Fig. 1
The influence of the muscle passive stretch on the amplitude of the transitory force decrease. Upper recordings: a set of sample recordings of the tetanic contractions of fast resistant motor unit stimulated with a 30–75–30 Hz pattern in a muscle stretched up to the passive forces of 30, 100, and 200 mN. The horizontal interrupted lines indicate the reference force at the end of tetanus used to calculate the amplitude of the force decrease. The red vertical arrows indicate the amplitude of the force decrease. Lower graph: amplitude of the force decrease obtained for the muscle passive stretch values of 30, 100, and 200 mN. Data for each set of recordings are connected by a line; the bold red line refers to motor unit illustrated upper. The figure presents combined data for 6 fast resistant motor units for 9 applied stimulation patterns. Note that, at 30 mN for some recordings, the transitory force decrease was not present. The black line connects the mean values at three tested levels of muscle passive stretch; level of significance of differences is indicated above. Significance of differences between groups is represented by * (p < 0.01)