Exercise In Cold Water Research Articles

The Effect of Cold-Water Swimming on Energy Metabolism, Dynamics, and Mitochondrial Biogenesis in the Muscles of Aging Rats.

Our study aimed to explore the potential positive effects of cold water exercise on mitochondrial biogenesis and muscle energy metabolism in aging rats. The study involved 32 male and 32 female rats aged 15 months, randomly assigned to control sedentary animals, animals training in cold water at 5 ± 2 °C, or animals training in water at thermal comfort temperature (36 ± 2 °C). The rats underwent swimming training for nine weeks, gradually increasing the duration of the sessions from 2 min to 4 min per day, five days a week. The results demonstrated that swimming in thermally comfortable water improved the energy metabolism of aging rat muscles (increased metabolic rates expressed as increased ATP, ADP concentration, TAN (total adenine nucleotide) and AEC (adenylate energy charge value)) and increased mRNA and protein expression of fusion regulatory proteins. Similarly, cold-water swimming improved muscle energy metabolism in aging rats, as shown by an increase in muscle energy metabolites and enhanced mitochondrial biogenesis and dynamics. It can be concluded that the additive effect of daily activity in cold water influenced both an increase in the rate of energy metabolism in the muscles of the studied animals and an intensification of mitochondrial biogenesis and dynamics (related to fusion and fragmentation processes). Daily activity in warm water also resulted in an increase in the rate of energy metabolism in muscles, but at the same time did not cause significant changes in mitochondrial dynamics.

No Changes In Appetite Stimulating Hormones Following Swimming And Cycling Exercise Interventions

Swimming is a favorable and ideal modality of exercise for individuals with obesity and arthritis as it encompasses a minimal weight-bearing stress and a reduced heat load. However, the available evidence indicates that regular swimming may not be effective in reducing body weight and body fatness. A current hypothesis is that exercise in cold water somehow stimulates appetite. PURPOSE: We determined the effect of swimming exercise training on fasting concentrations of ghrelin, insulin, leptin, and peptide YY in obese individuals with osteoarthritis. Cycling training was included as a non-weight bearing land-based comparison group. METHODS: Thirty-nine obese participants with osteoarthritis (age=59±1 years, BMI=33±1 kg/m2) were randomly assigned to 12 weeks of supervised swimming training (N=19) or cycling training (N=20). In the initial few weeks, participants exercised for 20-30 minutes/day, 3 days/week, at an exercise intensity of 40-50% of heart rate reserve (HRR). Subsequently, the intensity and duration of exercise were progressively increased to 40-45 minutes/day, 3 days/week, at an intensity of 60-70% of HRR. Fasting blood samples were analyzed for ghrelin, insulin, leptin, and peptide YY concentrations using ELISAs. RESULTS: There were no group differences in body weight, BMI, or appetite stimulating hormones prior to the exercise interventions. Fasting plasma concentrations of ghrelin (37±8 vs. 42±11 pg/ml), insulin (1,176±424 vs. 1,179±442 pg/ml), leptin (20,200±2,891 vs. 16,617±2,734 pg/ml), and peptide YY (51±6 vs. 54±7 pg/ml) did not change with the swimming exercise intervention (all p>0.05). Similarly, cycling exercise had no effect on ghrelin (36±10 vs. 44±8 pg/ml), insulin (978±321 vs. 964±311 pg/ml), leptin (29,261±5,438 vs. 26,308±4,771 pg/ml), or peptide YY (58±15 vs. 63±16 pg/ml) concentrations (all p>0.05). CONCLUSIONS: Our present results indicate that fasting levels of appetite stimulating hormones did not change with 12 weeks of swimming exercise intervention in obese participants with osteoarthritis and that there were no group differences in changes in these hormones between swimming and cycling exercise interventions.

The Effects of Swimming Training in Cold Water on Antioxidant Enzyme Activity and Lipid Peroxidation in Erythrocytes of Male and Female Aged Rats.

The aim of this study was to verify whether eight-week-long swimming exercise training would evaluate the level of selected indicators of the pro-oxidant/antioxidant status in response to cold water in comparison with swimming under thermoneutral conditions in sedentary male and female elderly rats. The exercise-trained groups swam four min/day and five days a week during eight weeks of housing. Exercise was performed by swimming in glass tanks containing tap water maintained according to group at 5 °C and 36 °C. At the end of treatment (48 h after the last session), all rats were anaesthetized. The level of chosen biomarkers of oxidative stress and antioxidant enzyme activity was determined in the red blood cells and plasma. The results of study show that female rats seem to be better adapted to changing thermal conditions of the environment, developing not only morphological, but also antioxidant, defense mechanisms, mainly in the form of increased erythrocyte superoxide dismutase (SOD) activity and glutathione (GSH) concentration to restore the pro-oxidant/oxidant balance of the organism. Significantly higher concentrations of GSH were observed in the female rats of the group swimming in cold water (by 15.4% compared to the control group and by 20.5% in relation to the group of female rats swimming at 36 °C). In the group exposed to swimming training exercise in cold water, a significantly higher activity of SOD1 (by 13.4%) was found compared to the control group. On the other hand, the organs of ageing male rats show a reduced capacity to increase the metabolic response to low temperatures compared to female ones. In addition, it was demonstrated that cold exposure leads to an increase in lipid peroxidation in tissues. On the other hand, the repeated exposure to low levels of oxidative stress may result in some adaptive changes in organisms that help them to resist stress-induced damage.

Effects of exercise in the cold on Ghrelin, PYY, and food intake in overweight adults.

Exercise in cold water has been shown to simulate postexercise energy intake (EI) in normal-weight individuals. However, the effect of cold exercise on EI in overweight individuals has yet to be examined. The present study investigated the effect of brisk walking in a cold (8°C) and neutral (20°C) environment on postexercise EI and appetite hormone responses. Sixteen overweight participants (10 men and six women; age, 50.1 ± 11.6 yr; body mass index, 28.9 ± 4.2 kg·m) completed a 45-min treadmill walk at 8°C and 20°C in a randomized counterbalanced design. Participants were presented with an ad libitum buffet meal 45 min after exercise, and EI was covertly measured. Skin and rectal temperature were monitored throughout exercise and for 30 min after exercise, and concentrations of the appetite hormones total ghrelin, acylated ghrelin, and total peptide YY were assessed before and after exercise and before and after meal. EI was significantly greater after exercise in the cold (1299 ± 657 kcal (mean ± SD)) compared with that after exercise in the neutral environment (1172 ± 537 kcal (mean ± SD)) (P < 0.05). The change in the acylated ghrelin concentrations and the acylated ghrelin AUC values were significantly greater during walking in the cold versus those during walking in the neutral condition (P < 0.05). These findings show that in overweight individuals, exercise in the cold stimulates postexercise EI to a greater extent than exercise in a neutral environment.

Risk factors for immersion pulmonary edema: hyperoxia does not attenuate pulmonary hypertension associated with cold water-immersed prone exercise at 4.7 ATA

Hyperoxia has been shown to attenuate the increase in pulmonary artery (PA) pressure associated with immersed exercise in thermoneutral water, which could serve as a possible preventive strategy for the development of immersion pulmonary edema (IPE). We tested the hypothesis that the same is true during exercise in cold water. Six healthy volunteers instrumented with arterial and PA catheters were studied during two 16-min exercise trials during prone immersion in cold water (19.9-20.9°C) in normoxia [0.21 atmospheres absolute (ATA)] and hyperoxia (1.75 ATA) at 4.7 ATA. Heart rate (HR), Fick cardiac output (CO), mean arterial pressure (MAP), pulmonary artery pressure (PAP), pulmonary artery wedge pressure (PAWP), central venous pressure (CVP), arterial and venous blood gases, and ventilatory parameters were measured both early (E, 5-6 min) and late (L, 15-16 min) in exercise. During exercise at an average oxygen consumption rate (Vo(2)) of 2.38 l/min, [corrected] CO, CVP, and pulmonary vascular resistance were not affected by inspired (Vo(2)) [corrected] or exercise duration. Minute ventilation (Ve), alveolar ventilation (Va), and ventilation frequency (f) were significantly lower in hyperoxia compared with normoxia (mean ± SD: Ve 58.8 ± 8.0 vs. 65.1 ± 9.2, P = 0.003; Va 40.2 ± 5.4 vs. 44.2 ± 9.0, P = 0.01; f 25.4 ± 5.4 vs. 27.2 ± 4.2, P = 0.04). Mixed venous pH was lower in hyperoxia compared with normoxia (7.17 ± 0.07 vs. 7.20 ± 0.07), and this result was significant early in exercise (P = 0.002). There was no difference in mean PAP (MPAP: 28.28 ± 8.1 and 29.09 ± 14.3 mmHg) or PAWP (18.0 ± 7.6 and 18.7 ± 8.7 mmHg) between normoxia and hyperoxia, respectively. PAWP decreased from early to late exercise in hyperoxia (P = 0.002). These results suggest that the increase in pulmonary vascular pressures associated with cold water immersion is not attenuated with hyperoxia.

Effects of head and body cooling on hemodynamics during immersed prone exercise at 1 ATA

Immersion pulmonary edema (IPE) is a condition with sudden onset in divers and swimmers suspected to be due to pulmonary arterial or venous hypertension induced by exercise in cold water, although it does occur even with adequate thermal protection. We tested the hypothesis that cold head immersion could facilitate IPE via a reflex rise in pulmonary vascular pressure due solely to cooling of the head. Ten volunteers were instrumented with ECG and radial and pulmonary artery catheters and studied at 1 atm absolute (ATA) during dry and immersed rest and exercise in thermoneutral (29-31 degrees C) and cold (18-20 degrees C) water. A head tent varied the temperature of the water surrounding the head independently of the trunk and limbs. Heart rate, Fick cardiac output (CO), mean arterial pressure (MAP), mean pulmonary artery pressure (MPAP), pulmonary artery wedge pressure (PAWP), and central venous pressure (CVP) were measured. MPAP, PAWP, and CO were significantly higher in cold pool water (P < or = 0.004). Resting MPAP and PAWP values (means +/- SD) were 20 +/- 2.9/13 +/- 3.9 (cold body/cold head), 21 +/- 3.1/14 +/- 5.2 (cold/warm), 14 +/- 1.5/10 +/- 2.2 (warm/warm), and 15 +/- 1.6/10 +/- 2.6 mmHg (warm/cold). Exercise values were higher; cold body immersion augmented the rise in MPAP during exercise. MAP increased during immersion, especially in cold water (P < 0.0001). Except for a transient additive effect on MAP and MPAP during rapid head cooling, cold water on the head had no effect on vascular pressures. The results support a hemodynamic cause for IPE mediated in part by cooling of the trunk and extremities. This does not support the use of increased head insulation to prevent IPE.

Evaluation of two cold thermoregulatory models for prediction of core temperature during exercise in cold water

Cold thermoregulatory models (CTM) have primarily been developed to predict core temperature (T(core)) responses during sedentary immersion. Few studies have examined their efficacy to predict T(core) during exercise cold exposure. The purpose of this study was to compare observed T(core) responses during exercise in cold water with the predicted T(core) from a three-cylinder (3-CTM) and a six-cylinder (6-CTM) model, adjusted to include heat production from exercise. A matrix of two metabolic rates (0.44 and 0.88 m/s walking), two water temperatures (10 and 15 degrees C), and two immersion depths (chest and waist) were used to elicit different rates of T(core) changes. Root mean square deviation (RMSD) and nonparametric Bland-Altman tests were used to test for acceptable model predictions. Using the RMSD criterion, the 3-CTM did not fit the observed data in any trial, whereas the 6-CTM fit the data (RMSD less than standard deviation) in four of eight trials. In general, the 3-CTM predicted a rapid decline in core temperature followed by a plateau. For the 6-CTM, the predicted T(core) appeared relatively tight during the early part of immersion, but was much lower during the latter portions of immersion, accounting for the nonagreement between RMSD and SD values. The 6-CTM was rerun with no adjustment for exercise metabolism, and core temperature and heat loss predictions were tighter. In summary, this study demonstrated that both thermoregulatory models designed for sedentary cold exposure, currently, cannot be extended for use during partial immersion exercise in cold water. Algorithms need to be developed to better predict heat loss during exercise in cold water.

Increased Caloric Intake Soon after Exercise in Cold Water

We examined the acute effect of cold-water temperature on post-exercise energy intake (EI) for 1 h. In a randomized, crossover design, 11 men (25.6 +/- 5 y) exercised for 45 min on a submersed cycle ergometer at 60 +/- 2% VO2max in 33 degrees C (neutral) and 20 degrees (cold) water temperatures, and also rested for 45 min (control). Energy expenditure (EE) was determined using indirect calorimetry before, during, and after each condition. Following exercise or rest, subjects had free access to a standard assortment of food items of known caloric value. EE was similar for the cold and neutral water conditions, averaging 505 +/- 22 (+/- standard deviation) and 517 +/- 42 kcal, respectively (P = NS). EI after the cold condition averaged 877 +/- 457 kcal, 44% and 41% higher (P < 0.05) than for the neutral and resting conditions, respectively. Cold-water temperature thus stimulated post-exercise EI. Water temperature warrants consideration in aquatic programs designed for weight loss.

The Effects of Swimming Training on Lymphocyte Proliferation and ROS Production in Spleen Lymphocytes of BALB/c Mice

Background: Aerobic training can be defined as any physical exercise that increases the heart rate and enhances the body's intake of oxygen long enough to benefit the condition of body. Running, cycling, and swimming are examples of aerobic activities. This type of exercise optimises immune functions. Recently several experimental findings suggested that the regular swimming training increase immune response, but there have been very few reports which compare warm water exercise with cold water exercise in spleen lymphocytes. Methods: This study was designed to examine the effects of regular swimming training on Index, the number of lymphocytes, proliferative activity and production of reactive oxygen species (ROS) by splenocytes in BALB/c mice. Thirty six mice (6 week old) were performed 10 weeks of regular swimming training and they were divided into 6 groups according to the regular swimming training (CRG: control resting group, CEG: control exercise group, WRG: warm water trained resting group, WEG: warm water trained exercise group, CORG: cold water trained resting group, COEG: cold water exercise group). Analytical items were weight change, spleen index, the number of lymphocytes, proliferative activity and production of ROS. All data were expressed as mean and standard deviation by using SPSS package program (ver. 10.0). Results: The swimming training significantly decreased body weight, and increased spleen index, the number of lymphocytes and proliferative activity in the presence or absence of Con A and LPS added conditions. For the WRG and CORG, the quantity of ROS from splenocytes was higher than CRG, whereas, ROS by spleen lymphocytes was lower following 90 min acute exercise stress. Conclusion: These results suggested that the swimming training not only increases the number of lymphocytes but also increases proliferative activity by splenocytes in vitro. (Immune Network 2002;2(2):96-101)

WHOLE-BODY ANTI-EXPOSURE SUITS REDUCE HEAT LOSS DURING ARM EXERCISE AND PROGRESSIVE IMMERSION IN COLD WATER 550

This study evaluated the effectiveness of three whole-body anti-exposure suits (AES) in maintaining body temperatures during arm exercise in cold water(7.5°C). Male subjects (n = 14) were monitored for rectal (Tre), chest (Tch), arm (Tar), thigh (Tth), calf(Tca), index finger (Tfi), and big toe (Tto) temperatures during randomly ordered trials of fire resistant coverall (CON), Marine Corps immersion suit (MARCOR), Naval Clothing and Textile suit (NAVCLO), and MultiFabs Survival suit (MULFAB). Coveralls served as undergarment for AES. Water immersion occurred progressively (20 min to knees, 20 min to waist, and up to 40 min to midchest). During each 10 min interval, subjects rested (2 min), performed a pipe patching task (6 min), and held 25 lb over head (2 min). Maximum exposure time was 80 min. Subjects were able to stay significantly longer (p<0.05) in cold water wearing MULFAB (76 min), NAVCLO(80 min), and MARCOR (74 min) compared to CON (47 min). Analysis of covariance(adjusted for preimmersion values) showed no difference in final Tre([horizontal bar over]X = 36.8°C) and Tfi ([horizontal bar over]X = 20.8°C) among AES and CON. AES Tch ([horizontal bar over]Xs = 35.4°C) and Tar ([horizontal bar over]Xs = 34.7°C) were higher (p < 0.05) compared to CON (29.9°C, 27.5°C, respectively). Final Tth for MULFAB (19.4°C) was higher (p < 0.05) than NAVCLO (16.0°C) and MARCOR (15.2°C) which were higher than CON (11.5°C). Final Tca for MULFAB (14.7°C) and NAVCLO(13.6°C) were higher than MARCOR (11.2°C) and CON (10.4°C). Final Tca for MARCOR (17.3°C) was higher than NAVCLO (13.2°C), MULFAB(11.6°C), and CON (12.1°C). Our findings indicate that during arm exercise and progressive immersion in cold water that MULFAB followed by NAVCLO and MARCOR provided the best maintenance of body temperatures.

Metabolic and thermal adaptations from endurance training in hot or cold water

Metabolic and thermal adaptations resulting from endurance training in hot vs. cold water were compared. It was hypothesized that training in hot water would have greater effects on muscle glycogen use and blood lactate accumulation during exercise than training in cold water. Eighteen men exercised at 60% of maximal oxygen uptake while immersed in hot (n = 9) or cold water (n = 9) for 1 h, 5 days/wk, for 8 wk. Training in hot water (35 degrees C) potentiated body temperature increases during exercise, and training in cold water (20 degrees C) blunted body temperature increases during exercise. Before and after training, cardiorespiratory and thermoregulatory responses and muscle glycogen and blood lactate changes were assessed during a 1-h exercise trial in hot water and, on a separate day using the same intensity, in cold water. Oxygen uptake was similar for all trials, averaging 2.0 +/- 0.1 l/min. It was observed that 1) training reduced glycogen use and lactate accumulation during exercise, with no difference between cold and hot water training groups in the magnitude of this effect; 2) lactate accumulation during exercise was the same in hot water as in cold water; and 3) skin temperature decreased more rapidly during cold-water exercise after than before training, with no difference between cold and hot water training groups in the magnitude of this effect. Thus, exercise-induced body temperature increases are not an important stimulus for glycogen-sparing effects and blunted lactate accumulation associated with endurance training.

Additive effects of caffeine and cold water during submaximal leg exercise

Ten males exercised for 55 min at 1.5 W.kg-1 in 28 degrees C and 18 degrees C water to determine whether cold water plus caffeine (CF) ingestion had additive effects on energy production or core temperature. Two immersions were done at each water temperature, once with CF (5 mg.kg-1) and once with placebo (PL). Cold water alone (28 PL vs 18 PL) decreased free fatty acid (FFA, -13 +/- 8%) and glycerol (-37 +/- 15%) and increased lactate (18 +/- 12%), VO2 (11 +/- 3%), and minute ventilation (VE, 8 +/- 4%) but did not change glucose, heart rate (HR), respiratory exchange ratio (RER), or rectal temperature. CF alone (28 PL vs 28 CF) increased FFA (52 +/- 18%), glycerol (14 +/- 8%), lactate (28 +/- 10%), VO2 (9 +/- 3%), VE (7 +/- 5%), HR (4 +/- 1%), and rectal temperature (2 +/- 0.4%) but did not alter RER. Significant additive effects of cold water + CF (28 PL vs 18 CF) were noted for FFA, glycerol, lactate, VO2, and VE but not for RER and rectal temperature. These findings indicate that additive effects of cold water + CF alter substrate availability and increase energy production, but without a change in lipid utilization or core temperature. It may be concluded that use of CF during exercise in cold water has no physiological benefit.

Effect of swimming to exhaustion, at low temperatures, on serum Zn, Cu, Mg and Ca in rats

In order to study the response of plasma trace minerals during exercise in cold water at varying temperatures, three groups of ten male Wistar rats each were forced to swim until exhaustion in water at different constant temperatures (10, 20 and 32°C), while another 3 groups were kept at rest in water at the same temperatures and another group at rest out of the water, at room temperature (21°C). Rectal temperature (RT) was measured before and after the exercise. Samples of arterial blood were obtained under anaesthesia (pentobarbital) from the abdominal aorta after the exercise, and serum concentrations of Cu, Zn, Mg and Ca were determined by flame atomic absorption spectrophotometry (FAAS). The swimming time (ST) decreased in cold water, the values obtained at 10 and 20°C being 3.3% and 8.5%, respectively, of those observed at 32°C. The RT of the animals swimming at 32°C was 32.5 ± 1.8°C (mean ± SD) and fell to 25.0 ± 2.0 and to 19.1 ± 1.5°C in those swimming, respectively, at 20 and 10°C. The concentrations of Mg, Cu and Ca were significantly higher ( +50%, +36% and +7%, respectively) in animals subjected to exercise with respect to the control groups in water, although there were no differences among the three groups. On the contrary, Zn rose progressively with the increase of WT ( +32% at 10°C, +60% at 20°C and +76% at 32°C). The present data show that exercise in cold water causes in rats: 1) a significant decrease in the swimming time; 2) an increase in serum Ca, Cu and Mg not related to WT or RT and 3) an increase in serum Zn which appears to be related to WT and/or to RT.

Temperature regulation during upper body exercise

This paper will consider human thermoregulatory response differences between upper and lower body exercise. In addition, the thermoregulatory problems of spinal cord injured individuals are examined. For able-bodied individuals, the rise in core temperature is independent of the skeletal muscle mass employed and dependent upon the metabolic rate during exercise. The avenues of heat exchange, however, are different for individuals performing upper body as opposed to lower body exercise. During upper body exercise, there is a greater dry heat loss from the torso; however, no additional heat loss (as compared to lower body exercise) occurs from the exercising arms. If an individual performs upper body exercise in cold water, there will be a greater heat loss and susceptibility to hypothermia than during lower body exercise. A spinal cord injury impairs one's ability to thermoregulate because of: (a) loss of autonomic nervous system control for vasomotor and sudomotor responses in the areas of the insensate skin; (b) a reduced thermoregulatory effector response for a given core temperature; and (c) a loss of skeletal muscle pump activity from the paralyzed limbs. As a result, a spinal cord injured person has a reduced ability to tolerate thermal extremes and to perform aerobic exercise. Surprisingly little research, however, has focused on the ability of the disabled to thermoregulate during exercise. Recent data suggest that rectal temperature measurements may underestimate the thermal burden imposed on wheelchair athletes during competition.

Potassium uptake in muscle during paramyotonic weakness

Previous studies have suggested that an abnormal release of potassium from muscle may accompany attacks of paramyotonic weakness. We investigated 3 patients with paramyotonia congenita before and after the induction of forearm muscle weakness by exercise in cold water. Two of these patients had paralysis periodica paramyotonica and the 3rd had paramyotonia congenita. At the time of paramyotonic weakness there was a marked increase in the arterialized-venous concentration difference of potassium across forearm muscle. This indicated a significant uptake of potassium by forearm muscle in all 3 patients. Normal controls showed a slight release of potassium both at rest and after exercise in cold water. These results suggest that (1) the sodium-potassium pump of the muscle fiber is operating efficiently during paramyotonic weakness; and (2) there is a different mechanism responsible for the generalized weakness that occurs in hyperkalemic periodic paralysis.

Tissue heat transfer in water: lessons from the Korean divers.

The factors which influence tissue heat transfer and temperature gradients from body core to skin surface are reviewed in the context of studies on Korean diving women. The resistance to heat transfer imposed by resting muscle is shown to be 2-3 times as great as that imposed by overlying fat and skin. However, exercising muscle imposes very little resistance to heat flux because of the increase in convective heat transfer. Accordingly, the limiting resistance to heat flow is shifted to subcutaneous fat and skin during exercise in cold water. Hypothetical examples are given of how important the subcutaneous fat can be in maintaining a high core-to-water temperature gradient in cold water and the same validated by examples from the literature. Last, hypothetical examples are given of the role cutaneous blood flow must play in controlling heat flux and temperature gradients across the subcutaneous fat layer.

Human thermal responses during leg-only exercise in cold water.

1. Exercise during immersion in cold water has been reported by several authors to accelerate the rate of fall of core temperature when compared with rates seen during static immersion. The nature of the exercise performed, however, has always been whole-body in nature. 2. In the present investigation fifteen subjects performed leg exercise throughout a 40 min head-out immersion in water at 15 degrees C. The responses obtained were compared with those seen when the subjects performed an identical static immersion. 3. Aural and rectal temperatures were found to fall by greater amounts during static immersion. 4. It is concluded that 'the type of exercise performed' should be included in the list of factors which affect core temperature during cold water immersion.

Perceptual and physiological responses during exercise in cool and cold water.

This investigation examined the interaction of exposure to cold water stress with both perceived exertion and thermal sensation during exercise. Eight male volunteers performed arm, leg, and combined arm and leg exercise for 45 min. in water at 20 and 26 degrees C. Exercise was performed at a low (n = 7) and a high (n = 8) intensity relative to the ergometer specific peak oxygen uptake (VO2 peak). In general, percent VO2 peak did not differ between types of exercise in either 20 or 26 degrees C water. During low intensity exercise when power output was matched across water temperatures (Tw), percent VO2 peak was greater in 20 degrees C water (52%) compared to 26 degrees C water (42%). Ratings of perceived exertion (RPE) did not differ between Tw. During high intensity exercise when percent VO2 peak was matched across Tw, RPE was lower during exercise in 20 degrees C compared to 26 degrees C. Multiple correlation analyses comparing both final RPE and thermal sensation (TS) with physiological and thermal measures were performed across type of exercise and Tw. RPE was moderately correlated with heart rate (r = 0.68) and ventilation (r = 0.61), whereas very slight relationships were established with TS (r = 0.16), skin and rectal temperatures (r = 0.10 and r = 0.20). TS was moderately correlated with skin and rectal temperatures (r = 0.64 and r = 0.73), whereas low correlations existed between TS and both heart rate (r = 0.32) and ventilation (r = -0.12). These data suggest that the change in oxygen uptake associated with exercise in cold water does not add to the over-all perception of exertion. This perception appears to be related to cardiopulmonary variables rather than thermal measures, whereas thermal sensation is related to thermal measures and not cardiopulmonary variables.

The Chair of Physic in Trinity College, Dublin, 1662 to 1962.

Previous studies have suggested that an abnormal release of potassium from muscle may accompany attacks of paramyotonic weakness. We investigated 3 patients with paramyotonia congenita before and after the induction of forearm muscle weakness by exercise in cold water. Two of these patients had paralysis periodica paramyotonica and the 3rd had paramyotonia congenita. At the time of paramyotonic weakness there was a marked increase in the arterialized-venous concentration difference of potassium across forearm muscle. This indicated a significant uptake of potassium by forearm muscle in all 3 patients. Normal controls showed a slight release of potassium both at rest and after exercise in cold water. These results suggest that (1) the sodium-potassium pump of the muscle fiber is operating efficiently during paramyotonic weakness; and (2) there is a different mechanism responsible for the generalized weakness that occurs in hyperkalemic periodic paralysis.