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Fig. 4. Tibial muscles and EMG recordings during walking. (A) A single tibia
extensor muscle (red, 135) extends dorsally throughout the entire length of
the femur. Four tibia flexor muscle bundles (green, 136a–d) were located
ventrally. A retractor unguis (pink, 139) runs anteriorly along the acoustic
trachea. (B) Simultaneous tibial extensor and tibial flexor EMG recordings
were taken at positions as indicated in A. Large amplitude muscle potentials
recorded in the extensor were directly related to small amplitude muscle
potentials measured in the flexor, and vice versa. (C) Amplitude histogram of
gliding length filtered tibial extensor EMG recording of a walking cricket.
Four different motor units were clearly identified. A muscle potential
attributed to FETi is shown only in the EMG recording because of its large
amplitude. FETi spikes occurred very rarely during walking (1 in 20 steps) and
are not visible in the histogram. (D) EMG recordings were obtained during
walking, with simultaneous recordings of forward-backward movements of the
femur as an indication of the step cycle. Peaks of the EMGs were sorted
according to amplitudes: FETi>SETi>FFTi>SFTi. The occurrence of motor
unit activity within each step was normalised to the mean duration of steps
(390 ms).
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