HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 101/1/256    most recent 01402.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Clark, B. C. Articles by Ploutz-Snyder, L. L. Search for Related Content PubMed PubMed Citation Articles by Clark, B. C. Articles by Ploutz-Snyder, L. L.

Adaptations in human neuromuscular function following prolonged unweighting: I. Skeletal muscle contractile properties and applied ischemia efficacy

Musculoskeletal Research Laboratory, Department of Exercise Science, Syracuse University, Syracuse, New York

Submitted 7 November 2005 ; accepted in final form 28 February 2006

Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor muscle properties following 4 wk of limb suspension (unilateral lower limb suspension), along with the effect of applied ischemia (Isc) on these properties. In the companion paper (Part II), we report our findings on the changes in neurological properties. Measurements of voluntary and evoked forces, the compound muscle fiber action potential (CMAP), and muscle cross-sectional area (CSA) were collected before and after 4 wk of unilateral lower limb suspension in adults (n = 18; 19–28 yr). A subset of subjects (n = 6) received applications of Isc 3 days/wk (3 sets; 5-min duration). In the subjects not receiving Isc, the loss in CSA and strength was as expected (9 and 14%). We observed a 30% slowing in the duration of the CMAP, a 10% decrease in evoked doublet force, a 12% increase in the twitch-to-doublet force ratio, and an altered postactivation potentiation response (11% increase in the postactivation potentiation-to-doublet ratio). We also detected a 10% slowing in the ability of the plantar flexor to develop force during the initial phase of an evoked contraction, along with a 6% reduction in in vivo specific doublet force. In the Isc subjects, no preservation was observed in strength or the evoked muscle properties. However, the Isc group did maintain CSA of the lateral gastrocnemius, as the control subjects’ lateral gastrocnemius atrophied 10.2%, whereas the subjects receiving Isc atrophied 4.7%. Additionally, Isc abolished the unweighting-induced slowing in the CMAP. These findings suggest that unweighting alters the contractile properties involved in the excitation-contraction coupling processes and that Isc impacts the sarcolemma.

disuse atrophy; electromyography; evoked force; bed rest

This article has been cited by other articles:

				J. Lundbye-Jensen and J. B. Nielsen Central nervous adaptations following 1 wk of wrist and hand immobilization J Appl Physiol, July 1, 2008; 105(1): 139 - 151. [Abstract] [Full Text] [PDF]

				T. M Manini, B. C Clark, M. A Nalls, B. H Goodpaster, L. L Ploutz-Snyder, and T. B Harris Reduced physical activity increases intermuscular adipose tissue in healthy young adults Am. J. Clinical Nutrition, February 1, 2007; 85(2): 377 - 384. [Abstract] [Full Text] [PDF]

				J. R. Pierce, B. C. Clark, L. L. Ploutz-Snyder, and J. A. Kanaley Growth hormone and muscle function responses to skeletal muscle ischemia J Appl Physiol, December 1, 2006; 101(6): 1588 - 1595. [Abstract] [Full Text] [PDF]