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The motor program is a concept that has had a major influence on theorizing in the field of motor control. However, there has been a lack of consensus as to what exactly is a motor program and its role in movement organization and execution. In 1994 Morris, Summers, Matyas, and Iansek concluded from a review of the application of the motor program concept in the field of physical therapy that continued use of the term may impede progress in the field. In this paper we examine what has happened to the motor program concept in the thirteen years since the previous evaluation. The review indicates that although the term is still being used in different ways, the theoretical existence of a motor program appears to be generally accepted by researchers in experimental psychology, movement science, and neurophysiology. The recent development of powerful brain imaging techniques may allow determination of whether the motor program should be regarded as a metaphorical or literal concept.

Two reliable findings in discrete, rapid aimed movements are that reaction time increases with decrease in target diameter (for the short-length movements), and reaction time is not affected by movement length [Journal of Experimental Psychology, Human Perception and Performance 104 (2) (1975) 147]. Participants normally use a short stylus (SS) to tap targets located on either side of a central (aligned with body midline) start-point with no restrictions imposed on the initial posture of the limb or segmental recruitment except as determined by movement conditions. Thus, the effects of movement parameters on reaction time in previous work are potentially confounded with the effect of initial posture of the limb at the start-point, along with order and amount of the contribution of segments recruited in response execution. Two experiments were performed to resolve the confounding between initial posture and recruitment of limb segments. In the first experiment a conventional stylus (pen-like) was employed and the starting position of the limb was aligned either with the body midline or with the participant's right shoulder. The effect of starting position on reaction time was not significant. In the second experiment the starting position was in line with the right shoulder. Two groups participated. One group used a conventional stylus. For the second group a modified (lengthened) stylus was used that permitted initial limb posture and number of limb segments recruited to be held constant across an extended range of movement lengths. When similar sets of limb segments were used, reaction time increased with decreasing movement length and diminishing target diameter. These findings suggest that uncontrolled initial limb posture, uncontrolled order of joint(s) recruitment, and the subsequent inclusion of reaction time values from incompatible sources may, in the final analysis, have confounded previous work investigating movement amplitude and target diameter effects on reaction time.