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Mechanism of force enhancement during stretching of skeletal muscle fibres investigated by high time-resolved stiffness measurements.
MedLine Citation:
PMID:  23296372     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Stretching of active muscles leads to a great enhancement of the force developed without increased ATP consumption. The mechanism of force enhancement is still debated and it is not clear if it is due to increased crossbridge strain or to a stretch-induced increase in crossbridge number. The present study, performed on single fibres from tibialis anterior or interosseus muscles of the frog at 5 °C, was aimed at clarifying this point. A striation follower device was used to measure sarcomere length changes. Force was measured during the application of stretches (0.15-3.9 ms duration, 3-7.8 nm per half-sarcomere amplitude) to activated fibres. Small 4 kHz sinusoidal length oscillations, superimposed on the stretches, were used to calculate fibre stiffness with high time resolution. Stiffness increased during the stretch then subsequently decayed, all in parallel with tension. Likewise, during quick releases, stiffness decreased during the release then subsequently recovered in parallel with tension. Comparison of tension and stiffness both during the tetanus rise and also during stretches which doubled tension, imposed on the tetanus rise, indicated that stretch-induced crossbridge recruitment was only about 11 %, suggesting that force enhancement by stretching is mainly due to an increase of individual crossbridge force, whereas crossbridge recruitment plays only a minor role. The accompanying stiffness changes can be explained by non-linearity of myofilament compliance.
Authors:
Marta Nocella; Maria Angela Bagni; Giovanni Cecchi; Barbara Colombini
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-8
Journal Detail:
Title:  Journal of muscle research and cell motility     Volume:  -     ISSN:  1573-2657     ISO Abbreviation:  J. Muscle Res. Cell. Motil.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8006298     Medline TA:  J Muscle Res Cell Motil     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Dipartimento di Scienze Fisiologiche and Istituto Interuniversitario di Miologia (IIM), Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134, Florence, Italy.
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