Most people still rely on stretching to increase flexibility and warm-up for workouts. But research shows eccentric exercises, which focus on a slow and controlled lengthening motion of the muscle, are much more effective at building flexibility and preventing injury.
Eccentric training occurs when you perform the “down” phase of an exercise at a heavier weight or with a longer tempo than the concentric or shortening phase. For instance, to increase flexibility in the hips you could do eccentric-enhanced squats by taking 6 to 10 seconds to lower yourself into the bottom position.
Then you would come back up (this is the concentric phase) as quickly as possible under control.
How effective is it for improving flexibility? A review of literature showed it can produce a clinically relevant increase in joint range-of motion. For example, at the hamstring, a 6-week eccentric training program increased hip range of motion by 13°.
A second 8-week study found that eccentrics were 50 percent more effective than a static stretching program for increasing flexibility. Range-of-motion increases were seen at the ankle, knee, and hip of about 7°.
Researchers think eccentric training is so effective because it results in the addition of sarcomeres in series within the muscle. This increases the joint angle at which peak strength is generated. Remember that sarcomeres are the basic unit of a muscle that make it contract. More sarcomeres mean a longer muscle length. In the studies reviewed, the length of distinct muscle fibers (called fascicles) increased significantly in the hamstring, calf, and quad.
For both athletes and the general population, better flexibility is a common goal that often falls by the wayside of more pertinent goals like fat loss and muscle development. Adding eccentric training for restricted joints is a no-brainer since it has repeatedly been shown to build muscle and falls in line with any program geared at improving body composition.