Open AccessDo interindividual differences in cardiac output during submaximal exercise explain differences in exercising muscle oxygenation and ratings of perceived exertion?
Author(s) -
Bentley Robert F.,
Jones Joshua H.,
Hirai Daniel M.,
Zelt Joel T.,
Giles Matthew D.,
Raleigh James P.,
Quadrilatero Joe,
Gurd Brendon J.,
Neder J. Alberto,
Tschakovsky Michael E.
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13570
Subject(s) - medicine , cardiology , cardiac output , exertion , skeletal muscle , vo2 max , stroke volume , heart rate , oxygenation , deoxygenation , incremental exercise , physical therapy , hemodynamics , blood pressure , chemistry , biochemistry , catalysis
Considerable interindividual differences in theQ ˙ − V ˙ O 2relationship during exercise have been documented but implications for submaximal exercise tolerance have not been considered. We tested the hypothesis that these interindividual differences were associated with differences in exercising muscle deoxygenation and ratings of perceived exertion (RPE) across a range of submaximal exercise intensities. A total of 31 (21 ± 3 years) healthy recreationally active males performed an incremental exercise test to exhaustion 24 h following a resting muscle biopsy. Cardiac output ( Q ˙ L/min; inert gas rebreathe), oxygen uptake ( V ˙ O 2L/min; breath‐by‐breath pulmonary gas exchange), quadriceps saturation (near infrared spectroscopy) and exercise tolerance (6–20; Borg Scale RPE) were measured. TheQ ˙ − V ˙ O 2relationship from 40 to 160 W was used to partition individuals post hoc into higher ( n = 10; 6.3 ± 0.4) versus lower ( n = 10; 3.7 ± 0.4, P < 0.001) responders. TheQ ˙ − V ˙ O 2difference between responder types was not explained by arterial oxygen content differences ( P = 0.5) or peripheral skeletal muscle characteristics ( P from 0.1 to 0.8) but was strongly associated with stroke volume ( P < 0.05). Despite considerableQ ˙ − V ˙ O 2difference between groups, no difference in quadriceps deoxygenation was observed during exercise (all P > 0.4). Lower cardiac responders had greater leg ( P = 0.027) and whole body ( P = 0.03) RPE only at 185 W, but this represented a higher %peakV ˙ O 2in lower cardiac responders (87 ± 15% vs. 66 ± 12%, P = 0.005). Substantially lowerQ ˙ − V ˙ O 2in the lower responder group did not result in altered RPE or exercising muscle deoxygenation. This suggests substantial recruitment of blood flow redistribution in the lower responder group as part of protecting matching of exercising muscle oxygen delivery to demand.