Effects of combined strength and endurance training on body composition and physical fitness in soldiers during a 6-month crisis management operation

Abstract

The aim of this thesis was to study a) physical activity, workload and stress in soldiers, b) effects of combined strength and endurance training on body composition and physical performance, and c) training-induced changes in endurance performance during a 6-month crisis management operation in Lebanon. In addition, d) a novel military simulation test (MST) was used to study associations between physical fitness, body composition and occupational performance variables in soldiers. Ninety-one male soldiers voluntarily took part in the baseline measurements. Blood and saliva samples, multifrequency bioimpedance analyses, neuromuscular, endurance and military-specific performance tests, and physical activity recordings were performed on three occasions during the operation in Lebanon. After the baseline measurements, the soldiers were randomly allocated to either the control group or one of the three combined strength and endurance training groups, which included different ratios of strength and endurance training. The main results indicated that a) soldier physical workload and stress level were low during the operation and their hormonal profiles indicated a sufficient recovery state; b) soldiers provided with a training program were able to maintain or improve their fitness level in all measured physical performance variables during deployment, whereas muscular power of the lower extremities decreased in the control group; c) soldiers whose endurance performance decreased during the intervention were initially physically fitter, had more muscle mass and less fat mass than their counterparts who were able to maintain or improve their endurance performance. Furthermore, d) muscular power of the lower extremities, aerobic fitness and muscle mass were positively associated with a higher MST performance. To conclude, physical attributes affecting soldier readiness during high-intensity work include aerobic fitness, muscular power of the lower body and muscle mass. Several of these variables were susceptible to decline in soldiers who were initially fitter. Thus, individually designed combined strength and endurance training with proper periodization should be implemented for soldiers during deployment. Moreover, the volume of endurance training should be at least as high as each individual’s existing level prior to the operation to attenuate decrements in aerobic fitness and operational readiness.