Muscle fatigue in frog semitendinosus: alterations in contractile function. Am J Physiol 1992 Jun;262(6 Pt 1):C1500-6
Date
06/01/1992Pubmed ID
1535482DOI
10.1152/ajpcell.1992.262.6.C1500Scopus ID
2-s2.0-0026647439 (requires institutional sign-in at Scopus site) 37 CitationsAbstract
The purpose of this study was to characterize the contractile properties of the frog semitendinosus (ST) muscle before and during recovery from fatigue, to relate the observed functional changes to alterations in specific steps in the crossbridge model of muscle contraction, and to determine how fatigue affects the force-frequency relationship. The frog ST (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. The fatigue protocol reduced peak twitch (Pt) and tetanic (Po) force to 32 and 8.5% of initial force, respectively. The decline in Pt was less than Po, in part due to a prolongation in the isometric contraction time (CT), which increased to 300% of the initial value. The isometric twitch duration was greatly prolonged as reflected by the lengthened CT and the 800% increase in the one-half relaxation time (1/2RT). Both Pt and Po showed a biphasic recovery, a rapid initial phase (2 min) followed by a slower (40 min) return to the prefatigue force. CT and 1/2RT also recovered in two phases, returning to 160 and 265% of control in the first 5 min. CT returned to the prefatigue value between 35 and 40 min, whereas even at 60 min 1/2RT was 133% of control. The maximal velocity of shortening, determined by the slack test, was significantly reduced [from 6.7 +/- 0.5 to 2.5 +/- 0.4 optimal muscle length/s] at fatigue. The force-frequency relationship was shifted to the left, so that optimal frequency for generating Po was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
Author List
Thompson LV, Balog EM, Riley DA, Fitts RHAuthor
Robert Fitts PhD Professor in the Biological Sciences department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
Analysis of VarianceAnimals
Electric Stimulation
In Vitro Techniques
Isometric Contraction
Kinetics
Microcomputers
Models, Biological
Muscle Contraction
Muscles
Myosins
Rana pipiens
Stress, Mechanical
Time Factors
