Ask a PT response: "An eccentric contraction involves a muscle enlongating rather than shortening (concentric contraction). An eccentric contraction is performed to help decelerate a body part or object. It is also performed to assist with lowering a load rather than letting it drop.

 

For example, at the shoulder, if you want to place an object in a cupboard in front of you, you are performing a concentric contraction of the shoulder flexors to achieve this action. Should you change your mind and decide not to place the item in the cupboard in front of you, you will be performing a concentric contraction of your shoulder extensors and an eccentric contraction of your shoulder flexors in order to slowly lower the object back down. I hope this makes sense to you.

 

As far as exercises for rotator cuff tendonitis, eccentric exercises are generally prescribed by therapists for this condition. It is believed that the positive effects of eccentric training on tendonitis might be either an effect of stretching, with a lengthening of the muscle-tendon unit, and consequently less strain during joint motion, or hypertrophy and increased tensile strength in the tendon (Alfredson et al). These exercises can be accomplished with tubing, hand weights, etc. Great care must be taken by the therapist to prescribe the appropriate exericses for each patient as each patient and his/her condition may vary. Having the patient perform an inappropriate exercise or a prescribed exercise improperly can lead to further irritation of the condition."