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Autonomic control of heart rate by the muscle metaboreflex in humans
Author(s) -
Fisher James P,
Seifert Thomas,
Hartwich Doreen,
Young Colin N,
Secher Niels H,
Fadel Paul J
Publication year - 2010
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.24.1_supplement.1020.6
Subject(s) - blockade , heart rate , medicine , isometric exercise , cardiology , blood pressure , anesthesia , receptor
We sought to examine the autonomic mechanisms of muscle metaboreflex control of heart rate (HR) in humans. In nine male subjects (23±5 yr) graded isolation of the muscle metaboreflex was achieved by post‐exercise ischemia (PEI) following moderate (PEI‐M) and high (PEI‐H) intensity isometric handgrip performed at 25% and 45% maximum voluntary contraction, respectively. Beat‐to‐beat HR and arterial blood pressure (BP) were measured. Trials were performed before and after beta‐adrenergic blockade as well as cardiac vagal blockade. In all conditions, mean BP was increased similarly from rest during PEI‐M, and was further augmented during PEI‐H, indicating graded metaboreflex activation. During PEI‐M under control conditions HR was slightly elevated from rest (Δ3±2 bpm), however this HR elevation was abolished with beta blockade (P<0.05 vs. control) but augmented with vagal blockade (Δ8±3 bpm, P<0.05 vs. control and beta blockade). The HR elevation during PEI‐H under control conditions (Δ9±3 bpm) was greater than with PEI‐M (P<0.05), and was again attenuated with beta blockade (Δ4±2 bpm, P<0.05 vs. control), but was unchanged with vagal blockade (Δ9±2 bpm, P>0.05 vs. control). These findings suggest that isolated muscle metaboreflex activation during PEI in humans elicits a modest sympathetically‐mediated tachycardia that is masked by cardiac parasympathetic reactivation during PEI‐M, but not PEI‐H.