Soleus fiber force and maximal shortening velocity after non-weight bearing with intermittent activity

• DOI: 10.1152/jappl.1996.80.3.981
• Publication Date: 2017-12-22T01:31:16Z
• Authors: J. J. Widrick; J. J. Bangart; M. Karhanek; R. H. Fitts
• Keywords: Hindlimb

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