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

Abstract

Blood flow (BF) in exercising muscles is an important factor for exercise capacity. Recently, a non-invasive method to estimate capillary BF (Q ) was introduced. Using this method, the Fick principle is re-arranged by using relative differences in deoxygenated haemoglobin (ΔHHb) as a surrogate for arteriovenous O difference and pulmonary oxygen uptake (VO ) instead of muscular oxygen uptake. The aim of this study was to examine (I) the relationship between Q and exercise intensity during and following exercise, and (II) to critically reflect the Q approach. Seventeen male subjects completed six bouts of cycling exercise with different exercise intensities (40-90% peak oxygen uptake, VO ) in randomized order. VO and ΔHHb were monitored continuously during the trail. Q was modelled bi-exponentially, and mean response time (MRT) was calculated during recovery as well as the dissociation of modelled VO and Q recovery kinetics (MRT/τVO ). End-exercise Q increased continuously with exercise intensity. This also applied to MRT. Postexercise MRT/τVO increased from 40 to 60% VO but remained stable thereafter. The results show that Q response to exercise is linearly related to exercise intensity. This is presumably due to vasoactive factors like shear-stress or endothelial-mediated vasodilation. MRT/τVO shows that postexercise Q is elevated for a longer period than VO , which is representative for metabolic demand following exercise ≥70% VO . This is a hint for prolonged local vasodilation. According to previous studies, Q could not be modelled properly in some cases, which is a limitation to the method and therefore has to be interpreted with caution.

Oxygen Availability in Respiratory Muscles During Exercise in Children Following Fontan Operation

“…As an estimate for the adjustment of microvascular perfusion, ΔHHb/ΔV.O2 ratio was calculated according to %HHbmax/%truetextV.O 2peak for each time point during the test. This parameter has been used in several previous studies (16–19).…”

Association between physiological stress and skin temperature response after a half marathon

“…Such conditions are known to some extent to increase muscle temperature, which may be reflected as changes in skin temperature (Hildebrandt et al 2010, Ring and Ammer 2012, Fernández-Cuevas et al 2017. Skin temperature was also related with skin blood flow (Cheuvront et al 2010, Schlager et al 2010, which can be sensitive to exercise intensity (Stöcker et al 2018).…”