Use them wisely with this fat-burning plan.

Usually, when something sounds too good to be true, it is. (We've had enough so-so setups to confirm this.)

So when we heard about The Quickie, a 20-minute, twice-a-week workout from Gravity Fitness at Le Parker Meridien, we were leery. But hope springs eternal...and 20 minutes? We had to learn more.

It turns out the program is rooted in research: Working your muscles to "failure"--keeping the weight high and the reps low--helps them become stronger. (And strengthening muscles means your resting metabolic rate increases, so you burn more fat.)

Our tester had a trainer take her through four weight machines that targeted her legs, arms, back, chest, and abs. By her second session, she felt stronger and was able to handle more weight. Plus, the workout ended lickety-split, perfect for midday lunch breaks.

What's not to like about a Quickie? 

Gravity Fitness, 119 W. 56th St., (212) 708-7340, MAP