Faculty Collaboration Database

Force-velocity-power and force-pCa relationships of human soleus fibers after 17 days of bed rest. J Appl Physiol (1985) 1998 Nov;85(5):1949-56

Date

11/06/1998

Pubmed ID

9804603

DOI

10.1152/jappl.1998.85.5.1949

Scopus ID

2-s2.0-15644378975 (requires institutional sign-in at Scopus site)   59 Citations

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.

Author List

Widrick JJ, Norenberg KM, Romatowski JG, Blaser CA, Karhanek M, Sherwood J, Trappe SW, Trappe TA, Costill DL, Fitts RH

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adult
Calcium
Humans
Isotonic Contraction
Male
Muscle Contraction
Muscle Fibers, Skeletal
Muscle, Skeletal
Myosin Heavy Chains
Rest