title: Recent developments in near-infrared spectroscopy (NIRS) for the assessment of local skeletal muscle microvascular function and capacity to utilise oxygen.
abstract: OBJECTIVE
  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 O2saturation, muscle oxygen consumption ([Formula: see text]) and blood flow. This article provides a brief overview of the use of CW NIRS to measure exercise-limiting factors in skeletal muscle.
  
  
  RESULTS
  NIRS parameters that measure O2delivery and capacity to utilise O2in 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.
  
  
  CONCLUSIONS
  CW NIRS can assess skeletal muscle O2delivery and utilisation without the use of expensive or invasive procedures and is useable in large population-based samples, including older adults.
authors.affiliation: Institute of Cardiovascular Science, University College London, WC1E 6BT, UK.
authors.forename: Siana
authors.initials: S
authors.lastname: Jones
authors.affiliation: Institute of Cardiovascular Science, University College London, WC1E 6BT, UK.
authors.forename: Scott T
authors.initials: ST
authors.lastname: Chiesa
authors.affiliation: Institute of Cardiovascular Science, University College London, WC1E 6BT, UK.
authors.forename: Nishi
authors.initials: N
authors.lastname: Chaturvedi
authors.affiliation: Institute of Cardiovascular Science, University College London, WC1E 6BT, UK.
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
keywords: Exercise; Near-infrared spectroscopy; Skeletal muscle