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(R) 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.
(C) 2011 National Strength and Conditioning Association