How much exercise do we really need?

Many of you have sent me this piece in the NYT which argues that a new study says that one minute of strenuous exercise achieved the same benefits as 45 minutes of endurance exercise. Let’s let Gretchen Reynolds describe the experiment:

One group was asked to change nothing about their current, virtually nonexistent exercise routines; they would be the controls.

A second group began a typical endurance-workout routine, consisting of riding at a moderate pace on a stationary bicycle at the lab for 45 minutes, with a two-minute warm-up and three-minute cool down.

The final group was assigned to interval training, using the most abbreviated workout yet to have shown benefits. Specifically, the volunteers warmed up for two minutes on stationary bicycles, then pedaled as hard as possible for 20 seconds; rode at a very slow pace for two minutes, sprinted all-out again for 20 seconds; recovered with slow riding for another two minutes; pedaled all-out for a final 20 seconds; then cooled down for three minutes. The entire workout lasted 10 minutes, with only one minute of that time being strenuous.

This went on for 12 weeks. The outcomes of interest were process measures, including peak oxygen intake, insulin sensitivity index, glucose tolerance tests, and skeletal muscle mitochondrial content. Bottom line, the gains were the same in the interval and the endurance group.

This is being touted as “one minute of strenuous exercise is as good as 45 minutes”. I’m… not so sure.

First of all, this was a study of 25 men, not evenly divided between groups. It’s process measures, so my usual grain of salt there. But the biggest thing I see here is that it wasn’t really “one minute of strenuous exercise”. It was probably 10 minutes (at least) of activity that likely led to an increased heart rate for more than that amount of time. Is this really different from, say, walking briskly for 10 minutes?

Cause if the take-home message of this is that you don’t need to exercise for an hour to get benefits, I’m all in. I already said that:

The recommendations are for 30 minutes of moderate activity five times a week. Is it possible that less would get the same goals? Maybe. I’d love to see more studies investigating that.


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