Impact of supine versus upright exercise on muscle deoxygenation heterogeneity during ramp incremental cycling is site specific

Abstract

Purpose We tested the hypothesis that incremental ramp cycling exercise performed in the supine position (S) would be associated with an increased reliance on muscle deoxygenation (deoxy[heme]) in the deep and superficial vastus lateralis (VLd and VLs, respectively) and the superficial rectus femoris (RFs) when compared to the upright position (U). Methods 11 healthy men completed ramp incremental exercise tests in S and U. Pulmonary $$\dot{V}$$ V ˙ O2 was measured breath-by-breath; deoxy[heme] was determined via time-resolved near-infrared spectroscopy in the VLd, VLs and RFs. Results Supine exercise increased the overall change in deoxy[heme] from baseline to maximal exercise in the VLs (S: 38 ± 23 vs. U: 26 ± 15 μM, P < 0.001) and RFs (S: 36 ± 21 vs. U: 25 ± 15 μM, P < 0.001), but not in the VLd (S: 32 ± 23 vs. U: 29 ± 26 μM, P > 0.05). Conclusions The present study supports that the impaired balance between O2 delivery and O2 utilization observed during supine exercise is a regional phenomenon within superficial muscles. Thus, deep muscle defended its O2 delivery/utilization balance against the supine-induced reductions in perfusion pressure. The differential responses of these muscle regions may be explained by a regional heterogeneity of vascular and metabolic control properties, perhaps related to fiber type composition.

No differences in splenic emptying during on-transient supine cycling between aerobically trained and untrained participants

“…Thus, it seems that participants with higher O 2 diffusion capacity achieved higher max. during CPET, compared to less trained individuals (Table 1 ), and in particular during supine cycling-exercise where predominantly type II fibers are activated (Goulding et al 2020b , 2021 ). These results also suggest that the increase in blood O 2 -carrying capacity via splenic emptying, and thus the potential for muscle O 2 supply from a greater amount of circulating RBC’s has no effect on O 2 kinetics during supine cycling at moderate intensity, inferring that the latter is mainly regulated by intracellular (metabolic) factors (Poole and Jones 2011 ; Grassi 2015), as recently demonstrated in series of papers by (Goulding et al 2020b , 2021 ), at least in young healthy men.…”

“…We took special attention to standardize all supine cycling procedures on custom-designed setup and data collection protocols. The distances between the crankshaft, shoulder and pelvis distance were recorded for each participant, and then replicated throughout the study (Goulding et al 2020a , b ; Goulding et al 2021 ; Zubac et al 2021a ). To reduce torso movement in the supine position and to improve ultrasonographic imaging of the spleen all participants were restrained to a bed during the supine position.…”

“…However, the pulmonary oxygen uptake kinetics ( ) of young healthy individuals during step-transition cycling in the upright and likely supine position(s) at moderate-intensity domain, are constrained by mitochondrial dynamics, rather than oxygen delivery (Rossiter 2011 ; Poole and Jones 2011 ). Furthermore, supine on-transient cycling is characterized by slower uptake kinetics, and greater deoxygenation amplitude of knee extensors (Goulding et al 2020a , b , 2021 ). Therefore, our study design included near-infrared spectroscopy (NIRS) measurements at the site of vastus lateralis (VL) muscle to gain a more comprehensive insight into local O 2 demand, although the underlying mechanisms of skeletal muscle bioenergetics during supine cycling at moderate and heavy intensity domains have been described elsewhere (Gouding et al 2020 , 2021 ).…”

“…Furthermore, supine on-transient cycling is characterized by slower uptake kinetics, and greater deoxygenation amplitude of knee extensors (Goulding et al 2020a , b , 2021 ). Therefore, our study design included near-infrared spectroscopy (NIRS) measurements at the site of vastus lateralis (VL) muscle to gain a more comprehensive insight into local O 2 demand, although the underlying mechanisms of skeletal muscle bioenergetics during supine cycling at moderate and heavy intensity domains have been described elsewhere (Gouding et al 2020 , 2021 ). Here, we reasoned that the reduction in splenic volume during supine cycling would be clearly observed, while the on-going debate in the literature regarding the role of the spleen in oxygen transport during aerobic exercise warrants further investigation.…”

Determination of exercise intensity domains during upright versus supine cycling: a methodological study

“…There is a growing interest among the research community and clinical practitioners to investigate CPET procedures and protocols utilized in supine cycling ( Dillon et al, 2021 , Goulding et al, 2021a , 2021b ; Steele et al, 2018 ). The supine cycling model has been increasingly utilized to study age-related changes in cerebral blood flow ( Smirl et al, 2016 ), acute spleen volume changes ( Zubac et al, 2021b ), cardiovascular adjustments during exercise in athletes ( La Gerche et al, 2013 ), the effects of gravity acceleration ( Bonjour et al, 2010 ) in addition to study skeletal muscle bioenergetics ( Goulding et al, 2020 ).…”