End‐exercise ΔHHb/ΔVO₂ and post‐exercise local oxygen availability in relation to exercise intensity

Abstract

Increased local blood supply is thought to be one of the mechanisms underlying oxidative adaptations to interval training regimes. The relationship of exercise intensity with local blood supply and oxygen availability has not been sufficiently evaluated yet. The aim of this study was to examine the effect of six different intensities (40-90% peak oxygen uptake, VO ) on relative changes in oxygenated, deoxygenated and total haemoglobin (ΔO Hb, ΔHHb, ΔTHb) concentration after exercise as well as end-exercise ΔHHb/ΔVO as a marker for microvascular O distribution. Seventeen male subjects performed an experimental protocol consisting of 3 min cycling bouts at each exercise intensity in randomized order, separated by 5 min rests. ΔO Hb and ΔHHb were monitored with near-infrared spectroscopy of the vastus lateralis muscle, and VO was assessed. ΔHHb/ΔVO increased significantly from 40% to 60% VO peak and decreased from 60% to 90% VO peak. Post-exercise ΔTHb and ΔO Hb showed an overshoot in relation to pre-exercise values, which was equal after 40-60% VO and rose significantly thereafter. A plateau was reached following exercise at ≥80% VO . The results suggest that there is an increasing mismatch of local O delivery and utilization during exercise up to 60% VO . This insufficient local O distribution is progressively improved above that intensity. Further, exercise intensities of ≥80% VO induce highest local post-exercise O availability. These effects are likely due to improved microvascular perfusion by enhanced vasodilation, which could be mediated by higher lactate production and the accompanying acidosis.

Does postexercise modelled capillary blood flow accurately reflect cardiovascular effects by different exercise intensities?

“…In general, the results from Q cap calculations support those which have been published previously (Stöcker et al ., ). However, considering all assumptions and data fitting, the method remains questionable.…”

“…In this regard, data which are obtained using CWS NIRS should not be analysed with mono-or bi-exponential fitting in general. Nevertheless, the fact that the Q cap approach works in some studies shows that those results are presumably based on the same mechanisms like endexercise DHHb/DVO 2 ratio or postexercise haemoglobin overcompensation (St€ ocker et al, 2015).…”

“…This suggests a dominant local vasodilation superimposing sympathetic vasoconstriction following exercise above 60% VO 2peak . Some results of this study have already been published elsewhere (Stöcker et al ., ). In that publication, we presented an increased postexercise oxygen availability and blood supply following exercise bouts at ≥70% VO 2peak , which shows a plateau following exercise bouts at ≥80% VO 2peak .…”

“…Hence, this parameter could provide additional information about the time-course of the relationship of oxygen uptake and muscle deoxygenation in order to examine the dependency of local muscle blood supply on exercise intensity but has to be interpreted with caution. In this study, the Q cap method is applied, critically reflected and compared to those results that have been presented in our previous work (St€ ocker et al, 2015).…”

“…When exercise is prescribed as repeated transitions from high to low exercise (high intensity training, HIT), subjects could benefit from improved blood supply and oxygen availability during the low intervals in response to the prior high interval. Recently, we have studied the effect of single exercise bouts on postexercise blood supply and oxygen availability and end-exercise matching of oxygen utilization and supply (St€ ocker et al, 2015). The results showed that exercise above 70% VO 2peak does enhance these parameters.…”