INTRODUCTION TO IMAGERY IN PHYSICAL PERFORMANCE
Item extracted from Rushall, B. S., & Lippman, L. G. (1997). The role of imagery in physical performance. International Journal for Sport Psychology, 29, 57-72.
This paper proposes that multiple models of mental practice, each distinguished by certain factors and structures, are necessary and appropriate for use within physical performance environments. The distinction between models is necessary because the use of elements and procedures to accomplish specific behavioral outcomes is different in sports performance and skill learning.
Although mental practice procedures and results are considered valid (see below), doubts about efficacy could be a result of confounding or misalignment between elements of specific practices and different applications. Within the realm of performance preparation, Biddle (1985) stressed that the different structures of mental practice depend upon their roles: ". . . mental practice of weight lifting skills may take place many minutes before physical performance, but the lifter may then switch to a psyching strategy just before the lift" (p. 71). It is possible that a different form of mental practice/preparation is appropriate for strength activities when compared to different movements such as fine skills of less than maximum amplitude.
Sport psychology, and psychology in general, would benefit from determining what forms of mental practice are appropriate for particular purposes and activities. Specification of how each model is used would allow even further gain. Appropriate distinctions would allow guidelines to be developed that could benefit research and minimize inappropriate use in applied settings.
There seems to be a paucity of research and commentary that propose different models based on application. Grouping research findings under the single mental practice label may obscure a need for separate models that have different uses in the physical activity domain. For example, it should seem obvious that the mental practice activity of a 10-year old's learning to play a forehand at a tennis lesson would be very different from that of a professional player preparing mentally for a Wimbledon match. Yet both are supposed to be able to use "mental practice" to their advantage. In a learning situation, mixing mental practice trials with physical practice trials should enhance skill acquisition. In a game situation mental practice prior to and possibly during a match should enhance the level and consistency of performance. Despite use of the same label for imagery actions in both situations, there is no assurance that the same processes are taking place or that the procedures have the same conceptual bases. The purpose of the present paper is to consider whether breaking the mental practice/imagery literature into separate classes might lead toward better understanding of mental practice effects, more focused and incisive research, and more effective applied practices.
Imagery-based tactics for influencing skill performance are usually described under the general rubric of "mental practice". Mental practice also has been given a variety of descriptive labels, some being mental rehearsal, implicit practice (Richardson, 1967b), and covert rehearsal (Corbin, 1967). In this paper the terms mental practice and imagery will be used as synonyms.
The practice of actions without making noticeable movements, as is often the case with imagery, can seem peculiar or suspicious. The Army Research Institute asked the National Academy of Sciences to arrange examinations of several "extraordinary" performance enhancement techniques that fall outside the mainstream of conventional scientific evolution and specification of behavioral processes (Swets & Bjork, 1990). A report (Feltz, Landers, & Becker, 1988), and an even more recent analysis (Hinshaw, 1991-92), verified that mental practice effects are real, confirming the general results of earlier reviews (Feltz & Landers, 1983; Richardson, 1967a, 1967b).
It is our observation that many reviews of mental practice fail to separate different imagery-based applications and implementations. One form, rarely considered in discussions of mental practice and physical performance, includes sundry behavior modification practices developed and elucidated by Cautela, such as covert reinforcement (1970) or extinction (1971). Those applications, as well as covert behavior modification, have been summarized satisfactorily (Cautela & Kearney, 1986) and will not be expanded here. It is contended, however, that two other uses of mental practice, skill learning and performance preparation, involve disparate processes and are employed for clearly different purposes. Yet, it appears that the literature generally has failed to treat them separately (e.g., Howe, 1991), leaving them combined and inappropriately undifferentiated.
For performance preparation, the focus is on factors that can enhance performance, such as motivation or activation. For skill development, the focus is upon the growth and mastery of skill elements or adapting a skill to specific circumstances. It should be noted that Suinn (1984, 1985) seemed to separate these two functions of mental practice within his "visuo-motor behavioral rehearsal" (VMBR) package of training. This "learning vs. performance" distinction is particularly clear-cut in Rushall's (1991) imagery training program which is an extension of Biddle's (1985) recommendation:
The relatively low effect sizes reported for strength tasks by Feltz and Landers (1983) could be the result of subjects' being asked to use a symbolic type of mental rehearsal rather than preparatory arousal strategies. (p. 70)
Many mental practice studies employ imagery over a less immediate time period and emphasize skill learning. One possible distinction between preparation and practice, therefore, could relate to performance and learning. Similarly, mental practice is used to reinforce learned movements and to establish movement coordination and sequencing. Mental preparation would appear to relate more to the establishment of a 'mental set' allied to immediate performance enhancement. (p. 71)
A delineation of mental practice models for learning physical skills and for performance preparation seems justified. Although these forms make use of imagery, they may engage very dissimilar processes and be implemented for clearly different purposes. Furthermore, even within the skill development application, the content of imagery will differ, depending upon the stage of learning the skill. But imagery serves a useful function from the very outset of learning a physical skill (Lippman & Selder, 1992.) It seems ironic that there is an apparent failure to separate learning and performance in a field where such a distinction is a central concern and defining attribute. Another closely allied purpose is to indicate areas where research evidence is limited or ambiguous, and to urge attention to them in order to afford practitioners a firmer foundation on which to base practical applications.
The Mechanisms Linking Mental and Physical Practice
Although there has been some doubt shed on the neuromuscular (or psychoneuromuscular) theory (Feltz & Landers, 1983), it is perhaps the most obvious and direct basis for understanding the connection between imagery and motor performance. Jacobson (1930, 1931, 1932; Hale, 1982) demonstrated that action potentials recorded from specific muscles changed during recall of movements. The finding that movement imagery produces impulses to perform the movement itself is called the "Carpenter effect" (Ulich, 1967), named after the individual who proposed the "ideo-motor principle" (Carpenter, 1894). Generally, recent evidence demonstrating specificity of muscle potentials has contributed reasonable support for the neuromuscular interpretation (e.g., Bird, 1984). As an example, Suinn (1980) observed that EMG recordings coincided with actual turns and jumps when a downhill skier had been instructed to "think about" racing.
Although agreement about an exact mechanism has not been reached, it generally appears that during physical practice, neurotransmitters along a particular neuromuscular pathway are stimulated every time a neural transmission follows that pathway. After the transmission, those chemicals remain for a short time; each subsequent stimulation along the pathway pattern is facilitated by the accumulated residual effects of the previous excitations. Thus, repeated physical trials lead to improvement until fatigue develops and starts to produce interference. According to neuromuscular theory, the excitation of the neuromuscular pattern associated with a particular skill can also be initiated through imagery; the same facilitation can take place with repeated trials of imagery--but without the risk of accumulated interference from fatigue. Thus, both mental and physical excitation of neuromuscular patterns associated with a specific movement yield facilitation in subsequent physical performance attempts.
Another interpretation of mental practice effects is in the form of a cognitive model (MacKay, 1981). According to this characterization, physical practice leads to the establishment of physical nodes; their development, in turn, leads to counterpart mental nodes. Once a mental node is established, its activation through mental practice induces activity and strengthening of its counterpart physical node. Perhaps the most obvious feature of this model is the assumption that mental nodes arise from physical nodes. Thus, it can be predicted that in the absence of previous task-relevant physical behavior, there would be no mental nodes, so attempts at mental practice to bring about changes in physical performance of a novel and unpracticed task would be futile. Imprecise physical practice or practice of inefficient actions would lead to development of non-ideal physical nodes plus faithfully-duplicated mental-node counterparts; therefore, mental practice would strengthen those inferior habits. It also suggests that an insufficient history of physical performance would yield fractional or incomplete mental nodes, thus limiting the efficacy of mental practice. Likewise, limited physical experience with novel tasks would render mental practice efforts ineffective, a finding clearly in keeping with results from tasks that are grossly limited in symbolic or cognitive features, such as a rotary pursuit (Feltz & Landers, 1983). Although processes and explanations of mental practice are debatable, its effects on physical performance have been rather well established.
The main difference between physical and mental (image-based) instigation of a neuromuscular pattern seems to be intensity. For example, Fujita (1973) examined EMG recordings of muscle responses in highly trained athletes who either imagined performing a skill or executed it physically. The muscle utilization patterns were similar, with the principal difference being that amplitudes were smaller for imagined performances. The implication here is that a mental image could be used to replicate the pattern and timing of a complicated physical skill. A further finding was that when athletes imagined an activity in slow motion, the response pattern changed drastically, appearing as an entirely different skill. It is a well established understanding that two attempts at a skill, one in normal time and the other in slow motion, produce discrete and unrelated neuromuscular patterns. Such findings form a basis for the "specificity of training" principle (Rushall & Pyke, 1990). It follows that slow-motion mental rehearsal of a skill could be of no value to full-speed physical execution. Not only must the images of movements be correct, but the intensity and timing of mental representations used in rehearsal also must match the terminal behavior if this covert practice is to lead to any performance improvement. However, there are some qualifications and additional considerations needed for this interpretation.
It is apparent that the mental mechanisms used for learning a physical skill are different from those used for recalling a well-learned activity. The recall function is intended to facilitate the initiation and execution of an established skill so that any "warm-up" time is minimized. This retrieval process is the principal role of mental practice as part of competition preparations. The single mechanism in that role is neuromuscular patterning and facilitation. Only those movements to be used specifically in the competition should be mentally practiced. On the other hand, the use of mental practice in learning incorporates several different mechanisms. Slow-motion mental and physical practice produce neuromuscular facilitation that is only transitory. Each pattern is lost as speed is gradually increased on successive trials of either mental or physical practice. The course of learning involves frequent changes in skill topography, resulting in neuromuscular patterning that may be inappropriate for terminal performances and a collection of movement patterns, none of which are preferred or dominant.
The perceived difficulty, speed, or complexity of a skill changes as it is learned. As mastery is approached, skills are often described as being "easy" or simpler than when they were first attempted. The ability to increase gradually the size of the grouping of skill elements leads to different content for skill recall. Consequently, what was mentally practiced during the first stages when kinesthetic recall was difficult, is not appropriate for later stages in the skill learning process when kinesthesis or "feel" is important. The data and descriptions of the mental involvements and mechanisms in the various phases of learning a skill are much less understood than the parameters involved in mental practice for competition preparation. Those differences warrant a distinction between the two forms and uses of mental practice. A description of their mechanisms and processes is needed.
References
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