The amount of exercise a person engages in per week may be more important than the intensity of the exercise. Unlike most exercise interventions, this finding suggests that amount may be equally or more important as exercise intensity.
“The classic exercise regimen has a component of intensity up to 80 percent of someone’s maximum for health benefits. Our study demonstrates that you can exercise at an intensity much less than that and still achieve fitness benefits,” said lead author Brian D. Duscha, Duke University Medical Center, Durham, North Carolina. “People find exercise ‘hard’ and few people want to exercise at an intensity higher than they have to. Walking briskly for 12 miles a week per week is realistic and does not require anyone to incorporate a hardcore training regimen. Increasing your mileage or intensity will give you even greater health benefits.”
Researchers from Duke University Medical Center examined the effects of different exercise training regimens on 133 sedentary, overweight, nonsmoking patients, ages 40 to 65 years, who had abnormal levels of fat in their blood. Patients were divided into four exercise groups: high-amount/high-intensity (HAHI), the equivalent of jogging 20 miles per week at 65 to 80 percent peak VO2; low-amount/high-intensity (LAHI), the equivalent of jogging/walking up an inclined treadmill approximately 12 miles per week at 65 to 80 percent peak VO2; low-amount/moderate intensity (LAMI), the equivalent of walking approximately 12 miles per week at 40 to 55 percent peak VO2; and a control group of non-exercising patients. All patients underwent cardiopulmonary exercise testing twice at baseline and after 7 to 9 months of exercise training.
All exercise groups significantly improved their absolute and relative peak oxygen consumption and time to exhaustion (TTE) compared to baselines scores. Although the HAHI group showed the greatest improvements in peak VO2 overall, increasing exercise intensity from 40 to 55 percent to 65 to 80 percent (at a controlled amount of 12 miles/week) did not significantly improve peak oxygen consumption, yet increasing the amount of exercise did produce improvements. An increase in exercise amount also demonstrated a graded increase in TTE between groups, although data were not statistically significant.
“Although our results did point toward amount being more important, it is very likely fitness levels can be improved by increasing either amount or intensity,” said Duscha. “This is illustrated by the tiered effect the exercise dose had on fitness improvements across our groups. We believe with more people in the study, increasing intensity would also have been significant.”
Body mass index (BMI) was reduced in the LAHI and HAHI, groups but remained unchanged in the LAMI group. All exercise groups lost an average of 2.87 pounds after exercise. Baseline characteristics of age, BMI, weight, peak and relative VO2, and TTE were not different between the groups.
“A second very important message is that subjects enjoyed fitness benefits in the absence of weight loss. Many people exercise with the purpose of losing weight. When they do not lose weight, they do not think the exercise is benefiting them and they stop exercising,” said Duscha. “The truth is, you can improve your cardiovascular fitness and reduce your risk for heart disease by exercising without losing weight. Even if individuals do not lose weight, it is likely that they will lose body fat and increase lean muscle mass while reducing other risk factors.”
“If you distill our results down, the public health message is: You only need to walk briskly for 12 miles per week or for approximately 125 to 200 minutes per week to improve your health,” said Duscha. “This sheds more light on the question, What is the minimum amount of exercise I need to do to get a health benefit?’