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The purpose of this study was to determine the effects of 8 weeks of circuit strength training (CST) followed by 8 weeks of jogging and then 8 weeks, of CST or jogging. During the final 8 weeks, the subjects were randomly assigned to either CST or jogging groups. The subjects (n=16, x age = 29 yrs) exercised 3 days/week. The strength training involved 2 circuits of reciprocal exercises using isokinetic devices with 10 to 15 repetitions/set and 30 seconds of rest between sets. The subjects jogged 3 miles/day during the jogging program. After the initial 8 weeks of CST, significant changes were found in treadmill performance time, maximum oxygen uptake (VO2max), maximum pulmonary ventilation (VEmax), body fat, total skinfold fat, fat weight, lean weight, isotonic bench and leg press, and isokinetic slow speed, fast speed, and power endurance measures. The jogging program elicited significantly greater changes in treadmill performance time and VO2max. Further reductions were found in total skinfolds and waist girth during the jogging program. Leg strength was maintained during jogging but upper body strength was reduced significantly. Physiologic levels were maintained during the final 8 weeks and showed no differences between the CST and jogging groups.