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Biomedical subjects

G R Brisson

Publications and source records attributed to G R Brisson.

At least 55 records · Page 3Linked to original sources
PubMed1989

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.

Adult↗
PubMed1989

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.

Adult↗
PubMed1989

Face cooling-induced reduction of plasma prolactin response to exercise as part of an integrated response to thermal stress.

This study was designed to verify if the decrease in blood prolactin (PRL) induced by selective face cooling during exercise could be part of a response to specific body thermal stress. Five healthy trained male cyclists presenting a significant plasma PRL elevation to exercise were, on three occasions and at weekly interval, submitted to a submaximal exercise (approx. 65% VO2max) on ergocycle with and without selective face cooling. In absence of face cooling a first trial served to establish reference values for workload, heart rate and plasma PRL levels, the latter increasing markedly (450% of resting values) in these conditions. On a second trial but with workload maintained at reference values (222 +/- 9 W), a significant bradycardia was observed with face cooling; furthermore, plasma PRL response to exercise was significantly reduced (to 31% of original response). On a third trial with face cooling, workload had to be significantly augmented (242 +/- 10 W) to maintain heart rate at reference level (78% HRmax); in addition, plasma PRL response to exercise was almost unchanged compared to the reference-value level. The absence of a significant face cooling-induced decrease in sympathetic tonus, as evaluated through peripheral plasma catecholamines response, does not indicate a role for the autonomic nervous system in the face cooling-induced reduction of both heart rate and PRL responses during exercise. Assay of circulating peripheral beta-endorphins could indicate that the face cooling-induced PRL blunted response does not necessarily involve an opioid mediation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Plasma atrial natriuretic peptide during brief upright and supine exercise in humans.

The factors associated with the exercise-induced increase in plasma atrial natriuretic peptide (ANP) have not been clearly established. Thus the purpose of the study was to further document the stimulus for the exercise-induced release of ANP and to examine the role of ANP in the control of hydromineral balance during exercise. Eight healthy male volunteers (25.1 +/- 4.5 yr) were submitted to a graded cycling exercise in both the upright and supine positions. Venous blood was sampled at rest and at the end of each 5-min work load at 40, 60, and 80% maximal oxygen uptake (Vo2max), at maximal exercise, and during recovery through an indwelling catheter for the determination of plasma vasopressin, aldosterone, catecholamines, plasma renin activity, and ANP concentrations. Results indicate a significant increase in ANP (pg/ml) from rest to maximal exercise in the upright position [rest, 21.9 +/- 10.2; 40%, 24.7 +/- 12.6; 60%, 32.4 +/- 17*; 80%, 47.8 +/- 27.7*; 100% Vo2max, 65.9 +/- 34.5* (*P less than or equal to 0.05)]. Supine concentrations were significantly higher than upright at 40 (37.9 +/- 15.2), 60 (54.0 +/- 18.8), and 80% Vo2max (68.9 +/- 16.6). Plasma ANP during maximal exercise was similar in both positions. Plasma vasopressin, aldosterone, renin activity, and catecholamines increased with increasing exercise intensity in both positions, although lower values were systematically observed in the supine position. The association of higher plasma ANP and blunted plasma vasopressin, plasma renin activity, and norepinephrine concentrations during supine exercise suggests that ANP may exert modulatory effects on the control of the hydromineral hormonal system during exercise.

Adult↗
PubMed1988

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.

Adult↗
PubMed1987

Effects of dietary manipulations on blood glucose and hormonal responses following supramaximal exercise.

The effects of supramaximal exercise on blood glucose, insulin, and catecholamine responses were examined in 7 healthy male physical education students (mean +/- SD: age = 21 +/- 1.2 years; VO2max = 54 +/- 6 ml X kg-1 X min-1) in response to the following three dietary conditions: a normal mixed diet (N); a 24-h low carbohydrate (CHO) diet intended to reduce liver glycogen content (D1); and a 24-h low CHO diet preceded by a leg muscle CHO overloading protocol intended to reduce hepatic glycogen content with increased muscle glycogen store (D2). Exercise was performed on a bicycle ergometer at an exercise intensity of 130% VO2max for 90 s. Irrespective of the dietary manipulation, supramaximal exercise was associated with a similar significant (p less than 0.01) increase in the exercise and recovery plasma glucose values. The increase in blood glucose levels was accompanied by a similar increase in insulin concentrations in all three groups despite lower resting insulin levels in conditions D1 and D2. Lactate concentrations were higher during the early phase of the recovery period in the D2 as compared to the N condition. At cessation of exercise, epinephrine and norepinephrine were greatly elevated in all three conditions. These results indicate that the increase in plasma glucose and insulin associated with very high intensity exercise, persists in spite of dietary manipulations intended to reduce liver glycogen content or increase muscle glycogen store.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

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.

Adolescent↗
PubMed1987

Evidence for an interference of selective face ventilation on hyperprolactinemia induced by hyperthermic treadmill running.

Selective face ventilation, known to interfere with bloodstreamed temperature signals, should alter exercise-induced prolactinemic (PRL) responses if, as recently suggested, the latter responses are associated with body temperature increases generated by working muscles. To test this hypothesis, 15 trained adult male and female volunteers were submitted to 45-min hyperthermic treadmill runs with and without selective face ventilation. Tympanic (Tt) and rectal (Tr) temperatures were measured in these experiments, and serum immunoreactive PRL was assayed on venous blood sampled immediately before and immediately after the exercise. Hyperthermic running induced significant Tr elevations whether selective face ventilation was present or not. In the absence of face ventilation, serum PRL rose markedly in 11 of the 15 hyperthermic runners, the lack of response in 4 runners confirming that exercise per se is not necessarily hyperprolactinotrophic. When the 11 responders (11/15) ran with face ventilation, serum PRL response was abolished in 6 of them, indicating a significant interference from face ventilation on temperature signals streamed through carotid blood; serum PRL-maintained responses in 5 of these 11 ventilated runners suggest the absence of a learning effect. It is concluded that the blood-streamed temperature signals arising from working muscles represent an important but not a unique determinant of blood PRL response during aerobic running. The contribution of TRH and plasma volume changes to blood PRL variations during hyperthermic running appeared nonsignificant.

Adult↗
PubMed1987

Menstrual cycle phase dissociation of blood glucose homeostasis during exercise.

The purpose of this investigation was to evaluate the effects of 24-h carbohydrate-poor diet on metabolic and hormonal responses induced by prolonged exercise in both follicular (FP) and luteal (LP) phases of the menstrual cycle. At mid-FP and at mid-LP, seven eumenorrheic young women [means +/- SE; chronological age, 21.1 +/- 0.6 yr; O2 uptake (VO2) peak, 43.7 +/- 2.0 ml X kg-1 X min-1; body fat, 19.2 +/- 2.0%] were subjected to a 90-min bicycle exercise period at an intensity representing 63% of their measured VO2 peak. Venous blood samples obtained before and during exercise were analyzed for levels of substrates (glucose, lactate, free fatty acids, glycerol) and hormones (luteinizing hormone, progesterone, estradiol, insulin, glucagon, cortisol, catecholamines). Contrary to FP, a significant (P less than 0.01) decrease in blood glucose concentration was observed after 70 and 90 min of exercise during LP. Significant phase differences were also observed for blood lactate (highest in FP), cortisol (highest in LP), and progesterone (highest in LP). Although not significantly different, tendencies for menstrual phase dissociations were noticed for some of the other measured variables. Hence, a menstrual phase dissociation in circulating glucose level, unmasked by a prolonged exercise performed after a 24-h carbohydrate-poor diet, suggests to the authors a specific metabolic involvement for gonadotrophic and/or gonadal hormones.

Blood Glucose↗
PubMed1987

Effect of exercise on the onset of puberty, gonadotropins, and ovarian inhibin.

Swimming 6 h/day from 11 days of age led to a significant delay of the onset of puberty of female rats compared with the sedentary group. Rats who were in contact with water but without the energy expenditure due to exercise (paddlers) had their vaginal opening in a middle point between control and exercising rats. Vaginal opening occurred at different ages but at a same body weight. Exercise and stress led to a marked decrease of the body weights between 19 and 40 days of age. Serum luteinizing hormone and follicle-stimulating hormone were increased with the exercise program at 30 days of age, whereas no significant differences between groups in serum gonadotropins were observed at 50 days of age. Only the anterior pituitary luteinizing hormone content was increased by exercise in adult rats. Total ovarian proteins were significantly reduced by stress and to a greater degree by exercise. Ovarian inhibin activity is not modified by exercise at 30 days of age, whereas it increased significantly in the exercising group at 50 days of age and to a lesser degree in paddlers. It is therefore suggested that the onset of puberty in rats is dependent on a critical weight and that exercise and stress can delay the onset of puberty. This delay could be explained by a deficiency of hormonal maturational process while exercising until sexual maturity alters the inhibin activity, which suggests that inhibin could play a major role for the normal reproductive function and this could possibly explain the menstrual disturbances in the female athlete.

Animals↗
PubMed1987

Inhibition of exercise-induced blood prolactin response by acute hypoxia.

Prolactin (PRL) secretion is regulated by a variety of factors, most of them being known for their enhancing effects on blood PRL levels. This study describes the inhibitory influence of an acute exposure to hypoxia (14.5% O2) on the blood PRL response induced by graded maximal exercise in eight trained male subjects.

Acute Disease↗
PubMed1986

Exercise-induced blood prolactin variations in trained adult males: a thermic stress more than an osmotic stress.

Blood prolactin (PRL) variations have been linked to temperature and osmotic changes in several species. The latter factors are here explored to better understand blood PRL responses frequently induced during physical exercise. Since body heat generated by exercise can lead to marked body fluid shifts, it was postulated that PRL changes observed during exercise could be associated with variations in body temperature and/or blood osmolality (OSM). A wide range (38.5-40.5 degrees C) of rectal temperatures (Tr; used here to appreciate core temperatures) were theoretically selected and randomly assigned as targets to male runners. Measured by thermistor probe, target Tr were obtained by a combination of factors: (a) increases heat production by treadmill running, and (b) decreases heat losses by appropriate clothing (decreases evaporation) in warmed (decreases radiation) and hypoventilated (decreases convection) laboratory conditions. For each subject, target Tr was attained not prior to 30 min after initiation of running, and had to be maintained for at least 10 min, for a mean (+/- SD) running time of 52.6 +/- 10.0 min. In a first protocol, hypohydration was provoked in 26 runners (23.9 +/- 4.7 years) by total restriction of water intake. In a second protocol (10 different runners: 22.3 +/- 3.3 years), euhydration was maintained by water intake (20 ml/kg body weight). Venous blood was sampled at rest before and immediately after the run. PRL was assayed by RIA; OSM was measured by freezing point depression; sodium was analyzed by flame photometry. At rest, before the heat-producing exercise, mean PRL values were 9.4 +/- 3.4 ng/ml for both eu/hypohydrated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Hormonal responses to repeated lactic acid anaerobic exercise in male subjects].

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.

Adult↗
PubMed1982

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.

Adrenal Glands↗
PubMed1981

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.

Adolescent↗