Study I. Participants were 43 Navy men (mean age = 32.1 yr) assigned to one of three exercise training protocols: aerobic/circuit weight training performed at either 40 or 60% of determined one-repetition maximum strength or aerobic/calisthenic training. During the 10-wk study, each exercise group participated in three training sessions per week performed on alternate days. The results of this study indicate that dynamic strength (both upper and lower) increased for the aerobic/circuit weight training groups but not for the aerobic/calisthenic group. With the exception of bench press endurance for the aerobic/calisthenic group, all groups showed significant increases in muscular endurance and stamina. No significant changes were seen in static strength or flexibility in any of the groups. Study II. Subjects were 87 male Navy personnel (mean age = 19.8 yr) receiving basic training at the Recruit Training Command, San Diego, CA. One company of recruits (N = 41) participated in an experimental aerobic/circuit weight training program at 70% of determined one-repetition maximum. A second company (N = 46) received the standard Navy recruit physical training program (aerobic/calisthenic training). During the 8-wk study, both groups participated in an identical running program performed three times per wk on alternate days. Additionally, aerobic/circuit weight training participants completed two circuits (1 circuit = 15 exercises) three times per wk on alternate days to running. Study findings show the experimental aerobic/circuit weight training program produced significantly greater dynamic muscular strength and muscular endurance changes than the standard aerobic/calisthenic program.(ABSTRACT TRUNCATED AT 250 WORDS)