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. 2025 Dec 6.
doi: 10.1007/s00421-025-06078-5. Online ahead of print.

The effect of muscle oxygenation on neuromuscular efficiency and force complexity

Petra Kis  1 , Colin W Kipper  1 , Kylie N Burleson  1 , Brenden L Roth  1 , Jerome Hausselle  2 , Joshua L Keller  3 , Shane M Hammer  4
Affiliations

The effect of muscle oxygenation on neuromuscular efficiency and force complexity

Petra Kis et al. Eur J Appl Physiol. .

Abstract

Purpose: Muscle oxygen availability influences contractile performance and neuromuscular control, yet it remains unclear whether graded reductions in oxygen saturation at rest elicit proportional impairments in neuromuscular function. This study tested whether progressive decreases in muscle tissue saturation (StO2) alter neuromuscular efficiency (NME) and force complexity during submaximal voluntary contractions.

Methods: Twenty-nine healthy adults (12 M, 17 F) performed dorsiflexion contractions at 50% of maximal voluntary contraction under four conditions: Control (n = 29) and arterial occlusion targeting 70% (n = 26), 60% (n = 25), and 50% (n = 9) StO2. During each condition, electromyography and force output were collected to assess normalized root mean square, NME, and measures of force variability and complexity.

Results: Reductions in StO2 progressively increased neural excitation requirements and decreased NME (both p < 0.001), with greater desaturation associated with greater impairments. Force output became more variable and less complex with declining StO2, as reflected by increased coefficient of variation and detrended fluctuation analysis α, and reduced approximate and sample entropy (all p < 0.05). These effects were evident during contractions initiated after minimal prior exertion, i.e., without fatigue, and followed a dose-responsive pattern.

Conclusion: These findings demonstrate that muscle oxygenation at rest influences excitation efficiency and disrupts the temporal structure of motor output at the onset of contractions. As StO2 declined, greater neural drive was required to maintain force, and force signals became less complex, suggesting a loss of adaptability in motor unit control. This work highlights the role of oxygen availability in preserving excitation efficiency and maintaining adaptable motor output, with potential clinical relevance for populations with impaired muscle oxygenation.

Keywords: Blood flow occlusion; Force complexity; Muscle oxygenation; Neuromuscular efficiency.

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Conflict of interest statement

Declarations. Competing interests: The authors report no competing interests for this work.

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