ACTN-3 Genotype, Body Composition, Fitness, and +G_z Tolerance in Senior Cadets

BACKGROUND: This study aimed to investigate the relationships among ACTN-3, body composition, fitness, and +G_z tolerance for senior cadet training development and their safe task performance.METHODS: The subjects were all senior cadets (N = 68) at the Korea Air Force Academy. All cadets are required to pass a physical fitness test (3-km running, sit-ups, push-ups) and body composition test on a semiannual basis. Isokinetic muscle function (strength and endurance), +G_z test (+6 G_z ⋅ 30 s^-1), and target gene (ACTN-3) were analyzed.RESULTS: The effects of body composition and physical fitness along with the relationship of the ACTN-3 genotype to the +6 G_z test results were determined. Consequently, no significant difference was found concerning the effect of ACTN-3 on the +6 G_z test result, body composition, and physical fitness; however, body fat (%) and isokinetic muscle strength (peak torque right leg extension and left leg flexion) showed significance between the pass and failure groups in the +G_z test.DISCUSSION: The cadets of the Korea Air Force Academy showed dominant fast genetic expression type based on their ACTN-3 genotype [RR and RX (N = 51, 75%) > XX (N = 17, 25%)]. Body fat (%) and isokinetic muscle strength (PT R EX, L FL) can be more effective predictors in the +6 G_z test for cadet training. Another speculation is that more RR- and RX-type-oriented training can promote cadets' G_z tolerance from the isokinetic factors such as high peak torque and low fatigue index.Shin S, Jee H. ACTN-3