Raumens sutrumpėjimo sukelta jėgos depresija elektrostimuliacija veikiamame žmogaus keturgalvyje šlaunies raumenyje (quadriceps femoris ) po tempimo-sutrumpėjimo ciklo pratimų

When muscle is allowed to shorten during an active contraction, the maximum force that redevelops after shortening is smaller than the isometric force at the same muscle length without prior shortening. This phenomenon is referred to as force depression (FD) following shortening contractions. The purpose of this study was to investigate the effects of muscle fatigue on shortening-induced FD in electrically activated human quadriceps muscle. Healthy untrained men (n=8) performed isometric reference contractions (ISOM) and isometric–concentric–isometric (ICI) contractions, using maximal electrical stimulation. FD was assessed by comparing the steady-state isometric forces produced following active muscle shortening with the purely isometric reference forces obtained at the corresponding muscle length. In order to test for effects of fatigue on FD stretch-shortening cycle exercise (SSC) was carried out consisting of 100 drop jumps performed from 0.5 m with counter-movement to 90° in the knee with immediate maximal rebound, with 30 s interval between the jumps. Besides, muscle soreness as well as CK activity up to 168 h after SSC exercise was determined. SSC exercise induced very intense muscle pain, the CK activity in the blood within 72 h after SSC exercise had increased approximately up to 1350 U/L-1 (p<0.05, as compared to the pre-exercise value). Thus, muscle damage (as judged from indirect indicators) was severe. Although FD was observed in all subjects in fresh and fatigued muscle it was significantly reduced only at 10 min following SSC exercise (p