Physical activity interventions: effects of duration and intensity

The purpose of this study was to examine the effects of exercising at different intensities over 7 weeks on components of physical fitness and CVD risk factors. Forty-seven boys and 10 girls, (16.4 +/- 0.7 years of age) were divided into a moderate, high intensity, or a control group. All participants had indices of obesity and blood pressure recorded in addition to four physical performance measures pre- and post-intervention. In addition, the intervention groups repeated the physical performance measures at the 4th week phase of the intervention. Following the intervention, significant improvements (P < 0.05) in the high-intensity group were found in the 20 MSFT, agility, CMJ and 10m sprint post-intervention. Participants in the moderate intensity group displayed significant improvements (P < 0.05) in both the CMJ and 20 MSFT post-intervention. Body fat % significantly improved (P < 0.01) in the moderate group only post-intervention. Interestingly, Systolic blood pressure significantly improved post-intervention (112 +/- 10 vs 106 +/- 11 mmHg) (P = 0.017) in the high intensity group. In conclusion, high-intensity exercise over 7 weeks is a very time efficient means of improving important components of physical fitness in adolescents.