Force and EMG measurements at the quadriceps femoris of marathon runners against sprinters and volleyball players under isometric explosive conditions

Abstract

To examine muscles with different fiber compositions as to their innervation and force behavior, EMG and force measurements were taken from the M. quadriceps femoris of 12 volleyball players (first national league), 12 sprinters (1 OOm best time mean = 10.8s), 12 marathon runners (42,2 km best time mean = 2.40 h) and 12 not specifically trained students of the physical education department. In a maximum isometric explosive contraction the torque (T) [%Torque max isometric static], power (P) [T/M], electromechanical delay (EMD), integrated EMG (IEMG) [%iEMGmax isometric static] and muscle fiber conduction velocity (MFCV) were measured and averaged across five repetitive trails. The EMD’s and iEMG’s of the three heads of the quadriceps were averaged to EMDm and iEMGm. The results revealed significantly increased Pmax values for the groups with presumably more fast-twitch fibers (volleyball players and sprinters) against the groups with more slow twitch fibers (students and marathon runners). Since the lowest EMDm was found for the group of the students and because of the high positive correlations between Pmax and EMDm and Pmax and T/iEMGm ratio (N=48), it is suggested that the time based interaction between different muscle units and specific muscle actions is important for the use of the whole morphological potential of a muscle.