Force-velocity-power and Force-pCa Relationships of Human Soleus Fibers After 17 Days of Bed Rest

Authors

Jeffrey J. Widrick, Marquette University
Kris M. Norenberg, Marquette University
C. A. Blaser, Marquette University
M. Karhanek, Marquette University
Jennifer J. Sherwood, Marquette University
Scott W. Trappe, Ball State University
Todd A. Trappe, Ball State University
David L. Costill, Ball State University
Robert H. Fitts, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

11-1998

Publisher

American Physiological Society

Source Publication

Journal of Applied Physiology

Source ISSN

0021-8987

Original Item ID

DOI: 10.1152/jappl.1998.85.5.1949

Abstract

Soleus muscle fibers from the rat display a reduction in peak power and Ca²⁺ sensitivity after hindlimb suspension. To examine human responses to non-weight bearing, we obtained soleus biopsies from eight adult men before and immediately after 17 days of bed rest (BR). Single chemically skinned fibers were mounted between a force transducer and a servo-controlled position motor and activated with maximal (isotonic properties) and/or submaximal (Ca²⁺ sensitivity) levels of free Ca²⁺. Gel electrophoresis indicated that all pre- and post-BR fibers expressed type I myosin heavy chain. Post-BR fibers obtained from one subject displayed increases in peak power and Ca²⁺ sensitivity. In contrast, post-BR fibers obtained from the seven remaining subjects showed an average 11% reduction in peak power (P < 0.05), with each individual displaying a 7–27% reduction in this variable. Post-BR fibers from these subjects were smaller in diameter and produced 21% less force at the shortening velocity associated with peak power. However, the shortening velocity at peak power output was elevated 13% in the post-BR fibers, which partially compensated for their lower force. Post-BR fibers from these same seven subjects also displayed a reduced sensitivity to free Ca²⁺(P < 0.05). These results indicate that the reduced functional capacity of human lower limb extensor muscles after BR may be in part caused by alterations in the cross-bridge mechanisms of contraction.

Comments

Accepted version. Journal of Applied Physiology, Vol. 85, No. 5 (November 1998): 1949-1956. DOI. © 1998 American Physiological Society. Used with permission.

Recommended Citation

Widrick, Jeffrey J.; Norenberg, Kris M.; Blaser, C. A.; Karhanek, M.; Sherwood, Jennifer J.; Trappe, Scott W.; Trappe, Todd A.; Costill, David L.; and Fitts, Robert H., "Force-velocity-power and Force-pCa Relationships of Human Soleus Fibers After 17 Days of Bed Rest" (1998). Biological Sciences Faculty Research and Publications. 448.
https://epublications.marquette.edu/bio_fac/448