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Effects of long-distance swimming in cold water on temperature, blood pressure and stress hormones in winter swimmers
Journal of Thermal Biology 25 (2000) 171±174
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Eects of long-distance swimming in cold water on temperature, blood pressure and stress hormones in winter swimmers P. Huttunen a,*, N.G. Lando b, V.A. Meshtsheryakov b, V.A. Lyutov b a Department of Forensic Medicine, University of Oulu, PO Box 5000, FIN-90410 Oulu, Finland Moscow Regional Centre `Human Adaptation to Extreme Conditions in Water Surroundings', Moscow, Russia
b
Abstract Long-distance swimmers swam in 10±148C water on four days. Responses in blood pressure and rectal temperature were determined every day, and hormonal responses on the third day. Swimming time lengthened with the days and diastolic blood pressure after swimming was signi®cantly lower on the fourth day than on the ®rst day. In rectal temperatures there were great individual variations. Noradrenaline was elevated more in the thin swimmers. A lesser rise in diastolic blood pressure and the longer duration of swimming on the fourth day may point to habituation to the cold. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Marathon cold water swimmers; Repeated immersion; Cold tolerance; NA; A; Cortisol
1. Introduction Humans respond to acute cold exposure with two major physiological adjustments, vasoconstriction and thermogenesis. These responses are aected by factors such as the sex, age, subcutaneous body fat and ®tness of the subject. Although chronic or repeated cold exposures produce adaptation of physiological responses to acute cold, the advantage of such adaptation with regard to the ability to maintain thermal balance under cold conditions is relatively small (Pandolf et al., 1988). We examine here the physiological responses of long-distance swimmers to repeated, prolonged swimming in cold water. The purpose was to get further information about the dierences that exist between
* Corresponding author. Fax: 358-8-330687. E-mail address: pirkko.huttunen@oulu.® (P. Huttunen).
individuals in their maintenance of thermal balance under prolonged immersion. Individual characteristics may increase or reduce the risk of adverse reactions. Long-distance swimmers were from the Moscow regional centre, where the possibilities of surviving accidents in cold water are studied. The swimmers have practiced long-distance swimming in cold water in the Bering Straits, Lake Baikal and in Severnaja Zemlja, but their physiological responses have not been documented earlier.
2. Material and methods Russian long-distance swimmers (6 males and 1 female) had a relay swim in Finland at the beginning of June. Physical characteristics of swimmers are presented in Table 1. The distance of the swim was about 50 kilometers and swimming was performed by day on
0306-4565/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 6 - 4 5 6 5 ( 9 9 ) 0 0 0 5 9 - 5
172
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174
Table 1 Physical characteristics of swimmers Skin fold thickness (mm) Subject
Sex
Age (years)
BMIa
Subscapular
Abdominal
Suprailiac
1. 2. 3. 4. 5. 6. 7. Mean2 SD
Male Male Male Male Male Male Female
59 38 44 51 39 51 26 44.0 210.8
33.9 30.8 27.7 26.5 24.7 23.6 23.0 27.123.9
25 15 15 15 10 5 5 12.8 26.9
20 15 10 10 10 5 5 10.7 25.3
20 15 15 15 10 5 20 14.225.3
a
BMI=body mass index (weight (kg)/height2 (m)).
four consecutive days. The swimmers swam on average two times per day at water temperatures varying from 108C to 148C. The responses induced by the ®rst swim of each day were determined. The duration of the ®rst swim on each day is presented in Table 2. The eects of the ®rst swim on blood pressure and rectal temperature were determined daily, but stress hormones such as noradrenaline, adrenaline and cortisol were determined only on the third day, since the swimmers refused to give more blood samples. Venous blood sample was taken before swimming in the morning 9:00±9:30 a.m. and after the ®rst swim. Plasma catecholamines were puri®ed by an Al2O3 with 3,4-dihydroxybenzylamine hydrobromide (Sigma, USA) as an internal standard and they were measured by high-performance liquid chromatography with an electrochemical detector (ESA Coulochem, model 5100 A, USA). Serum cortisol was determined by a radioimmunoassay method (Orion Diagnostica, Espoo Finland). The statistical analysis was performed by repeated
measures ANOVA or paired t-test and correlation with the Pearson correlation coecient. 3. Results On the ®rst and second day the duration of swimming correlated with skin-fold thickness in the subscapular area of swimmers (r = 0.802 and r = 0.844, P < 0.05). With the exception of one swimmer (case 5) the duration of swimming increased signi®cantly with the days (from 25.5 min to 39.0 min, F (3,15) 5.724, P = 0.011) (Table 2). There were no signi®cant changes in systolic blood pressure after swims, but diastolic blood pressure on the fourth day was signi®cantly lower than on the ®rst day (P < 0.05) (Table 3). Blood pressure of one swimmer (case 5) could not be measured because of vigorous shivering after swimming. There was a great individual variability in rectal temperatures measured after swims. In one person
Table 2 Duration of the ®rst swim for each day (min) and rectal temperature of swimmers after the swim (8C). Number of swims per day is presented in parenthesis First day
Second day
Third day
Fourth day
Subject
Min
8C
Min
8C
Min
8C
Min
8C
1. 2. 3. 4. 5. 6. 7. Mean2 SD
40 (2) 20 (2) 30 (2) 25 (2) 30 (1) 20 (2) 18 (2) 26.1 27.7
NMa 38.0 36.0 NM 35.8 37.3 NM 36.721.0
50 (2) 30 (2) 42 (2) 25 (2) 16 (2) 22 (3) 20 (3) 29.2 212.4
NM 38.0 36.2 NM 37.0 36.6 36.4 36.82 0.7
36 (2) 26 (2) 42 (2) 30 (2) 18 (2) 32 (2) 20 (2) 29.128.5
NM 38.0 35.6 NM 37.1 36.2 36.6 36.72 0.9
60 (2) 30 (2) 60 (2) 32 (2) 20 (2) 32 (2) 20 (2) 36.2216.9
NM 37.9 NM NM NM 35.4 35.4 36.2 21.4
a
NM=no measurements.
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174 Table 3 Blood pressure measured daily after the ®rst swima Blood pressure (mm/Hg) Day
Systolic
Diastolic
First Second Third Fourth
167.5221.3 174.1220.1 172.1221.9 164.3218.1
102.52 4.1 96.62 10.8 102.52 21.1 88.52 6.8b
a
Results are presented as mean 2SD, n = 6. P < 0.05 compared to the value on the ®rst day (paired ttest). b
(case 2) rectal temparature was high (388C) and it did not change with the days, whereas in one subject (case 3) it dropped to under 368C on the third day and in two other swimmers (cases 6 and 7) on the fourth day. In one person (case 5) rectal temperature fell markedly during immersion for 30 min on the ®rst day, but immersion for 16±18 min during the next days did not change it (Table 2). Two swimmers refused measurements of rectal temperature (cases 1 and 4). Swimming signi®cantly increased plasma NA levels (P = 0.01) and the smaller the body mass index was, the greater was this rise (r=ÿ0.915, P < 0.05). There were no changes in plasma adrenaline levels, while serum cortisol increased on average about 70% (P = 0.070) (Table 4).
4. Discussion Although the results show that there were great dierences between individuals in the responses to the
173
cold, a smaller diastolic blood pressure after swimming on the fourth day and the longer duration of swimming may point to habituation to the cold water in six swimmers out of seven. A greater drop in rectal temperature in three subjects without uncomfortable shivering on the two last days may point also to hypothermic adaptation in these swimmers. In one case fatness may have kept the rectal temperature high (388C). A rather great rise in serum cortisol level (about 70%) also suggests highly elevated metabolism in respect of carbohydrates. Observations on channel swimmers in the 1950s showed that rectal temperatures during ocean swimming ranged between 348C and 38.38C for exposures of nearly 18 h in water as cold as 168C (Pugh et al., 1960). Swimming exercise acclerated the drop in rectal temperature in thin subjects, whereas fat subjects maintained their rectal temperature (Pugh and Edholm, 1955). Rectal temperature after long-distance swimming in cold water has been shown to correlate with subcutaneous fat thickness (Dulac et al., 1987). Subcutaneous and deep body fat are major components determining the rate of internal heat transfer during immersion in water. The metabolic response to a fall in skin temperature in cold air has also been found to raise the rectal temperature in Caucasian males (Wyndham et al., 1964). Noradrenaline levels were elevated more in the thin swimmers. Noradrenaline controls vasoconstriction, and is involved together with cortisol in energy metabolism. Plasma adrenaline levels did not change, which suggests no cold-induced mental tension in the swimmers. Results show that there are great individual variations in the maintenance of core temperature under prolonged immersion and fatness is an essential requirement for this, but not the only one.
Table 4 Plasma NA and A (nmol/l) and serum cortisol (mmol/l) levels before and after the ®rst swim on the third day NA
A
Cortisol
Subjectc
BMId
Before
After
Before
After
Before
After
2. 3. 4. 5. 6. Mean2 SD
30.8 27.7 26.5 24.7 23.6
2.85 2.89 2.44 2.95 3.35 2.84 20.35
7.40 11.90 13.84 14.78 23.12 14.2125.73a
1.74 2.78 1.34 0.25 0.66 1.352 0.98
0.66 1.32 1.14 0.49 1.25 0.972 0.37
353 284 292 433 247 3222 73
586 316 394 600 786 5362 186b
a
P = 0.01. P = 0.70 compared to the corresponding value before swimming (paired t-test). c Two swimmers refused blood sampling (cases 1 and 7). d BMI=body mass index. b
174
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174
References Dulac, S., Quirion, A., DeCarufel, D., LeBlanc, J., Jobin, M., Cote, J., Brisson, G.R., Lavoie, J.M., Diamond, P., 1987. Metabolic and hormonal responses to longdistance swimming in cold water. Int. J. Sports Med. 8, 352±356. Pandolf, K.B., Sawka, M.N., Gonzalez, R.R., 1988. Human Performance Physiology and Environmental Medicine at Terrestrial Extremes. Benchmark Press, Inc, Indianapolis.
Pugh, L.G.C., Edholm, O.G., 1955. The physiology of channel swimmers. Lancet II, 761±768. Pugh, L.G.C., Edholm, O.G., Fox, R.H., Wol, H.S., Hervey, G.R., Hammond, W.H., Tanner, J.M., Whitehouse, R.H., 1960. A physiological study of channel swimming. Clin. Sci. 19, 257±273. Wyndham, D.H., Morrison, J.F., Ward, J.S., Bredell, G.A.G., Von Rahden, M.J.E., Holdsworth, L.D., Wenzel, H.G., Munro, A., 1964. Physiological reactions to cold of Bushmen, Bantu and Caucasian males. J. Appl. Physiol. 19, 868±876.
www.elsevier.com/locate/jtherbio
Eects of long-distance swimming in cold water on temperature, blood pressure and stress hormones in winter swimmers P. Huttunen a,*, N.G. Lando b, V.A. Meshtsheryakov b, V.A. Lyutov b a Department of Forensic Medicine, University of Oulu, PO Box 5000, FIN-90410 Oulu, Finland Moscow Regional Centre `Human Adaptation to Extreme Conditions in Water Surroundings', Moscow, Russia
b
Abstract Long-distance swimmers swam in 10±148C water on four days. Responses in blood pressure and rectal temperature were determined every day, and hormonal responses on the third day. Swimming time lengthened with the days and diastolic blood pressure after swimming was signi®cantly lower on the fourth day than on the ®rst day. In rectal temperatures there were great individual variations. Noradrenaline was elevated more in the thin swimmers. A lesser rise in diastolic blood pressure and the longer duration of swimming on the fourth day may point to habituation to the cold. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Marathon cold water swimmers; Repeated immersion; Cold tolerance; NA; A; Cortisol
1. Introduction Humans respond to acute cold exposure with two major physiological adjustments, vasoconstriction and thermogenesis. These responses are aected by factors such as the sex, age, subcutaneous body fat and ®tness of the subject. Although chronic or repeated cold exposures produce adaptation of physiological responses to acute cold, the advantage of such adaptation with regard to the ability to maintain thermal balance under cold conditions is relatively small (Pandolf et al., 1988). We examine here the physiological responses of long-distance swimmers to repeated, prolonged swimming in cold water. The purpose was to get further information about the dierences that exist between
* Corresponding author. Fax: 358-8-330687. E-mail address: pirkko.huttunen@oulu.® (P. Huttunen).
individuals in their maintenance of thermal balance under prolonged immersion. Individual characteristics may increase or reduce the risk of adverse reactions. Long-distance swimmers were from the Moscow regional centre, where the possibilities of surviving accidents in cold water are studied. The swimmers have practiced long-distance swimming in cold water in the Bering Straits, Lake Baikal and in Severnaja Zemlja, but their physiological responses have not been documented earlier.
2. Material and methods Russian long-distance swimmers (6 males and 1 female) had a relay swim in Finland at the beginning of June. Physical characteristics of swimmers are presented in Table 1. The distance of the swim was about 50 kilometers and swimming was performed by day on
0306-4565/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 6 - 4 5 6 5 ( 9 9 ) 0 0 0 5 9 - 5
172
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174
Table 1 Physical characteristics of swimmers Skin fold thickness (mm) Subject
Sex
Age (years)
BMIa
Subscapular
Abdominal
Suprailiac
1. 2. 3. 4. 5. 6. 7. Mean2 SD
Male Male Male Male Male Male Female
59 38 44 51 39 51 26 44.0 210.8
33.9 30.8 27.7 26.5 24.7 23.6 23.0 27.123.9
25 15 15 15 10 5 5 12.8 26.9
20 15 10 10 10 5 5 10.7 25.3
20 15 15 15 10 5 20 14.225.3
a
BMI=body mass index (weight (kg)/height2 (m)).
four consecutive days. The swimmers swam on average two times per day at water temperatures varying from 108C to 148C. The responses induced by the ®rst swim of each day were determined. The duration of the ®rst swim on each day is presented in Table 2. The eects of the ®rst swim on blood pressure and rectal temperature were determined daily, but stress hormones such as noradrenaline, adrenaline and cortisol were determined only on the third day, since the swimmers refused to give more blood samples. Venous blood sample was taken before swimming in the morning 9:00±9:30 a.m. and after the ®rst swim. Plasma catecholamines were puri®ed by an Al2O3 with 3,4-dihydroxybenzylamine hydrobromide (Sigma, USA) as an internal standard and they were measured by high-performance liquid chromatography with an electrochemical detector (ESA Coulochem, model 5100 A, USA). Serum cortisol was determined by a radioimmunoassay method (Orion Diagnostica, Espoo Finland). The statistical analysis was performed by repeated
measures ANOVA or paired t-test and correlation with the Pearson correlation coecient. 3. Results On the ®rst and second day the duration of swimming correlated with skin-fold thickness in the subscapular area of swimmers (r = 0.802 and r = 0.844, P < 0.05). With the exception of one swimmer (case 5) the duration of swimming increased signi®cantly with the days (from 25.5 min to 39.0 min, F (3,15) 5.724, P = 0.011) (Table 2). There were no signi®cant changes in systolic blood pressure after swims, but diastolic blood pressure on the fourth day was signi®cantly lower than on the ®rst day (P < 0.05) (Table 3). Blood pressure of one swimmer (case 5) could not be measured because of vigorous shivering after swimming. There was a great individual variability in rectal temperatures measured after swims. In one person
Table 2 Duration of the ®rst swim for each day (min) and rectal temperature of swimmers after the swim (8C). Number of swims per day is presented in parenthesis First day
Second day
Third day
Fourth day
Subject
Min
8C
Min
8C
Min
8C
Min
8C
1. 2. 3. 4. 5. 6. 7. Mean2 SD
40 (2) 20 (2) 30 (2) 25 (2) 30 (1) 20 (2) 18 (2) 26.1 27.7
NMa 38.0 36.0 NM 35.8 37.3 NM 36.721.0
50 (2) 30 (2) 42 (2) 25 (2) 16 (2) 22 (3) 20 (3) 29.2 212.4
NM 38.0 36.2 NM 37.0 36.6 36.4 36.82 0.7
36 (2) 26 (2) 42 (2) 30 (2) 18 (2) 32 (2) 20 (2) 29.128.5
NM 38.0 35.6 NM 37.1 36.2 36.6 36.72 0.9
60 (2) 30 (2) 60 (2) 32 (2) 20 (2) 32 (2) 20 (2) 36.2216.9
NM 37.9 NM NM NM 35.4 35.4 36.2 21.4
a
NM=no measurements.
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174 Table 3 Blood pressure measured daily after the ®rst swima Blood pressure (mm/Hg) Day
Systolic
Diastolic
First Second Third Fourth
167.5221.3 174.1220.1 172.1221.9 164.3218.1
102.52 4.1 96.62 10.8 102.52 21.1 88.52 6.8b
a
Results are presented as mean 2SD, n = 6. P < 0.05 compared to the value on the ®rst day (paired ttest). b
(case 2) rectal temparature was high (388C) and it did not change with the days, whereas in one subject (case 3) it dropped to under 368C on the third day and in two other swimmers (cases 6 and 7) on the fourth day. In one person (case 5) rectal temperature fell markedly during immersion for 30 min on the ®rst day, but immersion for 16±18 min during the next days did not change it (Table 2). Two swimmers refused measurements of rectal temperature (cases 1 and 4). Swimming signi®cantly increased plasma NA levels (P = 0.01) and the smaller the body mass index was, the greater was this rise (r=ÿ0.915, P < 0.05). There were no changes in plasma adrenaline levels, while serum cortisol increased on average about 70% (P = 0.070) (Table 4).
4. Discussion Although the results show that there were great dierences between individuals in the responses to the
173
cold, a smaller diastolic blood pressure after swimming on the fourth day and the longer duration of swimming may point to habituation to the cold water in six swimmers out of seven. A greater drop in rectal temperature in three subjects without uncomfortable shivering on the two last days may point also to hypothermic adaptation in these swimmers. In one case fatness may have kept the rectal temperature high (388C). A rather great rise in serum cortisol level (about 70%) also suggests highly elevated metabolism in respect of carbohydrates. Observations on channel swimmers in the 1950s showed that rectal temperatures during ocean swimming ranged between 348C and 38.38C for exposures of nearly 18 h in water as cold as 168C (Pugh et al., 1960). Swimming exercise acclerated the drop in rectal temperature in thin subjects, whereas fat subjects maintained their rectal temperature (Pugh and Edholm, 1955). Rectal temperature after long-distance swimming in cold water has been shown to correlate with subcutaneous fat thickness (Dulac et al., 1987). Subcutaneous and deep body fat are major components determining the rate of internal heat transfer during immersion in water. The metabolic response to a fall in skin temperature in cold air has also been found to raise the rectal temperature in Caucasian males (Wyndham et al., 1964). Noradrenaline levels were elevated more in the thin swimmers. Noradrenaline controls vasoconstriction, and is involved together with cortisol in energy metabolism. Plasma adrenaline levels did not change, which suggests no cold-induced mental tension in the swimmers. Results show that there are great individual variations in the maintenance of core temperature under prolonged immersion and fatness is an essential requirement for this, but not the only one.
Table 4 Plasma NA and A (nmol/l) and serum cortisol (mmol/l) levels before and after the ®rst swim on the third day NA
A
Cortisol
Subjectc
BMId
Before
After
Before
After
Before
After
2. 3. 4. 5. 6. Mean2 SD
30.8 27.7 26.5 24.7 23.6
2.85 2.89 2.44 2.95 3.35 2.84 20.35
7.40 11.90 13.84 14.78 23.12 14.2125.73a
1.74 2.78 1.34 0.25 0.66 1.352 0.98
0.66 1.32 1.14 0.49 1.25 0.972 0.37
353 284 292 433 247 3222 73
586 316 394 600 786 5362 186b
a
P = 0.01. P = 0.70 compared to the corresponding value before swimming (paired t-test). c Two swimmers refused blood sampling (cases 1 and 7). d BMI=body mass index. b
174
P. Huttunen et al. / Journal of Thermal Biology 25 (2000) 171±174
References Dulac, S., Quirion, A., DeCarufel, D., LeBlanc, J., Jobin, M., Cote, J., Brisson, G.R., Lavoie, J.M., Diamond, P., 1987. Metabolic and hormonal responses to longdistance swimming in cold water. Int. J. Sports Med. 8, 352±356. Pandolf, K.B., Sawka, M.N., Gonzalez, R.R., 1988. Human Performance Physiology and Environmental Medicine at Terrestrial Extremes. Benchmark Press, Inc, Indianapolis.
Pugh, L.G.C., Edholm, O.G., 1955. The physiology of channel swimmers. Lancet II, 761±768. Pugh, L.G.C., Edholm, O.G., Fox, R.H., Wol, H.S., Hervey, G.R., Hammond, W.H., Tanner, J.M., Whitehouse, R.H., 1960. A physiological study of channel swimming. Clin. Sci. 19, 257±273. Wyndham, D.H., Morrison, J.F., Ward, J.S., Bredell, G.A.G., Von Rahden, M.J.E., Holdsworth, L.D., Wenzel, H.G., Munro, A., 1964. Physiological reactions to cold of Bushmen, Bantu and Caucasian males. J. Appl. Physiol. 19, 868±876.