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The effect of number of lengthening contractions on rat isometric force production at different frequencies of nerve stimulation.

Authors
Willems-ME; Stauber-WT
Source
Acta Physiol 2009 Jul; 196(3):351-356
NIOSHTIC No.
20037017
Abstract
Aim: To test the effect of 3, 10, 60 and 240 lengthening contractions (LC) on maximal isometric force of rat plantar flexor muscles at different stimulation frequencies. Methods: Using a dynamometer and electrical nerve stimulation, maximally active skeletal muscles were stretched by ankle rotation to produce LC of the plantar flexor muscles in intact female rats. After the lengthening contraction protocols, maximal isometric force was measured at different frequencies of nerve activation to obtain frequency-dependent force deficits (weakness). Results: The magnitude of the force deficit, measured 1 h after the protocols at 80 Hz, increased as a function of repetition number (three LC, 33.3 +/- 1.7%; 10 LC, 37.2 +/- 2.3%; 60 LC, 67.6 +/- 1.5%; 240 LC, 77.7 +/- 1.2%). Force deficits were also measured at each stimulation frequency tested (5:120 Hz). Using a ratio of isometric force at 20:100 Hz stimulation, the relative depression of force at low frequency was determined. The relative depression of isometric force at low frequency was most prominent during the early repetitions. Conclusion: As low-frequency force depression appears to result primarily from excitation-contraction (E-C) coupling failure, the early LC in a series of repeated contractions probably contribute most to damage of the cellular components involved in E-C coupling.
Keywords
Animal-studies; Laboratory-animals; Muscle-cells; Muscle-physiology; Muscles; Muscle-tissue; Musculoskeletal-system; Physiological-effects; Physiological-measurements; Musculoskeletal-system-disorders; Physiological-testing; Repetitive-work; Skeletal-system; Statistical-analysis; Author Keywords: dynamometry; eccentric contractions; muscle damage
Contact
W. T. Stauber, Department of Physiology and Pharmacology, West Virginia University, PO Box 9229, Morgantown, WV 26506-9229, USA
CODEN
APSCAX
Publication Date
20090701
Document Type
Journal Article
Email Address
wstauber@mix.wvu.edu
Funding Amount
868663
Funding Type
Grant
Fiscal Year
2009
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-002918
Issue of Publication
3
ISSN
0001-6772
Source Name
Acta Physiologica
State
WV
Performing Organization
West Virginia University, Morgantown, West Virginia
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