Effect of high-intensity circuit training on obesity indices, physical fitness, and browning factors in inactive female college students

The recently discovered myokines, irisin and fibroblast growth factor-21, have emerged beneficial for metabolic health due to their role in regulating browning. This study examined the effects of high-intensity circuit training on obesity indices, physical fitness, and irisin and fibroblast growth factor-21 levels in inactive female college students. Ten female college students performed high-intensity circuit training (jogging, stretching, squat jumps, arm walking and push-ups, lunge jumps, burpee test, mountain climbers, side steps, and crunches and side crunches exercises). The exercise program consisted of 40 min of circuit training at 60%-80% hear rate reserve and was conducted 3 times per week for 4 weeks. The body composition, physical fitness, and concentration of plasma irisin and fibroblast growth factor-21 were analyzed before and after the exercise. The body weight (P=0.001), waist circumference (P=0.003), and body fat percentage (P=0.003) decreased, while the muscular strength (handgrip strength test, P=0.030; sit-ups test, P=0.024) and cardiorespiratory fitness (P=0.001) increased after the exercise program. However, there were no significant changes in the irisin and fibroblast growth factor-21 levels. These results suggest that high-intensity circuit training could be the ideal type of exercise in inactive female college students to induce a positive change in the obesity indices and physical fitness. Further studies are needed to determine the effects of exercise on the browning factors.