The
relationship between force (tension) development and velocity (rate) of
muscle contraction is said to be inverse. In this sense, eccentrics are
considered "slower" than isometric contractions, and isometrics are considered
"slower" than concentric contractions. Eccentric contractions can develop
more tension than isometric contractions, and isometric contractions can
develop more tension than concentric contractions. However, it may be clearer
to consider each type of contraction individually. Faster concentric contractions
develop less tension than slower concentric contractions. Faster eccentric
contractions develop more tension than slower eccentric contractions. Isometric
contractions develop more tension than concentrics, but less than eccentrics.
A word about the definition of "eccentric" is in order. In the context of the force-velocity relationship discussion, "eccentric" implies that the working muscle is being overloaded to the point where it cannot hold the external weight. The heavier the weight, the faster the velocity of eccentric contraction (because the muscle has increasing difficulty holding progressively heavier weights). It is probably true that a portion of the greater tension that develops with faster eccentric contractions is a result of passive elongation by the overpowering weight. This statement implies that lowering a light weight quickly will not increase the tension developed. To develop more tension, the faster eccentric contraction must be produced by an overpowering weight.