Fitness Changes Among Military Personnel Enrolled In A 6-month High Intensity Functional Training Exercise Trial

Abstract

PURPOSE: Improving and sustaining high fitness is important for United States (US) military personnel. Current Army Physical Readiness Training (APRT) has been criticized for subpar fitness preparation; concurrently significant grass roots participation in high intensity functional training (HIFT) programs has occurred. Neither has been tested in a randomized clinical trial (RCT) among military personnel, which was the purpose of this study. METHODS: Data are from protocol adherent participants (N = 59) of a 5-year cluster-RCT among active duty US military personnel. Participants were randomized in small groups to 6-months of training in APRT (n = 26; 38.5% women, 85% Officers, age 33.3 ± 5.3 yrs) or HIFT (n = 33; 21.2% women, 73% Officers, age 34.2 ± 6.6 yrs) 5 days/wk for approximately 60 minute sessions. APRT used the reset phase and the HIFT program was also ramped to increase in exercise complexity and intensity over time. At baseline and 6-months, participants completed fitness tests including the Army Physical Fitness Test (i.e., 2 min of push-ups, 2 min of sit-ups, 2 mile run), 1 rep max (1RM) deadlift, max reps pull-ups, horizontal jump, and timed dummy drag (165-lb). Within-groups analyses were conducted by sex using a single group t-test comparing change scores to no effect. A mixed effect model was conducted for between-group fitness changes. RESULTS: Within-group changes were statistically significant in APRT men for pull-ups (1.9 ± 2.4 reps; t = 2.99, p = .01), 1RM deadlift (23.3 ± 19.9 lbs; t = 4.55, p < .001), and dummy drag (-1.3 ± 2.0 sec, t = -2.6, p = .02); APRT women for sit-ups (7.4 ± 9.8 reps; t = 2.83, p = .04); HIFT men for pull-ups (2.1 ± 1.8 reps; t = 5.85, p < .001), 1RM deadlift (27.2 ± 32.6 lbs; t = 4.17, p < .001), dummy drag (-1.0 ± 2.0 sec; t = -2.49, p = .02), and horizontal jump (13.0 ± 12.1 cm; t = 5.38, p = .001); and HIFT women for 1RM deadlift (20.7 ± 13.7 lbs; t = 4.01, p = .007). No significant between-group differences were found (all p > .05). CONCLUSIONS: Results indicate both exercise programs increased fitness (i.e., upper body muscular endurance, abdominal endurance, and lower body strength and power). Men had more fitness gains, with no differences by treatment group. Despite unique participant challenges of time-consuming War College academics, a concurrent focus on exercise training produced fitness benefits.