A week's worth of workout just once a week?

LOS ANGELES Less than half of Americans meet the exercise guidelines of 30 minutes a day, five days a week. But new research shows great results with a program that's just once a week for one hour, no kidding.

Kids, school, work, dinner, homework -- at what time do you squeeze in a workout?

"There was no way I could have made to a gym three or four times a week," said Bryan Conrad.

For people that head to the gym just once a week for one hour and don't feel one bit of guilt, what's their secret? An exercise plan hatched in a strength science lab at the University of Florida.

It's based on "eccentric" or "negative-resistance" training. It takes advantage of the fact the body can lower weights that are too heavy to lift.

"When you lower a weight, the energy that you're lowering the weight from actually goes in the muscle," said orthopedic surgeon Dr. Michael MacMillan, a clinical associate professor at the /*University of Florida-Gainesville*/.

The machines use sensors that add weight when you lower the bar, then remove weight when you lift. That's double the workout in half the time. It's how Olympic champion skier /*Bode Miller*/ trains.

"The stretching of the muscle by this particular level of weight is a strong stimulus toward growth and repair," said MacMillan.

It pushes muscles to the limit in as few repetitions as possible. Then you rest over the next week. Studies show it increases flexibility and can be used as a rehabilitation option for people with tendonitis and hamstring injuries.

Bryan Conrad, a father of two, lost fat and gained control of his diabetes.

"Feels like it really maximizes the intensity of the workout," said Conrad. "With two little kids at home, so I don't have a lot of extra time."

No gym? No problem. Personal trainer /*Joy Di Palma*/ says negative training can be done with free weights, body weight or resistance tubing, with a formula.

"Four to five seconds in a movement. Probably a third of what you did on the positive part of the movement," said Di Palma.

But a workout like this is not without challenges.

For those who don't like to exercise, keep in mind that with a program like this, you do it once a week and you could be pretty darn sore.

"Once a week, the body's not going to get used to it at all. So every time you do it, it's going to hurt. Plus you're pushing your muscles with the negative training beyond where they would go with just positive training," said Di Palma.

And negative training doesn't involve cardiovascular fitness.

"It's going to help the muscle grow, but you still need your cardio, and you should still work out two, three times a week with weights, in my opinion," said Di Palma.

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