How your body position changes muscles activity?

Extracted from exercise.com

* Leg extensions: Rotating the legs in different directions can target different areas of the quadriceps. With the toes pointed in, you'll activate more vastus lateralis and vastus medialis (muscles in the outer and mid thigh) while rotating the toes out increases activity in the rectus femoris (mid-thigh).

* Squats: Pointing the toes out or in doesn't effect quadriceps activity, but a wide stance can elicit greater activity in the inner thigh (adductor longus) and glutes. During deeper squats, the glutes become more active.

* Lat pulldowns and seated rows: While many experts and exercisers alike think that wide grip lat pulldowns elicit more from the lats and triceps, while a close grip activates more chest and rear delts, studies show that neither is the case. The studies also show that seated rows are better for targeting the upper back muscles (traps, rhomboids and lats) than lat pulldowns and that retracting the shoulder blades, which is something many of us are told to do, had no effect on muscle activity.

* Bench Press: Studies show that the triceps and front deltoids are most active during the bench press (compared to the chest and biceps) and that a wide grip (almost double shoulder-width apart) elicits greater muscle activity in the chest, shoulders, triceps and biceps.

* Pushups: Studies show that the chest and triceps are more active with a narrow hand position rather than a neutral or wide hand position.

* Abs: Studies show that doing crunches on an unstable surface elicits more muscle activation than doing them on the floor (although, if you use a stability ball, you'll want to position it under the lower back, rather than under the upper back). They also show that you can't target an 'upper' or 'lower' portion of the rectus abominis because it's actually one muscle and muscles cannot contract with only part of their length.

Changing position is something many of us do to shake up our workouts and make things a little more interesting. Change is always a good thing and knowing a little more about how it actually effects your body may help you focus those changes in new directions.