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Muscle Potential: Range of Motion
Taken from Variables for Weight Lifting and Exercise © 2003 Anthony Sell - All Rights Reserved
Each muscle group in the body has a normal range of motion. This is the amount of movement in a given direction that the joint in question is designed to allow, while taking into consideration the flexibility of the muscles involved.
Throughout each range of motion, there are essentially three divisions or stages of motion within that range that deserve consideration. The first stage of motion occurs when the muscle is elongated. This is the weakest portion of the contraction, and it is the most difficult to focus on.
The second stage is the main contraction, and is the next strongest portion of the contraction. This is also responsible for the swell of the muscle in appearance, and is largely what is focused on during the contraction.
The third stage of motion is the final contraction, completing the range of motion into what is called the "Locked" position, and is the strongest stage of the three (but because of the effects of gravity and posture with the use of free weights, it is the second stage that is often felt as being the strongest stage of motion).
Exercises can be designed to focus on developing strength and/or endurance in each stage of motion (as with partial sets and variable resistance machines). Without varied resistance, so long as the exercise in question maintains pressure against the resistance throughout the entire range of motion, strength and endurance in each stage will be increased proportionately.
What this also means is that an imbalance of exercise per stage of motion will become a limiting factor in the growth potential per muscle. The muscle will not grow to its fullest potential unless the full range of motion is worked.
Likewise, the body is similar in that if you only work certain parts of the body (upper body only workouts are not uncommon among uninformed body builders) or if the volume of work is disproportionate per muscle group, you will not grow to your fullest potential.
For example, a weightlifter who is only concerned with the size of their arms and chest will not grow as large as another of similar body potential who is working the whole body as intensely.
If you are beginning to structure an exercise program, it is important to remember to have a balanced and complete approach towards working the body. This will insure efficient growth, and will help to avoid problems down the road.