From the earlier mnemonics we can see that:
Eccentric - Lengthen and down movement.
Contraction - Tension.
From this we can understand that:
Eccentric contraction is lengthening of the muscle in tension, or:
Eccentric contraction = Lengthening of the muscles
Eccentric contractions occur when you:
1. Move a dumbbell in a bicep curl downwards away your body.
2. When you squat down to a low position.
Note: Your quadriceps (quads) are made up of four muscles hence quad.
3. Doing a press up and moving your nose gradually towards the floor.