Recent developments in near-infrared spectroscopy (NIRS) for the assessment of local skeletal muscle microvascular function and capacity to utilise oxygen

Abstract

Purpose of review

Continuous wave near infrared spectroscopy (CW NIRS) provides non-invasive technology to measure relative changes in oxy- and deoxy-haemoglobin in a dynamic environment. This allows determination of local skeletal muscle O ₂ saturation, muscle oxygen consumption ( $\dot{\mathrm{V}}{\text{O}}_2$ ) and blood flow. This article provides a brief overview of the use of CW NIRS to measure exercise-limiting factors in skeletal muscle.

Recent findings

NIRS parameters that measure O ₂ delivery and capacity to utilise O ₂ in the muscle have been developed based on response to physiological interventions and exercise. NIRS has good reproducibility and agreement with gold standard techniques and can be used in clinical populations where muscle oxidative capacity or oxygen delivery (or both) are impaired. CW NIRS has limitations including: the unknown contribution of myoglobin to the overall signals, the impact of adipose tissue thickness, skin perfusion during exercise, and variations in skin pigmentation. These, in the main, can be circumvented through appropriate study design or measurement of absolute tissue saturation.

Summary

CW NIRS can assess skeletal muscle O ₂ delivery and utilisation without the use of expensive or invasive procedures and is useable in large population-based samples, including older adults.

Highlights

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  An overview of CW NIRS to measure O ₂ utilisation and delivery is presented.

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  CW NIRS is cheap, non-invasive, portable and useable in population-based samples.

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  It is useful for understanding underlying mechanisms of deterioration in capacity.