The trend in most strength training programs is to use mainly multi-joint, also known as compound, exercises. The reasons for this are many, but the most outstanding is that multi-joint exercises are supposed develop a multitude of different muscles in a coordinated manner.
As a result it is believed that you get many muscles strengthened and at the same time improve coordination. This is deemed to be more effective than doing many single joint exercises which do little for coordination as they only strengthen one specific muscle or group of muscles.
However, there are several flaws in this thinking. For example, it is true that more muscles are involved in a coordinated manner when doing multi-joint exercises. But the muscle contraction regimes experienced by the different muscles and the intensity of the contractions are different from those seen when doing single joint exercises.
Because of this, in compound exercises, even though the muscle undergoes a contraction, it does not mean that the muscle is getting stronger. Many of the muscles in a multi-joint exercise participate as stabilizers and only undergo an isometric contraction which does not transfer to dynamic movement.
As a result, the major muscles are strengthened greatly while the minor muscles become relatively weaker. This in turn can lead to a greater incidence of injury to the smaller, but often equally important, muscles.
This may be why we are seeing more non-contact injuries in many different sports. For example, a groin injury when swinging a bat, torn posterior cruciate ligament tears while diving for a ball, oblique injury when throwing a ball or swinging a baseball bat, and ankle sprain while changing direction during a run.
These types of injury should never, except in rare cases, occur to a well- conditioned athlete who is physically prepared to play the sport on the highest level. Because of this it may be wise to re-examine whether the trend toward more compound exercises is warranted.
In my work we do many single joint exercises together with multi-joint exercises. Rarely, and in most cases, never, do the athletes experience non-contact injuries. The key is to prepare the athletes specifically for the actions (skills) that must be executed in gameplay.
For more information in this area read Build a Better Athlete.