Low frequency fatigue after performing intermittent eccentric exercise and continuous eccentric-concentric exercise

The aim of the study was to test the hypothesis that exercise of maximal intensity (M) (50 continuous jumps) induces a smaller degree of low frequency fatigue in humans than eccentric intermittent exercise (E) (50 "eccentric" jumps). The main finding of the study is that only after the E exercise there was a statistically significant (P<0.05) decrease in the quadriceps muscle contraction force induced by stimulating the muscle at 1-50 Hz. After E exercise the force induced by low frequency stimulation (1-20 Hz) increased more significantly (P<0.05) than in the case of high frequency stimulation (50 Hz). This is indicative of the fact low frequency arose in the muscle. Two min after the end of E and M exercises the height of vertical jump and maximal voluntary contraction force were no different from their respective pre-exercise values. Following the E and M exercises there was no change in relative twitch force post-tetanic potentiation. This points to the fact that "metabolic" fatigue induced by performing exercise of maximal intensity can partially compensate for the decrease in muscle contraction force in the case of low frequency fatigue.