From the BBC website:
A few relatively short bursts of intense exercise, amounting to only a few minutes a week, can deliver many of the health and fitness benefits of hours of conventional exercise, according to new research, says Dr Michael Mosley. But how much benefit you get from either may well depend on your genes.
This seems unbelievable to me. But there is some limited data to back up the claims.
For a fuller explanation and some fascinating videos of the technique in action, checkout the Horizon broadcast (only for UK viewers I suspect).