Reliability of muscle blood flow and oxygen consumption response from exercise using near-infrared spectroscopy

Abstract

Near-infrared spectroscopy (NIRS), coupled with rapid venous (VO) and arterial occlusions (AO) can be used to non-invasively estimate resting local skeletal muscle blood flow (mBF) and oxygen consumption (mV̇O₂), respectively. However, the day-to-day reliability of mBF and mV̇O₂ responses to stressors such as incremental dynamic exercise has not been established.

Purpose

To determine the reliability of NIRS derived mBF and mV̇O₂ response from incremental dynamic exercise.

Methods

Measurements of mBF and mV̇O₂ were collected in the vastus lateralis of twelve healthy, physically active adults [7 m and 5 f; 25 y (SD 6)] over 3 non-consecutive visits within 10 days. After 10 mins rest, participants performed 3 mins of rhythmic isotonic knee extension (1 extension/4 s) at 5, 10, 15, 20, 25, and 30% of maximal voluntary contraction (MVC), prior to 4 VOs and then 2 AOs.

Results

mBF and mV̇O₂ proportionally increased with intensity (0.55 to 7.68 ml∙min⁻¹∙100 ml⁻¹ and 0.05 to 1.86 mlO₂∙min⁻¹∙100 g⁻¹, respectively) up to 25% MVC where it began to plateau at 30% MVC. Moreover, a mBF/mV̇O₂ mV̇Oratio of ∼5 was consistent for all exercise stages. The intra-class coefficient (ICC) for mBF indicated high to very high reliability for 10–30% MVC (0.82–0.9). There was very high reliability for mV̇O₂ across all exercise stages (ICC 0.91–0.96).

Conclusion

NIRS can reliably assess muscle blood flow and oxygen consumption responses to low-moderate exercise, meriting potential applications in clinical diagnosis and therapeutic assessment.

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