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Isotonic and Isometric Muscle Contractions

Isotonic and Isometric Muscle Contractions

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Related Experiment Video

Updated: May 26, 2026

Induction and Assessment of Exertional Skeletal Muscle Damage in Humans

Induction and Assessment of Exertional Skeletal Muscle Damage in Humans

Published on: December 11, 2016

Neural contributions to concentric vs. eccentric exercise-induced strength loss.

Travis W Beck¹, Paul R Kasishke, Matt S Stock

¹Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, USA. tbeck@ou.edu

Journal of Strength and Conditioning Research

|December 31, 2011

Summary

Muscle strength loss after exercise is partly due to neural factors, not just fatigue or damage. This suggests training should account for neural inhibition to minimize strength decrements during competition.

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Area of Science:

Exercise Physiology
Neuromuscular Function

Background:

Muscle fatigue and damage can reduce maximal voluntary contraction strength.
Understanding the underlying mechanisms of strength decrement is crucial for optimizing training and performance.

Purpose of the Study:

To investigate the strength, electromyographic (EMG), and mechanomyographic (MMG) responses following exercise protocols designed to induce fatigue and muscle damage versus fatigue alone.
To differentiate the contributions of neural and peripheral factors to strength loss after different exercise types.

Main Methods:

Thirteen healthy men performed maximal concentric (CONexercise) and eccentric (ECCexercise) isokinetic forearm flexor actions.
Peak torque (PT), surface EMG amplitude and frequency, and MMG signals were measured before and after exercise protocols and a control session.
Data were analyzed to compare changes in strength and neuromuscular activation between exercise conditions.

Main Results:

Both CONexercise and ECCexercise led to significant, equivalent decreases in peak torque (26% and 25%, respectively).
Normalized EMG amplitude decreased significantly (19% and 23% for CON and ECC, respectively), but EMG mean frequency and MMG parameters remained unchanged.
No significant changes were observed in the control condition, indicating exercise-induced effects.

Conclusions:

The observed strength decrement after both CONexercise and ECCexercise is partly mediated by neural factors.
Reduced muscle activation, potentially due to inhibition of alpha motor neurons from muscle damage or metabolic changes, contributes to strength loss.
Training strategies aimed at preserving strength during competition should consider and address these neural inhibitory mechanisms.