Eccentric movement is the lengthening phase of a muscle movement, slower movement is usually needed to do this.
(I like to use different tempo counts to help make the movements eccentric.)
Eccentric exercises strengthen not just the muscles, but also the connective tissues, helping to both rehab and pre-hab any aches and pains as well as prevent injuries ranging from tendinitis to strains!
Give this exercise a try:
1) Get a bench or seat - knee height is awesome
2) Stand on one leg and slowly - 4 count - lower
3) Try not to "plop" at the bottom
4) Switch legs
Let me know how you do!
The single leg squat is an amazing exercise, especially for runners, it is great to build the most strength in both the gluteus medius and gluteus maximus at the same time.
Give it a try and let me know how you do!