Effect of regulated military training on physical performance and body composition of Swedish soldiers

Introduction Military service places high physical demands on conscripts, requiring adequate aerobic capacity, strength, power, and body composition. This study examined longitudinal changes in body composition and physical performance among Swedish conscripts during military training. Methods A total of 218 Swedish conscripts completed 12 weeks of Basic Military Training (BMT) followed by 32 weeks of Specialized Military Training (SMT). Physical assessments were conducted at baseline, after BMT, and after SMT. Outcomes included aerobic capacity (V̇O₂peak), muscular strength and power, multitest performance, and body composition measured using bioelectrical impedance analysis. Results BMT elicited marked improvements in endurance, with V̇O₂peak increasing by 6.4%. By the end of service, V̇O₂peak had increased by 9.8% overall. Multitest performance improved by 35% across the full training period, with most gains occurring during BMT. Lower-body power showed modest unilateral improvements. Body composition changes included increased skeletal muscle mass and reduced body fat. Discussion Military training substantially improved aerobic fitness and overall physical performance, particularly during the initial BMT phase. However, improvements in muscle mass and power were limited. These findings highlight the need for training strategies that better optimize physical readiness and reduce fatigue-related risk during modern military operations.