Eccentric (Negative) Muscle Action

An eccentric action (also called negative action) is a dynamic action in which the active muscle is forcibly lengthened as it resists the external resistance — one in which a force external to the muscle overcomes the muscle force and the ends of the muscle are drawn further apart. In a repetition it is the eccentric phase: the lowering phase of movement, a lengthening against load.

Key properties:

• It increases muscle length (the "negative" half of a dynamic exercise).
• It is the primary instigator of delayed-onset muscle soreness (DOMS), and is associated with the connective tissue damage hypothesis of soreness (irritation or damage of connective tissue from exercise using eccentric contractions).
• The muscle produces more force in lowering (eccentric) action than in lifting (concentric) action — about 40% stronger than the concentric phase — so this phase should be accentuated and needs to be emphasized for optimal hypertrophy.
• It should be performed in a deliberate fashion; the lowering movement should be at least as long as the lifting movement. Typical prescribed tempos run about 2 to 3 seconds for the eccentric (negative) phase.
• Using a combination of concentric and eccentric actions, rather than only concentric actions, produces superior gains in strength.

Note on terminology: the source insists "There is no such thing as 'Eccentric Contractions'" — a lengthening muscle is not strictly contracting.

• Eccentric = negative action; external force overcomes muscle, ends drawn apart, muscle lengthens.
• The lowering phase of a repetition; increases muscle length.
• ~40% stronger than concentric; should be accentuated; key for hypertrophy.
• Primary instigator of DOMS; linked to connective tissue damage.
• Combining concentric + eccentric beats concentric-only for strength gains.

• concentric-action — the weaker lifting counterpart.
• isometric-action — the static action.
• muscle-action-terminology — "action" vs. "contraction"; no "eccentric contractions."
• muscle-soreness — acute vs. delayed soreness.
• doms-three-hypotheses — connective tissue damage hypothesis tied to eccentric work.
• tempo — repetition timing of the eccentric phase.
• resistance-training-safety-guidelines — the "control the eccentric as well as the concentric" guideline.