Concurrent Resistance and Aerobic Training Improve Physical Fitness in Sedentary Thai University Students: A 12-Week Intervention Study

Physical inactivity among university students is a growing public health concern, as academic demands and lifestyle transitions promote sedentary behavior and elevated cardiometabolic risk. Although combined resistance and aerobic training improve health-related fitness, evidence in student populations remains limited. This randomized controlled trial examined the effects of a 12-week combined training program on body composition, muscular strength, and VO2max in sedentary university students at Nakhon Phanom University, Thailand. Twenty-four participants were randomly assigned to experimental or control groups. The experimental group performed structured resistance and aerobic exercise three times weekly, while controls maintained habitual routines. BMI, skinfold thickness, upper- and lower-limb muscular strength, and VO2max were assessed at baseline, week 6, and week 12 using repeated-measures ANOVA, with effect sizes reported as partial eta-squared (η2) and Cohen's d; post hoc power analysis assessed sample size adequacy. At week 12, the experimental group showed significantly greater upper-body strength (F = 23.50, p = 0.001, η2 = 0.25, d = 0.95), lower-body strength (F = 4.36, p = 0.05, η2 = 0.06, d = 0.48), and VO2max (MD = +3.71 ml/kg/min; F = 4.63, p = 0.04, η2 = 0.06, d = 0.49) than controls. Within the experimental group, lower-body strength improved significantly (F = 4.00, p = 0.03, η2 = 0.20, d = 1.26); VO2max rose 12.1% (d = 0.81) and arm strength improved substantially (d = 0.73), though neither reached significance, reflecting insufficient power (1−β = 0.320-0.399) rather than a true null effect. Body composition (BMI, skinfold thickness) showed no significant change in either group (η2 = 0.01; 1−β = 0.065-0.142), with a slight, non-significant unfavorable trend in experimental-group subcutaneous fat (d = −0.24), possibly reflecting dietary compensation. These findings support incorporating concurrent training into university physical education to enhance muscular strength and cardiorespiratory fitness in sedentary students. However, meaningful body composition change likely requires longer interventions (16 weeks or more) with dietary control. Future studies should use larger samples (n ≥ 30 per group) for adequate power on moderate effect-size outcomes.