Behavioural Brain Research, 52 (1992) 167-174 9 1992 Elsevier Science Publishers B.V. All rights reserved. 0166-4328192/$05.00

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BBR01388

The effect of imagery perspectives on the psychophysiological responses to imagined exercise Y o u d e W a n g a n d W i l l i a m P. M o r g a n Department of Kinesiology, Unirersity of Wisconsin-Madison, Madison, IVI 53706 (USA) (Received 1 May 1992) (Revised version received 21 August 1992) (Accepted 30 September 1992)

Key )tvrds: Imagery perspective; Psychophysiological response; Blood pressure; EMG activity

The effect of imagery perspectives, i.e. internal imagery vs. external imagery, on the psychophysiological responses to imagined exercise was investigated in the present study. Thirty male and female college students were randomly assigned to perform either internal imagery, external imagery or simple rest in addition to actual exercise. Metabolic, cardiovascular and perceptual responses were recorded before, during and after imagined exercise, actual exercise and rest. The results indicated that internal imagery resulted in a significant increase in ventilation and this response differed from the control condition. Effort sense was higher with internal imagery compared with external imagery. However, both internal and external imagery produced significant elevations in systolic blood pressure (SBP) from pre- to post-imagery, and these values were identical to those observed with actual exercise. Therefore, some responses to imagery were like those seen during actual exercise. Oxygen consumption (~'o2), respiratory rate (RR), respiratory exchange ratio (RER), heart rate (HR) and diastolic blood pressure (DBP) were similar between internal and external imagery. It is concluded that the psychophysiological responses to internal imagery resemble actual exercise more than external imagery.

INTRODUCTION

Until recently evidence to support the argument that motor imagery may share neural mechanisms that are also responsible for motor programming has been mainly limited to the manifestation of E M G activity during imagery. There has also been limited research involving elevated metabolic, cardiovascular, and perceptual responses to imagined exercise under hypnotic suggestions. For instance, Jacobson ~3-~5 in the 1930's and Shaw z8'29 during the 1940's reported that muscular action potentials were observed during the imagination of an arm movement, and they were proportional to the amount of weight that was imagined. In the case of hypnotic studies it has been documented that (i) resting metabolic rate and cardiovascular responses can be altered when subjects in a resting state are given Reprint requests: W.P. Morgan, Sport Psychology Laboratory, Department of Kinesiology, 2000 Observatory Drive, University of Wisconsin-Madison, Madison, WI 53706, USA. Correspondence:Y. Wang, Exercise Physiology and Nutrition Center, 21 N. Quinsigamond Ave., Shrewsbury, MA 01545, USA.

suggestions of exercise19"21; (2)exercise metabolism and cardiovascular function can be changed when suggestions oflight and heavy exercise are given to subjects who exercise at a constant loadZl"22'24; and (3)perceived exertion can be modified in accordance with suggestions ofdifferent work loads z2"z3. In some ofthese studies oxygen consumption, ventilation and heart rate during imagined exercise were found to be similar to that of the actual exercise 21'22'24. Similar findings have recently been reported in several non-hypnotic studies. Roland et al. 27, for instance, have reported that the activation of cortical motor areas during an imagined sequence of movements was similar to that observed during actual execution of the same sequence of movements. Decety et al. 4 have found that regional cerebral blood flow (rCBF) increased significantly when subjects were instructed to imagine holding a tennis racket in their right arm and hitting a ball on the wall. However, no increase in surface E M G was observed in the proximal and distal muscles of the right arm. In a separate study Decety et al. 5 have reported that both heart rate and ventilation increased during mental imagery of locomotion, proportional to the

168 imagined walking speed. In other words, while the speed of imagined walking increased from 5 km/h to 8 km/h to 12 km/h a monotonic increase in heart rate and ventilation (~'E) was observed. However, little change in oxygen consumption was detected during the imagined walking at various speed, suggesting that "a significant fraction of this vegetative activation has to be of a central origin (p.4)". More recently, by simultaneous measurement of six autonomic nervous system (ANS) variables on 22 top level rifle shooters and archers, Deschaumes-Molinaro et al. 6 have shown that there is a similarity of ANS response between actual shooting and imagined shooting. In this research a decrease of skin blood flow, skin temperature, skin resistance, and an increase in skin potential as well as instantaneous heart rate and respiratory frequency were observed in actual and imagined shooting. While these results seem to indicate a link in neural mechanisms between motor imagery and actual movement, none of these studies has addressed the issue of imagery perspectives, i.e. internal imagery vs. external imagery. Internal imagery, in the context of motor imagery, requires one to imagine movement and the physical and emotional sensations experienced during actual action from a first person point of view, 'as if' one were really exercising. External imagery, on the other hand, requires one to recall a mental representation of movement from a third person point of view, 'as if' viewing oneself exercising, for example, on a television screen. Limited evidence from emotional imagery tends to indicate that imagery perspectives, in addition to imagery ability, play a significant role in solicitation of physiological responses. Lang e t a l . 17't8, for example, have demonstrated that internal imagery (response propositions) generated significantly greater physiological responses than the external imagery (stimulus propositions) during emotional imagery. In addition, Hale 8 and Harrison and Robinson 9 have also reported that EMG response was much greater during internal imagery of an elbow flexion than that of external imagery. These findings seem to suggest that perhaps it is the internal imagery, but not the external imagery, that triggers ANS response, establishing a correspondence between mental representation of a motor action and execution of the action. However, previous research has not focused on this possibility, and the present investigation was designed in an effort to elucidate the salience of imagery perspective. The purpos.e of this investigation was to study the effect of imagery perspectives (i.e. internal vs. external) on the psychophysiological responses to imagined exercise.

MATERIALS AND METHODS

Subjects The subjects were 30 male and female undergraduate and graduate students enrolled at a midwestern university. They ranged in age from 18 to 30 years with a mean age of 23.7 ( + 2.6).

Apparatus A Rayfield system was used to measure metabolic changes during physical as well as imagined exercise. The system was under the control of a computer. The computer software permitted sampling of Vo2, ventilatory minute volume (irE), respiratory exchange ratio (RER) and respiratory rate (RR) at selected intervals. Heart rate was measured continuously and averaged across 15-s epochs by means of radio telemetry using a Uniq Heartwatch unit (model 8799, Computer Instruments Corporation, Hemstead, New York). Blood pressure was assessed by means of an Ultrasonic Blood Pressure Monitor (Roche Arteriosonde, Model 1225). A cassette tape-recorder was used in conjunction with an intercom system to present the recorded image scripts. Procedures All testing was carried out under controlled laboratory conditions in a chamber with a sound level of 8 dB, temperature of 22 ~C ( + 2 oC) and relative humidity of 50~o ( + 5~o). The testing procedures for both Day 1 and Day 2 were monitored continuously by means of a video camera. Subjects participated in two sessions conducted on separate days. On day 1, each subject signed an Informed Consent Document. All subjects were, then, given a 10-min rest after the electrodes and blood pressure cuff were attached to the chest and non-exercise arm, respectively. An additional 5-min rest was given after subjects donned the face mask. Each subject next performed physical exercise with an individualized weight equal to 25 ~o of his or her maximum. The exercise consisted of elbow flexion with the preferred arm. Subjects assumed a seated position while lifting a dumbbell in his/her supinated, preferred hand for 3 min at 20 repetitions per min in cadence with a metronome. After a 3-min baseline period data were collected, instructions for physical exercise were administered by means of the following recorded script: You are about to lift dumbbells at a rate of 20 repetitions per minute for a 3-rain period. The weight that you will lift weighs about 25 % of the maximum weight that you can lift once, and you should make an effort to finish the 3-rain period. A metronome will be placed near you and set at a rate of 20 repetitions per

169 minute. Please set )'our pace in accordance with the rhythm of the metronome. Do not work any faster or slower than the metronome. You will be asked to rate )'our perceived exertion after exercise.

Immediately following exercise subjects were asked to provide ratings of perceived exertion for the arm and total body according to Borg's 2 original 6-20 rating scale. They were then instructed to sit quietly without moving. On Day 2 (24-48 h interval), in addition to performing the same exercise as Day 1, the 30 subjects were randomly assigned to one of the three groups: internal imagery (n = 10), external imagery (n -- 10), and control (n = 10). The order of the treatment was counterbalanced. Subjects in the internal and external imagery groups performed imagined exercise, and subjects in the control group rested for 3 min. A 5~ rest was provided between exercise and treatment. The instructions for each condition were: Instructions for imagined exercise (internal imagery): Now I would like you to imagine that you are lifting the dumbbells just as you did before during the actual exercise. Please close )'our eyes and start to imagine that )'our arm muscles are contracting, )'our heart is beating, and your breathing is changing. In other words, try to recall all the physical sensations that you experienced while actually lifting the dumbbells. Please nod your head if you can form this image. Now let's try this again. Can you see and feel )'our muscles are working, your heart is beating and )'our breath is getting faster and deeper? Very good! Let us start the test. Remember that you need to follow the rhythm of the metronome during imagery. Do not speed up or slow down but keep pace with the metronome. It is also important not to move any part of )'our body during imagery. When you hear a tone, stop and open ),our eyes. You will be asked to rate the vividness of the imagery and )'our ability to control the imagery. You will also be asked to rate )'our perceived exertion.

Instructions for imagined exercise (external imagery): Now I would like you to imagine that you are lifting dumbbells just as you did before during the actual exercise. Please close your eyes and start to imagine that you are lifting the dumbbells. Can you see yourself sitting there and lifting the dumbbells? Please nod )'our head if you are able to form this image. Now let us try this again. Close your eyes and imagine that you are sitting there and lifting the dumbbells. Can you see yourself lifting the dumbbells? Very good! Let us start the test. Remember that you need to follow the rhythm of the metronome during imagery. Do not speed up or slow down but keep pace ~ith the metronome. It is also important not to move any part of your body during imagery. When you hear a tone, stop and open )our eyes. You will be asked to rate the vividness of the imagery and ability to control the imagery. You will also be asked to rate )'our perceived exertion.

Immediately after imagery subjects were asked to rate the perceived exertion for the arm and total body. The3{ were also asked to rate the vividness of the image

produced on a 1-5 point scale (1 = perfectly vivid and clear image, 5 = no image at all), and the controllability of the image on a 1-5 scale (1 = fully controlled, 5 = no control at all). And finally they were asked to estimate the percent of time they were able to comply with the imagery instructions. The exact instructions follow: You have just finished the test. What is )'our rating of perceived exertion for your arm; for your total body? t t o w would you rate the vividness of your image D, on this 1-5 scale? How would you rate your ability to control the imagery on this 1-5 scale? And finally, were you able to maintain internal (external) imagery all the time? If no, please give the percentage of the time you were able to do so. Thank you. Now please keep )'our eyes open and sit quietly without moving until further instructions.

In the case of the conti-ol condition, the protocol was the same as that employed with the imagery groups except the following instructions were presented to the subjects: Instructions for control condition (rest): Now I would like you to sit quietly for 3 min. Please do not think about exercise at all. It is also important not to move any part of your body during the next 3 min.

Data redttction k'o,, /rE, RR and RER were sampled every 60 s and HR was recorded every 15 s for physical exercise, imagined exercise and the control condition. Blood pressure was taken before and after each treatment. Data collected during the first 3 min were averaged and used as the baseline. The next 2 min were used for instructions and blood pressure measurement. The average data of the 3 min after instructions consisted of the testing period, and the average ofthe 3 min after testing was used as a recovery period. Immediately following testing subjects provided the ratings of perceived exertion (RPE) for the arm and total body. Ratings of imagery vividness, imagery controllability and the percent of time complied with the desired imagery perspective was also provided after testing. RESULTS

Physiological responses Metabolic measures Paired t-tests for each variable revealed that neither the internal nor the external imagery resulted in any responses comparable to the actual exercise. That is, metabolic responses were significantly greater in every case for exercise.

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Means and standard deviations for variables P'o2, RR and RER are presented in Table I. Comparisons among the internal imagery, external imagery and control conditions did not yield any significant effects for //o2, RR and RER. It should be noted, however, that the patterns of the internal imagery tended to resemble actual exercise whereas external imagery and control did not.

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Fig. 1. glean

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S.E.M.) f"v scores for the imagery and control groups.

Comparisons in ~'E among the interval imagery, external imagery and control groups are plotted in Fig. 1. Repeated measures MANOVA with one group main factor (internal imagery, external imagery and control group) and one trial factor (baseline, testing and recovery) revealed a significant group by trial interaction effect (P

The effect of imagery perspectives on the psychophysiological responses to imagined exercise.

The effect of imagery perspectives, i.e. internal imagery vs. external imagery, on the psychophysiological responses to imagined exercise was investig...
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