Faculty Collaboration Database

Soleus fiber force and maximal shortening velocity after non-weight bearing with intermittent activity. J Appl Physiol (1985) 1996 Mar;80(3):981-7

Date

03/01/1996

Pubmed ID

8964764

DOI

10.1152/jappl.1996.80.3.981

Scopus ID

2-s2.0-0029868942 (requires institutional sign-in at Scopus site)   33 Citations

Abstract

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type I fiber force (in mN), tension (Po; force per fiber cross-sectional area in kN/m-2), and maximal unloaded shortening velocity (Vo, in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments were mounted between a force transducer and position motor and were studied at maximal Ca2+ activation, after which type I fiber myosin heavy-chain composition was confirmed by sodium dodecyl sufate-polyacrylamide gel electrophoresis. NWB resulted in a loss in relative soleus mass (-45%), with type I fibers displaying reductions in diameter (-28%) and peak isometric force (-55%) and an increase in Vo (+33%). In addition, NWB induced a 16% reduction in type I fiber Po, a 41% reduction in type I fiber peak elastic modulus [Eo, defined as (delta force/delta length) x (fiber length/fiber cross-sectional area] and a significant increase in the Po/Eo ratio. In contrast to NWB, IWB reduced the loss of relative soleus mass (by 22%) and attenuated alterations in type I fiber diameter (by 36%), peak force (by 29%), and Vo (by 48%) but had no significant effect on Po, Eo, or Po/Eo. These results indicate that a modest restoration of WB activity during 14 days of NWB is sufficient to attenuate type I fiber atrophy and to partially restore type I peak isometric force and Vo to WB levels. However, the NWB-induced reductions in Po and Eo, which we hypothesize to be due to a decline in the number and stiffness of cross bridges, respectively, are considerably less responsive to this countermeasure treatment.

Author List

Widrick JJ, Bangart JJ, Karhanek M, 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

Animals
Body Weight
Cell Count
Hindlimb
Male
Muscle Fibers, Skeletal
Muscle, Skeletal
Rats
Rats, Sprague-Dawley