Electromyographic activity controlled at different times in the human step cycle

• Published in: Human movement science 1983, Vol.2 (1), p.105-129
• Main Authors: Wetzel, Mary C., Gorman, Linda K., Ganoe, William H.
• Format: Article
• Language: English
• ISSN: 0167-9457; 1872-7646
• DOI: 10.1016/0167-9457(83)90010-6

Greater understanding of human stepping patterns will be gained when different successive portions of the step cycle can be attributed to specific origins. In this study the strength of a known behavior, an operant composed of a colored light as discriminative stimulus and electromyographic activity of the rectus femoris muscle as response, was compared with that of other ongoing behaviors at each of five times during the stance (down) and swing (up) phases. Under computer assistance, while subjects walked on a motorized treadmill a green light discriminated a burst of 100–400 msec within a performance duration of 700 msec, while a red light discriminated muscle silence. Red and green lights were scheduled first in systematic and later in random orders across the 10 consecutive steps of each successive trial. The green light produced large successful bursts in every position after relatively little training, to rule out any powerful competing source of reflexive or other stimulus control. These discriminated bursts were accompanied in some instances by longlasting low amplitude activity, either several hundred msec before heel strike or else prior to the colored light. Control for the first low EMG type might have been reflexive (built in) or acquired through conditioning, but control for the second was acquired and depended upon movement produced stimulation that was associated with each position of the light.