Exercise: How much matters, not how often
Previous physical activity guidelines recommended exercising on most or all days of the week, but a new study shows that doing 150 minutes of exercise all at one time is just as good for you as breaking it up into shorter sessions that you spread throughout the week.
The study, published in the journal Applied Physiology, Nutrition and Metabolism on June 20, 2013, found that adults who had built up 150 minutes of physical exercise over just two days per week were just as fit and healthy as those who exercised more frequently, breaking up the 150 minutes into shorter sessions they performed over several days during the week.
The researchers examined data on 2,325 adults throughout Canada to find out whether physical activity frequency impacts on the risk of diabetes, stroke and heart disease.
"The findings indicate that it does not matter how adults choose to accumulate their 150 weekly minutes of physical activity,” said Dr. Ian Janssen, one of the researchers involved in the study.
“For instance, someone who did not perform any physical activity on Monday to Friday, but was active for 150 minutes over the weekend, would obtain the same health benefits from their activity as someone who accumulated 150 minutes of activity over the week by doing 20-25 minutes of activity on a daily basis,” he explained.
Each of the adults participating in the study were asked to wear accelerometers on their waists throughout the week to allow the researchers to continuously measure their physical activity. An accelerometer is a small electrical device, which records a person's minute-by-minute movements.
The participants who exercised at least 150 minutes per week were then divided by the researchers into two groups:
1. The high frequency group, which exercised at least five days a week; and
2. The low frequency group, which exercised from just one to four days a week.
As a result, the researchers found that participants in the low frequency group were no less fit or healthy than those in the high frequency group. They therefore concluded what counts in exercise is how much, instead of how often.
"The important message is that adults should aim to accumulate at least 150 minutes of weekly physical activity in whatever pattern that works for their schedule," said Janssen.
So what about the recent study that found just 12 minutes of exercise a week is all you need? The distinction has to do with the intensity of the workout. As the study by Norwegian researchers concluded, four-minute bursts of intense physical activity three times a week can raise oxygen intake levels as well as reduce blood pressure and glucose levels.
However, those 4-minute workouts were high-intensity, and not for the faint of heart. The intense workouts may therefore be more suitable to the super-fit who want to save time.
“Regular exercise training improves maximal oxygen uptake, but the optimal intensity and volume necessary to obtain maximal benefit remains to be defined,” the researchers said. “A growing body of evidence suggests that exercise training with low-volume but high-intensity may be a time-efficient means to achieve health benefits."
Another recent study, published in the June issue of the American College of Sports Medicine’s Health & Fitness Journal, also found an ever-growing amount of evidence in support of shorter, more intense workouts.
“There’s very good evidence” that high-intensity circuit training provides “many of the fitness benefits of prolonged endurance training but in much less time,” says Chris Jordan, the director of exercise physiology at the Human Performance Institute in Orlando, Fla., and co-author of the new research.
According to the research, the resistance training incorporated into the workout contributes significantly to the amount of fat burned during a workout – and when resistance training uses multiple large muscles with very little rest between sets, it results in aerobic and metabolic benefits, which can last up to 72 hours after the workout is completed.
SOURCES: 1. Applied Physiology, Nutrition, and Metabolism 10.1139/apnm-2013-0049, "Is the frequency of weekly moderate-to-vigorous physical activity associated with the metabolic syndrome in Canadian adults?" Janine Clarke and Ian Janssen (June 20, 2013); 2. PLOS One, "Low- and High-Volume of Intensive Endurance Training Significantly Improves Maximal Oxygen Uptake after 10-Weeks of Training in Healthy Men", May/June 2013; doi:10.1371/journal.pone.0065382; 3. ACSM'S Health & Fitness Journal, 17(3):3, May/June 2013. doi: 10.1249/FIT.0b013e31828cb21c