In moving an object or resisting the motion of an object you use three types of muscle contractions based on what happens to the length of your muscle.
Concentric Contractions – In this type of contraction, muscles shorten during contraction.
When you shake hands, the muscles of your forearm shorten and allow you to grip. Stronger forearm muscles create more forceful contractions and a firmer grip.
Eccentric Contractions – During eccentric muscle contractions, muscles lengthen against resistance.
When you walk downstairs, the muscles in your quadriceps (front of your thighs) lengthen to allow your knee to bend as you step down.
In the same example, when you walk upstairs, the same quadriceps muscles shorten to straighten your knee. This is another example of a concentric contraction.
In going upstairs, you concentrically contract your quadriceps and in going downstairs you eccentrically contract them.
Isometric contractions – What happens if you stop in mid-stride? Your muscles hold the tension of your weight, but they are neither lengthening nor shortening. Their length remains fixed. This is an example of isometric contraction.
These types of muscular contractions are the base of every motion related experience. Your emphasis on each type of contraction determines how your muscles adapt and how they perform.
Training imbalances result in imbalanced muscular adaptations that often lead to weakness, chronic pain and repetitive injuries.
One of the major problems with most sports activity is the repetitive nature of what is required to excel at that sport. Most sports use one of these contractions much more than the other two.
Sport specific workout customization includes increasing the other two contractions that are usually left out.
When personal workouts are adopted from sports, they too create the same imbalances of that sports.