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When the other boys were outside kicking a ball around, I was lying in my bed reading books, so any scientific evidence supporting that lifestyle makes me happy.
However, all the studies discussed in that previous article were focused on the total number of MET’s (metabolic equivalent task) performed per week. In case you don’t know what a MET is, here’s what I wrote about it in my earlier article:
One MET is defined as the amount of calories a person expends in one hour when at rest. Walking at a slow pace expends two METs. Walking at normal walking speed (3 miles or 5 km per hour) expends three METs.
Bicycling at average speed (11 miles or 17 km per hour) expends six METs. Running at a speed of 6 miles per hour (10 km per hour) expends 10 METs. Generally, activity that expends three to six METs is considered moderate intensity, while activity that expends six METs or higher is considered vigorous intensity.
In order to be able to compare apples with apples, the studies discussed in the previous article were just looking at total MET’s expended per week. This led them to conclude that optimal life expectancy is achieved if you do more than 35 METs per week (equivalent to twelve hours of walking at a normal pace) but less than 75 METs per week (yes, too much exercise is bad for you).
Those studies didn’t compare different intensities of exercise, so they didn’t say whether someone who expends 50 METs per week running will live longer (or shorter) than someone who expends 50 METs per week walking. That’s where a new study that was recently published in JAMA Internal Medicine comes in.
This was a big observational study, involving 400,000 people in the United States. The authors reported no conflicts of interest. In order to be included in the study, participants had to be over the age of 18, and they had to have a decent level of physical function (those requiring help with activities of daily life were excluded).
People with heart disease, stroke, or cancer were also excluded from the study, which is a shame, because it would be interesting to see whether people with serious health problems can benefit from vigorous exercise.
My guess is that they were excluded out of fear that their participation would confound the results – these people are often not able to perform vigorous physical activity due to their illness, and they also have a short life expectancy due to their illness. This could make lack of exercise look worse than it is if the effect isn’t corrected for.
Participants were selected at random from the US population and asked to fill out a questionnaire. The first participants were recruited in 1997 and the last participants were recruited in 2013.
They were then followed over time to see whether they died or not. The median amount of follow-up per participant was ten years, and the average age at the time of inclusion in the study was 43 years.