THE USE OF PHYSIOLOGICAL PARAMETERS IN MEASURING THE VEGETATIVES CONSEQUENCES OF MENTAL IMAGERY
AbstractINTRODUCTION The effects of the mental repetition of an activity entail not only the improvement of motor performances, but create vegetative consequences, which are connected to the degree of imagined effort (Decety, Jeannerod, Germain et Pastene, 1991 ). These beneficial effects of imagery have been explained by considering that the central structures of programming allow the anticipation of the metabolic requirement according to the established goals. The authors who do not agree on the explanatory theory of vegetative changes observed during the mental imagery phase, also have differing opinions concerning the existence of measurable muscular activity. Traditional instruments of measure such as heart rate and electromyography were used as well as force measurement. The force allowed us to know the, mechanical force produced, which should be zero during imagery phase not to have a conclusion in favor of a mechanical action. METHODS If we consider, with Jagasinski and Nicholls (1984,1987) that the central structure involved in the programming of a real activity, as in an imagined activity, defines the contents of this activity according to a goal, we can then assume that the mental operations occuring before the beginning of an action affect the level of effort and the energetic or metabolic resources used. We asked 24 male subjects who had obtained good results at the Sheehan imagery questionnaire to imagine a precise isometric contraction : bending the elbow. Through the use of instructions, one group of 8 subjects had to complete the task (called the goal of implication in a task), 8 other subjects had to do better than the others, surpass them (ego implication goal) while the 8 remaining subjects were given no instructions to achieve the goal. All the subjects went through two sessions including positive\negative feed-backs. In the real execution phase as well as in the imaginary phase, the measurements of heart rate and the electromyography of the biceps brachi and the force used are the primary indicators concerning the vegetative changes. RESULTS They show no trace of electromyography activity during the imagined movement if we make sure of the absence of movement during this phase by using a force transducer. Besides, there is a significant rise in the heart rate, during a real movement as well as an imagined one and this is even more evident when the subjects go from the conditions of implication in a task and implication of ego. At the same time, the subjects stated that they made less effort when they were given a positive feed-back and made higher levels of effort when they received a negative feed-back in an implication of ego situation. DISCUSSION In the mental imagery phase, all significant muscular activity is due to a mechanical action. In the absence of force production, even with the creation of an image, the muscle produces no activity. The potential of a subliminal muscular activity would be the real action in weak proportions but mechanically not significant for the chosen movement. The benefits of the mental repetition are here considered according to a symbolic perspective. and emphasize the cognitive components of the mental repetition, in other words, the individual imagined the activity to be accomplished. This is a matter of purely cognitive process. If a muscular activity is visible, the individual has gone from the stage of an intention of movement to his effective achievement, this change would come from the representation of the activity that the subject creates himself. We may conclude that measurements made with biomechanical devices can be very useful to check psychological hypotheses in sport. REFERENCES 1-BERGUS ; JONES, E.E. : Drug choice as self handicapping strategy in response to no contingent success. Journal of personnality and social psychology 76 : 14E158.1978. 2-CARVER, C.S ; SCHEIER. M F. : Attention and self regulation. A confrol theory approach lo human behavior. New York : Sp~nger- Verlag. 1981 3JAGASINSK1, C.D.; NICHOLLS. J.G. : Concepttons of a Ability and Related in Task lnvolment and Ego Involrnanl. Journal of Educational Psychology 76 : 909-919. 1984
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