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Vasoregulatory mechanism response speed to step increases or decreases in exercise from steady state
Author(s) -
Poitras Veronica,
Matusiak Kristine,
Pickett Amy,
Tschakovsky Michael E.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.967.9
Subject(s) - medicine , heart rate , forearm , cardiology , vasodilation , hemodynamics , relaxation (psychology) , steady state (chemistry) , intensity (physics) , blood flow , exercise physiology , chemistry , endocrinology , blood pressure , surgery , physics , quantum mechanics
We tested the hypothesis that muscle vasoregulatory mechanisms respond rapidly to step increases and decreases in exercise intensity from steady state. 10 men and 9 women (21.8 ±3.6 yrs) performed repeated step‐transitions between 4 min bouts of low (L) and moderate (M) forearm handgrip exercise intensities. Forearm blood flow (FBF; Doppler ultrasound), mean arterial pressure (MAP, finometer), and heart rate (HR; ECG) were measured beat by beat. A cardiac cycle during each relaxation of the duty cycle (1s contract/2s relax) was used to quantify forearm hemodynamics (FBF relax ml/min; forearm vascular conductance, FVC relax ml/min/100 mmHg). Data mean ± SD. FBF relax increased rapidly following a step increase in exercise intensity (L steady state 243.1 ±103.6 vs. 1 st M relaxation 262.0 ±78.1, P = 0.075 vs. 2 nd M relaxation 289.8 ±82.2, P<0.001). This was due to a rapid vasodilation (FVC relax L steady state 258.8 ±93.0 vs. 1 st M relaxation 279.6 ± 71.8, P = 0.058; vs. 2 nd M relaxation 304.7 ±74.0, P<0.001). The same rapid responses were observed with decreases in exercise intensity (FVC relax M steady state 462.3 ± 120.5 vs. 1 st L relaxation 435.8 ±103.3, P<0.001; vs. 2 nd L relaxation 420.4 ±99.0, P<0.001). We conclude that vasoregulatory mechanisms are able to alter muscle blood flow rapidly and with little delay in response to sudden increases and decreases in exercise intensity from steady state. Supported by NSERC Canada.