“I just don’t have time to exercise”.
Have you ever heard that before? Maybe said it yourself? Lack of time is the most commonly cited barrier to physical activity. This perception that we don’t have enough time to fit-in meaningful exercise may well explain society’s obsession with determining just how little exercise we can “get away with.”
Last month the New York Times ran an article titled “The 4-minute workout” which (like similar stories before it) was met with great enthusiasm, as it suggested that fitness could be maintained with the investment of very little time. In fact, the research on which they were reporting suggested no more than 4 min a session, three times a week was necessary.
How does this possibly work? The most important caveat of this research is that this is not just any-old exercise, it is what we call high intensity interval training, or HIIT. High intensity intervals are not a new concept, in fact, they have been used by elite athletes for quite some time and it is well known that the added intensity is quite effective in boosting fitness gains. What is more novel is the idea of swapping time for intensity, that is exercising very hard for a short amount of time without sacrificing efficacy. Many people who are initially excited by the prospect of exercising only 4-6 minutes a day perhaps miss the point that this exercise is performed near maximal (often about 90%), either for one continuous bout (4 min) or for multiple shorter bouts, interspersed with lighter exercise between. Despite the higher intensity of this type of exercise, current evidence suggests that it is still quite safe (see the CACR webinar I presented on HIIT in cardiac rehab here), but there is no denying that the risk goes up slightly and extra effort and motivation to push oneself is required.
Seems to good to be true doesn’t it? There must be a catch. Not necessarily, but there are still a number of things that we do not yet understand, and some important limitations. Firstly, it needs to be noted that the research showing improvements in fitness with only 4 min a session was done using inactive participants (who we would expect to change the most from adopting ANY exercise), and comparisons were made to other forms of interval training to determine that increases in fitness were “not different”. Although other previous research has shown comparable (and even magnified) alterations in fitness using HIIT vs traditional longer and slower exercise, we need to recognize that the generalizability of these findings to the broad population are still unclear. Furthermore, the efficacy of this style of training for people with better baseline fitness may differ. We also don’t understand the longer term effects of adopting a condensed HIIT program vs doing more traditional exercise. For example, do the findings of a relatively short research intervention actually just show us who would win a 12 week “race to fitness?” That is, does HIIT simply speed up the adaption process that “regular” training would have eventually caused if given a little more time? If it does, there is still potential value in this, but we don’t yet know or understand what will happen in the longer term, or if these changes will plateau. Drawing from elite athlete experience and HIIT, it is also plausible that burnout and injury could become an issue, but this may also be avoided based on the low volume of exercise exposure.
In short, any exercise is probably better than none, and if you are going to only invest a short amount of time (or can only find a short amount of time), you might as well bump up the intensity to get a better “bang for your buck”. It is important to understand that fitness and fatness are not necessarily the same thing- and this type of training may help you to control fitness, but not fatness. The calorie burning of this type of workout may actually be well below that of a lower intensity exercise session that can be sustained for a longer period of time. Rather than looking at the “least possible” angle, a better interpretation may be that even little bits of high intensity added to your regular program will likely add further benefits. So, why not run up the stairs when no one is looking, chase your kids and dogs around the yard at full speed, and don’t be afraid to work up a real sweat during your workout? After all, its only a few minutes.