Function of the quadriceps femoris muscle under maximal concentric and eccentric contractions
Eloranta, V.; Komi, P.V.
Electromyography and Clinical Neurophysiology 20(2): 159
1980
ISSN/ISBN: 0301-150X PMID: 7379739 Document Number: 155028
Activation patterns of rectus femoris, vastus lateralis, vastus medialis and semimembranosus muscles were investigated under conditions of maximal concentric (CONC) and eccentric (ECC) contractions of both leg extension and resistance from a sitting position. Six normal college male students served as subjects. A special electrical dynamometer allowed recordings of EMG activity at 8 different constant linear velocities ranging from 0.12-0.97 m/s. The obtained force-velocity curve demonstrated a parabolic pattern in CONC with decreasing force with increase in the movement speed. In ECC the maximal forces were higher than in CONC but similar across all measured speeds. From the examined muscles rectus femors had similar maximal activation pattern in both CONC and ECC so that it was highest in the middle of movement (knee angle 100.degree.-120.degree.) and lowest in more extended positions. Both vastus lateralis and vastus medialis muscles had more plateau type maximal IEMG/knee angle curves with the activation being always least at smaller and larger knee angles. In EEC condition all the agonist muscles had the same average maximal activation at all measured speeds. In CONC, the peak IEMG of the vastus lateralis and medialis muscles tended to increase with increasing speeds of movement. Their average maximal IEMG activity was also higher (P < 0.01) in CONC than in ECC condition. The semimembranosus, an antagonist muscle demonstrated slight activity in all test contractions. In ECC its peak activity was independent on knee angle or contraction velocity. In CONC, IEMG activity of semimembranosus increased linearly with increasing movement speed and the activity pattern was always greatest at greater knee angles. The position of the knee angle may have influence on the maximum activation of the investigated muscles. The maximal EMG patterns of the quadriceps and semimembranosus muscles are linked to the mechanics of movement in CONC and ECC contractions.