What is Eccentric Exercise
Eccentric exercise involves the active lengthening of muscle fibers under an external load, such as when lowering a weight against gravity 1, 2.
Mechanical Definition
Eccentric contractions occur when a muscle generates force while being stretched or lengthened. This is fundamentally different from:
- Concentric contractions: muscle shortens while generating force (e.g., lifting a weight)
- Isometric contractions: muscle generates force without changing length
A practical example is the downward phase of a bicep curl—as you lower the weight, your bicep muscle lengthens while still contracting to control the descent 1.
Physiological Characteristics
Eccentric exercise has several unique properties that distinguish it from other contraction types:
Force Production
- Generates higher muscle force compared to concentric contractions at the same metabolic cost 2, 3
- Produces approximately 4-5 times lower energy cost than concentric work at similar mechanical power output 3
- This high force-to-energy ratio makes it particularly efficient for strength development
Metabolic and Cardiovascular Responses
When performed at the same mechanical power output as concentric exercise, eccentric work induces:
- Lower oxygen consumption (VO₂)
- Lower heart rate
- Reduced metabolic demand
However, a critical caveat: when both exercise modes are performed at the same VO₂ level, eccentric exercise actually produces greater cardiovascular stress 3. This means heart rate values can be misleading for training load management during eccentric exercise.
Clinical Considerations in Resistance Training Guidelines
The American Heart Association guidelines describe eccentric exercise in the context of proper resistance training technique. Exercises should be performed at a moderate to slow controlled speed (3 seconds concentric, 3 seconds eccentric) through a full range of motion 4. This controlled tempo during the eccentric phase is essential for:
- Preventing excessive muscle soreness
- Reducing injury risk
- Allowing proper musculoskeletal adaptation
- Maintaining proper breathing patterns (exhaling during concentric/exertion phase, inhaling during eccentric/relaxation phase)
Initial Effects and Adaptations
Early Phase (Unfavorable Effects)
In untrained individuals, eccentric exercise initially causes 5, 6:
- Subcellular muscle damage
- Delayed onset muscle soreness (DOMS)
- Muscle stiffness
- Reduced fiber excitability
- Temporary muscle weakness
- Disturbance of proprioception
Important pitfall: These negative effects are primarily due to muscle unaccustomedness to eccentric actions, not eccentric exercise per se 7. After adaptation (typically within 1-2 weeks), subsequent eccentric exercise produces minimal muscle damage 6, 7.
Long-term Adaptations
With proper progression, eccentric exercise induces beneficial adaptations including 5:
- Muscle hypertrophy
- Increased cortical activity
- Changes in motor unit behavior
- Improved muscle function
- Increased sarcomere number in muscle fibers
- Protection against future muscle injuries
Strength Training Outcomes
Eccentric-only training is superior for improving eccentric strength (approximately 27% vs 10% improvement), but provides similar improvements in concentric and isometric strength compared to concentric-only training 8. Strength gains are mode-specific, meaning you get better at what you practice.
Applications
Eccentric exercise is used for:
- Athletic performance: strength and power development in healthy individuals
- Rehabilitation: particularly effective for chronic tendinopathy (Achilles, patellar tendons) 9
- Clinical populations: elderly, cardiac patients, and those with limited exercise capacity can benefit from the high force/low metabolic cost ratio 3
- Injury prevention: adapted muscle is protected against more severe injuries 6