This study compares the effects of two aerobic exercise methods - loaded step-up exercise and treadmill running - on cardiovascular fitness, leg strength, heart rate variability, and recovery in sedentary adult males. Both exercise groups will train at 80-85% of maximum heart rate, three sessions per week for six weeks. A control group will not participate in any training. Measurements of estimated VO₂max, isometric leg strength, resting heart rate, heart rate variability indices, and heart rate recovery will be taken before and after the intervention.