What is "eccentric" training?

What is "eccentric" training?

John Spencer Ellis (Author, TV Show Host, Trainer and CEO, National Exercise & Sports Trainers Association) gives expert video advice on: What is the most common fitness mistake?; What is the difference between fitness and physical activity?; Why is exercise so important? and more...

Eccentric means "elongation of the muscle" or "elongation of the joint." Using the example of the bicep curl: if my arm's extended and I'm curling in, that's concentric. So eccentric is the elongation phase of the muscular contraction. In general terms, most of the muscular development takes place in the eccentric phase, so that's why it's always so important that you control the weight, both up and back, regardless of what the movement is.