Physical Activity during a 12 Days Military Field Training in Winter and the Effects on Muscular and Cardiorespiratory Fitness

The purpose of this study was to measure the amount of physical activity during a 12 days military winter training and to investigate whether the operation affects soldiers' muscular and cardiorespiratory fitness. The studied 12 days training was consisted of 6 days combat training followed by 6 days combat shooting training. Altogether 23 male jaegers served as test subjects. Each subject participated three times in a maximal oxygen consumption test (maxVO2) on a bicycle ergometer and in six muscle performance tests: maximal voluntary isometric knee extension (KE), static jump (SJ), counter movement jump (CMJ) and drop-jump (DJ) (40 cm bench) were performed on a contact mat, and for the measurements of mean anaerobic power (AP) subjects performed five consecutive CMJs; maximal isometric rotation of the wrist (WR) was also measured. The tests were carried out three days before the field operation (T1), at the 5th day of the operation (T2) and at the end of the operation (12th day, T3). Four of the subjects were also equipped with GPS recorders, which measured route, speed, distance, altitude and heart rate. The average daily temperature during training ranged from 0.5 °C to -11.8 °C. During combat phase the average speed of soldiers was 1.00 1.85 km/h. Duration of these operations ranged from 1:33 to 3:14 h, and they were 2.85 4.48 km long. During shooting training the values were 1.30 1.40 km/h, 1:45 2:21 h, and 2.55 3.21 km, respectively. During other activities on foot the average daily speed was 0.59 1.28 km/h. Resting period during night was on average 4:54 h. SJ increased and only WR declined on T2 and T3 in comparison to T1. Force production time during KE became significantly slower during T2 and T3 compared to T1. In cardiorespiratory fitness there was in relation to the first test a significant difference only in maximal heart rate. A slightly decreasing tendency was observed in other parameters. In conclusion, the studied winter operation had only minor effect on soldiers' maximal muscle performance, and no effects on maximal oxygen consumption, ventilation or ergometer work load. However, the significantly lower heart rate both in T2 and T3 in relation to T1 may reflect increased efficiency of cardiac function or increased plasma volume possibly due to the training. It seems that the studied training did not produce long term fatigue. Rintamäki, H.; Oksa, J.; Rissanen, S.; Mäkinen, T.; Kyröläinen, H.; Keskinen, O.; Kauranen, K.; Peitso, A. (2005) Physical Activity during a 12 Days Military Field Training in Winter and the Effects on Muscular and Cardiorespiratory Fitness. In Strategies to Maintain Combat Readiness during Extended Deployments – A Human Systems Approach (pp. 18-1 – 18-6). Meeting Proceedings RTO-MP-HFM-124, Paper 18. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. Physical Activity during a 12 Days Military Field Training in Winter and the Effects on Muscular and Cardiorespiratory Fitness 18 2 RTO-MP-HFM-124 1.0 INTRODUCTION Locomotion of soldiers on foot while carrying the garments, weapons and other equipments is the main component causing physical strain. Because of increased use of motorized all-terrain vehicles, locomotion on foot has decreased. However, the distance and speed of an individual soldier moving on foot in wintertime field operations are not well known. Therefore the purpose of this study was to quantify, how much and by which speed the soldiers are moving during a 12 days military winter training (Mäkinen et al. 2005). Cold environment can decrease physical performance by lowering tissue temperatures especially in the peripheral parts of the body, disturbing sleeping, causing hypohydration, changing endocrine responses and by increasing the physical strain of the tasks (e.g., Hackney et al., 1991, Hodgdon et al. 1991, D'Alesandro et al. 1992). Therefore we also investigated whether the winter training affects soldiers' muscular and cardiorespiratory fitness (Oksa et al. 2005, Rissanen et al. 2005). 2.0 MATERIAL AND METHODS The studied 12 days training was consisted of 6 days combat training followed by 6 days combat shooting training on December 2004. Altogether 23 male jaegers served as test subjects. Their physical characteristics were (mean ± SD): age 19.7 ± 0.7 years, height 176.4 ± 6.8 cm, weight 71.5 ± 9.9 kg and body fat 13.9 ± 2.6 %. Prior to the participation the subjects were briefed on the nature of the study and they gave a written consent to act as voluntary subjects. Each subject participated three times in a maximal oxygen consumption test (maxVO2) on a bicycle ergometer and in six muscle performance tests: maximal voluntary isometric knee extension (KE), static jump (SJ), counter movement jump (CMJ) and drop-jump (DJ) (40 cm bench) were performed on a contact mat, and for the measurements of mean anaerobic power (AP) subjects performed five consecutive CMJs; maximal isometric rotation of the wrist (WR) was also measured. The tests were carried out three days before the field training (T1), at the 5th day of the training (T2) and at the end of the training (12th day, T3). During the maxVO2-tests external load (starting from 75 W) was increased by 25 W every two minutes until exhaustion. Oxygen consumption and heart rate were measured continuously and maximal work load each subject was able to reach was recorded. Four jaegers (section leaders) were also equipped with GPS-recorders (FRWD Sport Performance Recorder. Finland), which measured route, speed, distance, altitude and heart rate, and stored the data with 5 sec. interval. During the 12 days training, measurements were done from day 1 (starting at 22 p.m.) to day 11 (ending at 19 p.m.). The recorders were changed twice a day to avoid battery exhaustion. The measurements were analysed to separate the locomotion performed on foot during combat and during other activities, by vehicle, and periods of rest.