Sex-related differences in muscle deoxygenation during ramp incremental exercise

Determination of respiratory point compensation in healthy adults: Can non-invasive near-infrared spectroscopy help?

“…Previous studies have reported a correspondence of NIRS-derived events with both ventilatory and lactate-based thresholds, 8,10,11 including an association between theV O 2 corresponding with the deoxyHb DP and the RCP. 12 The present study provides strong evidence for this relationship demonstrating this phenomenon in a much larger sample comprised of all ages.…”

“…Considering that this is a common characteristic observed in women of all ages (and more markedly in sedentary, older women), our analysis in women would have been limited only to those that do not share this attribute. Notably, Murias et al 12 demonstrated that deoxyHb DP could be detected during ramp incremental cycle exercise in a group of ten women and that theV O 2 associated with the deoxyHb DP was in close agreement to that of the RCP (although statistically underpowered). Therefore, it is expected that the phenomenon observed in the present study would likely extend to a large heterogeneous group of women.…”

“…The time course of deoxyHb in the vastus lateralis muscle during incremental exercise has been interpreted to reflect the balance between microvascular blood flow and muscle O 2 utilization and has been described and interpreted in detail elsewhere. 11,12 Briefly, as work rate progressively increases during incremental exercise, a steep slope in the deoxyHb signal is observed which may reflect a slower adjustment of microvascular blood flow compared to muscle O 2 utilization and a shift from predominantly slow-twitch muscle fibers to include more fast-twitch muscle fibers. The reduced slope/plateau in deoxyHb in the presence of an increase in muscleV O 2 that characterizes the "high-intensity" portion of the incremental exercise would imply an increased O 2 provision, likely related to the metabolic vasodilation 25 and sympathetically mediated redistribution of blood flow from less metabolically active tissues toward the active muscle.…”

“…Specifically, it has been shown that a deflection point in the NIRS-derived deoxygenated hemoglobin (deoxyHb) signal during incremental cycle exercise occurred at the sameV O 2 as that associated with the MLSS, 11 indicating that MLSS could be accurately determined using quantitative measures of deoxyHb. Recently, Murias et al 12 examined the sex-related differences in the responses of deoxyHb during ramp incremental exercise. In order to assess the practical meaningfulness of the deoxyHb-deflection point, the authors examined the relationship between the deoxyHb-deflection point and other thresholds observed during ramp incremental exercise (i.e., GET and RCP).…”

Muscle O2 extraction reserve during intense cycling is site-specific

“…This O 2 availability-utilization balance can be assessed noninvasively at rest and during exercise by considering changes in nearinfrared spectroscopy (NIRS)-derived muscle deoxygenation ([HHb]). To this end, several studies have examined the kinetic profile of [HHb] during incremental cycling exercise (7, 8, 14, 17, 19, 21, 29 -31, 35), and a near-plateau (30,31,35) has been described during the final moments of very intense exercise. Importantly, however, it has previously been shown that the peak [HHb] value (reflecting the peak fractional O 2 extraction) observed during dynamic, rhythmic exercise (i.e., cycling) is significantly less than that elicited during ischemic occlusion (OCC) at rest in healthy individuals (20).…”