Alveolar gas exchange and tissue oxygenation during incremental treadmill exercise, and their associations with blood O2 carrying capacity

Abstract

The magnitude and timing of oxygenation responses in highly active leg muscle, less active arm muscle, and cerebral tissue, have not been studied with simultaneous alveolar gas exchange measurement during incremental treadmill exercise. Nor is it known, if blood O 2 carrying capacity affects the tissue-specific oxygenation responses. Thus, we investigated alveolar gas exchange and tissue (m. vastus lateralis, m. biceps brachii, cerebral cortex) oxygenation during incremental treadmill exercise until volitional fatigue, and their associations with blood O 2 carrying capacity in 22 healthy men. Alveolar gas exchange was measured, and near-infrared spectroscopy (NIRS) was used to monitor relative concentration changes in oxy-( [O 2 Hb]), deoxy-( [HHb]) and total hemoglobin ( [tHb]), and tissue saturation index (TSI). NIRS inflection points (NIP), reflecting changes in tissue-specific oxygenation, were determined and their coincidence with ventilatory thresholds [anaerobic threshold (AT), respiratory compensation point (RC); V-slope method] was examined. Blood O 2 carrying capacity [total hemoglobin mass (tHb-mass)] was determined with the CO-rebreathing method. In all tissues, NIPs coincided with AT, whereas RC was followed by NIPs. High tHb-mass associated with leg muscle deoxygenation at peak exercise (e.g., [HHb] from baseline walking to peak exercise vs. tHb-mass: r = 0.64, p < 0.01), but not with arm muscle-or cerebral deoxygenation. In conclusion, regional tissue oxygenation was characterized by inflection points, and tissue oxygenation in relation to alveolar gas exchange during incremental treadmill exercise resembled previous findings made during incremental cycling. It was also found out, that O 2 delivery to less active m. biceps brachii may be limited by an accelerated increase in ventilation at high running intensities. In addition, high capacity for blood O 2 carrying was associated with a high level of m. vastus lateralis deoxygenation at peak exercise.

Twin Resemblance in Muscle HIF-1α Responses to Hypoxia and Exercise

“…Our current observations clearly contradict such conclusion. We did not measure intracellular PO 2 , indeed, yet in line with earlier observations (Richardson et al, 2006; Rissanen et al, 2012; D'Hulst et al, 2013) resting arterial oxygen saturation on average decreased from ~98% in normoxia to ~78% in 0.107 FIO 2 (Masschelein et al, 2015b), which should yield intracellular PO 2 values in the range of ~20–25 mmHg (Richardson et al, 2006). Nonetheless, HIF-1α protein expression on average increased ~ 2-fold and further increased during exercise (20 min @1.2 W/kg; see Figure 2).…”

Correlation analysis between surface electromyography and continuous-wave near-infrared spectroscopy parameters during isometric exercise to volitional fatigue

“…Use of the inflection point was previously employed for NIRS analysis for dynamic exercises [35][36][37][38][39], especially for the relationship of cardiopulmonary and NIRS parameters, i.e. for anaerobic point determination.…”

Accelerated point of muscle deoxygenation during the 20‐m shuttle run test

“…Near‐infrared spectroscopy (NIRS) noninvasively and continuously assesses changes in local tissue oxygenation profiles; thus, the technique is widely used to monitor muscle oxygenation during exercise (McCully & Hamaoka, ; Bhambhani, ). Previous studies reported that inflective changes in NIRS‐derived parameters occurred in both active and inactive (or less active) muscles during incremental exercises (Grassi et al ., ; Mizuno et al ., ; Ogata et al ., ; Peltonen et al ., ; Rissanen et al ., ; Wang et al ., ,b). Several authors reported the occurrence of inflection points indicating accelerated deoxygenation in the exercising m. vastus lateralis, based on bilinear regression analysis (Grassi et al ., ; Mizuno et al ., ; Wang et al ., ,b).…”

“…Thus, muscle oxygenation measured by NIRS provides valuable information for the understanding of physiological phenomena during exercise and their relationship with physical performance. If the point of accelerated deoxygenation of active muscle occurs during the 20mSRT, as has been reported in other incremental exercises (Grassi et al ., ; Mizuno et al ., ; Rissanen et al ., ; Wang et al ., ,b), it is possible that the accelerated point of muscle deoxygenation is related to exercise performance in the test. However, this issue has not been explored yet.…”