The beneficial health effects of physical activity and exercise are well established but the optimal amount and intensity of exercise continues to be debated. Many studies have suggested that, while increasing exercise levels provide increasing health benefits, the most benefit comes from the first increase in exercise.
An article in the May, 2014, issue of the journal Obesity investigated the “dose-response” of exercise on health risks. The subjects were healthy young (ages 20 to 40), sedentary and overweight men. The participants were screened for health status based on medical history, blood pressure, fasting blood glucose levels, stable weight, and no regular medications. After the screening, sixty-four subjects were randomized into three groups: no change in activity levels (control group), moderate (MOD) increase in activity levels (daily exercise expending 300 Calories), and high (HIGH) increase in activity levels (daily exercise expending 600 Calories). Fifty-three subjects completed the study balanced among the groups.
Subjects adhered to individual exercise prescriptions to attain the specified energy expenditure and intensity and the prescriptions were adjusted at intervals. The prescriptions called for three days per week of high intensity sessions with the other days calling for lower intensity but longer time to maintain the required energy expenditure. Compliance was good with average recorded energy expenditures of 337 and 644 Calories per exercise session in the MOD and HIGH groups, respectively, and average weekly expenditures of 2004 and 3774 Calories, respectively. Subjects were encouraged to vary the exercise mode to avoid injuries. Measures included anthropometrics (weight, height, body composition, waist and hip circumferences), blood pressure, glucose tolerance and insulin sensitivity, a quality of life survey, cardio-respiratory fitness (CRF) determined by oxygen uptake during a graded exercise test, muscle biopsies to determine muscle energy capacity, and blood lipid parameters and an inflammatory marker (CRP).
Both exercise groups lost significant weight, exclusively due to loss of fat mass, with the MOD group actually losing more weight than the HIGH group and both groups lost waist circumference. CRF improved in the exercise groups to a similar degree. Insulin sensitivity improved in both exercise groups, more so in the HIGH group. Muscle energy capacity increased in both exercise groups similarly. Both groups showed a similar improvement on the quality of life survey.
The authors concluded there was “only minor additional effect” of the higher amount of exercise on health parameters over the time period of the study in the young, healthy, moderately overweight subjects. This supports other studies suggesting that any exercise brings benefit.
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