The Truth: You don't have to constantly add new moves and workouts to your routine to prevent your body from adapting. Actually, you want adaptation -- this is how muscles grow. Sustain it with small weekly tweaks: Alter your grip, pace or rest. That can help your muscles adapt over time, preventing plateaus, says Nick Tumminello, C.P.T., owner of Performance University in Fort Lauderdale. For an intense workout with plenty of variety, check out The New Spartacus Workout -- On DVD!

The Truth: "Your body will slowly digest and absorb all protein you eat, even if you eat 125 grams in a sitting," says Alan Aragon, M.S., the author of Girth Control: The Science of Fat Loss & Muscle Gain. He recommends consuming 1 gram of protein a day per pound of your target body weight. If you weigh 180 pounds and are looking to shed 15, shoot for 165 a day. Still not satisfied with our science? Find out more about The Truth about Protein.

The Truth: Using your body as your barbell is a smart way to vary your routine and boost overall fitness, but it won't help you pack on serious size. "Your body weighs only so much, so your muscles become accustomed to it quickly, and then your gains stall," says Bill Hartman, C.S.C.S., co-owner of Indianapolis Fitness and Sports Training. "You need sufficient overload to spur growth; that's where weights come in."

The Truth: Be wary of any advice that promises positive results from negative actions. "If you know your next repetition is going to be slow and shaky, terminate the set," says Jim Smith, C.S.C.S., owner of Diesel Strength & Conditioning in Elmira, New York. "You'll recover faster and reduce your risk of injury." Bottom line: Focus on lifting with good form, not lifting to failure. For more ways to build an injury-proof body, discover The Secret to Staying Pain-free For Life.