Our objective was to determine the effects of high-intensity interval training (HIT) on fitness in Army Reserve Officers' Training Corps cadets. Twenty-six college-aged (20.5 ± 1.7 years) participants completed 4 weeks of exercise training 3 days∙wk−1 consisting of either approximately 60 minutes of typical physical training or HIT wholebody calisthenics involving 4 to 7 sets of 30-second “all out” burpees separated by 4 minutes of active recovery. Several pre- and postintervention fitness variables were compared. We observed no changes across time or differences between groups in aerobic capacity, anaerobic capacity, or Army Physical Fitness Test performance (p > 0.05). However, there was a significant Group × Time interaction (p = 0.015) for skeletal muscle mitochondrial function (Tc: time constant of recovery). For the typical physical training group, we observed improved mitochondrial function (Tc decreased 2.4 ± 4.6 seconds; Cohen’s d = −0.51); whereas, mitochondrial function decreased in HIT (Tc increased 2.4 ± 4.6 seconds; d = 0.50). HIT sustained fitness despite the short duration and reduced volume of activity. A program that includes HIT as part of a larger program may be well suited for maintaining fitness in moderately trained armed forces personnel without access to equipment.