Psychoneuroendocrinology.Vol.15,No.3. pp. 173-184.1990
0306-4530/90$3.00+0.00 01990PergamonPresspie
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HORMONAL RESPONSES TO EXHAUSTING PHYSICAL EXERCISE: THE ROLE OF PREDICTABILITY AND CONTROLLABILITY OF THE SITUATION K. VOIGT,1 M. ZIEGLER,2 M. GRONERT-FUCHS,3 U. BICKEL,l and G. FEHM-WoLFSDORF2 llnstitute of Normal and Pathological Physiology, University of Marburg, and 2Departments of Me.dieMPsychology and 3physiology, University of Ulm, ER.G. (Received 6 July 1988; In,~'ml form 25 October 1989)
SUMMARY Psychological conditions which produce sustained activation have been clearly identified. Among these are the predictability and the controllability of the situation. We studied the impact of these psychological variables on hormone secretion (cortisol, ACTH, vasopressin, prolactin, and hGH plasma levels) under a standardized physical load. Sixteen subjects participated in four sessions each, one week apart, with the task of riding a bicycle until exhaustion. During three sessions, all experimental conditions were held identical to ensure the situation was as predictable as possible. During the fourth session, instructions induced a certain level of uneontroUability. Whereas physiological and performance measures did not vary with experience in the task, eortisol, AOrH, and vasopressin responses declined with increasing experience. This emphasizes the importance of the psychological definition of the situation for endocrine stress responses.
INTRODUCTION SINCE Mason's (1968) pioneering work, comparison of stress responses in different systems has been widely neglected (for overview see Rose, 1984). Any stressful situation can lead to measurable changes at physiological, endocrine, behavioral, and subjective response levels. Stress reactions have been evaluated by numerous different indicators, urging further clarification of the definition and validity of the stress concept CLlrsin & Murison, 1984)." Depending on the psychological impact of the situation, reactions of these different systems can be dissociated, and such reactions will show remarkable inter-individual variations. Physical exercise has been repeatedly studied as a rather standardized stress situation. It induces meaningful physiological, endocrine, and subjective changes mainly in untrained subjects and at a high performance level (Davis et al., 1981; Fan'ell et al., 1983; Brandenberger et al., 1986; Berger et al., 1987). The present study was designed to further elucidate psychological factors modulating endocrine responses to exhaustive physical exercise. First, we tried to define physiological and psychological measures which can predict inter-individual differences in the endocrine response to loading. Methods and results of this part of the study will be reported elsewhere (Fehm-Wolfsdorf et al., 1990). Second, we studied how predictability and controllability as well-known psychological response modifiers can influence hormonal outcome after loading. "Predictability" was defined by repeating the task three times in an identical manner. "Controllability" Correspondence to be addressed to: Dr. Gabriele Fehm-Wolfsdorf, Institut ftir Psychologic, Universit/it Kiel, Olshausenstra~ 40/60, D-2300 Kiel, F.R.G. 173
174
K. Vole,';"et al.
was defined b y different task instructions to the subjects in a fourth session compared to the three preceding ones. F r o m animal studies (Natelson et al., 1988; Kant et al., 1989), adrenocortical stress responses would be expected to diminish following re-exposure to the same situation but to increase following an uncontrollable situation. The complete pattern o f h o r m o n a l responses to repeated exercise, however, cannot be clearly predicted from the studies so far. SUBJECTS AND METHODS Subjects Sixteen untrained student volunteers (mean age 23.5 years; eight male, eight female) participated in the study. Each subject underwent a medical examination at the beginning of each session; height and weight were measured. They completed schedules for their preceding sleep time, meals, physical activity, and other events. All subjects were non-smokers, the females were not taking contraceptives, and all gave written consent for their participation in the study. Design and procedure Subjects were instructed m ride on an ergometer bicycle until they were exhausted. In each session they earned a basic fee of DM 40 and could get another DM 40 maximum, depending on their performance level. We pretended to pay them ~ g to ~eir peak performance compared to their individual physiologicalcapacity, but all of them actually received the maximum sum. Loading on the bicycle started at one wattjkg body weight (BW) and was increased by one watt every 3 min. Four sessions per subject were scheduled at the same time, at 1400h or 1600h, varying among subjects. Sessions were held one week apart. Instructions to the subject as reported above were identical insessions 1-3. In the last session, the experimenter told the subject that today he/she was not allowed to stop inkling when he/she felt exhausted, bu! only when the experimenter permitted it. Otherwise he/she would get no money at all for this day..This mstrucuon was ha.yen at the very last moment befcce l.oa~." ~ prevent discussion ~ the subject. The expenmenter stopped the nding when the subject had reached the individual mean level (watt/kg BW) of the preceding three sessions. Performance level reached in each session served as a behavioral indicator. Before and after the exercise, subjects rated on a visual analogue scale the expectations of their performance level and feelings of strain. The experimenter also tried to predict performance and strain of each subject on an analogue scale. Upon each subject's arrival in the laboratory, an intravenous forearm catheter was inserted for blood sampfing. Forty milliliters blood were collected immediately, then at the end of loading and 20, 40, and 60 min later, with the subj~t lying on a couch. Blood samptes we~ cen.l~,u g h . and the plasma ~ was i ~ frozen, A_ner mserUon of the catheter,chest and extreaml~s electrodeswere applied to the subject,with statulardb~lar placements for heart rate recording. During exc,~ise, heart rate was reccaded at 30-see intervals. V02 was assessed at 3G-see intervals during loading. Blood pressure was measured at 3-rain intervals and 1, 3, and 5 rain after exercise. A semistrucmred interview at the end of the last session tried to elucidate how stressful parts of the experiment were and how subjects had coped with the task, mainly under conditions of reduced control. Hormone analyses All hormones were analyzed by radioinmaunoasuy (RIA) methods. Commercial RIA kits were used for deterruination of cortisol (DPC), growth hormone (hGH; Sorin ~ a ) , prolacfin (Serono), and va~aessin (INC). ACTH was measured by an RIA procedure consistiag o f IgG-ACTH-I anfisermn f ! ~ t i o n , USA), monoiodinated synthetic hACTHI_39 as [racer ( ~ Buchler, GB), and synthetic hACTHI_~9 standard (CIS, .Franc.e). Blood was collected into chilled tubes containing EDTA (4 raM), diisop~,pyl phosphate (l raM) and oestatm (20 gin) as anucoagulant, and protective agents (fianl concentrati0as). Plasma was s t m ~ frozen (-20 C)
~dex~
on polys~m.~~ s ~ :
W CO~o.~ USA) us~g a . ~
~
~.ssor ~.P L
uront, USA). Extracted and lyophiliZed ~ were reconsututad m assay butler (63 mM Na ~ pH 7.4, 13 mM EDTA, 0.02% NAN3, 3.5% bovine serum albumin, 250,000 KP,J Trasylo!/l, 1% Triton XI00). For full description of the extraction step see Bickel et al. (1988). Assay petfcmnauces are given in Table L Lactic acid was determined in duplicate amImmn~trically with enzyme-electrodes by lactate-analyzer La Roche with a precision of I% and an accuracy of 1.5%.
175
HORMONALRESPONSESTO EXHAUSTINGPHYSICALEXERCISE
TABLE I..ASSAY PERFORMANCE
Hormone
Cortisol Prolactin hGH Vasopressin ACTH
Inter-assay Variability Coefficient of Variation
Intra-assay Variability Coefficient of Variation
0306-4530/90$3.00+0.00 01990PergamonPresspie
PrintedinGreatBritain
HORMONAL RESPONSES TO EXHAUSTING PHYSICAL EXERCISE: THE ROLE OF PREDICTABILITY AND CONTROLLABILITY OF THE SITUATION K. VOIGT,1 M. ZIEGLER,2 M. GRONERT-FUCHS,3 U. BICKEL,l and G. FEHM-WoLFSDORF2 llnstitute of Normal and Pathological Physiology, University of Marburg, and 2Departments of Me.dieMPsychology and 3physiology, University of Ulm, ER.G. (Received 6 July 1988; In,~'ml form 25 October 1989)
SUMMARY Psychological conditions which produce sustained activation have been clearly identified. Among these are the predictability and the controllability of the situation. We studied the impact of these psychological variables on hormone secretion (cortisol, ACTH, vasopressin, prolactin, and hGH plasma levels) under a standardized physical load. Sixteen subjects participated in four sessions each, one week apart, with the task of riding a bicycle until exhaustion. During three sessions, all experimental conditions were held identical to ensure the situation was as predictable as possible. During the fourth session, instructions induced a certain level of uneontroUability. Whereas physiological and performance measures did not vary with experience in the task, eortisol, AOrH, and vasopressin responses declined with increasing experience. This emphasizes the importance of the psychological definition of the situation for endocrine stress responses.
INTRODUCTION SINCE Mason's (1968) pioneering work, comparison of stress responses in different systems has been widely neglected (for overview see Rose, 1984). Any stressful situation can lead to measurable changes at physiological, endocrine, behavioral, and subjective response levels. Stress reactions have been evaluated by numerous different indicators, urging further clarification of the definition and validity of the stress concept CLlrsin & Murison, 1984)." Depending on the psychological impact of the situation, reactions of these different systems can be dissociated, and such reactions will show remarkable inter-individual variations. Physical exercise has been repeatedly studied as a rather standardized stress situation. It induces meaningful physiological, endocrine, and subjective changes mainly in untrained subjects and at a high performance level (Davis et al., 1981; Fan'ell et al., 1983; Brandenberger et al., 1986; Berger et al., 1987). The present study was designed to further elucidate psychological factors modulating endocrine responses to exhaustive physical exercise. First, we tried to define physiological and psychological measures which can predict inter-individual differences in the endocrine response to loading. Methods and results of this part of the study will be reported elsewhere (Fehm-Wolfsdorf et al., 1990). Second, we studied how predictability and controllability as well-known psychological response modifiers can influence hormonal outcome after loading. "Predictability" was defined by repeating the task three times in an identical manner. "Controllability" Correspondence to be addressed to: Dr. Gabriele Fehm-Wolfsdorf, Institut ftir Psychologic, Universit/it Kiel, Olshausenstra~ 40/60, D-2300 Kiel, F.R.G. 173
174
K. Vole,';"et al.
was defined b y different task instructions to the subjects in a fourth session compared to the three preceding ones. F r o m animal studies (Natelson et al., 1988; Kant et al., 1989), adrenocortical stress responses would be expected to diminish following re-exposure to the same situation but to increase following an uncontrollable situation. The complete pattern o f h o r m o n a l responses to repeated exercise, however, cannot be clearly predicted from the studies so far. SUBJECTS AND METHODS Subjects Sixteen untrained student volunteers (mean age 23.5 years; eight male, eight female) participated in the study. Each subject underwent a medical examination at the beginning of each session; height and weight were measured. They completed schedules for their preceding sleep time, meals, physical activity, and other events. All subjects were non-smokers, the females were not taking contraceptives, and all gave written consent for their participation in the study. Design and procedure Subjects were instructed m ride on an ergometer bicycle until they were exhausted. In each session they earned a basic fee of DM 40 and could get another DM 40 maximum, depending on their performance level. We pretended to pay them ~ g to ~eir peak performance compared to their individual physiologicalcapacity, but all of them actually received the maximum sum. Loading on the bicycle started at one wattjkg body weight (BW) and was increased by one watt every 3 min. Four sessions per subject were scheduled at the same time, at 1400h or 1600h, varying among subjects. Sessions were held one week apart. Instructions to the subject as reported above were identical insessions 1-3. In the last session, the experimenter told the subject that today he/she was not allowed to stop inkling when he/she felt exhausted, bu! only when the experimenter permitted it. Otherwise he/she would get no money at all for this day..This mstrucuon was ha.yen at the very last moment befcce l.oa~." ~ prevent discussion ~ the subject. The expenmenter stopped the nding when the subject had reached the individual mean level (watt/kg BW) of the preceding three sessions. Performance level reached in each session served as a behavioral indicator. Before and after the exercise, subjects rated on a visual analogue scale the expectations of their performance level and feelings of strain. The experimenter also tried to predict performance and strain of each subject on an analogue scale. Upon each subject's arrival in the laboratory, an intravenous forearm catheter was inserted for blood sampfing. Forty milliliters blood were collected immediately, then at the end of loading and 20, 40, and 60 min later, with the subj~t lying on a couch. Blood samptes we~ cen.l~,u g h . and the plasma ~ was i ~ frozen, A_ner mserUon of the catheter,chest and extreaml~s electrodeswere applied to the subject,with statulardb~lar placements for heart rate recording. During exc,~ise, heart rate was reccaded at 30-see intervals. V02 was assessed at 3G-see intervals during loading. Blood pressure was measured at 3-rain intervals and 1, 3, and 5 rain after exercise. A semistrucmred interview at the end of the last session tried to elucidate how stressful parts of the experiment were and how subjects had coped with the task, mainly under conditions of reduced control. Hormone analyses All hormones were analyzed by radioinmaunoasuy (RIA) methods. Commercial RIA kits were used for deterruination of cortisol (DPC), growth hormone (hGH; Sorin ~ a ) , prolacfin (Serono), and va~aessin (INC). ACTH was measured by an RIA procedure consistiag o f IgG-ACTH-I anfisermn f ! ~ t i o n , USA), monoiodinated synthetic hACTHI_39 as [racer ( ~ Buchler, GB), and synthetic hACTHI_~9 standard (CIS, .Franc.e). Blood was collected into chilled tubes containing EDTA (4 raM), diisop~,pyl phosphate (l raM) and oestatm (20 gin) as anucoagulant, and protective agents (fianl concentrati0as). Plasma was s t m ~ frozen (-20 C)
~dex~
on polys~m.~~ s ~ :
W CO~o.~ USA) us~g a . ~
~
~.ssor ~.P L
uront, USA). Extracted and lyophiliZed ~ were reconsututad m assay butler (63 mM Na ~ pH 7.4, 13 mM EDTA, 0.02% NAN3, 3.5% bovine serum albumin, 250,000 KP,J Trasylo!/l, 1% Triton XI00). For full description of the extraction step see Bickel et al. (1988). Assay petfcmnauces are given in Table L Lactic acid was determined in duplicate amImmn~trically with enzyme-electrodes by lactate-analyzer La Roche with a precision of I% and an accuracy of 1.5%.
175
HORMONALRESPONSESTO EXHAUSTINGPHYSICALEXERCISE
TABLE I..ASSAY PERFORMANCE
Hormone
Cortisol Prolactin hGH Vasopressin ACTH
Inter-assay Variability Coefficient of Variation
Intra-assay Variability Coefficient of Variation
