Share this article on:


Saunders, N R.1; Tschakovsky, M E.1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S44
A-15R Free Communication/Poster Peripheral Circulation

1Queen's University, Kingston, ON Canada

Debate continues regarding the contribution of muscle pump vs. vasodilation to the “immediate” increase (first second following initial contraction release) in blood flow at the onset of exercise. Furthermore, studies have exclusively focused on this issue in the context of rest-to-exercise transitions.

Back to Top | Article Outline


To test the hypothesis that there is an “immediate” vasodilatory contribution to the increase in blood flow in an exercise-to-exercise transition.

Back to Top | Article Outline


7 healthy young volunteers (2 female, 5 male) lay supine with the forearm elevated above heart level. In this position, veins are virtually empty and no additional contraction-induced venous emptying occurs in either rest-to-exercise or exercise-to-exercise transitions (i.e. muscle pump is ineffective). A step increase from rest to 3 min of mild (10% maximal voluntary contraction, MVC;R-10step) rhythmic, dynamic forearm handgrip exercise (1-s contraction/2-s relaxation duty cycle) was followed by a further step to moderate (20% MVC; 10-20step) exercise. Beat-by-beat measures of brachial artery diameter and mean blood velocity (MBV; Doppler ultrasound), heart rate (HR; ECG) and arterial blood pressure (ABP; arterial tonometry) were performed.

Back to Top | Article Outline


All data are mean ± SE. HR and ABP did not change during the first few seconds of each transition. Forearm blood flow (FBF) increased following release of the initial contraction in the 10-20step by the same absolute amount as the R-10step, despite no gain in muscle pump effectiveness (Δ FBF: R-10step: 52.2 ± 12.3 ml/min vs. 10-20step: 63.5 ± 13.7 ml/min, P = 0.65). These values represent a different % Δ (R-10step: 126.3 ± 25.6% vs. 10-20step: 20.3 ± 5.2%, P = 0.001).

Back to Top | Article Outline


These data support the hypothesis that there is an “immediate” further vasodilation in exercising muscle in an exercise-to-exercise transition. The mechanisms responsible remain to be determined.

Supported by NSERC; CFI New Opportunities Fund.

©2003The American College of Sports Medicine