Originally Posted at: Lift Better, Look Better - Page 2 - MSN Health & Fitness - Diet & Fitness
Myth: "You need to do three or four exercises per muscle group."
The claim: This ensures that you work all the fibers of the target muscle.
The origin: Arnold, circa 1966.
The truth: You'll waste a lot of time. Here's why: Schwarzenegger's 4-decade-old recommendation is almost always combined with "Do three sets of eight to 12 repetitions." That means you'll complete up to 144 repetitions for each muscle group. Trouble is, if you can perform even close to 100 repetitions for any muscle group, you're not working hard enough. Think of it this way: The harder you train, the less time you'll be able to sustain that level of effort. For example, many men can run for an hour if they jog slowly, but you'd be hard-pressed to find anyone who could do high-intensity sprints - without a major decrease in performance—for that period of time. And once performance starts to decline, you've achieved all the muscle-building benefits you can for that muscle group.
The new standard: Instead of focusing on the number of different exercises you do, shoot for a total number of repetitions between 25 and 50. That could mean five sets of five repetitions of one exercise (25 repetitions) or one set of 15 repetitions of two or three exercises (30 to 45 repetitions.)
Myth: "Never let your knees go past your toes."
The claim: Allowing your knees to move too far forward during exercises such as the squat and lunge places dangerous shearing forces on your knee ligaments.
The origin: A 1978 study at Duke University found that keeping the lower leg as vertical as possible during the squat reduced shearing forces on the knee.
The truth: Leaning forward too much is more likely to cause injury. In 2003, University of Memphis researchers confirmed that knee stress was 28 percent higher when the knees were allowed to move past the toes during the squat. But the researchers also found a countereffect: Hip stress increased nearly 1,000 percent when forward movement of the knee was restricted. The reason: The squatters had to lean their torsos farther forward. And that's a problem, because forces that act on the hip are transferred to the lower back, a more frequent site of injury than the knees.
The new standard: Focus more on your upper body and less on knee position. By trying to keep your torso as upright as possible as you perform squats (and lunges), you'll reduce the stress on your hips and back. Two tips for staying upright: Before squatting, squeeze your shoulder blades together and hold them that way; and as you squat, try to keep your forearms perpendicular to the floor.