The purpose of this study were to investigate controllability of the pursuit movement of the leg muscles in various conditions. Leg extension and flection of 3 subjects were studied in the sitting position. Tracking was performed for 3 kinds of wave forms (sinusoidal, sawtooth and rectangular) on the oscilloscope. Various work loads were given with 0.3Hz of wave forms as follows, 0.5, 1, 2, 4 and 8kg.
The following results were obtained;
1. Characteristics of phase showed leg phenomenon of approximately 5 degree with increasing load, at all waves.
2. Characteristics of gain showed undershooting of approximately -0.2 to -0.5dB with increasing load at the sawtooth and rectangular waves.
3. Characteristics of control error area became best performance in the order, sinusoidal wave (20-40mm²), sawtooth wave (40-80mm²), rectangular wave (80-100mm²).
4. There was no significant difference between the exercise of flection and extension.

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According to the perceptual information presented to an operator, the manual control tracking system is classified into the compensatory tracking system and the pursuit tracking system. Many experimental studies have reported the superiority of the pursuit tracking system over the compensatory tracking system. One of the explanations for this superiority is that while compensatory tracking behavior is a simple feedback behavior, pursuit tracking behavior involves a feedforward element in addition to a feedback element. This feedforward element permits the operator to predict the target movement and to compensate for change of the controlled element dynamics. This study attempted to quantify how effectively the operator used the feedforward behavior in the pursuit tracking system.

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