Skin blood flow differentially affects near-infrared spectroscopy-derived measures of muscle oxygen saturation and blood volume at rest and during dynamic leg exercise

Abstract

The impact of skin blood flow changes on near-infrared spectroscopy (NIRS)-derived measures of muscle oxygen saturation (SmO(2)) and blood volume has not been fully established. We measured SmO(2) and total hemoglobin concentration ([tHb]) responses of the right vastus lateralis during rest and dynamic knee extension exercise in ten young, healthy males. The protocol was repeated four times: twice without thigh heating for reliability, and twice with different grades of thigh heating for assessing the impact of cutaneous vasodilation on SmO(2) and Δ[tHb]. The reliability of our SmO(2) and [tHb] measurements was good. Thigh heating at 37 and 42°C caused marked increases in cutaneous vascular conductance (CVC) during rest and exercise (P < 0.001 between each condition), and small increases in SmO(2) during rest (from 69 ± 8% to 71 ± 7% and 73 ± 6%, respectively; P < 0.05 between each condition), but not during exercise (e.g. 1 min exercise: 51 ± 11% vs. 51 ± 11% and 52 ± 11%, respectively; P > 0.05 at all time points). In contrast, heating-induced increases in %CVC(peak) were accompanied by increases in [tHb] at rest and during exercise and a decrease in Δ[tHb] during exercise (all P < 0.05). Our findings suggest that NIRS-derived measures of SmO(2) and blood volume are differentially affected by skin blood flow at rest and during exercise. The findings from this study should be considered in NIRS experiments where skin blood flow can change markedly (e.g. high-intensity and/or prolonged exercise).

The use of near-infrared spectroscopy in understanding skeletal muscle physiology: recent developments

“…A recent study [42] provided reassurance that changes in SmO 2 during exercise predominantly reflect muscle oxygenation, even during conditions where skin and muscle blood flow were elevated concomitantly (e.g. during prolonged, dynamic exercise).…”

Changes in Tissue Oxygen Saturation with Well- and Tight-Fitted Compression Sleeves During an Incremental Exercise on Treadmill

“…Indeed, StO 2 was recorded at a maximum depth of 15 mm including cutaneous and muscular vessels. Moreover, previous studies suggest that compression sleeves may affect cutaneous StO 2 through temperature changes (13,27) and pressure-induced skin vasodilation (26).…”

“…These results are in accordance with previous research, which reported that StO2 increased with calf compression sleeves before and after running or cycling exercises (13,19). The higher StO 2 was attributed to the increased muscle flow rate (9, 10) and changes in skin blood flow with calf compression sleeves (26,27). Indeed, wearing compression on the lower limbs is known to increase venous return (2), causing venous pressure to decrease (1).…”

“…The pressure applied by sleeves is transmitted into the tissue, thus reducing the transmural pressure gradient of the arterial vessels (29). Finally, changes in skin blood flow must also be considered (26,27). Indeed, StO 2 was recorded at a maximum depth of 15 mm including cutaneous and muscular vessels.…”

What Does Cerebral Oxygenation Tell Us About Central Motor Output?

“…NIRS gain or laser power must then be modulated to fit with the skin properties of a given subject; which can be performed automatically by the NIRS hardware before starting the data acquisition. Skin blood flow is one of the main confounding factors as the haemoglobin molecules present in the capillary beds located in the skin are the first (and last) exposed to NIRS light (Tew et al, 2010). In exercising subjects, blood flow is increasing in proportion to the intensity of exercise, for well-known thermoregulation reasons.…”