1. Shorten rest periods

PROGRESSIVELY SHAVING SECONDS off your rest period can help to raise your metabolism. Just don’t go too low, warns Joe Stankowski, C.P.T., a trainer in Grand Rapids, MI. “You need a minimum of 30 seconds’ rest or you risk burning out,” he says. The one exception: circuit training, which requires no rest between sets.

2. Train the entire body

If you’ve been following a split routine—upper-body exercises one day, lower-body ones the next—condense both into one day. Your growth hormone levels will spike, and that burns fat.