Physiological adjustments of facial cooling during exercise.

Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% VO2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10 degrees C, 4.6 M.S-1). Facial cooling at the end of greated maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (VO2 max), maximal heart rate (HR max), rectal temperature (Tre), work load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.

Metabolic and hormonal responses during exercise at 20 degrees, 0 degrees and -20 degrees C.

This study was designed to clarify the effects of cold air exposure on metabolic and hormonal responses during progressive incremental exercise. Eight healthy males volunteered for the study. Informed consent was obtained from every participant. The following protocol was administered to each subject on three occasions in a climatic chamber in which the temperature was 20 degrees, 0 degree or -20 degrees C with relative humidity at 60% +/- 1%. Exercise tests were conducted on an electrically braked ergocycle, and consisted of a progressive incremental maximal exercise. Respiratory parameters were continuously monitored by an automated open-circuit sampling system. Exercise blood lactate (LA), free fatty acids (FFA), glucose levels, bicarbonate concentration (HCO-3), acid-base balance, plasma epinephrine (E) and norepinephrine (NE) were determined from venous blood samples obtained through an indwelling brachial catheter. Maximal oxygen uptake was significantly different between conditions: 72.0 +/- 5.4 ml kg-1 min-1 at 20 degrees C; 68.9 +/- 5.1 ml kg-1 min-1 at 0 degree C and 68.5 +/- 4.6 ml kg-1 min-1 at -20 degrees C. Workload, time to exhaustion, glucose levels and rectal temperature decreased significantly at -20 degrees C. Catecholamines and lactate values were not significantly altered by thermal conditions after maximal exercise but the catecholamines were decreased during rest. Bicarbonate, respiratory quotient, lactate and ventilatory thresholds increased significantly at -20 degrees C. The data support the contention that metabolic and hormonal responses following progressive incremental exercise are altered by cold exposure and they indicate a marked decrease in maximal oxygen uptake, time to exhaustion and workload.

Effects of selective cooling of the facial area on physiological and metabolic output during graded maximal or prolonged submaximal exercise.

Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% VO2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10 degrees C, 4.6 m s-1). Facial cooling at the end of graded maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (VO2 max), maximal heart rate (HR max), rectal temperature (Tre), work-load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work-load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.

Lactate threshold and onset of blood lactate accumulation during incremental exercise after dietary modifications.

This study was designed to clarify the effects of dietary modifications on the lactate threshold (LT) and on the onset of blood lactate accumulation (OBLA) during progressive incremental exercise. Six healthy males volunteered for the study. Informed consent was obtained from every participant. The following protocol was administered to each subject on three occasions: a 48-h period of mixed dieting (53% carbohydrates, 30% lipids, 17% proteins) preceding the first exercise test, immediately followed by a 48-h period of either a carbohydrate-rich (68% CHO, 23% lipids, 9% proteins) or a fat-rich (19% CHO, 57% lipids, 26% proteins) iso-caloric diet leading to the second exercise and separated from the third test by a 12-days period. Exercise tests were conducted on an electrically-braked ergocycle, and consisted of a progressive incremental maximal exercise. Respiratory parameters were continuously monitored by an automated open circuit sampling system. Exercise blood lactate (LA), free fatty acids (FFA), glucose levels and acid-base balance were determined from venous blood samples obtained through an indwelling brachial catheter. Peak lactate values, workload and performance time were not significantly altered by imposed diets. Furthermore, dietary modifications had no significant effect on LT, OBLA fixed at 4 mmol and ventilatory threshold. Increased pH and FFA mobilization were observed with fat-rich diet, while CHO-rich diet markedly increased the respiratory exchange ratio (R). It is concluded that LT and OBLA are not significantly altered by fat or CHO enrichment of diets.

Metabolic and hormonal responses to long-distance swimming in cold water.

The acute effects of long-distance swimming in cold water on selected hormonal and metabolic variables were evaluated on 22 long-distance swimmers (16 males and 6 females) during a 32-km swimming competition (La Traversée Internationale du Lac St-Jean). The water temperature was 18.5 degrees C and the mean performance times were 8 h and 32 min for men (M) and 9 h and 1 min for women (F). The blood samples were withdrawn in the fasting state during the week preceding the event and within 30 min after completion of the race. A positive correlation was obtained, for both groups, between percent body fat and rectal temperature measured at the end of the competition. After the competition, an increase in plasma epinephrine, norepinephrine, cortisol, thyroxine, free fatty acids, lactate, a decrease in glucose and insulin and no change in growth hormone, triiodothyronine, triglycerides, and cholesterol concentrations were observed in both groups. The increase in plasma thyroxine was more pronounced in the slower swimmers while the change in blood cortisol concentrations was higher in the subjects having the most acute decrease in body temperature. Male and female swimmers have a similar metabolic and hormonal response to a long-distance swimming competition in cold water.

[Hormonal responses to repeated lactic acid anaerobic exercise in male subjects]. / Réponses hormonales à une répétition d'exercices anaérobies lactacides chez des sujects masculins.

The hormonal response to repeated lactic acid anaerobic exercise was investigated in 6 young male adults. The exercise protocol consisted of 3 one-minute bouts of voluntary maximal effort, each bout being separated from the subsequent one by a two-minute rest period. Venous blood samples were obtained at rest and at the end of each of the 3 work bouts, as well as following 15 minutes of recovery. A marked increase in plasma catecholamine concentrations was observed in response to the repeated exercise bouts, the rise being more important for the adrenaline (x 22) than the noradrenaline (x 10) concentrations. A progressive increase in plasma somatotropin hormone was observed between the first and the last venous sampling. Moreover, a delayed rise in plasma cortisol, insulin, prolactin, and androstenedione was also observed. Hormonal concentrations of LH, FSH, DHEA-SO4, testosterone, SHBG and testosterone/SHBG ratio were not modified in response to the type of exercise.

[Effects of cold wind on the response to muscular exercise]. / Effets du vent froid sur la réponse à l'exercice musculaire.

The purpose of the present studies was to determine if the response to exercise is modified by a cold wind. When the subjects exercised in the cold (with or without wind), cheek and forehead temperatures were higher, but the temperature of the nose was lower than in the resting state. The decrease in heart rate, normally observed when cold wind is blown on the face at rest, persisted and even became greater during exercise up to a heart rate of 150 beats/minute. However, this decrease was progressively eliminated as heart rate increased further up to maximum. These results have shown that a cold wind can diminish the heart rate response to submaximal exercise in comparison with a no wind condition (delta up to 20 beats/minute at a heart rate of 150 beats/minute).

The onset of menarche: a late event in pubertal progression to be affected by physical training.

Several studies have shown that involvement in certain sports activities could lead to a significant delay in the onset of menarche. It is here emphasized that the latter constitutes a late pubertal event and that research in kinanthropology should now focus on processes underlying menarche. Some findings indeed suggest an influence of certain physical activities upon the maturation rate of endocrine axes which lead to the onset of the first menses.

Prolactinemia in exercising male athletes.

8 male collegial athletes were submitted at random to three (55, 70 and 85% of VO2 max) ergocycle exercises of 20-min duration. Venous blood samples were obtained before, during and after ergocycling sessions by antecubital catheterization. Serum prolactin was measured by RIA using specific antiserum. The exercise treatments induced a blood prolactin response proportional to the intensity of the work loads.

Effects of age, sex, and physical fitness on responses to local cooling.

The response to local cooling was estimated by the cold hand test (5 degrees C for 2 min) and the cold face test (0 degrees C with 66 km.h-1 wind for 2 min). Heart rate, blood pressure, and skin temperature were measured before, during, and after the tests. The increase in blood pressure (cold hand test) and the fall in Tsk (cold face test) were reduced in trained subjects. Similarly older subjects (53-60 yr of age) responded less to a cold hand test than younger subjects aged 20-40. However, the bradycardia caused by the cold face test was more pronounced in the older subjects. The responses to the cold hand and cold face tests were the same for male and female subjects. During the 2 min after the test, blood pressure and heart rate fell below initial values in the female group but not in the male. It is concluded that, besides adaptation to cold, individual factors such as age, sex, and physical fitness also have a relative importance in the responses to local cooling.

Metabolic and cardiovascular responses to norepinephrine in trained and nontrained human subjects.

Forty young male adults, aged 18-30 yr, with maximal oxygen intake (VO2 max) varying between 35 and 76 ml-kg-1-min-1 were studied. The fasting subjects were perfused for 15 min with saline and thereafter for 30 min with norepinephrine (0.1 mug/kg per min). Blood variables were determined at the end of slaine perfusion, at 15 and 30 min during norepinephrine perfusion and 15 min after the end of NE perfusion. Trained subjects are characterized by lower basal plasma glucose and insulin concentration. NE perfusion produced a larger increase in plasma glucose in the trained subjects. Levels of insulin in the postperfusion period were smaller in the trained group. Serum free fatty acids (FFA) and glycerol increased less in the trained subjects during NE perfusion and this difference persisted in the post-perfusion period. During NE perfusion, blood lactate increased only in the nontrained subjects. Initial heart rate and blood pressure were lower in trained subjects but, during NE perfusion, elevated levels of blood pressure and decreased levels of heart rate were comparable in both groups. Because of similarities in responses to exercise and to NE in trained subjects, the results of the present study suggest a possible role for NE in exercise training.

Autonomic nervous system and adaptation to cold in man.

The responses to cold hand test (blood pressure increase and tachycardia) and to a cold face test (blood pressure increase and bradycardia) were used to study the role of the autonomic nevrous system in cold adaptation in humans. The Eskimos (men, women, children) were shown to have a very weak sympathetic response to cold but the vagal response (bradycardia) was identical to that of white people. A group of mailmen from Quebec city living outdoors approximately 30 h/wk throughout the year was also studied. A significant decline in the cold pressor response and an enhanced bradycardia (cold face test) were observed at the end of the winter. Similarly the fall in skin temperature of the cheek was not as pronounced when the measurements were made in May compared to those made in October. A group of soldiers was also studied before and after an Arctic expedition. It was found that the bradycardia of the cold face test was also more pronounced after sojourning in the cold. These results indicate that repeated exposures to severe cold in men activate some adaptive mechanisms characterized by a diminution of the sympathetic response and a concomitant enhancement of the vagal activation normally observed when the extremities and the face are exposed to cold.