It seems pretty obvious to us by this point that high intensity interval training is great exercise. Sure, we’ve been pushing that for a long time, but there is enough evidence that we think it’s pretty hard to deny by this point.
But when it comes to the intervals, how long should they be? They have to be intense, so they can’t be too long, but you also can’t workout for three seconds and then take a breather. Can you?
That is what researchers in Copenhagen wanted to know, so they found 12 cyclists, all men, and had them try out three different workouts, according to this article:
One involved riding a stationary bicycle for 50 minutes at a moderate pace (about 70 percent of maximum aerobic capacity). The other two were high-intensity interval sessions. For one of them, the men pedaled as hard as they could for five seconds, then rested for 30 seconds; they repeated this sequence 18 times. The third workout consisted of all-out intervals lasting 20 seconds, followed by two minutes of recovery, a sequence repeated six times.
They took blood and muscle samples right after the workouts and also three hours later. And what they found may nail the best length for one of those intervals. Again from the article:
…the 20-second intervals stimulated greater increases in adrenaline and lactate, which seems to have led to higher levels of a protein, PGC-1alpha, that contributes to the creation of new mitochondria. Mitochondria create energy within cells, and having more of them can improve health and fitness.
So what does this mean? Well, if you’re looking for the best interval time during your high-intensity training, 20 seconds may be about where you get the most bang for your buck. It could always change later, but if you’re doing high-intensity training we think you’re already on the right track.
