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Physiological response in the forearm during and after isometric intermittent handgrip
1Division of Applied Work Physiology, National Institute of Occupational Health, Solna, Sweden.
Summary
Local blood flow is insufficient during isometric handgrip exercise, even at low intensities. Intermittent exercise at 10% and 25% maximum voluntary contraction (MVC) with longer relaxation periods is acceptable to avoid local fatigue.
Area of Science:
- Physiology
- Exercise Science
- Sports Medicine
Background:
- Muscle fatigue is a complex phenomenon affecting physical performance.
- Understanding the physiological responses during isometric exercise is crucial for training and rehabilitation.
Purpose of the Study:
- To investigate the development of local fatigue during isometric intermittent handgrip exercise.
- To analyze the role of blood flow, electromyography, and subjective ratings in fatigue development.
Main Methods:
- Isometric intermittent handgrip exercise with varying contraction/relaxation times (10+10, 10+5, 10+2s, continuous) and intensities (10, 25, 40% MVC).
- Measurements included forearm blood flow (venous occlusion plethysmography), electromyography (EMG) frequency analysis, and subjective ratings of effort and pain.
Main Results:
- Forearm blood flow was insufficient even at low-intensity isometric contractions (10% MVC).
- Maximal forearm blood flow during relaxation was achieved at 25% MVC.
- Acceptable local fatigue was observed at 10% MVC (intermittent) and 25% MVC with longer relaxation periods (10+5s, 10+10s).
Conclusions:
- Vasodilating metabolites play a significant role in blood flow regulation during low-intensity isometric contractions.
- Fatigue development is characterized by a shift in blood flow, decreased EMG signal complexity, and increased subjective ratings.
- Optimizing contraction-relaxation periods is essential for managing local fatigue during isometric handgrip exercise.