Cerebral and Muscle Tissue Oxygenation During Incremental Cycling in Male Adolescents Measured by Time-Resolved Near-Infrared Spectroscopy

Abstract

Near-infrared spectroscopy (NIRS) has long been used to measure tissue-specific O2 dynamics in exercise, but most published data have used continuous wave devices incapable of quantifying absolute Hemoglobin (Hb) concentrations. We used time-resolved NIRS (TR-NIRS) to study exercising muscle (Vastus Lateralis, VL) and prefrontal cortex (PFC) Hb oxygenation in 11 young males (15.3 ± 2.1 yrs) performing incremental cycling until exhaustion (peak VO2 = 42.7 ± 6.1 ml/min/kg, mean peak power = 181 ± 38 W). TR-NIRS measurements of reduced scattering (μs′) and absorption (μa) at three wavelengths (759, 796, and 833 nm) were used to calculate concentrations of oxyHb ([HbO2]), deoxy Hb ([HbR]), total Hb ([THb]), and O2 saturation (stO2). In PFC, significant increases were observed in both [HbO2] and [HbR] during intense exercise. PFC stO2% remained stable until 80% of total exercise time, then dropped (−2.95%, p = .0064). In VL, stO2% decreased until peak time (−6.8%, p = .01). Segmented linear regression identified thresholds for PFC [HbO2], [HbR], VL [THb]. There was a strong correlation between timing of second ventilatory threshold and decline in PFC [HbO2] (r = .84). These findings show that TR-NIRS can be used to study physiological threshold phenomena in children during maximal exercise, providing insight into tissue specific hemodynamics and metabolism.

Quantification of extra-cerebral and cerebral hemoglobin concentrations during physical exercise using time-domain near infrared spectroscopy

“…In [18], the authors observed significantly higher relative SO 2 (r SO 2 ) at high intensity compared to rest, which is in the opposite direction of our extra-cerebral SO 2 . Non-significant changes in SO 2 measured with TD-NIRS in Ganesan et al [24] are consistent with our cerebral SO 2 . Furthermore, these studies were also compared with hemoglobin concentrations retrieved using our homogeneous model ( Table 5, Appendix A).…”

“…2, the significant increase in cerebral HbR between 80% and rest was coherent with two studies [16,17]. Our results in HbO 2 and HbT were also consistent with a CW-NIRS study performed at normal (150 m) altitude [18], while they were not in agreement with significant increases observed between moderate and high exercise intensity compared to rest [16,17,24]. In [18], the authors observed significantly higher relative SO 2 (r SO 2 ) at high intensity compared to rest, which is in the opposite direction of our extra-cerebral SO 2 .…”

“…The effect of incremental exercise on cerebral oxygenation using NIRS instrumentation has been investigated in the last decades (see this systematic meta-data analysis recently published [14]). Despite the inability to discriminate extra-cerebral response, these studies [14,[16][17][18][19][20][21][22][23][24][25] reported hemoglobin changes recovered from signals originated through the whole head. Few of them were performed with a similar experimental design based on incremental intensity levels quantified with individual V O 2 peak or ventilatory thresholds (VT1 and VT2, corresponding to moderate and high intensity exercise, respectively) [16][17][18]24].…”

“…Continuous-wave NIRS (CW-NIRS) systems allow to retrieve changes in relative oxy-(H bO 2 ) and deoxygenated (HbR) hemoglobin concentrations induced by neuronal activity [15]. These techniques have been used during incremental intensity exercise [14,[16][17][18][19][20][21][22][23][24][25]. However, CW-NIRS techniques (1) provide relative rather than absolute measurements and (2) are known to be strongly contaminated by extra-cerebral signals as hemoglobin changes were retrieved with a simple homogeneous head model.…”

Muscle Oxygenation During Exercise in Physically Active and Overweight 6–19-Year-Old Children

“…The mean time response for muscle tissue deoxygenation is significantly faster in children than adults at the onset of high intensity exercise (Willcokcs, Williams, Barker, Fulford, & Armstrong, 2010). 13-17-year-old boys demonstrate significant changes in absolute hemoglobin concentrations and oxygenation in the exercising muscle during incremental cycling and post-exercise recovery (Ganesan et al, 2016). 9-year-old girls demonstrate an earlier change in [HHb] compared with same age boys during ramp incremental exercise (McNarry et al, 2015).…”