Related Experiment Video
Updated: Aug 11, 2025
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Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
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Muscle fatigue during maximal eccentric-only, concentric-only, and eccentric-concentric bicep curl exercise with
James L Nuzzo1, Matheus D Pinto1, Kazunori Nosaka1
1Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.
Scandinavian Journal of Medicine & Science in Sports
|February 8, 2023
Summary
Connected adaptive resistance exercise (CARE) machines effectively induce muscle fatigue. Men and women experience different strength loss patterns based on contraction type, with women more affected by eccentric and men by concentric phases.
Area of Science:
- Exercise Physiology
- Biomechanical Engineering
- Sports Science
Background:
- Connected adaptive resistance exercise (CARE) machines represent novel technology designed to dynamically adjust exercise resistance based on real-time muscle fatigue.
- Understanding the acute physiological responses to different resistance exercise modalities on these machines is crucial for optimizing training protocols and injury prevention.
Purpose of the Study:
- To investigate muscle fatigue, specifically strength loss and perceived exertion, during maximal eccentric-only (ECCmax-only), concentric-only (CONmax-only), and coupled eccentric-concentric (ECCmax-CONmax) bicep curl exercises using CARE machine technology.
- To compare the susceptibility of men and women to strength loss across these different contraction types.
Main Methods:
- Eleven men and nine women participated in three randomized, separate sessions, each involving a different bicep curl protocol (ECCmax-only, CONmax-only, ECCmax-CONmax).
- Participants completed 4 sets of 20 maximal effort contractions per protocol, with the CARE machine automatically adjusting resistance to maintain maximal effort.
- Strength loss was quantified by comparing the load at the end of Set 4 to the highest load achieved in Set 1. Perceptions of fatigue and pain were also recorded.
Main Results:
- All protocols induced substantial muscle fatigue, characterized by significant strength loss and heightened perceptions of fatigue and pain.
- Women exhibited greater strength loss during exercises involving maximal eccentric efforts (ECCmax-only and ECCmax-CONmax), while men showed greater strength loss during maximal concentric efforts (CONmax-only and ECCmax-CONmax).
- Specifically, in CONmax-only exercise, men experienced 55.6% CON strength loss compared to 35.3% in women. In ECCmax-CONmax exercise, men had higher ECC (62.9% vs. 48.5%) and CON (77.0% vs. 66.2%) strength loss than women. Women generally reported more biceps pain.
Conclusions:
- CARE machine technology can feasibly deliver eccentric-only and accentuated eccentric exercise protocols, effectively inducing muscle fatigue.
- Sex-based differences in acute responses to maximal effort resistance exercise on CARE machines are evident, varying with the type of muscle contraction (eccentric vs. concentric).
- These findings highlight the importance of considering sex-specific responses when designing resistance training programs utilizing advanced adaptive resistance technology.
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