Definitions for "Eccentric Contraction"
The "negative" phase of the repetition, the part with resistance as you return the weight from the end of the positive phase, back to the beginning. Eg, in the bicep curl, it is when you let the weight come back slowly to the beginning position.
isotonic contraction in which muscle lengthens while under tension.
This is a contraction in which the muscle lengthens and works with gravity.