Dropping pounds quickly is an all-American pursuit, and there's always a brand-new "it" fitness method to help us do just that. Shawn T's Focus 25. Beach Body. Bootcamp. Metamorphosis. At Mainline Health & Fitness gym in Bryn Mawr Pennsylvania, an approach called X-Force, or negative force is all the rage.

The facility has an entire space-age looking room with machines dedicated to this method of weight training. "There is a canister that houses the weight stack," explained general manager Mary Hackett. "On the negative phase of the work out, the lowering part of the exercise, the canister flips, and puts 40 percent more weight onto the person exercising to lower down."

That extra resistance fatigues muscle much faster says Ellington Darden, Phd. Darden is 70, and looks like a drill sergeant. His new book is "The Body Fat Breakthrough."

Under Darden's stern guidance, I tried a few of the X-Force machines, starting with the chest press. The lowering phase is tough, with almost 1.5 times the weight, and it feels a bit like you're being crushed.

"Your muscles are contracting, and now they are un-contracting, you are tearing fibers across your chest," said Darden. "That's causing soreness, and it causes stimulation for the muscle to get bigger and stronger."

Gym users at the facility say they are seeing results more quickly, and are in better shape since they have started this approach.

The negative force machines are not widely available, so Darden has developed an at-home version of this kind of exercise - he calls it 30-30-30. "A 30 second lowering followed by a 30 second raising followed by another 30 second lowering, you can use your own body weight, or weights," said Darden. He used a deep knee bend as an example, when you bend your hips and knees to sit on your heels and then get back up. "You take 30 seconds to get down, 30 to come back up, and then another 30 to get back down. That will thoroughly fatigue hips and thighs; you will feel it immediately." 

Darden used a pushup as another example. He said most people focus on pushing themselves up when exercising, but he wants them to focus on lowering themselves. Instead of dropping down quickly, he said women should take 30 seconds to lower themselves, men should try for in 60. "Don't worry about ten repetitions, worry about the lowering. That will work the muscles more than doing 10 pushups fast."

Darden says this kind of exercise makes people very tired, very sleepy and very hungry. "If you reduce calories, do six to eight exercises, your body pulls calories from fat cells to build muscle. It's a process of muscle building and fat loss together," he said.

Darden cautioned that this is not easy, the exercises are very demanding, but the results start happening quickly.