The longer I work out, the fitter I'll get
Endless sets, long hours pounding the pavements; getting fit and staying lean is not about the duration of your workout sessions. In fact, research shows that short bursts of intense exercise will make you fitter quicker.
A team of scientists at McMaster University in Canada found that doing 10 one-minute bursts of activity, interspersed with short rest periods, is better at building muscle than hours of conventional cycling. So, though it may sound counterintuitive, less exercise can deliver more benefits. Try getting your heart rate up in a spin class or by doing interval training.