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Isometric and concentric performance of electrically stimulated ankle plantar flexor muscles in intact rat.

Authors
Willems-MET; Stauber-WT
Source
Exp Physiol 1999 Mar; 84(2):379-389
NIOSHTIC No.
20024479
Abstract
The relationship between muscle force and ankle position during isometric and pre-loaded slow concentric contractions (angular velocity, 0.52 rad s-1; range of motion, 1.22 rad) and the recovery of isometric force following concentric contractions at different velocities were determined for electrically stimulated plantar flexor muscles in intact rats. Pre-loaded refers to the isometric contraction which immediately precedes the concentric contraction. Ankle position was controlled by a dynamometer and force was recorded under the sole of the foot. The peak isometric force (19.2 N) was nearly constant at all ankle positions (range of motion, 1.57 rad). The muscle length and distal fibre length of gastrocnemius medialis at ankle positions between 0.79 rad and 2.01 rad were increased by 12.6 % and 20.3 %, respectively. During slow concentric contractions, the force progressively decreased (23.1+/-2.1 %); the force decreased by only 6.3 +/-0.9% during sustained isometric contractions of similar duration (3400 ms). The recovery of isometric force following concentric contractions with similar stimulation frequencies (80 Hz) was velocity dependent (i.e. more rapid at higher velocities). It is concluded that pre-loaded slow concentric contractions of the plantar flexor muscles in intact rats do not follow the same relationship as that of isometric force and ankle position. Our results in intact rats show that the force output of electrically stimulated ankle plantar flexor muscles measured under the sole of the foot can be used to study the physiological properties of skeletal muscle working in situ.
Keywords
Laboratory-animals; Animals; Animal-studies; Physiological-testing; Skeletal-disorders; Musculoskeletal-system-disorders; Muscle-stress
CODEN
EXPHEZ
Publication Date
19990301
Document Type
Journal Article
Email Address
wstauber@wvu.edu
Funding Amount
868663
Funding Type
Grant
Fiscal Year
1999
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-002918
Issue of Publication
2
ISSN
0958-0670
Priority Area
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Source Name
Experimental Physiology
State
WV
Performing Organization
West Virginia University, Morgantown, West Virginia
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