It is common knowledge that off-court training can add to the tennis player's ability to play the game as well as avoid injury. When you decide to make your entrance in the weight room for the purpose of conditioning your body for the rigors of the game, keep in mind that there are different ways in which muscles contract, and each has a role in the way you perform on the court. The way you perform a particular exercise can emphasize one form of contraction over another.

The three forms of muscle contraction that we'll be looking at in this article are: 1) eccentric 2) isometric and 3) concentric in that order.

- THERE ARE THREE TYPES OF MUSCULAR CONTRACTIONS -

1. ISOMETRIC CONTRACTIONS: result in no change in length of the muscle (example: pushing against a wall) 2. CONCENTRIC CONTRACTIONS: result in a shortening of the muscle (example: the up phase of a bicep curl) 3. ECCENTRIC CONTRACTIONS: result in a lengthening of the muscle (example: the down phase of a bicep curl)

The movers of the body are the muscles. Through their attachments to the bones by way of the tendons, they provide us with the unique ability to lengthen and resist tension, hold a static position, or shorten and produce tension. They do this by either pulling the muscle fibers together, keeping them still, or by letting them slide apart. The strength of a muscle contraction is determined by how many muscle fibers are involved, and by the cross-sectional size of a muscle. So, let's look at the types of muscle contractions that are available to us, how to stress the muscle in specific ways and how this can help your game.

"Eccentric" contractions are a very important type of muscle contraction. They are responsible for slowing movements down, and then reversing that direction. This means that without eccentric strength it would be impossible to run or even walk. If we didn't have a way to counter the force of gravity, the force that acts on your body as you stand, walk or run, we would be driven to the ground.

When we walk, we place approximately 3 times the weight of our body on each leg as it makes contact with the ground. When we run, this force can go up to 5 times our body weight. It is of interest that our bodies' ability to resist this force can be improved by building strength in the lower extremities, eccentric strength that is!

We can improve eccentric strength by performing an exercise so that we are aware of the speed movement during the lowering phase. For example, when performing a squat exercise, try performing one of your sets eccentrically.

After removing the bar from the rack, lower it slowly, using a count of 6 to reach the deepest position. This is called the "descent" phase of the lift. When you reach the bottom of your squat you'll have to enlist an isometric contraction to completely stop, then follow this with a concentric contraction to get out of the down position. The concentric phase is known as the "ascent" phase and consists of acceleration the bar up to a starting position on the count of two, This technique should be repeated for 6-8 repetitions in a single set. Perform these eccentric lifts once per week for one or two of your large muscle group exercises (squats, seated row) and see the difference in as little as three weeks. Your ability to get into the preparation position for hitting ground strokes will improve as your eccentric strength does also.

The next type of muscle contraction that we want to consider is the isometric contraction. This is a contraction in which there is no visible shortening of the muscle. Therefore, no motion occurs at the joint, but the muscle tightens with an all out effort to hold a particular position.

There was a time when people thought this was the way to improve strength. As time went by and research improved, it was found that isometric contractions really did improve the abilities of the muscle to generate force, but only at very specific angles. So, if you worked the muscles around a joint bend of 90 degrees, the strength built was only at that 90 degree angle. It didn't make sense to work every degree in the range of a joint with the muscle making the isometric contractions at each point, because the time required would really make for a long workout. Can you imagine a workout for the biceps muscle consisting of a single set of 145 contractions at each angle ranging from 0-145 degrees (the normal range of motion for the elbow).

However, think back to that squat exercise. As the body decelerates and lowers, there is a very brief "hold" position before it starts to rise again. Strength can be improved in the "hold" position by doing a set of functional isometrics. This can be accomplished by using a power rack or load that is impossible for you to move. Place the weighted bar in a position that you want to build strength in, i.e., 140 degrees of knee flexion. Get in a position underneath the bar and push upwards with maximal effort for 5-7 seconds (remember to exhale as you exert). Repeat this exercise for 5-6 reps. Although you don't want to make a steady diet of this type of exercise, it can provide variety as well as help you through the weaker points in the joint range of motion, at a sticking point or even help strengthen a particular position in your stroke.

The final contraction type is the "concentric" or shortening of a muscle. As you resist an external load in an exercise such as a squat, the concentric phase comes during the ascent or raising of the bar. As the bar is driven upward, it is accelerated. Acceleration of an object is always associated with a concentric muscle contraction. It is the phase we most associate with muscle development, hypertrophy or body building. As the muscle shortens, it bunches together and this bulk equates to muscle size. It should not however, be associated with strength output. A muscle does not have to be big and bulky to have the ability to develop force. It is of interest that strength studies have shown that the "speed of contraction" is important in a muscle's ability to create power (force development rapidly). So, the concentric contractions should be performed at a tempo that is fairly rapid in movement. This gives a tennis player the best chance to maximize the type of muscle contraction most applicable to hitting each stroke.

Now that we have looked at all types of muscle contraction, let's revisit the eccentric contractions. We need to have eccentric strength when we move side to side, as well as up and back. This ability allows us to come to a stop more quickly, and then reverse the direction we were coming from. All too often when you see people exercising with weights you can see them almost allowing the bar to "freefall" with gravity in the descent phase. They are not working the eccentric muscle contraction and in turn missing a big part of the muscle development necessary for improvement in tennis.

Eccentric contractions should be stressed occasionally in an exercise program for tennis development. Throwing in the occasional set of eccentric reps will help to develop many of the large muscle groups that are related to absorbing impact. With increased muscle development in this area, an athlete can become quicker and more injury free. So, the moral to the story becomes: every once in a while, work on slowing down, before you
speed up.

(Before beginning any exercise program consult with your physician.)

This article appeared in the USTA Sport Science for Tennis Newsletter - Fall 1995 issue.