The 3 Types of Muscle Contractions
There are three different types of muscle contractions: isometric, concentric, and eccentric.
If I hold the weight still, the muscle is engaged but doesn't change length. This is an isometric contraction.
When I bring that weight towards my shoulder, the biceps muscle shortens. This is a concentric contraction.
As I lower the weight, the biceps lengthens. This is an eccentric contraction.