Strength training mostly consists of concentric exercises (when the muscles shorten to lift something, as in lifting a weight to do a bicep curl) and eccentric exercises (when the muscles lengthen to lower something). But could one action provide more benefits than the other? A study found that half an hour of eccentric exercise a week boosted muscle strength and lowered insulin resistance more than concentric exercise.
Twenty women were randomly assigned to an exercise group that did either concentric or eccentric movements once a week for eight weeks. Exercises for both groups consisted of leg extensions, which target the quadriceps muscles in the front of the thigh.
Researchers discovered that after the short weekly bouts of movement, the eccentric exercise group substantially increased muscle strength and performance, decreased insulin resistance and improved blood lipid profiles more than concentric exercise. After two months, resting energy expenditure (the number of calories burned while at rest) increased 5%, similar to what people experience after endurance training or more traditional strength training that includes concentric and eccentric exercise.
In the study, which appears in the January issue of the journal Medicine & Science in Sports & Exercise, the authors concluded that eccentric exercise may provide some practical advantages. They wrote, "People who wish to participate in activities containing eccentric actions may perform exercises with strong eccentric component, such as bench stepping, downhill walking, or placing emphasis on the negative phase of conventional resistance exercises."