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MEDICINA DELLO SPORT
A Journal on Sports Medicine
Official Journal of the Italian Sports Medicine Federation
Indexed/Abstracted in: BIOSIS Previews, EMBASE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 0,163
FUNCTIONAL EVALUATION SECTION
Medicina dello Sport 2004 March;57(1):31-9
Contractile changes in knee extensor muscles after repetitive maximal isokinetic contractions in male power-lifters and untrained subjects
Ereline J., Gapeyeva H., Pasuke M.
Institute of Exercise Biology and Physiotherapy, University of Tartu, Tartu, Estonia
Aim. Changes in isometric maximal voluntary (MVC) and electrically evoked submaximal tetanic contraction characteristics of the knee extensor (KE) muscles after short-term high-intensity fatiguing isokinetic exercise were compared in male power-lifters (n=11) and untrained subjects (n=15) as controls.
Methods. During measurement of isometric MVC and evoked tetanic contraction characteristics the subjects were seated on a custom-made dynamometric chair. Submaximal isometric (~25%MVC) tetanic contraction of KE muscles was evoked by percutaneous electrical stimulation using rectangular pulses of 1-ms duration with the frequency of 50Hz. Fatigue test consisted of 30 repetitive maximal isokinetic knee extensions at angular velocity 1.57 rad·s-1 and at 0.5 Hz frequency on the Cybex II isokinetic dynamometer. Isometric MVC force, peak force of evoked tetanic contraction (PFES), and rates of force development during maximal isometric voluntary (RFD) and evoked tetanic (RFDES) contractions, as well as half-relaxation time of evoked tetanic contraction (HRTES) were measured before, and 1 and 10 min after the exercise.
Results. A total mechanical work output (TWO) during isokinetic exercise was 38% greater (p<0.05) in power-lifters than in controls. Power-lifters had a greater (p<0.05) fatigue index as compared to controls. Isometric MVC force, RFD, PFES and RFDEs were decreased (p<0.05), and HRTES was prolongated (p<0.05) 1 min after exercise for both groups as compared to pre-exercise level. These characteristics recovered to pre-exercise level for untrained men within 10 min after the cessation of exercise, while they did not recover for power-lifters.
Conclusion. It was concluded that power-lifters produced a significantly greater work output and fatigued faster during repetitive maximal isokinetic knee extensions compared with untrained subjects. The recovery of isometric MVC and electrically evoked submaximal tetanic contraction characteristics of KE muscles within 10 min after the isokinetic exercise was more delayed in powerlifters than in controls.