The sag response in human muscle contraction

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dc.contributor.authorSmith, Ian C.
dc.contributor.authorAli, Jahaan
dc.contributor.authorPower, Geoffrey A.
dc.contributor.authorHerzog, Walter
dc.date.accessioned2018-03-12T16:16:59Z
dc.date.available2018-03-12T16:16:59Z
dc.date.issued2018-03-08
dc.description.abstractPURPOSE: We examined how muscle length and time between stimuli (inter-pulse interval, IPI) influence declines in force (sag) seen during unfused tetani in the human adductor pollicis muscle. METHODS: A series of 16-pulse contractions were evoked with IPIs between 1 × and 5 × the twitch time to peak tension (TPT) at large (long muscle length) and small (short muscle length) thumb adduction angles. Unfused tetani were mathematically deconstructed into a series of overlapping twitch contractions to examine why sag exhibits length- and IPI-dependencies. RESULTS: Across all IPIs tested, sag was 62% greater at short than long muscle length, and sag increased as IPI was increased at both muscle lengths. Force attributable to the second stimulus increased as IPI was decreased. Twitch force declined from maximal values across all IPI tested, with the greatest reductions seen at short muscle length and long IPI. At IPI below 2 × TPT, the twitch with highest force occurred earlier than the peak force of the corresponding unfused tetani. Contraction-induced declines in twitch duration (TPT + half relaxation time) were only observed at IPI longer than 1.75 × TPT, and were unaffected by muscle length. CONCLUSIONS: Sag is an intrinsic feature of healthy human adductor pollicis muscle. The length-dependence of sag is related to greater diminution of twitch force at short relative to long muscle length. The dependence of sag on IPI is related to IPI-dependent changes in twitch duration and twitch force, and the timing of peak twitch force relative to the peak force of the associated unfused tetanus.en_US
dc.identifier.citationSmith IC, Ali J, Power GA, Herzog W. The sag response in human muscle contraction. Eur J Appl Physiol. 2018 Mar 8. doi: 10.1007/s00421-018-3840-0. [Epub ahead of print] PubMed PMID: 29520565.en_US
dc.identifier.doi10.1007/s00421-018-3840-0en_US
dc.identifier.doihttp://dx.doi.org/10.11575/PRISM/34228
dc.identifier.urihttp://hdl.handle.net/1880/106428
dc.language.isoenen_US
dc.publisherSpringeren_US
dc.publisher.facultyKinesiologyen_US
dc.publisher.hasversionPre-printen_US
dc.publisher.institutionUniversity of Calgaryen_US
dc.publisher.institutionUniversity of Guelphen_US
dc.publisher.policyhttp://www.springer.com/gp/open-access/authors-rights/self-archiving-policy/2124en_US
dc.rights.urihttps://creativecommons.org/licenses/by/4.0en_US
dc.subjectForce-frequency relationshipen_US
dc.subjectLength-tension relationshipen_US
dc.subjectMuscle contractionen_US
dc.subjectSummationen_US
dc.subjectUnfused tetanusen_US
dc.titleThe sag response in human muscle contractionen_US
dc.typejournal article
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