Lilian Roos

Hair cortisol concentration is unaffected by basic military training, but related to sociodemographic and environmental factors

Abstract The analysis of hair cortisol concentrations (HCC) is a promising new biomarker for retrospective measurement of chronic stress. The effect of basic military training (BMT) on chronic stress has not yet been reported. The aim of this study was to investigate the effect of 10-week BMT on HCC, while further exploring the role of known and novel covariates. Young healthy male recruits of the Swiss Army participated twice, 10 weeks apart, in data collection (1st examination: n = 177; 2nd examination: n = 105). On two occasions, we assessed HCC, perceived stress and different candidate variables that may affect HCC (e.g. socioeconomic status, meteorological data). Military training increased perceived stress from the first to the second examination, but did not affect HCC. In line with this, there was no correlation between HCC and perceived stress ratings. This could be interpreted as a missing influence of mainly physical stress (e.g. exercise) on HCC. In contrast, significant correlations were found between HCC and ambient temperature, humidity and education. Future studies should control for meteorological data and educational status when examining HCC.

Adapted marching distances and physical training decrease recruits' injuries and attrition

There is evidence that progressive loading of physical demands at the beginning of basic military service and specific physical training can reduce injury incidences. Therefore, aim of this study was to measure the effects of a progressive increase in marching distances and an adapted physical training program on injury incidence and attrition rate in a Swiss Army infantry training school. One company reduced the distances covered on foot during the first 4 weeks of basic military training. A second company performed an adapted physical training program for 10 weeks. A third company participated in both interventions combined, and a fourth company served as a control group without any intervention. The injury incidences and attrition rates of 651 male recruits were registered during 21 weeks of military service. Several predictor variables for injury and attrition, such as physical fitness, previous injuries, level of previous physical activity, smoking, motivation, and socioeconomic factors, were assessed as well. The data were analyzed using binary logistic backward regressions. Each intervention separately had a favorable effect on injury prevention. However, combining the 2 interventions resulted in the greatest reduction in injury incidence rate (-33%). Furthermore, the adapted physical training successfully reduced the military service attrition rates (-53%).

Musculoskeletal Injuries and Training Patterns in Junior Elite Orienteering Athletes

Findings about the relation between musculoskeletal injuries and training patterns in orienteering athletes are sparse. Therefore, the musculoskeletal injuries and training patterns of 31 Swiss elite orienteering athletes aged 18-19 years were analyzed in a retrospective study. Individual training diaries and medical records were used to assess training data and injury history, respectively. Group comparisons and a multiple linear regression (MLR) were performed for statistical analysis. The junior elite orienteering athletes performed 7.38 ± 2.00 training sessions weekly, with a total duration of 455.75 ± 98.22 minutes. An injury incidence rate (IIR) of 2.18 ± 2.13 injuries per 1000 hours of training was observed. The lower extremity was affected in 93% of all injuries, and the knee (33%) was the most commonly injured location. The MLR revealed that gender and six training variables explained 60% of the variance in the injury severity index in this study. Supported by the low IIR in the observed age group, the training protocol of the junior elite orienteering athletes was generally adequate. In comparison to elite track, marathon, and orienteering athletes, the junior elite athletes performed less high-intensity interval training (HIIT). However, more frequent HIIT seems to be a protective factor against injuries.

The Wearing Comfort and Acceptability of Ambulatory Physical Activity Monitoring Devices in Soldiers

OCCUPATIONAL APPLICATIONS We investigated the wearing comfort of nine devices for monitoring physical activity in a military context. In general, the questionnaire-based survey revealed that the devices were highly acceptable. For long-term monitoring of physical activity in soldiers (>5 days), slightly more participants (85.2%) found that sensors not located at the chest would be more acceptable compared to the chest-worn devices (66.7%). More specifically, our results suggest that devices placed on or around the upper arm, the hip, or the shoe will be preferred over devices worn around the wrist or on or around the chest in a military context. The placement of physical activity monitoring devices around the chest, in particular, can be expected to lead to discomfort due to incompatibilities with military equipment. TECHNICAL ABSTRACT Background: Military organizations use body-worn devices for ambulatory monitoring of physical activity in soldiers. However, little is known regarding the wearing comfort and acceptability of ambulatory monitoring devices as used in the military context. Purpose: To investigate the wearing comfort and acceptability of nine body-worn devices for monitoring physical activity in soldiers. Methods: A total of 27 male volunteers wore three randomly assigned devices simultaneously for one day of basic military training. The participants then completed a questionnaire designed to assess comfort and acceptability. Results: Devices worn on or around the chest were associated with lower wearing comfort and acceptability scores (overall scores of 59.7, 70.8, and 80.9 for Hidalgo EQ02, TICKR X, and ActiHeart, respectively). Devices worn around the wrist, Mio FUSE (80.9), GENEActiv (81.3), and fēnix 3 (85.3), had mid-range scores. The highest scores were obtained for the devices Blue Thunder, worn on the shoe (85.5), Axiamote PADIS 2.0, worn on the hip and the backpack (88.9), and Everion, worn on the upper arm (90.1). Conclusions: Body-worn devices for monitoring physical activity are well-accepted in soldiers. The differences between the devices were small for several parameters. Nevertheless, devices that are attached to, or around, the chest, were typically perceived as having a slightly more negative impact on the body. Both wrist- and chest-worn devices received some reports of interfering with military equipment or military tasks.

An evaluation of measurement systems estimating gait speed during a loaded military march over graded terrain

This study aimed to evaluate the accuracy of three measurement systems estimating gait speed during a loaded military march over graded terrain. Systems developed by the Swiss and Netherlands Armed Forces and a commercial wrist-based device were evaluated in comparison to a Global Positioning System. The first part of the paper focuses on the development of the Dutch system, where speed is estimated from a chest worn accelerometer and body measurements. For this validation study 36 subjects were walking or running 13 laps of 200 m at different speeds. Results showed that walking and running speed can be estimated with a R2adj of 0.968 and 0.740, respectively. In the second part of this paper, data from 64 soldiers performing a 35 km march were used to evaluate the accuracy of three measurement systems in estimating speed. Data showed that estimating gait speed with a single accelerometer can be accurate for military activity, even without prior individual calibration measurements. However, predictions should be corrected for confounders such as body size and shoe type to be accurate. Both, downhill and uphill walking led to changes in gait characteristics and to an overestimation of speed by up to 10%. Correcting for slope or gradient using altimetry in future algorithms/experiments could improve the estimation of gait speed.