Often referred to as "negative training" eccentric strength is a vital component to any fitness program.
Eccentric strength is the lengthening of a muscle such as down phase of a bicep curl. This type of training help cause more muscle damage which results in stronger, leaner muscles.
Any training would be impossible with out eccentric strength contractions as they are responsible for slowing down movements and then reversing your direction. We would not be able to walk or run as we would be unable to counter the force of gravity and be driven into the ground. It is easy to use eccentric strength to your advantage when you have the right tips and tools.
When you are performing any weight bearing exercise, concentrate on the lowering phase of the exercise. You need to be aware of the speed of this movement.
For example, when you do a chest press, count to 2 when you press into the movement and lower the weights back down for a count of 4. You can also use a partner to assist you do you can concentrate of lifting more weight on the negative phase of the exercise.
Make sure that you are performing the exercise safely as you risk causing damage to the connective muscle tissue. You want to use this training method sparingly as you do become over trained. However, by incorporating this type of training into your current program you can create move overload to the muscle which will result in greater gains and growth.