230
Stability and Variability in Hormonal Responses to Prolonged Exercise A. Viru, K. Karelson, T Smirnova Department of Exercise Biology, Tartu University, 18 Ylikooli, Tartu EE2400 Estonia
A. Viru, K. Karelson, and T. Smirnova, Stabil-
ity and Variability in Hormonal Responses to Prolonged Exercise. IntJ Sports Med, Vol 13, No 3, pp 230—235, 1992.
generally acknowledged concent. In a number of cases, the discrepancies may be due to the differences in time when the blood samples were collected, because at different moments of time we may get information about various phases of the whole dynamics. It cannot be ruled out either that the same time point may correspond in various persons to different phases of the dynamics.
Accepted after revision: September 24, 1991
To study the dynamics of alterations in blood hormones and their individual variability during prolonged exercise, changes in plasma levels of corticotropin, cortisol, aldosterone, testosterone, progesterone, somatotropin, insulin and C-peptide were recorded in 32 endurance athletes
and 50 untrained persons during a 2-hour exercise on a cycle ergometer at 60% VO2max. Common changes were activation of the pituitary corticotropin function, mostly at the end of exercise, rises in aldosterone and somatotropin
concentrations and decreases in insulin and C-peptide
levels during exercise. The activation of pituitaryadrenocortical system and the decrease of insulin but not Cpeptide levels were more pronounced in athletes than in untrained persons. A large inter-individual variability existed
in changes of cortisol, testosterone and progesterone in both groups. Five variants were found in the dynamics of cortisol concentration. Whereas the alterations of corticotropin were characterized mainly by a biphasic increase, the dynamics of corticotropin and cortisol coincided only in one variant out of five. Most characteristic for the postexercise recovery period were decreased activity of the pituitary-adrenocortical system and delayed normalization of aldosterone level. Key words
Dynamics of hormone responses, exercise, hormone, intra-individual variability, threshold duration of exercise, training
Introduction A great amount of data have been accumulated about the changes of hormone levels in blood during various types of exercise (6, 18). The main factors determining the hormone responses were elucidated. Nevertheless, there are a lot
of studies, results of which are not in accordance with the
In order to study the dynamics of alteration in blood hormones and their individual variability, the changes in plasma levels of corticotropin, cortisol, aldosterone, testost-
erone, progesterone, somatotropin, insulin and C-peptide were studied in 82 endurance-trained and untrained male perSons during a 2-hour continuous cycling exercise.
Material and Methods
Subjects 82 males (17—35 years old) performed a 2-hour exercise on an electrically braked cycle ergometer (the Experi-
mental Workshop of Tartu University). The main characteristics of the groups are presented in Table 1. The group of athletes consisted of 8 distance runners, 17 cross-country skiers and 7 road cyclists. University students who had never participated in sports training were used for the untrained group. The experiment was repeated 2—3 times during a year on 4 sportsmen and 4 untrained persons. Before the experiment the persons gave their consent to participate in the study and they were fully informed about the characteristics and the aim of the research project.
Procedure Three to eight days before the experiment the VO2max was assessed with the aid of a stepwise increased exercise test on a bicycle ergometer (15). The level of 60% of individual power output during maximal exercise was used for
the endurance trial. The relative exercise intensity was controlled by the determination of oxygen uptake. All experiments began between 8.00 and 10.00 a. m. The participants had a standardized breakfast containing 57 g of protein, 100 g of lipids and 81 g of carbohydrates (1493 kcal). After breakfast a Teflon catheter was inserted into the antecubital vein. The 2-h exercise commenced 1.5 h after breakfast. Venous blood samples were collected into cooled polystyrene tubes containing EDTA before exercise, at the 10th, 20th, 3 0th, 60th and 120th mm of exercise and 1, 6 and 24
hrs after the end of exercise. The plasma was separated immemt. J. SportsMed. 13(1992)230—235 GeorgThieme Verlag StuttgartNew York
diately through centrifugation at + 4 °C. The plasma was stored at —20 °C.
Downloaded by: University of British Columbia. Copyrighted material.
Abstract
mt. J. Sports Med. 13(1992) 231
Stability and Variability in HormonaiResponses to Prolonged Exercise Table 1 The main characteristics of subjects (mean SD). Group
n
Age
Body
(years)
weight
Height (cm)
Relative intensity of performed exercise (%ofVO2max)
VO2max
(mlmin1kg1)
(kg)
Untrained men
50
22.5±3.5
72.4±7.3
178±6
49.0±4.9
60±9
Athletes
32
21.2±2.3
75.5±5.4
181±5
68.8± 1.5
55±7
Table 2 lndividual changes in hormone levels dunng 2-h exercise: percent of cases of change s in comparison with value s before exercise. Arbitrary
Corticotropin
Cortisol
Testosterone
pgm11 nMolL1
5 nMolL1
10 mm
20 mm 30 mm 60 mm
Increase
48% 10%
45% 50% 29% 26%
60%
Decrease Increase
Decrease
46% 30%
46% 42% 44% 44%
Increase
17%
Decrease Progesterone
Aldosterone
Somatotropin
5 nMolL1 pgmr1
5 ngml
C-peptide
3 iUm11 0.1 nMolL1
8%
120 mm
10 mm 20 mm
30 mm
60 mm
120 mm
62% 24%
53% 72%
66%
81% 31%
91%
32% 64%
56%
50% 53% 38% 35%
41% 41%
56%
88%
38%
9%
25% 31% 47%
44%
31%
28%
14%
6%
14% 24% 10% 4%
17%
8%
4%
4%
10%
0% 6%
17%
11%
44%
0%
0%
0%
75% 89% 4% 18%
92%
96% 0%
96%
4%
35% 65%
77%
97%
97%
0%
0%
0%
4% 77%
4%
0%
81%
93%
0% 96%
11%
14%
9% 9%
42%
39%
36% 25% 43%
50%
17%
Decrease
0%
4%
4%
0%
Increase
78%
92% 97% 100%
100%
Decrease
5%
0%
0%
Increase
23%
49% 72% 77%
86% 0%
Increase
Decrease Insulin
Endurance athletes
Untrained persons
Change
criteria of the change
Increase
0%
2%
Decrease
69%
Increase Decrease
61%
3%
0% 0% 5% 0% 0%
0%
2% 3% 79% 84%
84%
0%
5%
3%
0%
80% 75%
86%
3%
Analytical Methods All analyses were carried out in duplicate, quality controls were included in all sets of determinations. The
coefficients of variation between duplicate analyses were
0% 0% 4% 0%
0%
5% 93%
85% 81%
3% 86%
0% 4%
7%
0%
71% 82%
75%
93%
6%
0%
arbitrary criteria, presented in Table 2. The used arbitrary criteria were found on the bases of SEM values, presented in Fig. 1. Regarding corticotropin, cortisol, aldosterone, insulin and
C-peptide, the criteria were close to SEM values. For pro-
In blood samples the concentrations of corticotropin, cortisol,
gesterone, testosterone and somatotropin, higher criteria were used because modest changes in sex hormone levels could be caused by altered elimination rate or plasma volume, and also because the usual somatotropin response was 5—20 times more
aldosterone, progesterone, testosterone, somatotropin, in-
than initial values (6, 18).
within 5—9%. All analyses for a particular hormone in one subject were made at the same time to avoid inter-assay variations.
sulin and C-peptide were determined by radioimmunoassays (10) using commercial kits: CEA Sorin kit for corticotropin, cortisol, aldosterone and somatotropin, the Institute of Bioorganic chemistry of Academy of Science of Byelorussin SSR kits for testosterone, progesterone and insulin, and the Mallinckrodt Diagnostika kit for C-peptide. The within-assay as well as the between-assay variabilities were < 10%. The accuracy tests indicated the recovery of added standard within 95 to 115%. All assays were highly specific. The exclusions were complete cross-reaction of corticotropin antiserum with 31—24 corticotropin (synacthene) as well as 50% binding of prednisolone by cortisol antiserum and 20% binding of dehydrotestosterone by testosterone antiserum. For statistical analysis of the obtained data the comparison of group mean values was performed with the aid of a t-test. The existence or lack of response was evaluated by
Results
Analysis by group values The cycling exercise of 2-h duration caused activation of the pituitary corticotropin function, which was most pronounced at the end of exercise. Only then did it associate with an increased level of cortisol in blood (Fig. 1). In athletes the activation of the pituitary-adrenocortical function was more pronounced. Within 6—24 h of post-exercise recovery a decreased activity of the pituitary-adrenocortical sys-
tem was common. The aldosterone concentration rose throughout the period of exercise, with delayed normalization after the end of exercise. Common changes were also a pro-
nounced increase in somatotropin and a decrease in insulin and C-peptide levels during exercise. The somatotropin concentration returned to initial values within 1 h and insulin con-
Downloaded by: University of British Columbia. Copyrighted material.
Hormone
232 mt. .1. Sports Med. 13(1992)
A. Viru, K. Karelson, T. Smirnova
nMoI —1
Fig. 1 Dynamics of mean values of
corUsol
700
cortisol, corticotropin, testosterone, progesterone, aldosterone, soma-
ng .
400
dosterone
600 300
totropin, insulin and C-peptide in endurance athletes (solid lines) and untrained persons (interrupted lines)
500 200 400
300
0102030
60
120
16 24
0 10 20 30
60
, -—j during 2-h exercise of bicycle ergome-
pg 190
corticotropln
ter at 55±7%
ngmI'
170
'IO2max in athletes
somatotropin
150
and at 60±9% VO2max in un-
30
130
trained persons. Vertical lines indi-
110
90
20
cate the SEM. Time
70
is indicated in mm
50 30
iiI
0102030
60
120
ii
10
during exercise and in hrs after the end of exercise.
1 6 24
60
120
1 6 24
30 LU Insulin
25
nMoI I — 40 35 30
25 20 15
10
S
testosterone
0 10 20 30
40 35
60
120 1 6 24
15
I,
10
5
ii 10
nMoI I-i
0 10 20 30
60
30 25
20 15
10
5 60
120 1 6 24
centration up to the 6th post-exercise hour. In athletes the re-
sponse of insulin but not C-peptide was more pronounced compared with the untrained persons. The molar ratio between insulin and C-peptide was decreased during the whole period of exercise in athletes, but only during the first hour of exercise in untrained men. The group values did not reveal significant changes in levels of progesterone and testosterone, except for a decrease in the testosterone concentration within the first 6 hrs of the post-exercise recovery period.
120 I 6 24
nMoI- —1 C-peptide
9 8 7 6 5 4 3 2
progesterone
0 10 20 30
20
/ 0 10 20 30
60
120 1 6 24
Individual analysis
Actually, changes in hormone levels were found in most persons (Table 2). Due to differences in individual dynamics, the increased hormone levels were observed at different time points in various persons. A rise in a!-
dosterone and somatotropin concentrations as well as a decrease in insulin and C-peptide levels were found in all persons. In all trained persons the corticotropin response was es-
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800
mt. J. Sports Med. 13(1992) 233
Stability and Variability in HormonaiResponses to Prolonged Exercise
Fig. 2 Five vari-
140
ants of cortisol dynamics during 2-h exercise. Each part of figure (1 2,
130 800 120
700
110
190 300
100
170
90 600
150
80
130
70 500
110
60
90
50 400
70
40
50
30 300)
30
0 10 20 30
3, 4 and 5) is based on the mean values
500
of persons exhibited the corresponding variant.
00
Solid lines — corti-
300
soP in nMolH, interrupted lines —
200
0102030
60
60
120 1 6 24
190
corticotropin in pgmr1.Time is indicated as in Fig. 1.
170 IOOC
150900
\
130
130800
90600
90• 70 50
-I
30
0102030
0102030
120 1 6 24
60
60
1201 624
140 120
1
100
80 60 400 40
.4
20
0 10 20 30
60
tablished. A large inter-individual variability was evident in the changes of cortisol, testosterone and progesterone.
120 1 6 24
(2)a biphasic increase (peak values during first 30 mm and at the end of exercise), with a decrease after the first peak (in 10 untrained and 11 trained persons);
In a number of cases a delayed hormone response was observed. Most frequently it was observed in somatotropin response (in 70% of untrained persons and in 65% of athletes). The delayed response of corticotropin concentration was evident in 40% of untrained and 47% of trained persons and of cortisol concentration in 28 % of untrained and 47% of trained persons. In the aldosterone level it was established in 17% and 23% and in the insulin level in 25% and 15% of cases, respectively.
Individual variants of dynamics In dynamics of cortisol concentration 5 vari-
(3)a monophasic increase during the whole period of exercise (in 7 untrained and 3 trained persons); (4)a lack of alterations or a moderate decrease during the first 20—60 mm of exercise and a pronounced increase during the second hour of exercise (in 9 untrained and 12 trained persons);
(5)a decrease during the whole period of exercise (14 untrained and 1 trained person).
There was no significant difference between
ants were discriminated (Fig. 2):
the persons showing various variants of dynamics in regard to
(1)an initial increase followed by a decrease (after 20—30 mm
VO2max), the initial level of cortisol and responses of other hormones. When at the end of exercise the cortisol level was high (the 2nd, 3rd and 4th variants), then I h after the end of exercise cortisol concentrations remained above the initial one
of exercise) to basal levels or below (in 10 untrained and 5 trained persons);
VO2max, relative intensity of performed exercise (% of
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110700
110
A. Viru, K. Karelson, T Smirnova
mt. J. Sports Med. 13(1992)
in most cases. In the 1St and 5th variants at least during the 1st hour a low cortisol level persisted. Six or 24 hrs after exercise the cortisol level was decreased or close to the initial values in all variants.
VO2max, relative intensity of performed exercise and the initial level of cortisol. In repeated experiments with the same
persons the cortisol dynamics were in most cases approximately identical, suggesting a dependence on the individual peculiarities of the person. Only when the intensity of exercise
In 8 persons the 2-hour exercise was repeated
was substantially decreased, the biphasic increase was
2—3 times during a year at the same or varied level of intensity.
changed by a decrease during the whole period of exercise. This result has been previously described by Davies and Few (3).
When the relative intensity of exercise was the same, then the cortisol dynamics were identical. When the intensity of exercise was substantially decreased, the biphasic increase was re-
placed by a decrease during the whole period of exercise.
In most cases the alterations of the corti-
However, there were persons with an overall decrease of blood cortisol level despite the difference in exercise intensity.
cotropin level were characterized by a biphasic increase (peak values during the first 20 mm and also at the end of exercise). Thus the dynamics of corticotropin and cortisol levels coin-
In most cases the alterations in the corticotropin level were characterized by a biphasic increase (peak values during the first 20 mm and also at the end of exercise). So the dynamics of corticotropin and cortisol levels coincided
cided only in the second variant. In the other variants the adrenal cortex did not respond to one or both corticotropin peaks. Consequently, a blockade of adrenocortical response to corticotropin may arise during exercise.
only in the second variant (Fig. 2).
The bursts of corticotropin secretion at the In the dynamics of somatotropin two main variants were distinguished: (1) the increase in the somatotropin concentration up to the end of exercise, and (2) the increase up to the peak level (mostly at 60th mm of exercise) followed by a constant niveau or a slight decrease. In changes of testosterone or progesterone, no common variants were distinguished.
beginning of exercise and also after some period of exercise suggest that the activation of the pituitary-adrenocortical system is determined by two thresholds: (1) threshold by exercise intensity, determining the activation at the beginning of exercise; (2) threshold by exercise duration, that becomes decisive after a certain time of exercise. While the first activation is of
short duration, a stable and prolonged activation follows Discussion
when the threshold by exercise duration was surmounted (19).
The results allowed us to discriminate common stable and variable hormonal responses to exercise. The increase in aldosterone and somatotropin concentrations as well as the decrease in insulin and C-peptide concentrations composed a group of common stable responses both in trained and
In cases of stable hormone responses, the intraindividual differences revealed in the magnitude of responses as well as in minor characteristics of dynamics. The latter concerned the existence of an initial lag period that was reported
untrained persons. In endurance athletes the elevation of
glucagon (4, 13) responses. Our results confirmed the possibility of a lag phase, but it was not a general pattern of re-
blood corticotropin level is also common. At the same time a great individual variability was typical for changes of cortisol, testosterone and progesterone. Due to different time characteristics, as well as to the coincidence of phases of an increased level in some persons with phases of a decreased level in other persons, the actual changes were not expressed in the mean values of the group. Consequently, the conclusions about the
lack of hormone responses, deduced from the unchanged mean values may not correspond to the actual situation.
to precede to somatotropin (1, 8, 17), insulin (9, 13) and sponse. Most frequently we found the lag period before the somatotropin response. In most previous studies the peak values of somatotropin concentration in the blood were observed between the 25th and the 60th mm of exercise (1, 7, 17). We ob-
served the peak level of somatotropin concentration mostly found at the 60th mm of exercise and it was followed by a constant niveau or a slight decrease. Accordingly it was found that
the somatotropin concentration may decline after the peak values were obtained (7).
The cortisol response to prolonged exercise was discriminated into five variants of dynamics (Fig. 2). In previous studies the following variants were observed: (1) an
initial increase in the cortisol level which changed by a decrease up to the basal level or below it (the first variant by our
definition) (16, 18); (2) a continuous increase during the exercise (the third variant) (3, 7, 18). However, in some studies the possibilities of an increase only after a comparatively long duration of exercise (the fourth variant) (11) or a decreased level during the whole period of exercise (the fifth variant) (3, 11) were noticed. A biphasic increase in the pituitary-adrenocortical activity is shown during the longlasting action of various stressors (2, 12). The results of this study demonstrated that none of these variants can be considered as a common one, excluding the others.
It was not possible to relate the existence of various variants of cortisol dynamics with the values of
Our data showed a decrased molar ratio of insulin to the C-peptide concentration confirming enhanced insulin elimination and degradation during exercise (5, 14). In trained persons the decrease in the molar ratio was more pronounced. References Buckler J. M.: Exercise as a screening test for growth hormone re2
'
lease. Acta Endocrinol 69:219—229, 1972. Dallman M. F., Jones M. T.: Corticosteroid feedback control of
ACTH secretion: effect of stress-induced corticosterone secretion on subsequent stress response in the rat. Endocrinology 93: 1367— 1375, 1973. Davies C. T. M., Few J. D.: Effect of exercise on adrenocortical function. JApplPhysiol35: 688—891, 1972. Felig P., Wahren I., Hendler R., Ahlborg G.: Plasma glucagon levels in exercising man. NEnglJMed 287: 184—185, 1972.
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mt. I Sports Med. 13(1992) 235
Stability and Variability in HormonaiResponses to Prolonged Exercise
366—373, 1971. 6 Galbo H.: Hormonal and Metabolic Adaptation Stuttgart, New York, G. Thieme Verlag, 1983.
8
15
Hartley L. H., Mason J. W., Hogan R. P., Jones L. G., KotchonT. A., Mongey E. H., Wherry F. E., Pennington L. L., Ricketts P. T.: Multiple hormonal responses to prolonged exercise in relation to physical training. JApplPhysiol33: 607—610, 1972. Hunter W. M., Fonsenka C. C., Passmore R.: Growth hormone: important role in muscular exercise in adults. Science 150: 1051— 1052, 1965. during muscular exercise. JPhysiol 196: 1 lOP—li 2P, 1968. Jaffe B. M., Behrman H. R. (eds.): Methods of Hormone Radioimmunoassay. New York, Acad. Press, 1979.
Keibel D.: Nebennierenrinden-Hormone und Sportliche Leistung.MedSport 14:65—76, 1974. Knigge K. M., Penrad C. H., Schindler W. J.: In vitro and in vivo adrenal corticosteroid secretion following stress. Am J Physiol 96: 570—582, 1959. '3 Luyckx A. S., Pirnay F., Lefebvre P. J.: Effect of glucose on plasma glucagon and free fatty acids during prolonged exercise. EurJAppl Physiol39: 53—61, 1978. Niyazmukhammedov M. B., Yakovlev N. N.: Changes of 3'-S'-
12
''
AMP phosphodiesterase activity and inactivation of insulin
1976. Pärnat J., Vim A., Savi T., Nurmekivi A.: Indices of aerobic work
capacity and cardio-vascular responses during exercise in athletes specializing in different events. JSports Med Phys Fitness 15: 100—
to Exercise.
Hunter W. M., Sukkar M. Y.: Changes in plasma insulin levels 10
during muscular activity. Sechenov PhysiolJ USSR 62: 768—775,
16
17
18
105, 1975. Staehelin
D., Labhart A., Froesch R., Kägi H. R.: The effect of
muscular exercise and hypoglycemia on the plasma level of 1 7-hydroxysteroids in normal adults and in patients with the adrenogenital syndrome. Acta Endocrinol 18: 521— 529, 1955. Sutton J. R., Lazarus L.: Growth hormone in exercise: comparison of physiologic and pharmacologic stimuli. JAppI Physiol 41: 523— 527, 1976. Viru A.: Hormones in Muscular Activity. Vol. I Hormonal Ensemble in Exercise. Boca Raton, CRC Press, 1985. Viru A., Karelson K., Smirnova T., Port K.: Activity of pituitaryadrenocortical system during various exercises, in Nazar K., Kaciuba-Ucilko H., Terjung R. L., Budohoski L. (eds.): International Perspectives in Exercise Physiology. Champaign, Human KineticsPubl. 1990, pp 160—165.
Prof A. Viru Dept. of Exercise Biology 18 Ylikooli, Tartu EE2400 Estonia
Downloaded by: University of British Columbia. Copyrighted material.
Franckson J. R. M., Vanroux R., Leclercq R., Braunengraler H., Ooms H. A.: Labelled insulin catabolism and pancreatic responsiveness during long-term exercise in man. Horm Metab Res 3:
Stability and Variability in Hormonal Responses to Prolonged Exercise A. Viru, K. Karelson, T Smirnova Department of Exercise Biology, Tartu University, 18 Ylikooli, Tartu EE2400 Estonia
A. Viru, K. Karelson, and T. Smirnova, Stabil-
ity and Variability in Hormonal Responses to Prolonged Exercise. IntJ Sports Med, Vol 13, No 3, pp 230—235, 1992.
generally acknowledged concent. In a number of cases, the discrepancies may be due to the differences in time when the blood samples were collected, because at different moments of time we may get information about various phases of the whole dynamics. It cannot be ruled out either that the same time point may correspond in various persons to different phases of the dynamics.
Accepted after revision: September 24, 1991
To study the dynamics of alterations in blood hormones and their individual variability during prolonged exercise, changes in plasma levels of corticotropin, cortisol, aldosterone, testosterone, progesterone, somatotropin, insulin and C-peptide were recorded in 32 endurance athletes
and 50 untrained persons during a 2-hour exercise on a cycle ergometer at 60% VO2max. Common changes were activation of the pituitary corticotropin function, mostly at the end of exercise, rises in aldosterone and somatotropin
concentrations and decreases in insulin and C-peptide
levels during exercise. The activation of pituitaryadrenocortical system and the decrease of insulin but not Cpeptide levels were more pronounced in athletes than in untrained persons. A large inter-individual variability existed
in changes of cortisol, testosterone and progesterone in both groups. Five variants were found in the dynamics of cortisol concentration. Whereas the alterations of corticotropin were characterized mainly by a biphasic increase, the dynamics of corticotropin and cortisol coincided only in one variant out of five. Most characteristic for the postexercise recovery period were decreased activity of the pituitary-adrenocortical system and delayed normalization of aldosterone level. Key words
Dynamics of hormone responses, exercise, hormone, intra-individual variability, threshold duration of exercise, training
Introduction A great amount of data have been accumulated about the changes of hormone levels in blood during various types of exercise (6, 18). The main factors determining the hormone responses were elucidated. Nevertheless, there are a lot
of studies, results of which are not in accordance with the
In order to study the dynamics of alteration in blood hormones and their individual variability, the changes in plasma levels of corticotropin, cortisol, aldosterone, testost-
erone, progesterone, somatotropin, insulin and C-peptide were studied in 82 endurance-trained and untrained male perSons during a 2-hour continuous cycling exercise.
Material and Methods
Subjects 82 males (17—35 years old) performed a 2-hour exercise on an electrically braked cycle ergometer (the Experi-
mental Workshop of Tartu University). The main characteristics of the groups are presented in Table 1. The group of athletes consisted of 8 distance runners, 17 cross-country skiers and 7 road cyclists. University students who had never participated in sports training were used for the untrained group. The experiment was repeated 2—3 times during a year on 4 sportsmen and 4 untrained persons. Before the experiment the persons gave their consent to participate in the study and they were fully informed about the characteristics and the aim of the research project.
Procedure Three to eight days before the experiment the VO2max was assessed with the aid of a stepwise increased exercise test on a bicycle ergometer (15). The level of 60% of individual power output during maximal exercise was used for
the endurance trial. The relative exercise intensity was controlled by the determination of oxygen uptake. All experiments began between 8.00 and 10.00 a. m. The participants had a standardized breakfast containing 57 g of protein, 100 g of lipids and 81 g of carbohydrates (1493 kcal). After breakfast a Teflon catheter was inserted into the antecubital vein. The 2-h exercise commenced 1.5 h after breakfast. Venous blood samples were collected into cooled polystyrene tubes containing EDTA before exercise, at the 10th, 20th, 3 0th, 60th and 120th mm of exercise and 1, 6 and 24
hrs after the end of exercise. The plasma was separated immemt. J. SportsMed. 13(1992)230—235 GeorgThieme Verlag StuttgartNew York
diately through centrifugation at + 4 °C. The plasma was stored at —20 °C.
Downloaded by: University of British Columbia. Copyrighted material.
Abstract
mt. J. Sports Med. 13(1992) 231
Stability and Variability in HormonaiResponses to Prolonged Exercise Table 1 The main characteristics of subjects (mean SD). Group
n
Age
Body
(years)
weight
Height (cm)
Relative intensity of performed exercise (%ofVO2max)
VO2max
(mlmin1kg1)
(kg)
Untrained men
50
22.5±3.5
72.4±7.3
178±6
49.0±4.9
60±9
Athletes
32
21.2±2.3
75.5±5.4
181±5
68.8± 1.5
55±7
Table 2 lndividual changes in hormone levels dunng 2-h exercise: percent of cases of change s in comparison with value s before exercise. Arbitrary
Corticotropin
Cortisol
Testosterone
pgm11 nMolL1
5 nMolL1
10 mm
20 mm 30 mm 60 mm
Increase
48% 10%
45% 50% 29% 26%
60%
Decrease Increase
Decrease
46% 30%
46% 42% 44% 44%
Increase
17%
Decrease Progesterone
Aldosterone
Somatotropin
5 nMolL1 pgmr1
5 ngml
C-peptide
3 iUm11 0.1 nMolL1
8%
120 mm
10 mm 20 mm
30 mm
60 mm
120 mm
62% 24%
53% 72%
66%
81% 31%
91%
32% 64%
56%
50% 53% 38% 35%
41% 41%
56%
88%
38%
9%
25% 31% 47%
44%
31%
28%
14%
6%
14% 24% 10% 4%
17%
8%
4%
4%
10%
0% 6%
17%
11%
44%
0%
0%
0%
75% 89% 4% 18%
92%
96% 0%
96%
4%
35% 65%
77%
97%
97%
0%
0%
0%
4% 77%
4%
0%
81%
93%
0% 96%
11%
14%
9% 9%
42%
39%
36% 25% 43%
50%
17%
Decrease
0%
4%
4%
0%
Increase
78%
92% 97% 100%
100%
Decrease
5%
0%
0%
Increase
23%
49% 72% 77%
86% 0%
Increase
Decrease Insulin
Endurance athletes
Untrained persons
Change
criteria of the change
Increase
0%
2%
Decrease
69%
Increase Decrease
61%
3%
0% 0% 5% 0% 0%
0%
2% 3% 79% 84%
84%
0%
5%
3%
0%
80% 75%
86%
3%
Analytical Methods All analyses were carried out in duplicate, quality controls were included in all sets of determinations. The
coefficients of variation between duplicate analyses were
0% 0% 4% 0%
0%
5% 93%
85% 81%
3% 86%
0% 4%
7%
0%
71% 82%
75%
93%
6%
0%
arbitrary criteria, presented in Table 2. The used arbitrary criteria were found on the bases of SEM values, presented in Fig. 1. Regarding corticotropin, cortisol, aldosterone, insulin and
C-peptide, the criteria were close to SEM values. For pro-
In blood samples the concentrations of corticotropin, cortisol,
gesterone, testosterone and somatotropin, higher criteria were used because modest changes in sex hormone levels could be caused by altered elimination rate or plasma volume, and also because the usual somatotropin response was 5—20 times more
aldosterone, progesterone, testosterone, somatotropin, in-
than initial values (6, 18).
within 5—9%. All analyses for a particular hormone in one subject were made at the same time to avoid inter-assay variations.
sulin and C-peptide were determined by radioimmunoassays (10) using commercial kits: CEA Sorin kit for corticotropin, cortisol, aldosterone and somatotropin, the Institute of Bioorganic chemistry of Academy of Science of Byelorussin SSR kits for testosterone, progesterone and insulin, and the Mallinckrodt Diagnostika kit for C-peptide. The within-assay as well as the between-assay variabilities were < 10%. The accuracy tests indicated the recovery of added standard within 95 to 115%. All assays were highly specific. The exclusions were complete cross-reaction of corticotropin antiserum with 31—24 corticotropin (synacthene) as well as 50% binding of prednisolone by cortisol antiserum and 20% binding of dehydrotestosterone by testosterone antiserum. For statistical analysis of the obtained data the comparison of group mean values was performed with the aid of a t-test. The existence or lack of response was evaluated by
Results
Analysis by group values The cycling exercise of 2-h duration caused activation of the pituitary corticotropin function, which was most pronounced at the end of exercise. Only then did it associate with an increased level of cortisol in blood (Fig. 1). In athletes the activation of the pituitary-adrenocortical function was more pronounced. Within 6—24 h of post-exercise recovery a decreased activity of the pituitary-adrenocortical sys-
tem was common. The aldosterone concentration rose throughout the period of exercise, with delayed normalization after the end of exercise. Common changes were also a pro-
nounced increase in somatotropin and a decrease in insulin and C-peptide levels during exercise. The somatotropin concentration returned to initial values within 1 h and insulin con-
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Hormone
232 mt. .1. Sports Med. 13(1992)
A. Viru, K. Karelson, T. Smirnova
nMoI —1
Fig. 1 Dynamics of mean values of
corUsol
700
cortisol, corticotropin, testosterone, progesterone, aldosterone, soma-
ng .
400
dosterone
600 300
totropin, insulin and C-peptide in endurance athletes (solid lines) and untrained persons (interrupted lines)
500 200 400
300
0102030
60
120
16 24
0 10 20 30
60
, -—j during 2-h exercise of bicycle ergome-
pg 190
corticotropln
ter at 55±7%
ngmI'
170
'IO2max in athletes
somatotropin
150
and at 60±9% VO2max in un-
30
130
trained persons. Vertical lines indi-
110
90
20
cate the SEM. Time
70
is indicated in mm
50 30
iiI
0102030
60
120
ii
10
during exercise and in hrs after the end of exercise.
1 6 24
60
120
1 6 24
30 LU Insulin
25
nMoI I — 40 35 30
25 20 15
10
S
testosterone
0 10 20 30
40 35
60
120 1 6 24
15
I,
10
5
ii 10
nMoI I-i
0 10 20 30
60
30 25
20 15
10
5 60
120 1 6 24
centration up to the 6th post-exercise hour. In athletes the re-
sponse of insulin but not C-peptide was more pronounced compared with the untrained persons. The molar ratio between insulin and C-peptide was decreased during the whole period of exercise in athletes, but only during the first hour of exercise in untrained men. The group values did not reveal significant changes in levels of progesterone and testosterone, except for a decrease in the testosterone concentration within the first 6 hrs of the post-exercise recovery period.
120 I 6 24
nMoI- —1 C-peptide
9 8 7 6 5 4 3 2
progesterone
0 10 20 30
20
/ 0 10 20 30
60
120 1 6 24
Individual analysis
Actually, changes in hormone levels were found in most persons (Table 2). Due to differences in individual dynamics, the increased hormone levels were observed at different time points in various persons. A rise in a!-
dosterone and somatotropin concentrations as well as a decrease in insulin and C-peptide levels were found in all persons. In all trained persons the corticotropin response was es-
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800
mt. J. Sports Med. 13(1992) 233
Stability and Variability in HormonaiResponses to Prolonged Exercise
Fig. 2 Five vari-
140
ants of cortisol dynamics during 2-h exercise. Each part of figure (1 2,
130 800 120
700
110
190 300
100
170
90 600
150
80
130
70 500
110
60
90
50 400
70
40
50
30 300)
30
0 10 20 30
3, 4 and 5) is based on the mean values
500
of persons exhibited the corresponding variant.
00
Solid lines — corti-
300
soP in nMolH, interrupted lines —
200
0102030
60
60
120 1 6 24
190
corticotropin in pgmr1.Time is indicated as in Fig. 1.
170 IOOC
150900
\
130
130800
90600
90• 70 50
-I
30
0102030
0102030
120 1 6 24
60
60
1201 624
140 120
1
100
80 60 400 40
.4
20
0 10 20 30
60
tablished. A large inter-individual variability was evident in the changes of cortisol, testosterone and progesterone.
120 1 6 24
(2)a biphasic increase (peak values during first 30 mm and at the end of exercise), with a decrease after the first peak (in 10 untrained and 11 trained persons);
In a number of cases a delayed hormone response was observed. Most frequently it was observed in somatotropin response (in 70% of untrained persons and in 65% of athletes). The delayed response of corticotropin concentration was evident in 40% of untrained and 47% of trained persons and of cortisol concentration in 28 % of untrained and 47% of trained persons. In the aldosterone level it was established in 17% and 23% and in the insulin level in 25% and 15% of cases, respectively.
Individual variants of dynamics In dynamics of cortisol concentration 5 vari-
(3)a monophasic increase during the whole period of exercise (in 7 untrained and 3 trained persons); (4)a lack of alterations or a moderate decrease during the first 20—60 mm of exercise and a pronounced increase during the second hour of exercise (in 9 untrained and 12 trained persons);
(5)a decrease during the whole period of exercise (14 untrained and 1 trained person).
There was no significant difference between
ants were discriminated (Fig. 2):
the persons showing various variants of dynamics in regard to
(1)an initial increase followed by a decrease (after 20—30 mm
VO2max), the initial level of cortisol and responses of other hormones. When at the end of exercise the cortisol level was high (the 2nd, 3rd and 4th variants), then I h after the end of exercise cortisol concentrations remained above the initial one
of exercise) to basal levels or below (in 10 untrained and 5 trained persons);
VO2max, relative intensity of performed exercise (% of
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110700
110
A. Viru, K. Karelson, T Smirnova
mt. J. Sports Med. 13(1992)
in most cases. In the 1St and 5th variants at least during the 1st hour a low cortisol level persisted. Six or 24 hrs after exercise the cortisol level was decreased or close to the initial values in all variants.
VO2max, relative intensity of performed exercise and the initial level of cortisol. In repeated experiments with the same
persons the cortisol dynamics were in most cases approximately identical, suggesting a dependence on the individual peculiarities of the person. Only when the intensity of exercise
In 8 persons the 2-hour exercise was repeated
was substantially decreased, the biphasic increase was
2—3 times during a year at the same or varied level of intensity.
changed by a decrease during the whole period of exercise. This result has been previously described by Davies and Few (3).
When the relative intensity of exercise was the same, then the cortisol dynamics were identical. When the intensity of exercise was substantially decreased, the biphasic increase was re-
placed by a decrease during the whole period of exercise.
In most cases the alterations of the corti-
However, there were persons with an overall decrease of blood cortisol level despite the difference in exercise intensity.
cotropin level were characterized by a biphasic increase (peak values during the first 20 mm and also at the end of exercise). Thus the dynamics of corticotropin and cortisol levels coin-
In most cases the alterations in the corticotropin level were characterized by a biphasic increase (peak values during the first 20 mm and also at the end of exercise). So the dynamics of corticotropin and cortisol levels coincided
cided only in the second variant. In the other variants the adrenal cortex did not respond to one or both corticotropin peaks. Consequently, a blockade of adrenocortical response to corticotropin may arise during exercise.
only in the second variant (Fig. 2).
The bursts of corticotropin secretion at the In the dynamics of somatotropin two main variants were distinguished: (1) the increase in the somatotropin concentration up to the end of exercise, and (2) the increase up to the peak level (mostly at 60th mm of exercise) followed by a constant niveau or a slight decrease. In changes of testosterone or progesterone, no common variants were distinguished.
beginning of exercise and also after some period of exercise suggest that the activation of the pituitary-adrenocortical system is determined by two thresholds: (1) threshold by exercise intensity, determining the activation at the beginning of exercise; (2) threshold by exercise duration, that becomes decisive after a certain time of exercise. While the first activation is of
short duration, a stable and prolonged activation follows Discussion
when the threshold by exercise duration was surmounted (19).
The results allowed us to discriminate common stable and variable hormonal responses to exercise. The increase in aldosterone and somatotropin concentrations as well as the decrease in insulin and C-peptide concentrations composed a group of common stable responses both in trained and
In cases of stable hormone responses, the intraindividual differences revealed in the magnitude of responses as well as in minor characteristics of dynamics. The latter concerned the existence of an initial lag period that was reported
untrained persons. In endurance athletes the elevation of
glucagon (4, 13) responses. Our results confirmed the possibility of a lag phase, but it was not a general pattern of re-
blood corticotropin level is also common. At the same time a great individual variability was typical for changes of cortisol, testosterone and progesterone. Due to different time characteristics, as well as to the coincidence of phases of an increased level in some persons with phases of a decreased level in other persons, the actual changes were not expressed in the mean values of the group. Consequently, the conclusions about the
lack of hormone responses, deduced from the unchanged mean values may not correspond to the actual situation.
to precede to somatotropin (1, 8, 17), insulin (9, 13) and sponse. Most frequently we found the lag period before the somatotropin response. In most previous studies the peak values of somatotropin concentration in the blood were observed between the 25th and the 60th mm of exercise (1, 7, 17). We ob-
served the peak level of somatotropin concentration mostly found at the 60th mm of exercise and it was followed by a constant niveau or a slight decrease. Accordingly it was found that
the somatotropin concentration may decline after the peak values were obtained (7).
The cortisol response to prolonged exercise was discriminated into five variants of dynamics (Fig. 2). In previous studies the following variants were observed: (1) an
initial increase in the cortisol level which changed by a decrease up to the basal level or below it (the first variant by our
definition) (16, 18); (2) a continuous increase during the exercise (the third variant) (3, 7, 18). However, in some studies the possibilities of an increase only after a comparatively long duration of exercise (the fourth variant) (11) or a decreased level during the whole period of exercise (the fifth variant) (3, 11) were noticed. A biphasic increase in the pituitary-adrenocortical activity is shown during the longlasting action of various stressors (2, 12). The results of this study demonstrated that none of these variants can be considered as a common one, excluding the others.
It was not possible to relate the existence of various variants of cortisol dynamics with the values of
Our data showed a decrased molar ratio of insulin to the C-peptide concentration confirming enhanced insulin elimination and degradation during exercise (5, 14). In trained persons the decrease in the molar ratio was more pronounced. References Buckler J. M.: Exercise as a screening test for growth hormone re2
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D., Labhart A., Froesch R., Kägi H. R.: The effect of
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Prof A. Viru Dept. of Exercise Biology 18 Ylikooli, Tartu EE2400 Estonia
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Franckson J. R. M., Vanroux R., Leclercq R., Braunengraler H., Ooms H. A.: Labelled insulin catabolism and pancreatic responsiveness during long-term exercise in man. Horm Metab Res 3:
