Prediction of Core Body Temperature from Multiple Variables.

This paper aims to improve the prediction of rectal temperature (T re) from insulated skin temperature (T is) and micro-climate temperature (T mc) previously reported (Richmond et al., Insulated skin temperature as a measure of core body temperature for individuals wearing CBRN protective clothing. Physiol Meas 2013; 34:1531-43.) using additional physiological and/or environmental variables, under several clothing and climatic conditions. Twelve male (25.8±5.1 years; 73.6±11.5kg; 178±6cm) and nine female (24.2±5.1 years; 62.4±11.5kg; 169±3cm) volunteers completed six trials, each consisting of two 40-min periods of treadmill walking separated by a 20-min rest, wearing permeable or impermeable clothing, under neutral (25°C, 50%), moderate (35°C, 35%), and hot (40°C, 25%) conditions, with and without solar radiation (600W m(-2)). Participants were measured for heart rate (HR) (Polar, Finland), skin temperature (T s) at 11 sites, T is (Grant, Cambridge, UK), and breathing rate (f) (Hidalgo, Cambridge, UK). T mc and relative humidity were measured within the clothing. T re was monitored as the 'gold standard' measure of T c for industrial or military applications using a 10cm flexible probe (Grant, Cambridge, UK). A stepwise multiple regression analysis was run to determine which of 30 variables (T is, T s at 11 sites, HR, f, T mc, temperature, and humidity inside the clothing front and back, body mass, age, body fat, sex, clothing, Thermal comfort, sensation and perception, and sweat rate) were the strongest on which to base the model. Using a bootstrap methodology to develop the equation, the best model in terms of practicality and validity included T is, T mc, HR, and 'work' (0 = rest; 1 = exercise), predicting T re with a standard error of the estimate of 0.27°C and adjusted r (2) of 0.86. The sensitivity and specificity for predicting individuals who reached 39°C was 97 and 85%, respectively. Insulated skin temperature was the most important individual parameter for the prediction of T re. This paper provides novel information about the viability of predicting T c under a wide range of conditions, using predictors which can practically be measured in a field environment.

Physiological responses of Police Officers during job simulations wearing chemical, biological, radiological and nuclear personal protective equipment.

The aim of this study was to quantify the physiological responses of Police Officers wearing chemical, biological, radiological and nuclear personal protective equipment (CBRN PPE) during firearms house entry (FE) unarmed house entry (UE) and crowd control (CC) simulations. Participants volunteered from the UK Police Force [FE (n = 6, age 33 ± 4 years, body mass 85.3 ± 7.9 kg, (·)VO2max 53 ± 5 ml · kg⁻¹ · min⁻¹), UE and CC (n = 11, age 34 ± 5 years, body mass 88.5 ± 13.8 kg, (·)VO2max 51 ± 5 ml · kg⁻¹ · min⁻¹)]. Heart rate reserve (HRR) during FE was greater than UE (74 ± 7 vs. 62 ± 6%HRR, p = 0.01) but lower in CC (39 ± 7%HRR, p < 0.01). Peak core body temperature was greater during FE (39.2 ± 0.3°C) than UE (38.9 ± 0.4°C, p < 0.01) and CC (37.5 ± 0.3°C, p < 0.01), with similar trends in skin temperature. There were no differences in the volume of water consumed (1.13 ± 0.44 l, p = 0.51) or change in body mass (-1.68 ± 0.65 kg, p = 0.74) between simulations. The increase in body temperature was a primary physiological limitation to performance. Cooling strategies and revised operating procedures may improve Police Officers' physical performance while wearing CBRN PPE. PRACTITIONER SUMMARY: In recent years, the likelihood of Police Officers having to respond to a chemical, biological, nuclear or radiological (CBRN) incident wearing personal protective equipment (PPE) has increased. Such apparel is likely to increase physiological strain and impair job performance; understanding these limitations may help improve Officer safety and operational effectiveness.

Comparison of the physical demands of single-sex training for male and female recruits in the British Army.

This study compared the physical demands and progression of basic training for male and female British Army recruits in single-sex platoons. Thirty male and 30 female recruits were monitored for energy expenditure (EE) (doubly labeled water), physical activity (3-dimensional accelerometry) and cardiovascular strain (percent heart rate reserve) during 6 weeks over the 14-week course. First time pass rate was similar for male (60%) and female (57%) recruits. Average daily percent heart rate reserve (female 31 +/- 4%; male 32 +/- 5%), physical activity levels (female 2.2 +/- 0.2; male 2.3 +/- 0.2) and percentage improvements in 2.4-km run time (female 10 +/- 4%; male 10 +/- 5%) were similar for both sexes (p > 0.05), although male recruits had 12% higher physical activity counts (p < 0.01). Although the absolute physical demands of basic training were greater for male recruits, the relative cardiovascular strain experienced was similar between sexes.

Injuries and injury risk factors among British army infantry soldiers during predeployment training.

PURPOSE: This prospective cohort study examined injuries and injury risk factors in 660 British Army infantry soldiers during a predeployment training cycle. METHODS: Soldiers completed a questionnaire concerning physical characteristics, occupational factors, lifestyle characteristics (including physical training time) and previous injury. Direct measurements included height, body mass, sit-ups, push-ups and run time. Electronic medical records were screened for injuries over a 1-year period before operational deployment. Backward-stepping Cox regression calculated HR and 95% CI to quantify independent injury risk factors. RESULTS: One or more injuries were experienced by 58.5% of soldiers. The new injury diagnosis rate was 88 injuries/100 person-years. Most injuries involved the lower body (71%), especially the lower back (14%), knee (19%) and ankle (15%). Activities associated with injury included sports (22%), physical training (30%) and military training/work (26%). Traumatic injuries accounted for 83% of all injury diagnoses. Independent risk factors for any injury were younger age (17-19 years (HR 1.0), 20-24 years (HR 0.71, 95% CI 0.55 to 0.93), 25-29 years (HR 0.89, 95% CI 0.66 to 1.19) and 30-43 years (HR 0.41, 95% CI 0.27 to 0.63), previous lower limb injury (yes/no HR 1.49, 95% CI 1.19 to 1.87) and previous lower back injury (yes/no HR 1.30, 95% CI 1.03 to 1.63). CONCLUSION: British infantry injury rates were lower than those reported for US infantry (range 101-223 injuries/100 soldier-years), and younger age and previous injury were identified as independent risk factors. Future efforts should target reducing the incidence of traumatic injuries, especially those related to physical training and/or sports.

Influence of hydration volume and ambient temperature on physiological responses while wearing CBRN protective clothing.

This study examined a low (L; 5 ml/kg per h) and high (H, 10 ml/kg per h) rate of fluid replacement in moderate (18°C) and hot (30°C) conditions on physiological responses while wearing personal protective equipment (PPE). PPE included the gas-tight suit (GTS), the powered respirator protective suit (PRPS) and the civil responder 1 (CR1). Relative to the moderate condition, physiological responses were greater in the hot condition. The percentage change in body mass was different (p < 0.05) between L and H in the hot (L vs. H, GTS: -0.83 vs. -0.38%; PRPS: -1.18 vs. -0.71%; CR1: -1.62 vs. -0.57%) and moderate conditions, although in GTS and CR1 body mass increased (L vs. H, GTS: -0.48 vs. 0.06%; PRPS: -0.66 vs. -0.11%; CR1: -0.18 vs. 0.67%). Fluid replacement strategies for PPE should be adjusted for environmental conditions in order to avoid >1% body mass loss and/or net body mass gain. STATEMENT OF RELEVANCE: Currently, the UK Emergency Services do not have specific evidence-based fluid replacement guidelines to follow when wearing chemical, biological, radiological and/or nuclear (CBRN) PPE. Although ad libitum fluid replacement is encouraged (when breathing apparatus permits), recommendations from evidence-based findings specific to different PPE and to different environmental conditions are lacking. This study provides novel evidence supporting the need to develop fluid replacement strategies during CBRN deployments in both moderate and hot environmental conditions for CBRN PPE.

The effect of cool water ingestion on gastrointestinal pill temperature.

UNLABELLED: Telemetric gastrointestinal (GI) temperature pills are now commonly used to measure core body temperature and could minimize the risk of heat illness while maximizing operational effectiveness in workers subject to high levels of thermal strain. PURPOSE: To quantify the effect of repeated cool water ingestion on the accuracy of GI pill temperature. METHODS: Ten operational firefighters ingested a pill to measure GI temperature (T1int) before overnight sleep. Two hours following breakfast and 11.5 h after ingesting T1int, the firefighters ingested a second pill (T2int) before performing 8.5 h of intermittent activity (repetitive cycles of 30 min of seated rest followed by 30 min of general firefighter duties). During the first 2 min of each 30-min rest period, the firefighters consumed 250 mL of chilled water (5-8 degrees C). RESULTS: Water ingestion had a highly variable effect both within and between subjects in transiently (32 +/- 10 min) reducing the temperature of T2int in comparison with T1int. In general, this transient reduction in T2int became progressively smaller as time following ingestion increased. In some firefighters, the difference between T1int and T2int became negligible (+/- 0.1 degrees C) after 3 h, whereas in two others, large differences (peaking at 2.0 degrees C and 6.3 degrees C) were still observed when water was consumed 8 h after pill ingestion. CONCLUSION: These results show that a GI pill ingested immediately prior to physical activity cannot be used to measure core body temperature accurately in all individuals during the following 8 h when cool fluids are regularly ingested. This makes GI temperature measurement unsuitable for workers who respond to emergency deployments when regular fluid consumption is recommended operational practice.

Energy balance and physical demands during an 8-week arduous military training course.

This study assessed soldier's physical demands and energy balance during the Section Commanders' Battles Course (SCBC). Forty male soldiers were monitored during the 8-week tactics phase of the SCBC. Energy expenditure was measured using the doubly labeled water method. Cardiovascular strain (heart rate) and physical activity (using triaxial accelerometer) were also monitored. Average sized portions of meals were weighed, with all recipes and meals entered into a dietary analysis program to calculate the calorie content. Energy expenditure averaged 19.6 ± 1.8 MJ · d(-1) in weeks 2 to 3 and 21.3 ± 2.0 MJ · d(-1) in weeks 6 to 7. Soldiers lost 5.1 ± 2.6 kg body mass and body fat percent decreased from 23 ± 4% to 19 ± 5%. This average weight loss equates to an estimated energy deficit of 2.69 MJ · d(-1). The Army provided an estimated 14.0 ± 2.2 MJ · d(-1) in weeks 2 to 3 and 15.7 ± 2.2 MJ · d(-1) in weeks 6 to 7. Although this provision adheres to the minimum requirement of 13.8 MJ · d(-1) set by Army regulations, soldiers were in a theoretical 5.6 MJ · d(-1) energy deficit. The physical demands of SCBC were high, and soldiers were in energy deficit resulting in loss in body mass; primarily attributed to a loss in fat mass.

Relationship between the 2.4-km run and multistage shuttle run test performance in military personnel.

In the United Kingdom, all branches of the armed forces use 2.4-km run time and/or the 20-m multistage shuttle run test (MSRT) to assess the aerobic fitness of their personnel. This study quantified the relationship between these two tests in 156 army recruits and officer cadets (100 men and 56 women) to ensure equivalence in the required aerobic fitness standards. The 2.4-km run was performed on surfaced roads and tracks around the training establishment and the MSRT in a gymnasium. Ordinary least product regression was used to describe the relationship between average 2.4-km running speed (km · h(-1)) and the total number of shuttles completed on the U.K. version of the MSRT (r = 0.91, p < 0.01), showing MSRT shuttles = (9.708×2.4-km run speed) - 52.56, with a standard error of prediction of approximately 8 shuttles or 0.8 km · h(-1). The British Army 2.4-km run biannual fitness assessment standard for young men of 10:30 min:s equates to a MSRT score of 82 shuttles (level 10 and 1 shuttle) and for young women of 13:00 min:s equates to 56 shuttles (level 7 and 6 shuttles), with a standard error of estimate of approximately 8 shuttles.

Comparison of step-wise and ramp-wise incremental rowing exercise tests and 2000-m rowing ergometer performance.

PURPOSE: This study examined parameters derived from both an incremental step-wise and a ramp-wise graded rowing exercise test in relation to rowing performance. METHODS: Discontinuous step-wise incremental rowing to exhaustion established lactate threshold (LT), maximum oxygen consumption (VO(2maxSTEP)), and power associated with VO(2max) (W VO(2max)). A further continuous ramp-wise test was undertaken to derive ventilatory threshold (VT), maximum oxygen consumption (VO(2maxRAMP)), and maximum minute power (MMW). Results were compared with maximal 2000-m ergometer time-trial power. RESULTS: The strongest correlation with 2000-m power was observed for MMW (r = .98, P < .001), followed by W VO(2max) (r = .96; P < .001). The difference between MMW and W VO(2max) compared with the mean of MMW/W VO(2max) showed a widening bias with a greater difference coincident with greater power. However, this bias was reduced when expressed as a ratio term and when a baseline VO2 was accounted for. There were no differences (P = .85) between measures of VO(2maxSTEP) and VO(2maxRAMP); rather, the measures showed strong association (r = .97, P < .001, limits of agreement = -0.43 to 0.33 L/min). The power at LT and VT did not differ (P = .6), and a significant association was observed (r = .73, P = .001, limits of agreement = -54.3 to 20.2 W, SEE = 26.1). CONCLUSIONS: This study indicates that MMW demonstrates a strong association with ergometer rowing performance and thus may have potential as an influential monitoring tool for rowing athletes.

Development of an operational fitness test for the Royal Air Force.

Since 2002, the Royal Air Force (RAF) has been working towards developing role-related physical tests for use as an operational fitness test (OFT). The purpose of this study was to establish reliability of the OFT (comprising four tests), investigate gym-based tests as predictors of performance and establish performance standards. Fifty-eight RAF personnel performed the OFT on three occasions. A separate cohort carried out fitness and anthropometric tests before performing the OFT, by way of establishing performance predictors. Documented evidence and views of an expert panel were used to determine OFT standards. Reliability ranged from moderate to good for three tests, with one test (Dig) showing poor reliability. The 95% limits of agreement for the prediction models ranged from good to poor (6.7-34.2%). The prediction models were not sufficiently accurate to estimate confidently OFT performance, but could be used as a guide to quantify likely outcome and training needs.