RESUMO
It is proved, that the physiological interpretation of the peaks in the quadriceps femoris muscle twitch mechanogramme is possible. The measuring chain (sensor-amplifier-magnetic data recorder-plotter) has a resonance frequency of 170 Hz and is suitable for the true representation of the tension-time-course. In order to compare the tensions with one another, it is necessary to standardize the tensions on the lower leg or body mass. Considering the fact that the twitch mechanogramme is a summation of the contractions of the fast twitch fiber (FTF) and slow twitch fiber population (STF), it has been assumed that both FTF and STF show contraction peaks. Essential methodological influences on the tension-time-course result from the relationship between tension sensor and biological system (lower leg mass). The measuring chain and lower leg mass represent a feather-mass system. The provoked oscillations of the lower leg mass may produce methodological peaks in the twitch mechanogramme. In general, the mechanogramme shows contractions superimposed by mechanical processes. The tonogramme shows that the tension-time-course of the twitch is characterized by several peaks too. In the tonogramme characteristic changes depending on the portion of the quadriceps femoris muscle (rectus femoris, vastus lateralis) can be seen. Following the muscle action potential (MAP) there are frequently reflex-MAP's variable in form and amplitude in the time range between 120-180 ms after the stimulus impulse. They allow to explain the peaks in the mechanogramme with contraction times (CT) of 140-160 ms, or they provoke an extension of the relaxation times. Some reflex-MAP may have a latency of only 80 ms. The analysis of the methodological components influencing the mechanogramme of the muscle twitch shows that the interpretation as FT- or ST-peaks has to be done from the point of view of physiology. The following results indirectly speak for the interpretation as FT- or ST-peaks (CT: 30-50 ms and 75 to 95 ms, respectively). There are the corresponding average CT for groups with clearly different lower leg mass, the relatively higher increase of the peaks with CT between 60-70 ms after a maximal voluntary contraction (MVC) of 10 seconds, the higher average tensions for the ST-peaks by long distance runners and the results for the CT when the lower leg mass is artificially elevated. Furthermore the mechanogrammes of the long distance runners show that the maximum may come to a CT of 100-130 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
