Does oxygen delivery explain interindividual variation in forearm critical impulse?

Physiological Reports

J. Mikhail Kellawan²  Robert F. Bentley¹  Michael F. Bravo¹  Jackie S. Moynes¹ 

[1] Human Vascular Control Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada;Department of Kinesiology, School of Education, University of Wisconsin, Madison, Wisconsin

关键词: Aerobic capacity;    critical power;    exercise hyperemia;    forearm exercise;    pressor response;   

DOI  :  10.14814/phy2.12203

来源: Wiley

【 摘 要 】

Abstract

Within individuals, critical power appears sensitive to manipulations in O₂ delivery. We asked whether interindividual differences in forearm O₂ delivery might account for a majority of the interindividual differences in forearm critical force impulse (critical impulse), the force analog of critical power. Ten healthy men (24.6 ± 7.10 years) completed a maximal effort rhythmic handgrip exercise test (1 sec contraction-2 sec relaxation) for 10 min. The average of contraction impulses over the last 30 sec quantified critical impulse. Forearm brachial artery blood flow (FBF; echo and Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography) were measured continuously. O₂ delivery (FBF arterial oxygen content (venous blood [hemoglobin] and oxygen saturation from pulse oximetry)) and forearm vascular conductance (FVC; FBF·MAP⁻¹) were calculated. There was a wide range in O₂ delivery (59.98–121.15 O₂ mL·min⁻¹) and critical impulse (381.5–584.8 N) across subjects. During maximal effort exercise, O₂ delivery increased rapidly, plateauing well before the declining forearm impulse and explained most of the interindividual differences in critical impulse (r² = 0.85, P < 0.01). Both vasodilation (r² = 0.64, P < 0.001) and the exercise pressor response (r² = 0.33, P < 0.001) independently contributed to interindividual differences in FBF. In conclusion, interindividual differences in forearm O₂ delivery account for most of the interindividual variation in critical impulse. Furthermore, individual differences in pressor response play an important role in determining differences in O₂ delivery in addition to vasodilation. The mechanistic origins of this vasodilatory and pressor response heterogeneity across individuals remain to be determined.

【 授权许可】

CC BY   
© 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

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