The action of an eccentric muscle contraction occurs when muscles are firing while elongating simultaneously.
An example of this is when you're straightening your arms back out after doing a bicep curl. This form of contraction is constantly ignored by many people in the gym but focusing on this movement has actually shown to create even greater results for muscle building and overall strength of muscles.
Eccentric contractions are already the strongest form of contraction that your muscles can perform; it is also the form that will have minimal risk for injury. With this in mind this is also a great way for people suffering from injuries to reduce muscle loss in the area involved.
So how should you perform an eccentric contraction exercise?
Let's start with an easy example of eccentric calf raises. Simply go up to some stairs and stand on the first step, then keep the balls of your feet on the edge of the stairs and your weight shifted towards your toes. After rising up on your toes just simply go back down as slow as possible while maintaining constant movement (roughly 3-5 seconds back down). The idea behind doing this on stairs or a small ledge is to allow for a greater range of motion for your calf muscles to fire through.
This is just ONE example of how to utilize eccentric contractions for your exercises. It can be used for bench press, squats, deadlift, pull-ups, biceps curls, etc. Adding a focus to eccentric contractions can help maximize your workouts and thus your results. Keep in mind that adding eccentric contraction focus to your exercises will most likely increase difficulty and thus either an reduction of weight and or repetitions is recommended so that you can gauge how this new addition affects the rate at which your muscles fatigue.
I hope you enjoyed reading this post and adding another angle at which to attack your muscles to optimize results.