Muscle contractions form the basis of every movement and occur in three distinct phases. Concentric and eccentric contractions are considered isotonic, meaning the muscle changes length while moving a load [1]. Isometric contractions, in contrast, produce force without changing muscle length. Understanding the applications of each can help you train more effectively and lower your risk of injury. Here’s what you need to know about each type.
Concentric
Concentric actions are generally what we imagine when thinking about lifting weights: the phase where muscles shorten to move a load. This contraction generates the force needed to overcome resistance and produce movement. Concentric work is necessary for increasing strength and power and supports explosive actions like jumping, sprinting, and pushing. It also demands more energy (ATP) and neural activation than other types of contractions due to the active shortening of muscle fibers. While essential for performance, concentric contractions typically cause less muscle damage and soreness than eccentric movements [2].
Examples:
- Upward phase of a bicep curl
- Pushing the bar up during a bench press
- Standing up from a squat
Eccentric
Eccentric contractions happen when a muscle lengthens while still producing force, essentially controlling rather than initiating movement. This type of contraction plays a critical role in coordination, deceleration, and injury prevention. Eccentric training is especially effective for building strength, hypertrophy, and improving control, as it allows muscles to handle greater loads than concentric work [1][2][3]. Even though it uses less energy, it places more stress on the muscle fibers, which is why it’s often associated with muscle soreness after unfamiliar or intense workouts [3][4].
Examples:
- Running downhill
- Lowering into a squat
- Lowering portion of a Nordic hamstring curl
Isometric
Isometric contractions involve holding a muscle under tension without any movement at the joint [1]. Isometric actions help maintain posture, improve joint stability, and build strength in a specific position. While they don’t involve visible motion, they challenge muscles to resist movement, making them valuable for injury rehab, core training, and control under fatigue. Isometric work typically requires less energy than dynamic movements but can still be mentally and physically demanding, especially when held for extended periods.
Examples:
- Holding a wall sit
- Maintaining a plank position
- Pausing during a lift
Main Points:
Concentric: Muscle produces force while shortening.
Eccentric: Muscle produces force while lengthening.
Isometric: Muscle produces force while maintaining its original length; no visible joint movement.
References
- Siff M. What Is Muscle Action? Concentric, Eccentric, and Isometric. blog.nasm.org. Published 2022. Accessed August 3, 2025. https://blog.nasm.org/what-is-muscle-action
- Hellicar L. Eccentric Exercise Benefits and Examples. Medicalnewstoday.com. Published June 16, 2023. Accessed August 3, 2025. https://www.medicalnewstoday.com/articles/eccentric-exercise#vs-concentric
- Douglas J, Pearson S, Ross A, McGuigan M. Chronic Adaptations to Eccentric Training: A Systematic Review. Sports Medicine. 2016;47(5):917-941. doi:https://doi.org/10.1007/s40279-016-0628-4
- Hody S, Croisier JL, Bury T, Rogister B, Leprince P. Eccentric Muscle Contractions: Risks and Benefits. Frontiers in physiology. 2019;10(10):536. doi:https://doi.org/10.3389/fphys.2019.00536
