Effect of training on hormonal responses to exercise in competitive swimmers

Reducing sugar intake through chronic swimming training: Exploring palatability changes and central vasopressin mechanisms

Excessive sugar intake has been associated with the onset of several non-communicable chronic diseases seen in humans. Physical activity could affect sweet taste perception which may affect sugar intake. Therefore, it was investigated the chronic effects of swimming training on sucrose intake/preference, reactivity to sucrose taste, self-care in neurobehavioral stress, and the possible involvement of the vasopressin type V1 receptor in sucrose solution intake. Male Wistar rats, of from different cohorts were used, subjected to a sedentary lifestyle (SED) or swimming training (TR - 1 h/day, 5×/week, for 8 weeks, with no added load). Weekly intake was verified in SED and TR rats after access to a sucrose solution 1×/week, 2 h/day, for eight weeks. Chronic effects of swimming and/or a sedentary lifestyle were carried out three days after the end of the physical exercise protocol. Swimming training reduced the intake of sucrose solution from the third week onwards in the two-bottle test measured once a week for 8 weeks. After the ending of the swimming protocol, sucrose intake was also reduced as per its preference. This reduced intake is probably correlated with the carbohydrate aspect of sucrose since saccharin intake was not affected. In addition, chronic swimming training was shown to reduce ingestive responses, increase neutral responses, without interfering with aversive, in the sucrose solution taste reactivity test. In addition, these results are not related to a depressive-like behavior, nor to neurobehavioral stress. Furthermore, treatment with vasopressin V1 receptor antagonist abolished the reduced sucrose intake in trained rats. The results suggest that swimming performed chronically is capable of reducing intake and preference for sucrose by decreasing the palatability of sucrose without causing depressive-type behavior or stress. In addition, the results also suggest that central V1 vasopressin receptors are part of the mechanisms activated to reduce sucrose intake in trained rats.

Exercise training bradycardia is largely explained by reduced intrinsic heart rate

INTRODUCTION

Resting heart rate (RHR) declines with exercise training. Possible mechanisms include: 1) increased parasympathetic tone, 2) decreased responsiveness to beta-adrenergic stimulation, 3) decreased intrinsic heart rate or 4) combination of these factors.

OBJECTIVE

To determine whether an increase in resting parasympathetic tone or decrease in response to beta-adrenergic stimulation contributes to the decrease in RHR with training.

METHODS

51 screened healthy subjects aged 18-32 (n=20, mean age 26, 11 female) or 65-80 (n=31, mean age 69, 16 female) were tested before and after 6months of supervised exercise training. Heart rate response to parasympathetic withdrawal was assessed using atropine and beta-adrenergic responsiveness during parasympathetic withdrawal using isoproterenol.

RESULTS

Training increased VO2 max by 17% (28.7±7.7 to 33.6±9.20ml/kg/min, P<0.001). RHR decreased from 62.8±6.6 to 57.6±7.2 beats per minute (P<0.0001). The increase in heart rate in response to parasympathetic withdrawal was unchanged after training (+37.3±12.8 pre vs. +36.4±12.2 beats per min post, P=0.41). There was no change in the heart rate response to isoproterenol after parasympathetic blockade with training (+31.9±10.9 pre vs. +31.0±12.0 post beats per min, P=0.56). The findings were similar in all four subgroups.

CONCLUSIONS

We did not find evidence that an increase in parasympathetic tone or a decrease in responsiveness to beta-adrenergic activity accounts for the reduction in resting heart rate with exercise training. We suggest that a decline in heart rate with training is most likely due to decrease in the intrinsic heart rate.

Hormonal Neuroendocrine and Vasoconstrictor Peptide Responses of Ball Game and Cyclic Sport Elite Athletes by Treadmill Test

OBJECTIVE

Our objective was to evaluate complex hormonal response in ball game and cyclic sport elite athletes through an incremental treadmill test, since, so far, variables in experimental procedures have often hampered comparisons of data.

METHODS

We determined anthropometric data, heart rate, maximal oxygen uptake, workload, plasma levels of lactate, adrenaline, noradrenaline, dopamine, cortisol, angiontensinogen and endothelin in control (n = 6), soccer (n = 8), handball (n = 12), kayaking (n = 9) and triathlon (n = 9) groups based on a Bruce protocol through a maximal exercise type of spiroergometric test.

RESULTS

We obtained significant increases for adrenaline, 2.9- and 3.9-fold by comparing the normalized means for soccer players and kayakers and soccer players and triathletes after/before test, respectively. For noradrenaline, we observed an even stronger, three-time significant difference between each type of ball game and cyclic sport activity.

CONCLUSIONS

Exercise related adrenaline and noradrenaline changes were more pronounced than dopamine plasma level changes and revealed an opportunity to differentiate cyclic and ball game activities and control group upon these parameters. Normalization of concentration ratios of the monitored compounds by the corresponding maximal oxygen uptake reflected better the differences in the response level of adrenaline, noradrenaline, dopamine and cortisol.

Metabolic and endocrine response to exercise: sympathoadrenal integration with skeletal muscle

Skeletal muscle has the capacity to increase energy turnover by ∼1000 times its resting rate when contracting at the maximum force/power output. Since ATP is not stored in any appreciable quantity, the muscle requires a coordinated metabolic response to maintain an adequate supply of ATP to sustain contractile activity. The integration of intracellular metabolic pathways is dependent upon the cross-bridge cycling rate of myosin and actin, substrate availability and the accumulation of metabolic byproducts, all of which can influence the maintenance of contractile activity or result in the onset of fatigue. In addition, the mobilisation of extracellular substrates is dependent upon the integration of both the autonomic nervous system and endocrine systems to coordinate an increase in both carbohydrate and fat availability. The current review examines the evidence for skeletal muscle to generate power over short and long durations and discusses the metabolic response to sustain these processes. The review also considers the endocrine response from the perspective of the sympathoadrenal system to integrate extracellular substrate availability with the increased energy demands made by contracting skeletal muscle. Finally, the review briefly discusses the evidence that muscle acts in an endocrine manner during exercise and what role this might play in mobilising extracellular substrates to augment the effects of the sympathoadrenal system.

Catecholamines and the effects of exercise, training and gender

Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while. As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the 'sports adrenal medulla'. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.

Effect of hyperoxia on metabolic responses and recovery in intermittent exercise

The aim of the present study was to investigate whether the breathing of hyperoxic gas affects hemoglobin oxygen saturation (S(a)O(2)) and blood acidosis during intense intermittent exercise and recovery in sprint runners. The hypothesis was that the breathing of hyperoxic gas prevents S(a)O(2) from decreasing, delays blood acidosis during the exercise and improves the rate of heart rate recovery after the exercise. Nine sprinters ran three sets of 300 m at different velocities on a treadmill in normoxia (NOX) and in two hyperoxic conditions (ERHOX and RHOX; F(I)O(2) 0.40) in a randomized order. In ERHOX the inspired air was hyperoxic during the entire exercise and recovery and in RHOX the hyperoxic air was only inhaled during recovery periods. Blood pH and S(a)O(2) were measured from fingertip blood samples taken after each set of runs. The mean heart rate for the final 15 s of the last run in each set (HR(work)), the mean heart rate for the final 15 s of the first minute of recovery (HR(rec)) and the difference of HR(work) and HR(rec) (HR(dec)) were determined. In NOX, S(a)O(2) decreased from 95.0 +/- 2.0% to 88.7 +/- 2.0% (p < 0.001) but S(a)O(2) did not change in ERHOX (from 95.4 +/- 1.3% to 95.9 +/- 1.8%). A significant correlation was observed between the S(a)O(2) decrease in NOX and the effect of hyperoxia on blood pH in ERHOX (r = 0.63) and on HRdec in both ERHOX (r = 0.74) and RHOX (r = 0.69). We concluded that hemoglobin oxygen de-saturation occurred during intensive intermittent exercise in normoxia but hyperoxic gas during the exercise prevents S(a)O(2) from decreasing. Furthermore, the present results suggested that the beneficial effects of hyperoxia on heart rate recovery and blood acidosis during intensive intermittent exercise were related to hemoglobin de-saturation in normoxia.

Psychological monitoring of overtraining and staleness

It is widely agreed that overtraining should be employed in order to achieve peak performance but it is also recognised that overtraining can actually produce decrements in performance. The challenge appears to be one of monitoring stress indicators in the athlete in order to titrate the training stimulus and prevent the onset of staleness. The present paper summarises a ten-year research effort in which the mood states of competitive swimmers have been monitored at intervals ranging from 2-4 weeks during individual seasons for the period 1975-1986. The training cycle has always involved the indoor season which extends from September to March and the athletes who served as subjects were 200 female and 200 male competitive swimmers. The results indicate that mood state disturbances increased in a dose-response manner as the training stimulus increased and that these mood disturbances fell to baseline levels with reduction of the training load. Whilst these results have been obtained in a realistic setting devoid of experimental manipulation, it is apparent that monitoring of mood state provides a potential method of preventing staleness.

Applied physiology of swimming

Scientific research in swimming over the past 10 to 15 years has been oriented toward multiple aspects that relate to applied and basic physiology, metabolism, biochemistry, and endocrinology. This review considers recent findings on: 1) specific physical characteristics of swimmers; 2) the energetics of swimming; 3) the evaluation of aerobic fitness in swimming; and 4) some metabolic and hormonal aspects related to swimmers. Firstly, the age of finalists in Olympic swimming is not much different from that of the participants from other sports. They are taller and heavier than a reference population of the same age. The height bias in swimming may be the reason for lack of success from some Asian and African countries. Experimental data point toward greater leanness, particularly in female swimmers, than was seen 10 years ago. Overall, female swimmers present a range of 14 to 19% body fat whereas males are much lower (5 to 10%). Secondly, the relationship between O2 uptake and crawl swimming velocity (at training and competitive speeds) is thought to be linear. The energy cost varies between strokes with a dichotomy between the 2 symmetrical and the 2 asymmetrical strokes. Energy expenditure in swimming is represented by the sum of the cost of translational motion (drag) and maintenance of horizontal motion (gravity). The cost of the latter decreases as speed increases. Examination of the question of size-associated effects on the cost of swimming using Huxley's allometric equation (Y = axb) shows an almost direct relationship with passive drag. Expressing energy cost in litres of O2/m/kg is proposed as a better index of technical swimming ability than the traditional expression of VO2/distance in L/km. Thirdly, maximal direct conventional techniques used to evaluate maximal oxygen consumption (VO2 max) in swimming include free swimming, tethered swimming, and flume swimming. Despite the individual peculiarities of each method, with similar experimental conditions similar results for VO2 max will be found. Free swimming (unimpeded) using the backward extrapolation method will, however, lead to reliable and valid results obtained in a condition that is closer to the competitive situation than with a direct test. A maximal indirect field-test has been recently made available. This test can predict VO2 max with an acceptable accuracy (r = 0.877), and provides a mean to evaluate the functional maximal aerobic power in swimming which corresponds to the maximal aerobic swimming velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood lactate and glycerol after 400-m and 3,000-m runs in sprint and long distance runners

Lactate, glycerol, and catecholamine in the venous blood after 400-m and 3,000-m runs were determined in eight sprint runners, eight long distance runners, and seven untrained students. In 400-m sprinting, average values of velocity, peak blood lactate, and adrenaline were significantly higher in the sprint group than in the long distance and untrained groups. The mean velocity of 400-m sprinting was significantly correlated with peak blood lactate in the untrained (r = 0.76, P less than 0.05) and long distance (r = 0.71, P less than 0.05) groups, but not in the sprint group. In the 3,000-m run, on the other hand, average values of velocity and glycerol were significantly higher in the long distance group than in the sprint and untrained groups, but there are no significant differences in lactate levels between the three groups. These results suggest that 1) performance in 400-m sprinting may depend mainly upon an energy supply from glycolysis in the long distance and untrained group, but in the sprinters is influenced not only by glycolysis, but also by other factors such as content of ATP or force per unit muscle cross-sectional area; 2) peak blood lactate obtained after 400-m sprinting may be used as a useful indication of anaerobic work capacity in the long distance and untrained groups, but not in the sprinters. 3) high speed in the 3,000-m run could be maintained in the long distance runners by means of a greater energy supply from lipid metabolism as compared with sprinters or untrained subjects.

Metabolic and hormonal responses of elite swimmers during a regular training session

Metabolic and hormonal measures of eight elite swimmers were taken at rest and during a regular training session after a prolonged bout of swimming (4560 +/- 68 m) at moderate intensity (MI) and after medium duration-high intensity (HI) swimming exercise (1471 +/- 157 m). MI and HI swims were respectively associated with significant increases in free fatty acids (0.4 at rest to 0.8 and 0.67 microeq . ml-1) glycerol (0.1 to 0.26 and 0.25 mmol . l-1), growth hormone (14 to 65 and 51 ng . ml-1) and norepinephrine (0.5 to 3.9 and 4.1 ng . ml-1). HI contrary to MI swimming was also associated with a significant (p less than 0.01) increase in blood lactate (1.5 to 8.8 mmol . l-1) and epinephrine (0.13 to 0.71 ng . ml-1) concentrations. Glucose, insulin, glucagon, and cortisol concentrations were not changed during the training session. It is concluded that a regular training session in elite swimmers is associated with an increase in lipid utilization, and a modest change in some of the hormones directly involved in the regulation of blood glucose level.

Catecholamines, growth hormone, cortisol, insulin, and sex hormones in anaerobic and aerobic exercise

Seventeen male physical education students performed three types of treadmill exercise: (1) progressive exercise to exhaustion, (2) prolonged exercise of 50 min duration at the anaerobic threshold of 4 mmol . l-1 blood lactate (AE), (3) a single bout of short-term high-intensity exercise at 156% of maximal exercise capacity in the progressive test, leading to exhaustion within 1.5 min (ANE). Immediately before and after ANE and before, during, and after AE adrenaline, noradrenaline, growth hormone, cortisol, insulin, testosterone, and oestradiol were determined in venous blood, and glucose and lactate were determined in arterialized blood from the earlobe. Adrenaline and noradrenaline increased 15 fold during ANE and 3--4 fold and 6--9 fold respectively during AE. The adrenaline/noradrenaline ratio was 1 : 3 during ANE and 1 : 10 during AE. Cortisol increased by 35% in ANE (12% of which appeared in the postexercise period) and 54% in AE. Insulin increased during ANE but decreased during AE. Testosterone and oestradiol increased by 14% and 16% during ANE and by 22% and 28% during AE. The results point to a markedly higher emotional stress and higher sympatho-adrenal activity in anaerobic exercise. Growth hormone and cortisol appear to be the more affected by intense prolonged exercise. Taking plasma volume changes and changes of metabolic clearance rates into consideration, neither of the exercise tests appeared to affect secretion of testosterone and oestradiol.

Circulating reverse triiodothyronine in humans during exercise

Circulating thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3) as well as blood lactate and glucose concentrations were measured in a group of 12 trained volunteer subjects prior to and after swimming 0.18 or 0.9 km, to determine if increase in metabolic activity was accompanied by diversion of T4 monodeiodination from the active (T4 to T3) to the inactive (T4 to rT3) pathway. The resting T4, T3, and rT3 levels were 8.5 micrograms . 100 ml-1, 108 ng . 100 ml-1, and 57 ng . 100 ml-1, respectively, whereas after 0.18 km of swimming the corresponding levels were 9.5 micrograms . 100 ml-1, 135 ng. 100 ml-1 and 70 ng . 100 ml-1. After 0.9 km of swimming, T4, T3, and rT3 levels were 9.0 micrograms . 100 ml-1, 126 ng . 100 ml-1, and 66 ng . 100 ml-1, respectively. The swimming was accompanied by hemoconcentration and increase in blood lactate but not in glucose concentrations. In two other investigations thyroid hormones were measured prior to and after 60 or 90 min of moderate exercise on a bicycle ergometer. This exercise had no effect on circulating thyroid hormone levels. Free thyroxine (FT4) concentration and thyroxine binding globulin (TBG) capacity were unaltered after exercise. In conclusion, brief strenuous swimming or moderate bicycle exercise had minor or no effect on thyroid hormone concentrations when consideration was given to the attendant hemoconcentration. Even when exercise induced small T3 and rT3 changes were noted, they were in the same direction (increase) thus demonstrating a lack of diversion of peripheral T4 monodeiodination.

Plasma vasopressin, renin activity, and aldosterone: effect of exercise and training

The influence of endurance-training on hematocrit, plasma vasopressin, renin activity, and aldosterone changes at rest and at the end of an exercise performed until exhaustion at a given and constant relative work-load (87% of maximal oxygen uptake) has been studied in four untrained subjects submitted to a 5-month training. At the end of this period, maximal oxygen uptake increased of 15.2% (p less than 0.01). Hematocrit at rest slightly rose after training, and if exercise constantly induced increases in hematocrit before (p less than 0.001) and after training (p less than 0.005), the per cent increase after training was lower than before (p less than 0.05). Comparison between the importance of weight loss and hematocrit variation showed that when untrained subjects become trained the variation of hematocrit after exercise becomes smaller while weight loss is more important (p less than 0.01). Plasma renin activity (PRA), aldosterone (Aldo) and vasopressin (AVP) levels, compared to control values, displayed a significant increase after exercise before as well as after training. Control values remained unchanged after training for aldosterone and AVP, but were significantly lower (p less than 0.05) for PRA. This latter observation could be explained by the change in blood volume induced by exercise.

Plasma AVP, neurophysin, renin activity, and aldosterone during submaximal exercise performed until exhaustion in trained and untrained men

The effect of intense muscular work (80% of maximal oxygen uptake) on responses of plasma hormones involved in electrolyte and water balance were measured in 14 male subjects. They were divided into three groups according to their maximal oxygen uptake and the duration of exercise performed until exhaustion: well trained subjects (group I), trained subjects (group II), and untrained subjects (group III). Pulmonary gas exchange, heart rate, rectal and skin temperature, and weight loss were measured as well as hematocrit and plasma and urine sodium and potassium concentrations. Rectal temperature increased significantly in all subjects after exhaustion. The variation of hematocrit was smallest and the weight loss greatest in the well-trained subjects. Plasma aldosterone, renin activity (PRA), vasopressin (AVP), and neurophysin (Np) displayed highly significant increases after exercise in all three groups: PRA was increased 4.5 times (p < 0.01), aldosterone 13 times (p < 0.05), Np 2.6 times (p pe 0.05), and AVP 4.8 times (p < 0.05). Nevertheless, there was no correlation between the changes in PRA and those in plasma aldosterone, nor between aldosterone and plasma sodium or potassium. At the urinary level, the only striking observation was that free water clearance tends to become positive after exercise. Our results provide evidence that this kind of exercise produces a highly significant increase in plasma levels of the hormones involved in electrolyte and water balance. They also indicate that it is among the well-trained subjects that sweat loss is highest though the hematocrit increase is the smallest; this suggests that water is shifted more efficiently from the extravascular compartment.