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Increases in Blood Flow and Shear Stress to Nonworking Limbs during Incremental Exercise


Medicine & Science in Sports & Exercise: January 2006 - Volume 38 - Issue 1 - pp 81-85
Basic Sciences: Original Investigations

Purpose: Regular exercise augments endothelium-dependent vasodilatory capacity in the vasculature located in the nonworking limbs. We determined whether blood flow as well as shear stress would change in inactive limbs during acute incremental exercise.

Methods: Eight young healthy female subjects performed graded exercise on arm and leg cycle ergometers that had been modified to minimize the movement of nonworking limbs and to facilitate the placement of Doppler transducers. Both brachial and femoral blood flow was monitored using Doppler ultrasonography. EMG activity was also measured to document that there was no muscular activity in nonworking muscles.

Results: During leg exercise, brachial blood flow and calculated shear stress gradually and curvilinearly increased (P < 0.05). At the peak work rate, there was an approximately fourfold increase in blood flow in the brachial artery (19 ± 6 vs 77 ± 16 mL·min−1). Femoral blood flow and calculated shear stress increased progressively and linearly during arm exercise (P < 0.05).

Conclusion: We concluded that blood flow to the nonworking limbs increases markedly in proportion to the work intensity. These results suggest that the conduit arteries in the nonworking limbs are exposed to increases in blood flow and shear stress during exercise.

1Research Institute of Physical Fitness, Japan Women's College of Physical Education, Setagaya, Tokyo, JAPAN; and 2Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX

Address for correspondence: Hirofumi Tanaka, Ph.D., Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX 78712; E-mail:

Submitted for publication April 2005.

Accepted for publication July 2005.

The authors thank Yukihiro Yamamoto from the GE Yokogawa Medical Systems for technical assistance. H.T. was supported by a fellowship grant from Japan Society for Promotion of Science (13780041) during his stay in Japan.

©2006The American College of Sports Medicine