JoumaElUm Apepanopf l i e d Physiology
Eur J Appl Physiol (1992) 65:573-578
and Occupational Physiology © Springer-Verlag1992
Effects of hypnosis on plasma proenkephalin peptide F and perceptual and cardiovascular responses during submaximal exercise William J. Kraemer I, Randolph V. Lewis 2, N. Travis Triplett I, L. Perry Koziris ~, Steve Heyman 3, and Bruce J. Noble 4 Center for Sports Medicine, The PennsylvaniaState University, UniversityPark, PA 16802, USA 2 Department of Molecular Biologyand 3 Department of Psychology,The Universityof Wyoming,Laramie, WY 82071, USA 4 Department of PhysicalEducation, Health and Recreation Studies, Purdue University, West Lafayette; IN 47907, USA Accepted July 28, 1992
Summary. Little information is available concerning the influence of subconscious mechanisms on neuroendocrine function, more specifically, proenkephalin peptide F release. Ten men [5 middle distance runners (21.6 (SD 0.54 years) and 5 untrained men (24.0 (SD 4.3 years)] consented to be volunteers in this investigation. Submaximal exercise intensities of 25% and 50% of peak oxygen consumption (1702) (8 min stages) were used for both the control and hypnosis treatments. A traditional hypnotic induction was used, with the suggestion of two higher intensities of exercise stress (50% and 75% peak 1)-O2) previously experienced in familiarization and testing by each subject. Each minute oxygen consumption was measured using open circuit spirometry, heart rate via an ECG, and ratings of perceived exertion (RPE) using the Borg scale. Plasma peptide F immunoreactivity (it) [preproenkephalin-(107-140)] in blood sampled from an indwelling cannula was measured by radioimmunoassay at 7-8 min of each stage of the exercise test. Expected significant increases were observed for all cardiorespiratory and perceptual variables over the increasing exercise intensities and there were no significant differences between trained and untrained groups for peptide F ir response patterns. Hypnosis did not significantly affect peptide F ir concentrations (P>0.05) and did not significantly alter exercise heart rate, RPE or minute ventilation (P> 0.05). However, hypnosis did significantly increase oxygen consumption during exercise (P = 0.0095) but not of the magnitude needed for the metabolic demands of the higher exercise intensities. Thus, traditional hypnosis was unable to make functionally significant changes in the cardiorespiratory variables. Training did not alter responses to exercise under hypnosis. The results of this study indicate that when using traditional hypnosis and a suggestion of harder exercise in highly selected groups, it may not be possible functionally to stress adrenal medullary secretion of proenkephalin fragments, RPE or cardiorespiratory variables. Correspondence to: W. J. Kraemer, Center for Sports Medicine,
117 Ann Bldg., The Pennsylvania State University, University Park, PA 16802, USA
Key words: Enkephalins - Endogenous opioid peptides - Endurance exercise
Introduction Peptide F, an enkephalin-containing polypeptide with opiate-like actions found in the adrenal medulla, is sensitive to the same release stimuli as epinephrine (Kilpatrick et al. 1981; Lewis 1982; Livett et al. 1981; Viveros et al. 1979). Exercise has been shown to increase plasma levels of proenkephalin peptide F immunoreactivity (ir) [proenkephalin-(107-140)] (Kraemer et al. 1985, 1988a, 1988b, 1990). Plasma peptide F i r concentrations have been shown to be responsive in humans to a wide variety of stimuli including environmental heat, caffeine, altitude, and exercise stress (Kraemer et al. 1985, 1988a, 1988b, 1990). Highly trained endurance athletes have also demonstrated differential plasma responses of epinephrine and peptide F ir to exercise (Kraemer et al. 1985). Nevertheless the influence of subconscious mechanisms on plasma proenkephalin peptide F ir remains unknown. To date, no studies have evaluated psychological influences on peptide F release at rest or during exercise in humans. It has been shown that hypnotic suggestions can significantly increase cardiorespiratory variables at rest and during exercise, i.e., heart rate (fc), oxygen consumption (~rO2) , and minute ventilation (VE) (Agosti and Camerota 1965; Erickson 1977; Morgan 1970). Studies by Morgan and co-workers in the 1970s have also observed increases in ratings of perceived exertion (RPE) when subjects exercised under the hypnotic suggestion of heavy work (Morgan 1970, 1972; Morgan et al. 1973, 1976). It was hypothesized that hypnotic suggestion of more intense exercise would increase cardiorespiratory variables and RPE and in turn influence increased release of peptide F from the adrenal medulla. The primary purpose of this study was to examine the effects of hypnosis and the suggestion of higher intensity exercise on cardiorespiratory variables, RPE, and plasma concentrations of peptide F i r in endurance trained and untrained subjects.
574 Preliminary sessions
Hypnotic susceptibility test Experimental orientaion Consent form signatures Practice on Equipment Lifestyle/activity guidelines Medical screening
Experimental sessions Determination of peak I~'O2 on cycle ergometer exercise test session (25,50,75, and 100% peak ~"02 peak)
Randomized treatment conditions 1. Control (C) - 8rain exercise at 25 and 50% of peak _I~flz 2. Hypnosis (H) - same as control but suggests 50 and 75% of peak l~O2
Peak
C
H
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8 rnin
Induction performed
Insert indwelling cannula
-
-
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Fig. 1. Overview of experimental design
Methods Subjects. Two groups of healthy men volunteered as subjects for this study. Five trained (T) subjects, aged 21-24 years, were Division I competitive college middle-distance track runners. Subject characteristics for the trained group were as follows [mean (SD)]: age, 21.6 (0.5) years; height, 1.8 (0.06) m; body mass, 67.6 (4.9) kg; fat, 6.7 (1.1)070 and peak 1202, 59.5 (1.8) m l . k g - a . m i n -1. Five untrained (UT) subjects aged 19-30 years served as controls and were matched with the trained athletes for approximate body size. The control subjects had not been involved in any formal training program during the previous 2 years. Subject characteristics for the UT group were [mean (SD)]: age, 24.0 (4.3) years; height, 1.8 (0.09)m; body mass, 74.8 (19.1) kg; fat, 13.6 (6.6)07o; and peak 12Oz, 37.2 (11.6) m l , k g - l . m i n -1. Peak 1202 was the only measured subject characteristic which demonstrated a significant difference (P< 0.05) between the T and UT groups. The "Harvard Group Scale of Hypnotic Susceptibility" (HGSHS) was used to screen introductory psychology classes and the varsity track team for potential subjects (Barber 1966; Shot and Orne 1962). The top five individuals in each of the T and UT groups who scored 10-12 on the HGSHS were considered to be highly susceptible to hypnosis and asked to consider being subjects in this investigation by having the study explained to them individually in detail, including potential risks. Untrained subjects were selected after being interviewed as to their activity profile over the last 2 years. Subjects wishing to volunteer for study, read and signed an informed consent document which had been approved by the University's institutional review board for use of human subjects. All of the subjects (n = 10) who qualified for the study as T or UT subjects and were invited to participate in the investigation consented to be subjects. All testing took place at altitude (78.0 kPa).
Experimental protocol. A series of preliminary sessions were conducted with each subject involving familiarization, determination of peak I202 and a progressive exercise session at each exercise intensity (25, 50, 75 and 100% peak 12Oz). These preliminary sessions allowed the subject to go through progressive exercise practice tests of 25, 50, and 75°7o of peak 1202 at two different times prior to the control (C) and hypnosis (H) experimental tests. The subjects were told what the exercise intensity was and were asked to remember what the exercise stress felt like and to identify the percentage peak 120~ associated with it. This was done so that the suggestion of specific relative exercise intensities (50070 and 75070) would have meaning for the subject in future test sessions. Randomized C and H sessions were performed at the same time of day on different test days 3 days apart. The experimental design can be seen in Fig. 1. Borg scale instructions were again reviewed and involved reading the instructions to each subject (Borg 1961, 1973). Subjects were placed in a supine position and a Teflon cannula (20 gauge, Jelco Laboratories) was inserted into an antecubital vein. After proper placement of the cannula, subjects were repositioned and equilibrated in the seated position, which was used for all blood samples. The catheter was kept open by a continuous flow of heparinfree isotonic saline ( 3 0 m l . h - I ) . Each subject cycled at 50 rev.min -1 for two continuous 8 min periods at 25°70 and 50070 peak 1202 (Weltman and Regan 1982). f o 1202 (Beckman metabolic system), and RPE were obtained every minute of the test. In addition to an overall RPE, differentiated ratings (local and central ratings) were also obtained each minute (Pandolf 1982). Blood samples were obtained between rain 7 and rain 8 of each stage for measurement of plasma peptide F it. We had previously demonstrated that increases in peptide F i r are observed between 54 and 75070 of the peak 1202 during the cycle exercise protocol used in this investigation in T and UT subjects (Kraemer et al. 1985). If psychological influences upon
575 adrenal medullary release mechanisms were to be observed, hypnotic suggestion of exercise in this intensity range while the subjects were performing exercise at a much lower intensity would provide the largest possible window for an effect. In this study a standard hypnotic induction was performed (Hilgard 1969). During the induction the subject was seated on the friction-braked cycle ergometer (Monark, Varberg, Sweden). The hypnotic induction and suggestion was administered once, immediately prior to the pre-exercise blood sample and the exercise test. The hypnotic induction took approximately 20 rain and involved progressively advancing the subject into a deeply focused and relaxed state. After induction, about 2-3 min were taken to give the suggestio n to the subject and explain what was going to be asked of him (e.g., "You will be asked to rate your feelings of exertion using the RPE scale you used before"). The hypnotic suggestion was that the two exercise intensities were going to be 50% and 75% of maximum. Each subject had experienced these intensities previously in familiarization sessions. In reality, the exercise intensities were 25% and 50% of peak 1202, the same intensities used for the C condition. All exercise took place under hypnosis and each subject was brought out of hypnosis following the two exercise intensities and a 2-rain cool down. Again, the randomly selected C and H treatment sessions consisted of the subject performing the 25% and 50% of peak 1202 exercise intensities using the same methodology except for the use of hypnosis and suggestion of harder exercise in the H treatment. Blood was sampled via a three-way stop-cock adaptor connected to a plastic syringe. The subject was repositioned in a seated position for 20 min after insertion of the cannula. Then a seated resting blood sample was taken for determination of resting baseline levels of plasma peptide F i r . Blood samples (4 ml) were immediately transferred into sterile pre-chilled (0° C) vacutainers containing sodium heparin and 100 gl of aprotinin (Sigma, St. Louis, MO) which acted as a protease inhibitor. Blood samples were immediately centrifuged at 3000 rev.min -t (1700g, 0° C) for 10 min and the plasma portion was placed into plastic test tubes and stored at - 800 C until analyzed.
Biochemical methods. Plasma peptide F i r for each sample was determined by radioimmunoassay (RIA) using a commercially available t25I ligand and antisera (Peninsula Laboratories, Belmont, Calif.). All samples were analyzed in duplicate in a single assay set-up to avoid interassay variation.
To avoid non:specific displacement in the RIA, the peptide F from each sample was partially purified using HPLC-type minicolumns. Recovery of peptide F was determined by pipetting approximately 2000 counts.rain- 1 of 125I-peptideF into the plasma samples. Counts were measured following the purification steps and the percentage of recovery was determined for each sample. The mean recovery of radioactively labelled peptide F was 80.7%. The partially purified samples were then stored at - 8 0 ° C until assayed using previously described RIA techniques (Kraemer et al. 1985, 1988a; Lewis 1982). The antisera used in this assay exhibited the following percentage cross-reactivities with other opioid peptides: met-enkephalin 0.947, leu-enkephalin 0.046, alpha-neo-endorphin 0.041, dynorphin 1-17 0.037, fl-endorphin 0.034. The plasma ir showed parallel displacement of peptide F. Further identification of the peptide showed that no substantial degradation of peptide F occurred with these methods. This was demonstrated by the radioactivity (>92%) eluted with authentic labelled peptide (Kraemer et al. 1985). Intra-assay variance was less than 5%.
Statistical analyses. Statistical evaluation of the data was accomplished using a multivariate analysis of covariance (ANCOVA) with repeated measures [groups (T vs UT), treatments (H vs C), and two repeated measures for exercise intensities (25% and 50%)]. Covariate analyses with subsequent post-hoc tests were used to control for each subject's hypnotic susceptibility score. Independent t-tests were used to make group comparisons of subject characteristics. The level of significance chosen was P_< 0.05.
Results
Covariate analyses demonstrated that the scores for hypnotic susceptibility did not influence any of the dependent variables examined. The group responses (mean, 1 SD) for peptide F i r levels for both the C and H treatment conditions are shown in Fig. 2. No significant increases were observed above rest for T and UT subjects. The H treatment did not significantly change the concentrations of plasma peptide F ir in either group when compared to the C treatment.
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Fig. 2. Responses of plasma proenkephalin peptide F immunoreactivity (mean, 1 SD) to control (C) and hypnosis (H) treatments
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Fig. 3. Responses (mean, 1 SD) of oxygen consumption to exercise intensities of 25 and 50O/oof peak 17Ozfor control (C) and hypnosis (/4) treatments. * = p < 0.05 from corresponding C treatment
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Exercise intensity (%peak I~'O~)
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Fig. 5. Responses (mean, 1 SD) of heart rate to exercise intensities of 25 and 5007oof peak 1202 for the control (C) and hypnosis (H) treatments
H
50%
Untrained
Fig. 4. Responses (mean, 1 SD) of minute ventilation to exercise intensities of 25 and 50% of peak 1202 for control (C) and hypnosis (H) treatments
l>Oz significantly increased above resting values with exercise for both groups and treatments (Fig. 3). Significant differences were observed between T and UT groups for 1202. The T subjects had a significantly higher 1202 at both exercise intensities and in both treatments. There was a significant difference between C and H ;reatment conditions: H values were significantly higher than C values at 25% and 50% of peak l?Oz for T subjects. For UT subjects H significantly increased values at 50% peak l)Oz. Both groups had significant increases in VE at both exercise intensities (Fig. 4). There was a significant difference between T and UT subjects for VE. T subjects had significantly higher V~ at the 50% peak 1202 exercise intensity. There were no significant differences between the H and C treatment conditions. Heart rate responses to C and H treatments are shown in Fig. 5. There were significant increases in fc
above resting conditions at 25% and 50% peak 1202. Values at 50% were greater then corresponding values at 25% peak 1202. No significant differences were observed between T and U T or between C and H treatment conditions. No significant differences were observed between C and H conditions for any other cardiorespiratory variable including respiratory frequency, tidal volume, and ventilatory equivalent. The perceptual responses for overall, local, and central RPE can be observed in Fig. 6. There were no significant differences between T and UT groups for the overall RPE although a significant exercise-induced increase in RPE did occur over the two exercise intensities. Overall ratings at 50% of peak 1202 were all significantly greater than 25% of peak 1202. There were no significant differences between H and C treatments. The local RPE showed almost the identical pattern of responses as the overall RPE. There were no significant differences between T and UT subjects. Local ratings also significantly increased over the two exercise intensities with local ratings at 50% of peak ~ r O 2 significantly greater than 25% values. Again, the H treatment had no effect on the local RPE. The response patterns for the central RPE were again similar to the overall and local ratings. No differences were observed between training groups. Significant increases were observed over the two exercise intensities with RPE at 50% of peak 1202 significantly greater than the 25% values. Hypnosis did not significantly alter the central RPE.
577
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/y/ Perceived extertion Treatments Ecercise intensity (%peak f'O2)
0
L C
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Trained-Co Untrained-CO
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25%
0
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Tra]rled-Co Untrained-Co
O L C
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Fig. 6. Responses of overall (O), local (L), and central (C) ratings of perceived exertion (mean, 1 SD) to exercise intensities of 25070and 50°7o of peak 1)'O2for control (Co) and hypnosis (/-/) treatments
Discussion
Catecholamines and proenkephalin peptides are found in the same chromaffin cells and are sensitive to similar stimuli (Kilpatrick et al. 1981; Livett et al. 1981; Viveros et al. 1979). To date, other than the adrenal medulla, no other significant source of peptide F has been identified. No previous study has examined the effects of hypnosis on proenkephalin fragments (e.g., peptide F) in the peripheral circulation. The most prominent finding of this investigation was that a traditional hypnotic induction and suggestion of harder exercise was unable to increase proenkephalin peptide F ir in the peripheral blood. The intensities of the exercise suggested were 50°7o and 75°70 of peak 1202. Each subject had previously experienced these intensities of exercise in prior sessions. Other investigations have clearly shown that exercise of 54-75°70 of peak 1202 elicits significant elevations in plasma peptide F i r (Kraemer et al. 1985, 1990). In this study the trend toward higher concentrations of peptide F at 50°70 of peak 1202 was observed in T but not UT. Our previous studies had demonstrated a significant increase in peptide F i r at 54°7o of peak 1202 in T but not UT subjects, which was thought to have been caused by noncolinear release of enkephalin fragments and epinephrine from the adrenal medulla due to a training adaptation (Kraemer et al. 1985). The lack of a significant increase in this study at 50°70 of peak 1202 in the T group may indicate that a higher threshold for exercise intensity exists for the release of peptide F. Alternatively, it is also possible that due to large variances typically seen in neuroendocrine variables, including peptide F, the trend
observed was difficult to demonstrate statistically in this study. Why peptide F concentrations were not higher at rest for the T group compared to the UT group in our previous study (Kraemer et al. 1985) remains unclear at this time. Factors which modulate resting levels of peptide F with training remain unknown. It had been hypothesized that psychological factors were most likely a significant influence at the lower exercise intensities where the greatest potential for increase appears to exist. The lack of change may suggest that the mechanism(s) responsible for increased plasma peptide F ir elevations may not be influenced by psychological factors as mediated by hypnosis and the suggestion of harder exercise. Significant increases in I7"O2 while exercising under hypnosis were observed in this study. This demonstrates that the hypnotic suggestion of greater exercise stress was in some way physiologically expressed by the subjects. This finding is consistent with previous investigations which have observed increases in 1202 using hypnotic suggestions of harder exercise intensities (Morgan 1970; Morgan et al. 1973). In this study however, the increases in IYO2 under hypnosis do not represent the magnitude of functional increases required to perform exercise at 50070 and 75°7o of peak 1202 values. Furthermore, expected associated changes in other cardiorespiratory measures (e.g., ventilation) did not occur and it may be that the increase observed was a statistical anomaly. It might be speculated that the increases in 1202 observed were due to biomechanical changes in the subject's upper body musculature while on the cycle ergometer. Such small increases in 1202 might have been
578 caused by increased isometric grasping or pulling on the handle bars in response to the suggestion of a harder exercise intensity. Exact causes of the isolated increase in 12Oa with hypnotic suggestion in this study remain unknown. In this study the hypnotic suggestion of a higher relative intensity exercise stress did not alter RPE. Sensations of exercise stress come from all parts of the body. The exercising muscles, heart, and lungs all send cues of various signal strengths regarding the effort exerted in a given exercise task (Borg 1961; Pandolf 1982). In this study, the hypnotic suggestion might have not been able to overpower the true exercise sensations. Since fo and VE demonstrate similar patterns of response as RPE, the lack of any changes in these variables may have removed potential cues for perceptual changes to occur with hypnotic suggestion of higher exercise intensity. Our study differed from those of Morgan and colleagues in many ways making direct comparisons difficult. Studies by Morgan and co-workers used longer durations of total exercise, absolute exercise intensities for all subjects, and different intensities of exercise from the present study. During the actual exercise session under hypnotic suggestion, subjects in Morgan's studies had to verify the desired state (e.g., nod their head; Morgan et al. 1976). In addition, a great deal of the suggestion supported cues for greater fatigue in the legs, difficulty to be experienced with the exercise, and the stress of harder breathing. In our study, the suggestion cued primarily upon the memory of the associated individual feelings of fatigue and stress each subject identified with the two intensities of exercise (50 and 75%). Morgan and coworkers had linked the increase in overall RPE to changes observed in IrE. Since VE and fo were not affected by hypnosis and the suggestion of harder exercise in the present investigation, it is likely that such physiological cues for perception were absent and could partially explain the lack of change in perception observed in this study. The responses of T and UT subjects were similar. This suggests that irrespective of endurance fitness levels, factors related to psychological changes associated with hypnosis do not affect the changes in plasma proenkephalin peptide F ir concentrations in the blood in response to submaximal exercise. Thus, the exercise responses during lower-intensity submaximal exercise under hypnosis do not appear to be influenced by the endurance fitness level of the subjects. The rationale for this study was based on the supposition that hypnosis would cause an increase in the cardiorespiratory variables which would be followed by a concomitant increase in RPE, all of which might mediate increases in plasma concentrations of proenkephalin peptide F. The present investigation demonstrates that hypnosis and the suggestion of harder exercise do not appear to influence plasma concentrations of peptide F in a highly selected group of either trained or untrained subjects at lower exercise intensities. Such data provide additional insights into the influences on endogenous opioid peptides, more specifically proenkephalin peptide F, alterations during exercise.
Acknowledgements. We would like to thank a dedicated group of test subjects for their efforts in this investigation. Additionally, we would like to thank Ken Robertson, M.D. for acting as medical monitor for this study. The authors also thank Joann Ruble for her help in the preparation of the manuscript. References Agosti E, Camerota G (1965) Some effects of hypnotic suggestion on respiratory function. Int J Clin Exp Hypn 13 : 149-156 Barber T (1966) The effects of hypnosis and motivational suggestions on strength and endurance: a critical review of research studies. Br J Soc Clin Psychol 5:42-50 Borg G (1961) Perceived exertion in relation to physical work load and pulse rate. Kungl Fysiografiska Sallskepets I Lund Forhandlinger 31 : 105-115 Borg GAV (1973) Perceived exertion: a note on history and methods. Med Sci Sports 5:90-93 Erickson MH (1977) Control of physiological functions by hypnosis. Am J Clin Hypn 20:8-19 Hilgard ER (1969) The experience of hypnosis. Harcourt Brace Javanovich, New York Kilpatrick DL, Lewis RV~ Stein S, Udenfriend S (1981) Release of enkephalins and enkephalin-containing polypeptides from perfused beef adrenal glands. Proc Nat Acad Sci USA 78 : 3265-3268 Kraemer W J, Noble B, Culver B, Lewis RV (1985) Changes in plasma proenkephalin peptide F and catecholamine levels during graded exercises in men. Proc Natl Acad Sci USA 82 : 634%6351 Kraemer W J, Armstrong LE, Marchiteli LJ, Hubbard RW, Leva N (1988a) Plasma opioid peptide responses during heat acclimation in humans. Peptides 8 : 715-719 Kraemer WJ, Rock PB, Fulco CS, Gordon SE, Bonner JP, Cruthirds CD, Marchitelli LJ, Trad L, Cymerman A (1988b) Influence of altitude and caffeine during rest and exercise on plasma levels of proenkephalin peptide F. Peptides 9: 1115-1119 Kraemer WJ, Dziados JE, Gordon SE, Marchitelli LJ, Fry AC, Reynolds KL (1990) The effects of graded exercise on plasma proenkephalin peptide F and catecholamine responses at sea level. Eur J Appl Physiol 61:214-217 Lewis RV (1982) Enkephalin biosynthesis in the adrenal medulla. In: Costa E, Trabucchi M (eds) Advances in biochemical psychopharmacology, vol 33. Raven Press, New York, pp 167-174 Lewis RV, Stern AS (1983) Biosynthesis of the enkephalin-containing polypeptides. Annu Rev Pharmacol Toxicol 23:353-372 Livett BG, Deanne DM, Whelan LG, Udenfriend S, Rossier J (1981) Co-release of enkephalin and catecholamines from cultured adrenal chromaffin cells. Nature 289:317-319 Morgan WP (1970) Oxygen uptake following hypnotic suggestion. In: Kenyon GS (ed) Contemporary psychology of sport. Athletic Institute, Chicago, pp 283-286 Morgan WP (1972) Hypnosis and muscular performance. In: Morgan WP (ed) Ergogenic aids and muscular performance. Academic Press, New York, pp 193-233 Morgan WP, Raven PB, Drinkwater BL, Horvath SA (1973) Perceptual and metabolic responsivity to standard bicycle ergometry following various hypnotic suggestions. Int J Clin Exp Hypn 21 : 86-101 Morgan WP, Koichi H, Weitz GA, Balke B (1976) Hypnotic perturbation of perceived exertion: ventilatory consequences. Am J Clin Hypn 18:182-190 Pandolf KB (1982) Differentiated ratings of perceived exertion during physical exercise. Med Sci Sports Exerc 14:347-405 Shor RE, Orne EC (1962) Harvard group scale of hypnotic susceptibility manual. Consulting Psychologists Press, Palo Alto Viveros OH, Diliberto E J, Hazum E, Chang KJ (1979) Opiate-like materials in the adrenal medulla: evidence for storage and secretion with catecholamines. Mol Pharmacol 16: 1101-1108 Weltman A, Regan J (1982) A reliable method for the measurement of constant load maximal endurance performance on the bicycle ergometer. Res Q Exerc Sport 53 : 176-179
Eur J Appl Physiol (1992) 65:573-578
and Occupational Physiology © Springer-Verlag1992
Effects of hypnosis on plasma proenkephalin peptide F and perceptual and cardiovascular responses during submaximal exercise William J. Kraemer I, Randolph V. Lewis 2, N. Travis Triplett I, L. Perry Koziris ~, Steve Heyman 3, and Bruce J. Noble 4 Center for Sports Medicine, The PennsylvaniaState University, UniversityPark, PA 16802, USA 2 Department of Molecular Biologyand 3 Department of Psychology,The Universityof Wyoming,Laramie, WY 82071, USA 4 Department of PhysicalEducation, Health and Recreation Studies, Purdue University, West Lafayette; IN 47907, USA Accepted July 28, 1992
Summary. Little information is available concerning the influence of subconscious mechanisms on neuroendocrine function, more specifically, proenkephalin peptide F release. Ten men [5 middle distance runners (21.6 (SD 0.54 years) and 5 untrained men (24.0 (SD 4.3 years)] consented to be volunteers in this investigation. Submaximal exercise intensities of 25% and 50% of peak oxygen consumption (1702) (8 min stages) were used for both the control and hypnosis treatments. A traditional hypnotic induction was used, with the suggestion of two higher intensities of exercise stress (50% and 75% peak 1)-O2) previously experienced in familiarization and testing by each subject. Each minute oxygen consumption was measured using open circuit spirometry, heart rate via an ECG, and ratings of perceived exertion (RPE) using the Borg scale. Plasma peptide F immunoreactivity (it) [preproenkephalin-(107-140)] in blood sampled from an indwelling cannula was measured by radioimmunoassay at 7-8 min of each stage of the exercise test. Expected significant increases were observed for all cardiorespiratory and perceptual variables over the increasing exercise intensities and there were no significant differences between trained and untrained groups for peptide F ir response patterns. Hypnosis did not significantly affect peptide F ir concentrations (P>0.05) and did not significantly alter exercise heart rate, RPE or minute ventilation (P> 0.05). However, hypnosis did significantly increase oxygen consumption during exercise (P = 0.0095) but not of the magnitude needed for the metabolic demands of the higher exercise intensities. Thus, traditional hypnosis was unable to make functionally significant changes in the cardiorespiratory variables. Training did not alter responses to exercise under hypnosis. The results of this study indicate that when using traditional hypnosis and a suggestion of harder exercise in highly selected groups, it may not be possible functionally to stress adrenal medullary secretion of proenkephalin fragments, RPE or cardiorespiratory variables. Correspondence to: W. J. Kraemer, Center for Sports Medicine,
117 Ann Bldg., The Pennsylvania State University, University Park, PA 16802, USA
Key words: Enkephalins - Endogenous opioid peptides - Endurance exercise
Introduction Peptide F, an enkephalin-containing polypeptide with opiate-like actions found in the adrenal medulla, is sensitive to the same release stimuli as epinephrine (Kilpatrick et al. 1981; Lewis 1982; Livett et al. 1981; Viveros et al. 1979). Exercise has been shown to increase plasma levels of proenkephalin peptide F immunoreactivity (ir) [proenkephalin-(107-140)] (Kraemer et al. 1985, 1988a, 1988b, 1990). Plasma peptide F i r concentrations have been shown to be responsive in humans to a wide variety of stimuli including environmental heat, caffeine, altitude, and exercise stress (Kraemer et al. 1985, 1988a, 1988b, 1990). Highly trained endurance athletes have also demonstrated differential plasma responses of epinephrine and peptide F ir to exercise (Kraemer et al. 1985). Nevertheless the influence of subconscious mechanisms on plasma proenkephalin peptide F ir remains unknown. To date, no studies have evaluated psychological influences on peptide F release at rest or during exercise in humans. It has been shown that hypnotic suggestions can significantly increase cardiorespiratory variables at rest and during exercise, i.e., heart rate (fc), oxygen consumption (~rO2) , and minute ventilation (VE) (Agosti and Camerota 1965; Erickson 1977; Morgan 1970). Studies by Morgan and co-workers in the 1970s have also observed increases in ratings of perceived exertion (RPE) when subjects exercised under the hypnotic suggestion of heavy work (Morgan 1970, 1972; Morgan et al. 1973, 1976). It was hypothesized that hypnotic suggestion of more intense exercise would increase cardiorespiratory variables and RPE and in turn influence increased release of peptide F from the adrenal medulla. The primary purpose of this study was to examine the effects of hypnosis and the suggestion of higher intensity exercise on cardiorespiratory variables, RPE, and plasma concentrations of peptide F i r in endurance trained and untrained subjects.
574 Preliminary sessions
Hypnotic susceptibility test Experimental orientaion Consent form signatures Practice on Equipment Lifestyle/activity guidelines Medical screening
Experimental sessions Determination of peak I~'O2 on cycle ergometer exercise test session (25,50,75, and 100% peak ~"02 peak)
Randomized treatment conditions 1. Control (C) - 8rain exercise at 25 and 50% of peak _I~flz 2. Hypnosis (H) - same as control but suggests 50 and 75% of peak l~O2
Peak
C
H
50% Veak/'O2
8 rnin
Induction performed
Insert indwelling cannula
-
-
50% Suggested
Blood sample pre-exercise
8 min
75% Suggested
Blood sample
Blood sample
Fig. 1. Overview of experimental design
Methods Subjects. Two groups of healthy men volunteered as subjects for this study. Five trained (T) subjects, aged 21-24 years, were Division I competitive college middle-distance track runners. Subject characteristics for the trained group were as follows [mean (SD)]: age, 21.6 (0.5) years; height, 1.8 (0.06) m; body mass, 67.6 (4.9) kg; fat, 6.7 (1.1)070 and peak 1202, 59.5 (1.8) m l . k g - a . m i n -1. Five untrained (UT) subjects aged 19-30 years served as controls and were matched with the trained athletes for approximate body size. The control subjects had not been involved in any formal training program during the previous 2 years. Subject characteristics for the UT group were [mean (SD)]: age, 24.0 (4.3) years; height, 1.8 (0.09)m; body mass, 74.8 (19.1) kg; fat, 13.6 (6.6)07o; and peak 12Oz, 37.2 (11.6) m l , k g - l . m i n -1. Peak 1202 was the only measured subject characteristic which demonstrated a significant difference (P< 0.05) between the T and UT groups. The "Harvard Group Scale of Hypnotic Susceptibility" (HGSHS) was used to screen introductory psychology classes and the varsity track team for potential subjects (Barber 1966; Shot and Orne 1962). The top five individuals in each of the T and UT groups who scored 10-12 on the HGSHS were considered to be highly susceptible to hypnosis and asked to consider being subjects in this investigation by having the study explained to them individually in detail, including potential risks. Untrained subjects were selected after being interviewed as to their activity profile over the last 2 years. Subjects wishing to volunteer for study, read and signed an informed consent document which had been approved by the University's institutional review board for use of human subjects. All of the subjects (n = 10) who qualified for the study as T or UT subjects and were invited to participate in the investigation consented to be subjects. All testing took place at altitude (78.0 kPa).
Experimental protocol. A series of preliminary sessions were conducted with each subject involving familiarization, determination of peak I202 and a progressive exercise session at each exercise intensity (25, 50, 75 and 100% peak 12Oz). These preliminary sessions allowed the subject to go through progressive exercise practice tests of 25, 50, and 75°7o of peak 1202 at two different times prior to the control (C) and hypnosis (H) experimental tests. The subjects were told what the exercise intensity was and were asked to remember what the exercise stress felt like and to identify the percentage peak 120~ associated with it. This was done so that the suggestion of specific relative exercise intensities (50070 and 75070) would have meaning for the subject in future test sessions. Randomized C and H sessions were performed at the same time of day on different test days 3 days apart. The experimental design can be seen in Fig. 1. Borg scale instructions were again reviewed and involved reading the instructions to each subject (Borg 1961, 1973). Subjects were placed in a supine position and a Teflon cannula (20 gauge, Jelco Laboratories) was inserted into an antecubital vein. After proper placement of the cannula, subjects were repositioned and equilibrated in the seated position, which was used for all blood samples. The catheter was kept open by a continuous flow of heparinfree isotonic saline ( 3 0 m l . h - I ) . Each subject cycled at 50 rev.min -1 for two continuous 8 min periods at 25°70 and 50070 peak 1202 (Weltman and Regan 1982). f o 1202 (Beckman metabolic system), and RPE were obtained every minute of the test. In addition to an overall RPE, differentiated ratings (local and central ratings) were also obtained each minute (Pandolf 1982). Blood samples were obtained between rain 7 and rain 8 of each stage for measurement of plasma peptide F it. We had previously demonstrated that increases in peptide F i r are observed between 54 and 75070 of the peak 1202 during the cycle exercise protocol used in this investigation in T and UT subjects (Kraemer et al. 1985). If psychological influences upon
575 adrenal medullary release mechanisms were to be observed, hypnotic suggestion of exercise in this intensity range while the subjects were performing exercise at a much lower intensity would provide the largest possible window for an effect. In this study a standard hypnotic induction was performed (Hilgard 1969). During the induction the subject was seated on the friction-braked cycle ergometer (Monark, Varberg, Sweden). The hypnotic induction and suggestion was administered once, immediately prior to the pre-exercise blood sample and the exercise test. The hypnotic induction took approximately 20 rain and involved progressively advancing the subject into a deeply focused and relaxed state. After induction, about 2-3 min were taken to give the suggestio n to the subject and explain what was going to be asked of him (e.g., "You will be asked to rate your feelings of exertion using the RPE scale you used before"). The hypnotic suggestion was that the two exercise intensities were going to be 50% and 75% of maximum. Each subject had experienced these intensities previously in familiarization sessions. In reality, the exercise intensities were 25% and 50% of peak 1202, the same intensities used for the C condition. All exercise took place under hypnosis and each subject was brought out of hypnosis following the two exercise intensities and a 2-rain cool down. Again, the randomly selected C and H treatment sessions consisted of the subject performing the 25% and 50% of peak 1202 exercise intensities using the same methodology except for the use of hypnosis and suggestion of harder exercise in the H treatment. Blood was sampled via a three-way stop-cock adaptor connected to a plastic syringe. The subject was repositioned in a seated position for 20 min after insertion of the cannula. Then a seated resting blood sample was taken for determination of resting baseline levels of plasma peptide F i r . Blood samples (4 ml) were immediately transferred into sterile pre-chilled (0° C) vacutainers containing sodium heparin and 100 gl of aprotinin (Sigma, St. Louis, MO) which acted as a protease inhibitor. Blood samples were immediately centrifuged at 3000 rev.min -t (1700g, 0° C) for 10 min and the plasma portion was placed into plastic test tubes and stored at - 800 C until analyzed.
Biochemical methods. Plasma peptide F i r for each sample was determined by radioimmunoassay (RIA) using a commercially available t25I ligand and antisera (Peninsula Laboratories, Belmont, Calif.). All samples were analyzed in duplicate in a single assay set-up to avoid interassay variation.
To avoid non:specific displacement in the RIA, the peptide F from each sample was partially purified using HPLC-type minicolumns. Recovery of peptide F was determined by pipetting approximately 2000 counts.rain- 1 of 125I-peptideF into the plasma samples. Counts were measured following the purification steps and the percentage of recovery was determined for each sample. The mean recovery of radioactively labelled peptide F was 80.7%. The partially purified samples were then stored at - 8 0 ° C until assayed using previously described RIA techniques (Kraemer et al. 1985, 1988a; Lewis 1982). The antisera used in this assay exhibited the following percentage cross-reactivities with other opioid peptides: met-enkephalin 0.947, leu-enkephalin 0.046, alpha-neo-endorphin 0.041, dynorphin 1-17 0.037, fl-endorphin 0.034. The plasma ir showed parallel displacement of peptide F. Further identification of the peptide showed that no substantial degradation of peptide F occurred with these methods. This was demonstrated by the radioactivity (>92%) eluted with authentic labelled peptide (Kraemer et al. 1985). Intra-assay variance was less than 5%.
Statistical analyses. Statistical evaluation of the data was accomplished using a multivariate analysis of covariance (ANCOVA) with repeated measures [groups (T vs UT), treatments (H vs C), and two repeated measures for exercise intensities (25% and 50%)]. Covariate analyses with subsequent post-hoc tests were used to control for each subject's hypnotic susceptibility score. Independent t-tests were used to make group comparisons of subject characteristics. The level of significance chosen was P_< 0.05.
Results
Covariate analyses demonstrated that the scores for hypnotic susceptibility did not influence any of the dependent variables examined. The group responses (mean, 1 SD) for peptide F i r levels for both the C and H treatment conditions are shown in Fig. 2. No significant increases were observed above rest for T and UT subjects. The H treatment did not significantly change the concentrations of plasma peptide F ir in either group when compared to the C treatment.
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Fig. 2. Responses of plasma proenkephalin peptide F immunoreactivity (mean, 1 SD) to control (C) and hypnosis (H) treatments
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Fig. 3. Responses (mean, 1 SD) of oxygen consumption to exercise intensities of 25 and 50O/oof peak 17Ozfor control (C) and hypnosis (/4) treatments. * = p < 0.05 from corresponding C treatment
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Fig. 5. Responses (mean, 1 SD) of heart rate to exercise intensities of 25 and 5007oof peak 1202 for the control (C) and hypnosis (H) treatments
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Fig. 4. Responses (mean, 1 SD) of minute ventilation to exercise intensities of 25 and 50% of peak 1202 for control (C) and hypnosis (H) treatments
l>Oz significantly increased above resting values with exercise for both groups and treatments (Fig. 3). Significant differences were observed between T and UT groups for 1202. The T subjects had a significantly higher 1202 at both exercise intensities and in both treatments. There was a significant difference between C and H ;reatment conditions: H values were significantly higher than C values at 25% and 50% of peak l?Oz for T subjects. For UT subjects H significantly increased values at 50% peak l)Oz. Both groups had significant increases in VE at both exercise intensities (Fig. 4). There was a significant difference between T and UT subjects for VE. T subjects had significantly higher V~ at the 50% peak 1202 exercise intensity. There were no significant differences between the H and C treatment conditions. Heart rate responses to C and H treatments are shown in Fig. 5. There were significant increases in fc
above resting conditions at 25% and 50% peak 1202. Values at 50% were greater then corresponding values at 25% peak 1202. No significant differences were observed between T and U T or between C and H treatment conditions. No significant differences were observed between C and H conditions for any other cardiorespiratory variable including respiratory frequency, tidal volume, and ventilatory equivalent. The perceptual responses for overall, local, and central RPE can be observed in Fig. 6. There were no significant differences between T and UT groups for the overall RPE although a significant exercise-induced increase in RPE did occur over the two exercise intensities. Overall ratings at 50% of peak 1202 were all significantly greater than 25% of peak 1202. There were no significant differences between H and C treatments. The local RPE showed almost the identical pattern of responses as the overall RPE. There were no significant differences between T and UT subjects. Local ratings also significantly increased over the two exercise intensities with local ratings at 50% of peak ~ r O 2 significantly greater than 25% values. Again, the H treatment had no effect on the local RPE. The response patterns for the central RPE were again similar to the overall and local ratings. No differences were observed between training groups. Significant increases were observed over the two exercise intensities with RPE at 50% of peak 1202 significantly greater than the 25% values. Hypnosis did not significantly alter the central RPE.
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Fig. 6. Responses of overall (O), local (L), and central (C) ratings of perceived exertion (mean, 1 SD) to exercise intensities of 25070and 50°7o of peak 1)'O2for control (Co) and hypnosis (/-/) treatments
Discussion
Catecholamines and proenkephalin peptides are found in the same chromaffin cells and are sensitive to similar stimuli (Kilpatrick et al. 1981; Livett et al. 1981; Viveros et al. 1979). To date, other than the adrenal medulla, no other significant source of peptide F has been identified. No previous study has examined the effects of hypnosis on proenkephalin fragments (e.g., peptide F) in the peripheral circulation. The most prominent finding of this investigation was that a traditional hypnotic induction and suggestion of harder exercise was unable to increase proenkephalin peptide F ir in the peripheral blood. The intensities of the exercise suggested were 50°7o and 75°70 of peak 1202. Each subject had previously experienced these intensities of exercise in prior sessions. Other investigations have clearly shown that exercise of 54-75°70 of peak 1202 elicits significant elevations in plasma peptide F i r (Kraemer et al. 1985, 1990). In this study the trend toward higher concentrations of peptide F at 50°70 of peak 1202 was observed in T but not UT. Our previous studies had demonstrated a significant increase in peptide F i r at 54°7o of peak 1202 in T but not UT subjects, which was thought to have been caused by noncolinear release of enkephalin fragments and epinephrine from the adrenal medulla due to a training adaptation (Kraemer et al. 1985). The lack of a significant increase in this study at 50°70 of peak 1202 in the T group may indicate that a higher threshold for exercise intensity exists for the release of peptide F. Alternatively, it is also possible that due to large variances typically seen in neuroendocrine variables, including peptide F, the trend
observed was difficult to demonstrate statistically in this study. Why peptide F concentrations were not higher at rest for the T group compared to the UT group in our previous study (Kraemer et al. 1985) remains unclear at this time. Factors which modulate resting levels of peptide F with training remain unknown. It had been hypothesized that psychological factors were most likely a significant influence at the lower exercise intensities where the greatest potential for increase appears to exist. The lack of change may suggest that the mechanism(s) responsible for increased plasma peptide F ir elevations may not be influenced by psychological factors as mediated by hypnosis and the suggestion of harder exercise. Significant increases in I7"O2 while exercising under hypnosis were observed in this study. This demonstrates that the hypnotic suggestion of greater exercise stress was in some way physiologically expressed by the subjects. This finding is consistent with previous investigations which have observed increases in 1202 using hypnotic suggestions of harder exercise intensities (Morgan 1970; Morgan et al. 1973). In this study however, the increases in IYO2 under hypnosis do not represent the magnitude of functional increases required to perform exercise at 50070 and 75°7o of peak 1202 values. Furthermore, expected associated changes in other cardiorespiratory measures (e.g., ventilation) did not occur and it may be that the increase observed was a statistical anomaly. It might be speculated that the increases in 1202 observed were due to biomechanical changes in the subject's upper body musculature while on the cycle ergometer. Such small increases in 1202 might have been
578 caused by increased isometric grasping or pulling on the handle bars in response to the suggestion of a harder exercise intensity. Exact causes of the isolated increase in 12Oa with hypnotic suggestion in this study remain unknown. In this study the hypnotic suggestion of a higher relative intensity exercise stress did not alter RPE. Sensations of exercise stress come from all parts of the body. The exercising muscles, heart, and lungs all send cues of various signal strengths regarding the effort exerted in a given exercise task (Borg 1961; Pandolf 1982). In this study, the hypnotic suggestion might have not been able to overpower the true exercise sensations. Since fo and VE demonstrate similar patterns of response as RPE, the lack of any changes in these variables may have removed potential cues for perceptual changes to occur with hypnotic suggestion of higher exercise intensity. Our study differed from those of Morgan and colleagues in many ways making direct comparisons difficult. Studies by Morgan and co-workers used longer durations of total exercise, absolute exercise intensities for all subjects, and different intensities of exercise from the present study. During the actual exercise session under hypnotic suggestion, subjects in Morgan's studies had to verify the desired state (e.g., nod their head; Morgan et al. 1976). In addition, a great deal of the suggestion supported cues for greater fatigue in the legs, difficulty to be experienced with the exercise, and the stress of harder breathing. In our study, the suggestion cued primarily upon the memory of the associated individual feelings of fatigue and stress each subject identified with the two intensities of exercise (50 and 75%). Morgan and coworkers had linked the increase in overall RPE to changes observed in IrE. Since VE and fo were not affected by hypnosis and the suggestion of harder exercise in the present investigation, it is likely that such physiological cues for perception were absent and could partially explain the lack of change in perception observed in this study. The responses of T and UT subjects were similar. This suggests that irrespective of endurance fitness levels, factors related to psychological changes associated with hypnosis do not affect the changes in plasma proenkephalin peptide F ir concentrations in the blood in response to submaximal exercise. Thus, the exercise responses during lower-intensity submaximal exercise under hypnosis do not appear to be influenced by the endurance fitness level of the subjects. The rationale for this study was based on the supposition that hypnosis would cause an increase in the cardiorespiratory variables which would be followed by a concomitant increase in RPE, all of which might mediate increases in plasma concentrations of proenkephalin peptide F. The present investigation demonstrates that hypnosis and the suggestion of harder exercise do not appear to influence plasma concentrations of peptide F in a highly selected group of either trained or untrained subjects at lower exercise intensities. Such data provide additional insights into the influences on endogenous opioid peptides, more specifically proenkephalin peptide F, alterations during exercise.
Acknowledgements. We would like to thank a dedicated group of test subjects for their efforts in this investigation. Additionally, we would like to thank Ken Robertson, M.D. for acting as medical monitor for this study. The authors also thank Joann Ruble for her help in the preparation of the manuscript. References Agosti E, Camerota G (1965) Some effects of hypnotic suggestion on respiratory function. Int J Clin Exp Hypn 13 : 149-156 Barber T (1966) The effects of hypnosis and motivational suggestions on strength and endurance: a critical review of research studies. Br J Soc Clin Psychol 5:42-50 Borg G (1961) Perceived exertion in relation to physical work load and pulse rate. Kungl Fysiografiska Sallskepets I Lund Forhandlinger 31 : 105-115 Borg GAV (1973) Perceived exertion: a note on history and methods. Med Sci Sports 5:90-93 Erickson MH (1977) Control of physiological functions by hypnosis. Am J Clin Hypn 20:8-19 Hilgard ER (1969) The experience of hypnosis. Harcourt Brace Javanovich, New York Kilpatrick DL, Lewis RV~ Stein S, Udenfriend S (1981) Release of enkephalins and enkephalin-containing polypeptides from perfused beef adrenal glands. Proc Nat Acad Sci USA 78 : 3265-3268 Kraemer W J, Noble B, Culver B, Lewis RV (1985) Changes in plasma proenkephalin peptide F and catecholamine levels during graded exercises in men. Proc Natl Acad Sci USA 82 : 634%6351 Kraemer W J, Armstrong LE, Marchiteli LJ, Hubbard RW, Leva N (1988a) Plasma opioid peptide responses during heat acclimation in humans. Peptides 8 : 715-719 Kraemer WJ, Rock PB, Fulco CS, Gordon SE, Bonner JP, Cruthirds CD, Marchitelli LJ, Trad L, Cymerman A (1988b) Influence of altitude and caffeine during rest and exercise on plasma levels of proenkephalin peptide F. Peptides 9: 1115-1119 Kraemer WJ, Dziados JE, Gordon SE, Marchitelli LJ, Fry AC, Reynolds KL (1990) The effects of graded exercise on plasma proenkephalin peptide F and catecholamine responses at sea level. Eur J Appl Physiol 61:214-217 Lewis RV (1982) Enkephalin biosynthesis in the adrenal medulla. In: Costa E, Trabucchi M (eds) Advances in biochemical psychopharmacology, vol 33. Raven Press, New York, pp 167-174 Lewis RV, Stern AS (1983) Biosynthesis of the enkephalin-containing polypeptides. Annu Rev Pharmacol Toxicol 23:353-372 Livett BG, Deanne DM, Whelan LG, Udenfriend S, Rossier J (1981) Co-release of enkephalin and catecholamines from cultured adrenal chromaffin cells. Nature 289:317-319 Morgan WP (1970) Oxygen uptake following hypnotic suggestion. In: Kenyon GS (ed) Contemporary psychology of sport. Athletic Institute, Chicago, pp 283-286 Morgan WP (1972) Hypnosis and muscular performance. In: Morgan WP (ed) Ergogenic aids and muscular performance. Academic Press, New York, pp 193-233 Morgan WP, Raven PB, Drinkwater BL, Horvath SA (1973) Perceptual and metabolic responsivity to standard bicycle ergometry following various hypnotic suggestions. Int J Clin Exp Hypn 21 : 86-101 Morgan WP, Koichi H, Weitz GA, Balke B (1976) Hypnotic perturbation of perceived exertion: ventilatory consequences. Am J Clin Hypn 18:182-190 Pandolf KB (1982) Differentiated ratings of perceived exertion during physical exercise. Med Sci Sports Exerc 14:347-405 Shor RE, Orne EC (1962) Harvard group scale of hypnotic susceptibility manual. Consulting Psychologists Press, Palo Alto Viveros OH, Diliberto E J, Hazum E, Chang KJ (1979) Opiate-like materials in the adrenal medulla: evidence for storage and secretion with catecholamines. Mol Pharmacol 16: 1101-1108 Weltman A, Regan J (1982) A reliable method for the measurement of constant load maximal endurance performance on the bicycle ergometer. Res Q Exerc Sport 53 : 176-179
