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Updated: Jul 11, 2026
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Skeletal Muscle Neurovascular Coupling, Oxidative Capacity, and Microvascular Function with 'One Stop Shop' Near-infrared Spectroscopy
Published on: February 20, 2018
Biceps brachii myoelectric and oxygenation changes during static and sinusoidal isometric exercises
Francesco Felici1, Valentina Quaresima, Luigi Fattorini
1Department of Human Movement and Sport Sciences, Istituto Universitario di Scienze Motorie, Piazza Lauro De Bosis 6, 00194 Roma, Italy. francesco.felici@iusm.it
Summary
This study combined near-infrared spectroscopy (NIRS) and surface electromyography (sEMG) to investigate muscle oxygen saturation during isometric contractions. Findings show muscle oxygen demand is linked to motor unit activation, not contraction type.
Area of Science:
- Exercise Physiology
- Biomedical Engineering
- Muscle Physiology
Background:
- Surface electromyography (sEMG) quantifies muscle electrical activity during contractions using parameters like median power spectral frequency.
- Near-infrared spectroscopy (NIRS) non-invasively measures local muscle oxygen saturation during exercise.
- Combining sEMG and NIRS offers a comprehensive view of muscle function and metabolic status.
Purpose of the Study:
- To investigate the relationship between sEMG parameters and muscle metabolic status (oxygen saturation) in the biceps brachii.
- To analyze these relationships under various isometric contraction types: static and sinusoidal.
- To determine how force output and contraction modality influence muscle oxygenation and electrical activity.
Main Methods:
- Simultaneous NIRS and sEMG recordings were performed on the biceps brachii during isometric contractions.
- Contraction protocols included static (20-80% MVC) and sinusoidal (40+/-20%, 60+/-20% MVC) modalities.
- Analysis focused on muscle oxygen desaturation phases, sEMG variables (CV, MDF), and their correlation with force output and NIRS-derived Tissue Oxygenation Index (TOI).
Main Results:
- Muscle O(2) desaturation exhibited distinct fast and slow phases, independent of contraction modality.
- The rate of O(2) desaturation strongly correlated with force output (R=0.92).
- sEMG parameters (CV, MDF) also correlated with force level (R=0.87, R=0.86), and showed high correlation with NIRS TOI slope (R=0.73, R=0.72).
Conclusions:
- Muscle oxygen demand during isometric contractions is primarily influenced by the recruitment of specific motor units, rather than the contraction's modality (static vs. sinusoidal).
- The combined NIRS-sEMG approach effectively links muscle electrical activity changes to metabolic status.
- This integrated method provides insights into the physiological responses of skeletal muscle to varying mechanical demands.
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