Inflection points of cardiovascular responses and oxygenation are correlated in the distal but not the proximal portions of muscle during incremental exercise

Masaki Mizuno, Ken Tokizawa, Takashi Iwakawa, Isao Muraoka

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

To test whether there is a regional difference in the exercise pressor reflex within a given muscle, we investigated the relationship between the inflection points of cardiovascular responses and muscle oxygenation during exercise. Seven subjects performed incremental exercise, which consisted of incremental 30-s static knee extensions, each separated by 30 s of recovery. The workload started at 5% maximal voluntary contraction (MVC) and increased by 5% MVC for each increment until exhaustion. Changes (Δ) in the concentrations (denoted by brackets) of oxygenated Hb (O2Hb) and deoxygenated Hb (HHb) were monitored in proximal and distal portions of the vastus lateralis by near-infrared spectroscopy. The inflection points of mean arterial pressure (MAP), calf vascular resistance (CVR), and muscle deoxygenation index (Δ[O2Hb - HHb]) were calculated as the intersection point of two regression equations obtained at lower and higher workloads. The inflection point of Δ[O2Hb - HHb] differed significantly between proximal and distal portions (28.5 ± 3.0 vs. 39.5 ± 3.0% MVC, P < 0.05). Linear regression analysis showed significant correlations between the inflection point of Δ[O2Hb - HHb] in the distal portion and MAP (r = 0.89; P < 0.01) and CVR (r = 0.89; P < 0.05), but no significant relationship between the inflection point in the proximal portion and MAP or CVR. These data show that the inflection point of muscle deoxygenation differs between proximal and distal portions within the vastus lateralis during incremental exercise and suggest that the distal portion of the vastus lateralis contributes more to the pressor response than does the proximal portion.

Original languageEnglish
Pages (from-to)867-873
Number of pages7
JournalJournal of Applied Physiology
Volume97
Issue number3
DOIs
Publication statusPublished - 2004 Sep 1

Keywords

  • Exercise pressor reflex
  • Near-infrared spectroscopy
  • Regional difference

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Fingerprint Dive into the research topics of 'Inflection points of cardiovascular responses and oxygenation are correlated in the distal but not the proximal portions of muscle during incremental exercise'. Together they form a unique fingerprint.

  • Cite this