Confused by conflicting exercise advice and guidelines? So are we!

Separate fact from fiction by following the advice of celebrity trainer and The Ultimate New York Diet author David Kirsch (Heidi Klum does!):

My knees can go past my toes when lunging.
Generally, no?it's incorrect form and puts too much pressure on the knees. “When lunging, put your brain in your butt,” says David. “The focus should be on your glutes, and not your quadriceps or hamstrings.”

If I lift, I will get bigger.
Women have less testosterone than men, so bulking up is more difficult. David says definition depends on intensity (the weight and number of repetitions). “Heavier weight doesn't necessarily cause a woman to get larger, provided she can handle the weight and repetitions required with proper form.”

It's good to be sore after a workout.
“It is important for the muscle to feel engaged but not incapacitated,” explains David. “Expect to feel sore for 1 - 3 days after a good workout. But be mentally aware of your limits while exercising to prevent injury.”