Ok so this is something I knew but REALLY, REALLY, REALLY learned first hand in the last few years. An eccentric contraction is when the muscle is used to go down a hill, step, or lower something. Eccentric contractions are harder, no matter what they’re harder. They’re harder if you haven’t had a brain injury or a knee replacement, they’re just harder. Every single patient that I ever saw had more trouble with eccentric contractions. It’s significantly harder for me to go down a hill than up a hill. And I live in Pittsburgh – there are a lot of hills here. And I have a dog so I have to walk on those hills everyday multiple times a day. If you really work on that motion, you’ll automatically gain more control over the concentric contraction. A concentric contraction is the opposite – it’s when going up a hill or staircase, or lifting something. An isometric contraction is when you contract the muscle but there is no movement. So push against a wall really hard, nothing moves – that’s an isometric contraction. To start out strengthening a really weak muscle, use isometric contractions. Then move to concentric, then do eccentric contractions like crazy.