Numerous studies have documented the value of exercise in controlled clinical trials. However, few large scale studies have evaluated the effects of initiation of resistance-training programs. PURPOSE: To evaluate the impact of a 30-day international fitness intervention on fitness and health behaviors in a large-scale population. METHODS: 72,870 sedentary women (44.0 ± 13 yrs, 83.3 ± 19.7 kg, 31.9 ± 7 kg/m2 BMI, 37.9 ± 7% fat) responding to advertisements for a 30-day fitness challenge at Curves® clubs in the United States and Canada volunteered to participate in this study. Subjects gave online consent and then completed exercise, food frequency, and physical activity-related questionnaires. In addition, baseline body composition, obtained using a handheld bioelectrical impedance analyzer (BIA), blood pressure, and circumference measurements were taken by trained personnel. Participants followed the Curves 30-min circuit training program 3 d/wk. Each circuit-style workout consisted of 14 hydraulic resistance-exercises that targeted opposing muscle groups in a concentric-only fashion. Subjects performed the resistance-exercise for 30-sec followed by performing floor-based callisthenic (e.g. walking/skipping in place, arm circles, etc.) exercises for a 30-sec time period in an effort to maintain heart rate between 60% and 85% of age-predicted maximum heart rate. Participants were also encouraged to walk on non-training days and make positive changes in their diet. After 4-wks, subjects repeated questionnaires and had post-measurements recorded. Data were analyzed by dependent T-tests and are presented as mean ± SD changes from baseline. RESULTS: Post-study results were obtained on 34,677 participants. Participants experienced significant (p < 0.05) decreases in body weight (−0.86 ± 2.2 kg, −1.1%; n = 34,667), percent fat (−0.7 ± 2.5%, −1.9%; n = 34,349), total centimeters (−7.62 ± 17.78 cm, −1.5%; n = 33,899), BMI (−0.47 ± 2.7 kg/m2, −1.5%; n = 12,167), systolic BP (−2.6 ± 12.5 mm Hg, −2.1%; n = 11,767), and diastolic BP (−2.3 ± 9.0 mm Hg, −2.9%; n = 11,711), as well as an increase in fat-free weight (0.05kg ± 2.4 kg, 0.1%; n = 34,312). Participants also reported significantly less (p<0.05) weekly (−10%) and monthly (−17%) alcohol consumption, sugar intake (−24%), and fat intake (−22%) with greater calcium intake (5.3%), and fiber intake (6.8%). CONCLUSIONS: Significant improvements in body composition, markers of health, and positive health behaviors can be achieved through short-term circuit training fitness initiatives. PRACTICAL APPLICATIONS: Short-term circuit-training programs can be effectively used to promote positive changes in fitness and attitudes about health. ACKNOWLEDGMENTS: This study was supported by Curves International, Waco TX and Avon Inc., New York NY.
© 2011 National Strength and Conditioning Association