The other men began a typical program of moderate exercise, cycling in the lab five times a week at a pace they could comfortably sustain for 30 to 40 minutes.
Over the next six weeks, the HIIT group pedaled intensively for less than an hour in total, while the moderate intensity group exercised at least 2.5 hours per week for the same period.
At the end of the six weeks, both groups returned to the laboratory for retesting, after which the scientists combed their results for any differences. They found a lot.
The men were almost all fitter and about the same in whatever way they had trained. But only those in the moderate exercise group had lost a lot of body fat, improved blood pressure, or were better able to metabolize the extra fat from the creamy shaking.
Perhaps most interestingly, everyone’s blood sugar control at home was only best on the days they exercised, that is, three times a week for the HIIT drivers and five times for the moderate group. The blood sugar level tended to rise on the remaining days.
Overall, the results show that intervals and traditional exercise change our bodies in different ways, and we may want to consider what exercise we want to achieve when deciding how best to exercise, says Jamie Burr, professor at the University of Guelph who carried out the new study with his PhD student Heather Petrick and other colleagues.
“All exercise is good,” says Dr. Burr. But “there are nuances.” Frequent, almost daily, moderate exercise may be preferable to infrequent intervals for improving blood pressure and ongoing blood sugar control, while a little HIIT is likely to get you in shape as effectively as hours and hours of light cycling or similar exertion.
Of course, this study was small-scale, short-term and only included obese, unfit men, so we can’t be sure if the results apply to the rest of us. But the main lesson seems to be widely applicable. “Do you move around often,” says Dr. Burr, which means if you go HIIT today, go and repeat tomorrow.