BOTH HALVES OF THE REP CAN BUILD MUSCLE.
- 01
Concentric actions shorten muscle while producing force; eccentric actions produce force while the muscle-tendon unit lengthens under load.
- 02
Eccentric actions can tolerate high external forces and often cost less metabolic energy for a given force.
- 03
Current meta-analysis does not support a large universal hypertrophy advantage for eccentric-only versus concentric-only training.
- 04
Normal resistance training usually contains both actions, which is a strong default unless a specific sport, rehabilitation or overload goal justifies emphasis.
SHORTENING AND LENGTHENING ARE DIFFERENT MECHANICAL CONDITIONS.
During a concentric action, the muscle produces force while shortening. During an eccentric action, active muscle resists while lengthening. Isometric action sits between them with force produced at nearly constant joint position.
ECCENTRICS CAN HANDLE HIGH FORCE.
Skeletal muscle can generally resist greater loads eccentrically than it can lift concentrically, although the size of the difference is smaller and more variable in human voluntary testing than in isolated muscle. Neural inhibition, technique and apparatus influence measured values.
THE GAP IS SMALLER THAN THE HYPE.
Recent systematic review and meta-analysis found no statistically clear overall hypertrophy difference between eccentric- and concentric-focused programs, with substantial heterogeneity. Earlier work also suggested both modes are effective.
USE ECCENTRIC EMPHASIS FOR A REASON.
Eccentric overload can be useful when equipment or spotters allow safe exposure to loads above concentric capacity, and slower eccentrics can help standardize technique. But simply making every lowering phase extremely slow reduces repetitions and changes the training dose.
NOVEL ECCENTRICS CAN CREATE MORE SORENESS.
Unaccustomed eccentric loading can produce pronounced muscle damage and delayed soreness. The repeated-bout effect reduces this response after exposure, so introduce aggressive eccentric work progressively rather than using soreness as a target.
DON’T CONFUSE HIGH FORCE WITH GUARANTEED GROWTH.
Common mistakes include treating eccentric strength as proof of superior hypertrophy, using excessive tempo that ruins loading, seeking damage as a growth mechanism and neglecting the concentric phase of normal lifting.
READ THE EVIDENCE.
- 01da Silva et al. (2025).
Eccentric versus concentric muscle actions on hypertrophy: systematic review and meta-analysis.
PUBMED ↗ - 02Schoenfeld et al. (2017).
Hypertrophic effects of concentric versus eccentric muscle actions: systematic review and meta-analysis.
PUBMED ↗ - 03ACSM Position Stand (2026).
Resistance training prescription for hypertrophy and performance.
PUBMED ↗ - 04Review (2007).
Eccentric exercise and adaptation of the muscle length-tension relationship.
PUBMED ↗
Educational content only. It is not medical advice. See the Fitness Disclaimer.