Kevin Netto

The Effect of Body Armor on Performance, Thermal Stress, and Exertion: A Critical Review

Armed forces worldwide utilize some form of body armor as part of their personal protective system. This is particularly essential in recent times because of the increased sophistication of weapons employed during modern warfare and the advent of unconventional combat methods (such as the increased use of improvised explosive devices). There is some evidence to show, however, that the usage of military body armor impairs physical performance. This review of the literature will focus on the effect of body armor on the performance of, and physiological and subjective responses during, military-style physical tasks. Because of the paucity of research investigating body armor, this review will also draw upon more generalized personal protective clothing and equipment literature from a range of physically demanding occupations (i.e., firefighting and other emergency services). The review will conclude with suggested directions for future research in this area.

Validity of a trunk-mounted accelerometer to assess peak accelerations during walking, jogging and running

Abstract The purpose of this study was to validate peak acceleration data from an accelerometer contained within a wearable tracking device while walking, jogging and running. Thirty-nine participants walked, jogged and ran on a treadmill while 10 peak accelerations per movement were obtained (n = 390). A single triaxial accelerometer measured resultant acceleration during all movements. To provide a criterion measure of acceleration, a 12-camera motion analysis (MA) system tracked the position of a retro-reflective marker affixed to the wearable tracking device. Peak raw acceleration recorded by the accelerometer significantly overestimated peak MA acceleration (P < 0.01). Filtering accelerometer data improved the relationship with the MA system (P < 0.01). However, only the 10 Hz and 8 Hz cut-off frequencies significantly reduced the errors found. The walk movement demonstrated the highest accuracy, agreement and precision and the lowest relative errors. Linear increases in error were observed for jog compared with walk and for run compared to both other movements. As the magnitude of acceleration increased, the strength of the relationship between the accelerometer and the criterion measure decreased. These results indicate that filtered accelerometer data provide an acceptable means of assessing peak accelerations, in particular for walking and jogging.

Validity of an upper-body-mounted accelerometer to measure peak vertical and resultant force during running and change-of-direction tasks.

This study assessed the validity of a tri-axial accelerometer worn on the upper body to estimate peak forces during running and change-of-direction tasks. Seventeen participants completed four different running and change-of-direction tasks (0°, 45°, 90°, and 180°; five trials per condition). Peak crania-caudal and resultant acceleration was converted to force and compared against peak force plate ground reaction force (GRF) in two formats (raw and smoothed). The resultant smoothed (10 Hz) and crania-caudal raw (except 180°) accelerometer values were not significantly different to resultant and vertical GRF for all running and change-of-direction tasks, respectively. Resultant accelerometer measures showed no to strong significant correlations (r = 0.00–0.76) and moderate to large measurement errors (coefficient of variation [CV] = 11.7–23.9%). Crania-caudal accelerometer measures showed small to moderate correlations (r = − 0.26 to 0.39) and moderate to large measurement errors (CV = 15.0–20.6%). Accelerometers, within integrated micro-technology tracking devices and worn on the upper body, can provide a relative measure of peak impact force experienced during running and two change-of-direction tasks (45° and 90°) provided that resultant smoothed values are used.

Classification of team sport activities using a single wearable tracking device

Wearable tracking devices incorporating accelerometers and gyroscopes are increasingly being used for activity analysis in sports. However, minimal research exists relating to their ability to classify common activities. The purpose of this study was to determine whether data obtained from a single wearable tracking device can be used to classify team sport-related activities. Seventy-six non-elite sporting participants were tested during a simulated team sport circuit (involving stationary, walking, jogging, running, changing direction, counter-movement jumping, jumping for distance and tackling activities) in a laboratory setting. A MinimaxX S4 wearable tracking device was worn below the neck, in-line and dorsal to the first to fifth thoracic vertebrae of the spine, with tri-axial accelerometer and gyroscope data collected at 100Hz. Multiple time domain, frequency domain and custom features were extracted from each sensor using 0.5, 1.0, and 1.5s movement capture durations. Features were further screened using a combination of ANOVA and Lasso methods. Relevant features were used to classify the eight activities performed using the Random Forest (RF), Support Vector Machine (SVM) and Logistic Model Tree (LMT) algorithms. The LMT (79-92% classification accuracy) outperformed RF (32-43%) and SVM algorithms (27-40%), obtaining strongest performance using the full model (accelerometer and gyroscope inputs). Processing time can be reduced through feature selection methods (range 1.5-30.2%), however a trade-off exists between classification accuracy and processing time. Movement capture duration also had little impact on classification accuracy or processing time. In sporting scenarios where wearable tracking devices are employed, it is both possible and feasible to accurately classify team sport-related activities.

Validation of a Trunk-mounted Accelerometer to Measure Peak Impacts during Team Sport Movements

This study assessed the validity of an accelerometer to measure impacts in team sports. 76 participants completed a team sport circuit. Accelerations were collected concurrently at 100 Hz using an accelerometer and a 36-camera motion analysis system. The largest peak accelerations per movement were compared in 2 ways: i) pooled together and filtered at 13 different cut-off frequencies (range 6-25 Hz) to identify the optimal filtering frequency, and ii) the optimal cut-off frequency split into the 7 movements performed (n=532). Raw and 25-16 Hz filtering frequencies significantly overestimated and 6 Hz underestimated motion analysis peak accelerations (P <0.007). The 12 Hz filtered accelerometer data revealed the strongest relationship with motion analysis data (accuracy - 0.01±0.27 g, effect size - 0.01, agreement - 0.55 to 0.53 g, precision 0.27 g, and relative error 5.5%; P=1.00). The accelerometer underestimated peak accelerations during tackling and jumping, and overestimated during walking, jogging, sprinting and change of direction. Lower agreement and reduced precision were associated with sprinting, jumping and tackling. The accelerometer demonstrated an acceptable level of concurrent validity compared to a motion analysis system when filtered at a cut-off frequency of 12 Hz. The results advocate the use of accelerometers to measure movements in team sport.

Validity and relevance of the pack hike wildland firefighter work capacity test: a review

Fighting wildland fire is a physically demanding occupation. Wildland firefighters need to be physically fit to work safely and productively. To determine whether personnel are fit for duty, many firefighting agencies employ physical competency tests, such as the pack hike test (PHT). The PHT involves a 4.83-km hike over level terrain carrying a 20.4-kg pack within a 45-min period. The PHT was devised to test the job readiness of US wildland firefighters but is also currently used by some fire agencies in Australia and Canada. This review discusses the history and development of the PHT with emphasis on the process of test validation. Research-based training advice for the PHT is given, as well as discussion of the risks associated with completing the PHT. Different versions and modifications to the PHT have emerged in recent years and these are discussed with regard to their validity. Finally, this review addresses the relevance and validity of the PHT for Australian and Canadian wildland firefighters. Statement of Relevance: This paper reviews the history, development and validity of the PHT, an internationally recognised and utilised wildland firefighter work capacity test. It is concluded that while the PHT has general content validity for US wildland firefighters, verification of its reliability, criterion and construct validity is still needed.

Validation of GPS and accelerometer technology in swimming

OBJECTIVES To evaluate the validity of an integrated accelerometer and Global Positioning System (GPS) device to quantify swimming kinematics variables in swimming. DESIGN Criterion validation study. METHODS Twenty-one sub-elite swimmers completed three 100 m efforts (one butterfly, breaststroke and freestyle) in an outdoor 50 m Olympic pool. A GPS device with an integrated tri-axial accelerometer was used to obtain mid-pool velocity and stroke count of each effort. This data was compared to velocity and stroke count data obtained from concurrently recorded digital video of the performance. RESULTS A strong relationship was detected between the accelerometer stroke count and the video criterion measure for both breaststroke (r>0.98) and butterfly (r>0.99). Also, no significant differences were detected between the GPS velocity and video obtained velocity for both freestyle and breaststroke. There was a significant difference between the GPS velocity and criterion measure for butterfly. Acceptable standard error and 95% limits of agreement were obtained for freestyle (0.13 m s(-1), 0.36 m s(-1)) and breaststroke (0.12 m s(-1), 0.33 m s(-1)) compared to butterfly (0.18 m s(-1), 0.50 m s(-1)). Relative error measurements ranged between 10.2 and 13.4% across the three strokes. CONCLUSIONS The integrated accelerometer and GPS device offers a valid and accurate tool for stroke count quantification in breaststroke and butterfly as well as measuring mid-pool swimming velocity in freestyle and breaststroke. The application of GPS technology in the outdoor training environment suggests advantageous practical benefits for swimmers, coaches and sports scientists.

Validating 'fit for duty' tests for Australian volunteer fire fighters suppressing bushfires.

INTRODUCTION This study compared fire fighters work-rates and performance between the Pack Hike Test (PHT), Field Walk Test (FWT) and critical bushfire suppression tasks. METHODS Nineteen volunteer fire fighters undertook the PHT, whilst a further 11 also performed the FWT. All 30 fire fighters completed four critical tasks. Physical, physiological and subjective ratings were measured during tasks and tests. RESULTS Peak and mean heart rate during the Hose Drag was lower than during the FWT. Mean velocities for the PHT and FWT were higher than in all tasks except Hose Drag. Finishing times in the PHT and FWT were strongly correlated with finishing times for three and four of the critical tasks. CONCLUSIONS The PHT and FWT may be valid fit for duty tests for Australian rural fire fighters though the clear differences between the tests and some tasks may prompt fire agencies to consider other tests that more accurately simulate bushfire suppression work.

Frequency, Intensity, Time And Type Of Tasks Performed During Wildfire Suppression

Objective: To quantify the frequency, intensity, duration, and type of tasks performed by Australian rural fire crews when suppressing wildfires. Methods: Twenty-eight Australian rural firefighters worked across four, six-hour shifts fighting to curtail the spread of wildfire. Each firefighter wore a heart rate monitor and personal global positioning system (GPS) unit and was followed by a researcher filming their work activity. Video footage of each firefighter was synchronized with their heart rate and GPS data to quantify the frequency, intensity and duration of individual fireground tasks. Fireground tasks were isolated using a previously conducted job task analysis. Results: Firefighters performed 32 distinct fireground tasks. Task frequencies ranged from once to 103 times per six-hour shift. Individual tasks lasted 4 ± 2 s to 461 ± 387 s, were performed at speeds ranging from 0.12 ± 0.08 m•s-1 to 0.79 ± 0.40 m•s-1 and elicited mean heart rates that ranged between 97 ± 16 beats•min-1 (55.7 ± 8.7 percentage of age-predicted maximum heart rate (HRmax)) and 157 ± 15 beats•min-1 (86.2 ± 10.8%HRmax). Conclusion: Fireground tasks were, generally speaking, shorter, slower, and elicited lower heart rates than equivalent tasks previously simulated and reported in the literature. The differences between naturally occurring and simulated tasks question the value of isolated task simulations for conducting physical demands analyses en-route to developing job-specific fitness tests.

Coronary heart disease risk in volunteer firefighters in Victoria, Australia

ABSTRACT Coronary heart disease (CHD) is a major problem for firefighters, even when considering the healthy worker effect (HWE). Although volunteer firefighters outnumber paid personnel, previous research has focused on paid US firefighters. By contrast, no CHD data for Australian firefighters exist. Risk factor data were collected from 2,943 Australian volunteer firefighters and CHD risk was compared with reference “low-risk” and Australian population data. Predicted CHD risk for male and female firefighter was 19.2% and 5.1%, respectively. Female firefighters high blood pressure and fasting glucose was significantly lower than the general population, whereas all other risk factors was similar to the general population. Firefighters’ CHD risk was greater than other volunteer and paid emergency services, but the prevalence for most risk factors was similar to the general population. Therefore, Australian volunteer firefighters may not benefit from the HWE.