Diffuse correlation spectroscopy and frequency-domain near-infrared spectroscopy for measuring microvascular blood flow in dynamically exercising human muscles

• Published in: Journal of applied physiology (1985) Vol. 127; no. 5; pp. 1328 - 1337
• Main Authors: Quaresima, Valentina, Farzam, Parisa, Anderson, Pamela, Farzam, Parya Y., Wiese, Daniel, Carp, Stefan A., Ferrari, Marco, Franceschini, Maria Angela
• Format: Journal Article
• Language: English
• Published: United States 01.11.2019
• Subjects: exercise; near-infrared spectroscopy; diffuse correlation spectroscopy; blood flow; muscle oxidative metabolism
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.00324.2019

In the last 20 yr, near-infrared diffuse correlation spectroscopy (DCS) has been developed for providing a noninvasive estimate of microvascular blood flow (BF) as a BF index (BF i ) in the human skin, muscle, breast, brain, and other tissue types. In this study, we proposed a new motion correction algorithm for DCS-derived BF i able to remove motion artifacts during cycling exercise. We tested this algorithm on DCS data collected during cycling exercise and demonstrated that DCS can be used to quantify muscle BF i during dynamic high-intensity exercise. In addition, we measured tissue regional oxygen metabolic rate (MRO 2i ) by combining frequency-domain multidistance near-infrared spectroscopy (FDNIRS) oximetry with DCS flow measures. Recreationally active subjects ( n = 12; 31 ± 8 yr, 183 ± 4 cm, 79 ± 10 kg) pedaled at 80–100 revolutions/min until volitional fatigue with a work rate increase of 30 W every 4 min. Exercise intensity was normalized in each subject to the cycling power peak (W peak ). Both rectus femoris BF i and MRO 2i increased from 15% up to 75% W peak and then plateaued to the end of the exercise. During the recovery at 30 W cycling power, BF i remained almost constant, whereas MRO 2i started to decrease. The BF i /MRO 2i plateau was associated with the rising of the lactate concentration, indicating the progressive involvement of the anaerobic metabolism. These findings further highlight the utility of DCS and FDNIRS oximetry as effective, reproducible, and noninvasive techniques to assess muscle BF i and MRO 2i in real time during a dynamic exercise such as cycling. NEW & NOTEWORTHY To the best of our knowledge, this study is the first to demonstrate that diffuse correlation spectroscopy in combination with frequency-domain near-infrared spectroscopy can monitor human quadriceps microvascular blood flow and oxygen metabolism with high temporal resolution during a cycling exercise. The optically measured parameters confirm the expected relationship between blood flow, muscle oxidative metabolism, and lactate production during exercise.