AJP - Heart and Circulatory Physiology, Vol 272, Issue 5 2107-H2114, Copyright © 1997 by American Physiological Society

ARTICLES

In vivo microvascular structural and functional consequences of muscle length changes

D. C. Poole, T. I. Musch and C. A. Kindig
Department of Kinesiology, Kansas State University, Manhattan 66506-5602, USA.

As muscles are stretched, blood flow and oxygen delivery are compromised, and consequently muscle function is impaired. We tested the hypothesis that the structural microvascular sequellae associated with muscle extension in vivo would impair capillary red blood cell hemodynamics. We developed an intravital spinotrapezius preparation that facilitated direct on-line measurement and alteration of sarcomere length simultaneously with determination of capillary geometry and red blood cell flow dynamics. The range of spinotrapezius sarcomere lengths achievable in vivo was 2.17 +/- 0.05 to 3.13 +/- 0.11 microns. Capillary tortuosity decreased systematically with increases of sarcomere length up to 2.6 microns, at which point most capillaries appeared to be highly oriented along the fiber longitudinal axis. Further increases in sarcomere length above this value reduced mean capillary diameter from 5.61 +/- 0.03 microns at 2.4-2.6 microns sarcomere length to 4.12 +/- 0.05 microns at 3.2-3.4 microns sarcomere length. Over the range of physiological sarcomere lengths, bulk blood flow (radioactive microspheres) decreased approximately 40% from 24.3 +/- 7.5 to 14.5 +/- 4.6 ml.100 g-1.min-1. The proportion of continuously perfused capillaries, i.e., those with continuous flow throughout the 60-s observation period, decreased from 95.9 +/- 0.6% at the shortest sarcomere lengths to 56.5 +/- 0.7% at the longest sarcomere lengths and was correlated significantly with the reduced capillary diameter (r = 0.711, P < 0.01; n = 18). We conclude that alterations in capillary geometry and luminal diameter consequent to increased muscle sarcomere length are associated with a reduction in mean capillary red blood cell velocity and a greater proportion of capillaries in which red blood cell flow is stopped or intermittent. Thus not only does muscle stretching reduce bulk blood (and oxygen) delivery, it also alters capillary red blood cell flow dynamics, which may further impair blood-tissue oxygen exchange.

This article has been cited by other articles:

				T. Sonobe, T. Inagaki, D. C. Poole, and Y. Kano Intracellular calcium accumulation following eccentric contractions in rat skeletal muscle in vivo: role of stretch-activated channels Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2008; 294(4): R1329 - R1337. [Abstract] [Full Text] [PDF]

				D. C. Poole, M. D. Brown, and O. Hudlicka Counterpoint: There is not capillary recruitment in active skeletal muscle during exercise J Appl Physiol, March 1, 2008; 104(3): 891 - 893. [Full Text] [PDF]

				D. J. Padilla, P. McDonough, B. J. Behnke, Y. Kano, K. S. Hageman, T. I. Musch, and D. C. Poole Effects of Type II diabetes on capillary hemodynamics in skeletal muscle Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2439 - H2444. [Abstract] [Full Text] [PDF]

				Y. Kano, D. Padilla, K. S. Hageman, D. C. Poole, and T. I. Musch Downhill running: a model of exercise hyperemia in the rat spinotrapezius muscle J Appl Physiol, September 1, 2004; 97(3): 1138 - 1142. [Abstract] [Full Text] [PDF]

				J. A. Russell, C. A. Kindig, B. J. Behnke, D. C. Poole, and T. I. Musch Effects of aging on capillary geometry and hemodynamics in rat spinotrapezius muscle Am J Physiol Heart Circ Physiol, June 5, 2003; 285(1): H251 - H258. [Abstract] [Full Text] [PDF]

				C. A. Kindig, T. E. Richardson, and D. C. Poole Skeletal muscle capillary hemodynamics from rest to contractions: implications for oxygen transfer J Appl Physiol, June 1, 2002; 92(6): 2513 - 2520. [Abstract] [Full Text] [PDF]

				J. K. Bailey, C. A. Kindig, B. J. Behnke, T. I. Musch, G. W. Schmid-Schoenbein, and D. C. Poole Spinotrapezius muscle microcirculatory function: effects of surgical exteriorization Am J Physiol Heart Circ Physiol, December 1, 2000; 279(6): H3131 - H3137. [Abstract] [Full Text] [PDF]

				C. A. Kindig, T. I. Musch, R. J. Basaraba, and D. C. Poole Impaired capillary hemodynamics in skeletal muscle of rats in chronic heart failure J Appl Physiol, August 1, 1999; 87(2): 652 - 660. [Abstract] [Full Text] [PDF]