Interval training is tough , but it's the best way to keep in shape when you don't have a lot of time on your hands. That said, if you want to do it right, The New York Times suggests you stick with very specific timing.
Photo by William Warby
As the name suggests, interval training tasks you with pushing your body to the max for a short duration, then relaxing, and pushing again in intervals. Everyone does this a bit differently, but the Times points to research that suggests it is best to stick to 30 or 60 second intervals:
The takeaway of both studies is that it is best, if you wish to perform high-intensity interval training, to stick to what is well documented as effective: a few sessions per week of 30- or 60-second intervals so strenuous you moan, followed by a minute or so of blessed recovery, and a painful repetition or four. Done correctly, such sessions, in my experience, get you out of the gym quickly and inspire truly inventive cursing.
While researchers aren't totally clear on why the timing matter, it does seem that sticking to these 30-60 second bursts produces better and longer lasting results.
How to Get Fit in a Few Minutes a Week [The New York Times]