24 ± 2 years; stature 1.76 ± 0.09 m; body mass 79.1 ± 10.8 kg) British Army Officer Cadets undergoing 44 weeks of training at the Royal Military Academy Sandhurst volunteered to participate. Weekly training load (cumulative 7-day moderate-vigorous physical activity [MVPA], vigorous PA [VPA], and the ratio between MVPA and sedentary-light PA [SLPA; MVPA:SLPA]) was monitored using a wrist-worn accelerometer (GENEActiv, UK). Self-report injury data were collected and combined with musculoskeletal injuries recorded at the Academy medical center. Training loads were divided into quartiles with the lowest load group used as the reference to enable comparisons using odds ratios (OR) and 95% confidence intervals (95% CI). Overall injury incidence was 60% with the most common injury sites being the ankle (22%) and knee (18%). High (load; OR; 95% CI [>2327 mins; 3.44; 1.80-6.56]) weekly cumulative MVPA exposure significantly increased odds of injury. Similarly, likelihood of injury significantly increased when exposed to low-moderate (0.42-0.47; 2.45 [1.19-5.04]), high-moderate (0.48-0.51; 2.48 [1.21-5.10]), and high MVPA:SLPA loads (>0.51; 3.60 [1.80-7.21]). High MVPA and high-moderate MVPA:SLPA increased odds of injury by ~2.0 to 3.5 fold, suggesting that the ratio of workload to recovery is important for mitigating injury occurrence.

Nutrition and Physical Activity During British Army Officer Cadet Training: Part 1-Energy Balance and Energy Availability.

Military training is characterized by high daily energy expenditures which are difficult to match with energy intake, potentially resulting in negative energy balance (EB) and low energy availability (EA). The aim of this study was to quantify EB and EA during British Army Officer Cadet training. Thirteen (seven women) Officer Cadets (mean ± SD: age 24 ± 3 years) volunteered to participate. EB and EA were estimated from energy intake (weighing of food and food diaries) and energy expenditure (doubly labeled water) measured in three periods of training: 9 days on-camp (CAMP), a 5-day field exercise (FEX), and a 9-day mixture of both CAMP and field-based training (MIX). Variables were compared by condition and gender with a repeated-measures analysis of variance. Negative EB was greatest during FEX (-2,197 ± 455 kcal/day) compared with CAMP (-692 ± 506 kcal/day; p < .001) and MIX (-1,280 ± 309 kcal/day; p < .001). EA was greatest in CAMP (23 ± 10 kcal·kg free-fat mass [FFM]-1·day-1) compared with FEX (1 ± 16 kcal·kg FFM-1·day-1; p = .002) and MIX (10 ± 7 kcal·kg FFM-1·day-1; p = .003), with no apparent difference between FEX and MIX (p = .071). Irrespective of condition, there were no apparent differences between gender in EB (p = .375) or EA (p = .385). These data can be used to inform evidenced-based strategies to manage EA and EB during military training, and enhance the health and performance of military personnel.

Nutrition and Physical Activity in British Army Officer Cadet Training Part 2-Daily Distribution of Energy and Macronutrient Intake.

Dietary intake and physical activity impact performance and adaptation during training. The aims of this study were to compare energy and macronutrient intake during British Army Officer Cadet training with dietary guidelines and describe daily distribution of energy and macronutrient intake and estimated energy expenditure. Thirteen participants (seven women) were monitored during three discrete periods of military training for 9 days on-camp, 5 days of field exercise, and 9 days of a mixture of the two. Dietary intake was measured using researcher-led food weighing and food diaries, and energy expenditure was estimated from wrist-worn accelerometers. Energy intake was below guidelines for men (4,600 kcal/day) and women (3,500 kcal/day) during on-camp training (men = -16% and women = -9%), field exercise (men = -33% and women = -42%), and combined camp and field training (men and women both -34%). Carbohydrate intake of men and women were below guidelines (6 g·kg-1·day-1) during field exercise (men = -18% and women = -37%) and combined camp and field training (men = -33% and women = -39%), respectively. Protein intake was above guidelines (1.2 kcal·kg-1·day-1) for men and women during on-camp training (men = 48% and women = 39%) and was below guidelines during field exercise for women only (-27%). Energy and macronutrient intake during on-camp training centered around mealtimes with a discernible sleep/wake cycle for energy expenditure. During field exercise, energy and macronutrient intake were individually variable, and energy expenditure was high throughout the day and night. These findings could be used to inform evidenced-based interventions to change the amount and timing of energy and macronutrient intake around physical activity to optimize performance and adaptations during military training.

Monitoring work and training load in military settings - what's in the toolbox?

Military personnel are required to complete physically demanding tasks when performing work and training, which may be quantified through the physical stress imposed (external load) or the resultant physiological strain (internal load). The aim of this narrative review is to provide an overview of the techniques used to monitor work and training load in military settings, summarise key findings, and discuss important practical, analytical, and conceptual considerations. Most investigations have focused upon measuring external and internal load in military training environments; however, limited data exist in operational settings. Accelerometry has been the primary tool used to estimate external load, with heart rate commonly used to quantify internal load. Supplemental to heart rate, psychophysiological and biochemical measures have also been investigated to elucidate aspects of internal load. Broadly, investigations have revealed that military training requires personnel to perform relatively large volumes of physical activity (e.g. averaging ∼15,000 steps·day-1) of typically low-moderate intensity activity (<6 MET), although considerable temporal and inter-individual variability is observed from these gross mean estimates. There are limitations associated with these measures and, at best, estimates of external and internal load can only be inferred. These limitations are particularly pertinent for military tasks such as load carriage and manual material handling, which often involve complex activities performed individually or in teams, in a range of operational environments, with multiple layers of protection, over a protracted duration. Comprehensively quantifying external and internal loads during these functional activities poses substantial practical and analytical challenges.

Development of physical employment standards of specialist paramedic roles in the National Ambulance Resilience Unit (Naru).

AIM: To develop evidence-based role-specific physical employment standards and tests for National Ambulance Resilience Unit (NARU) specialist paramedics. METHODS: Sixty-two (53 men, 9 women) paramedics performed an array of (1) realistic reconstructions of critical job-tasks (criterion job performance); (2) simplified, easily-replicable simulations of those reconstructions and; (3) fitness tests that are portable and/or practicable to administer with limited resources or specialist equipment. Pearson's correlations and ordinary least products regression were used to assess relationships between tasks and tests. Performance on reconstructions, subject-matter expert and participant ratings were combined to derive minimum acceptable job performance levels, which were used to determine cut-scores on appropriate correlated simulations and tests. RESULTS: The majority of performance times were highly correlated with their respective simulations (range of r: 0.73-0.90), with the exception of those replicating water rescue (r range: 0.28-0.47). Regression compatibility intervals provided three cut-scores for each job-task on an appropriate simulation and fitness test. CONCLUSION: This study provides a varied and easily-implementable physical capability assessment for NARU personnel, empirically linked to job performance, with flexible options depending on organisational requirements.

Implementation of Physical Employment Standards for Physically Demanding Occupations.

OBJECTIVE: The aim of this paper was to describe an approach to implementing and integrating physical employment standards into an organizational procedure, to ensure the safe and effective supervision of physical fitness of workers in a physically demanding occupation, using a real-world example. METHODS: Using previously published cardiorespiratory, muscular strength, and endurance physical demands data from UK firefighters, a process to manage all levels of physical capability was developed with industry stakeholders. RESULTS: Performance standards and associated cut-scores relating to acceptable, uncertain, and unacceptable job performance, using a traffic-light style process, were agreed by stakeholders to ensure the safe and effective management of incumbent's physical fitness. CONCLUSIONS: This paper describes the processes involved in implementing a physical capability management procedure, for the administration of routine in-service physical employment standards and tests in the UK Fire & Rescue Service.

Validity of energy expenditure estimation methods during 10 days of military training.

Wearable physical activity (PA) monitors have improved the ability to estimate free-living total energy expenditure (TEE) but their application during arduous military training alongside more well-established research methods has not been widely documented. This study aimed to assess the validity of two wrist-worn activity monitors and a PA log against doubly labeled water (DLW) during British Army Officer Cadet (OC) training. For 10 days of training, twenty (10 male and 10 female) OCs (mean ± SD: age 23 ± 2 years, height 1.74 ± 0.09 m, body mass 77.0 ± 9.3 kg) wore one research-grade accelerometer (GENEActiv, Cambridge, UK) on the dominant wrist, wore one commercially available monitor (Fitbit SURGE, USA) on the non-dominant wrist, and completed a self-report PA log. Immediately prior to this 10-day period, participants consumed a bolus of DLW and provided daily urine samples, which were analyzed by mass spectrometry to determine TEE. Bivariate correlations and limits of agreement (LoA) were employed to compare TEE from each estimation method to DLW. Average daily TEE from DLW was 4112 ± 652 kcal·day-1 against which the GENEActiv showed near identical average TEE (mean bias ± LoA: -15 ± 851 kcal. day-1 ) while Fitbit tended to underestimate (-656 ± 683 kcal·day-1 ) and the PA log substantially overestimate (+1946 ± 1637 kcal·day-1 ). Wearable physical activity monitors provide a cheaper and more practical method for estimating free-living TEE than DLW in military settings. The GENEActiv accelerometer demonstrated good validity for assessing daily TEE and would appear suitable for use in large-scale, longitudinal military studies.

Validity and Reliability of Firefighting Simulation Test Performance.

OBJECTIVE: To assess the validity and reliability of a firefighting simulation test (FFST). METHODS: Sixty-nine operational firefighters completed a best-effort FFST on one occasion and 22 participants completed a further FFST. All participants completed a maximal treadmill test to determine cardiorespiratory fitness (VO2max). RESULTS: Time to complete the FFST demonstrated a strong inverse relationship with VO2max (r = -0.73), although the prediction error was high. Reliability of the FFST was high (r = 0.84, P = 0.01), demonstrating a coefficient of variation of 4.5%. CONCLUSIONS: The FFST demonstrated reasonable validity as a surrogate assessment of cardiorespiratory fitness for firefighting. The FFST also demonstrated good reliability. Given the apparent magnitude of the prediction error, the FFST would be best used as a training tool, rather than as a primary means of assessing cardiorespiratory fitness for firefighting.

Physical and Physiological Performance Determinants of a Firefighting Simulation Test.

OBJECTIVE: To examine determinants of firefighting simulation test performance. METHODS: Sixty-eight (63 male; 5 female) firefighters completed a firefighting simulation (eg, equipment carry, casualty evacuation) previously validated to test occupational fitness among UK firefighters. Multiple linear regression methods were used to determine physiological and physical attributes that best predicted completion time. RESULTS: Mean (±SD) time taken to complete the simulation was 610 (±79) seconds. The prediction model combining absolute cardiorespiratory capacity (L min) and fat mass explained the greatest variance in performance and elicited the least random error (R = 0.765, R = 0.585, standard error of the estimate [SEE]: ±52 seconds). Higher fitness and lower fat mass were associated with faster performance. CONCLUSIONS: Firefighter simulation test performance is associated with absolute cardiorespiratory fitness and fat mass. Fitter and leaner individuals perform the task more quickly. Work-based interventions should enhance these attributes to promote safe and effective operational performance.

Physical Employment Standards for UK Firefighters: Minimum Muscular Strength and Endurance Requirements.

OBJECTIVE: The aim of this study was to assess sensitivity and specificity of surrogate physical ability tests as predictors of criterion firefighting task performance and to identify corresponding minimum muscular strength and endurance standards. METHODS: Fifty-one (26 male; 25 female) participants completed three criterion tasks (ladder lift, ladder lower, ladder extension) and three corresponding surrogate tests [one-repetition maximum (1RM) seated shoulder press; 1RM seated rope pull-down; repeated 28 kg seated rope pull-down]. Surrogate test standards were calculated that best identified individuals who passed (sensitivity; true positives) and failed (specificity; true negatives) criterion tasks. RESULTS: Best sensitivity/specificity achieved were 1.00/1.00 for a 35 kg seated shoulder press, 0.79/0.92 for a 60 kg rope pull-down, and 0.83/0.93 for 23 repetitions of the 28 kg rope pull-down. CONCLUSIONS: These standards represent performance on surrogate tests commensurate with minimum acceptable performance of essential strength-based occupational tasks in UK firefighters.

A Task Analysis Methodology for the Development of Minimum Physical Employment Standards.

OBJECTIVE: The aim of this study was to develop a systematic task analysis process for determination of minimum acceptable job performance in arduous safety-related occupations. METHODS: A task analysis using modifications on established methods was completed in UK firefighters. Subject-matter experts (all male) identified critical, physically arduous tasks generic to all UK firefighters and developed individual, role-specific task simulations. Video footage and blinded voting were used to determine minimum acceptable task performance. RESULTS: Eight tasks were identified in combination with role-specific variations, task simulations suitable for use in a physical demands analysis, and corresponding minimum acceptable performance. CONCLUSIONS: The bespoke steps highlighted here allow structured identification of task-specific minimum performance standards and simulations from which physical employment standards could be based. However, including a more divergent expert panel with respect to age, sex, and race would strengthen the applicability of this framework in future practice.