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PubMed2006

Blood lipid profile and myocardial superoxide dismutase in swim-trained young and middle-aged rats: comparison between left and right ventricular adaptations to oxidative stress.

Region-wise interactive effects of age, swim intensity, and duration on exercise performance in the myocardium and serum lipid profile in young (4 months) and middle-aged (12 months) rats were examined. Animals were allocated to the sedentary control (SE-C) or one of the nine trainee groups. Swim training was for 6 days/week and for 4 weeks at 3 durations (20, 40, and 60 min/day) and intensities (2%, low; 3%, medium; 5%, high). Swim velocity and external work showed an age-related decline with low-intensity of 20 min/day in the middle aged. Reduction in serum cholesterol, low-density lipoproteins (LDLs), and triglycerides were accompanied by elevated levels in high-density lipoprotein in the low-to-moderately trained ones for 20 and 40 min/day. Training at 2%, intensity for 20 min/day was sufficient to alter the blood lipid profile and improve swim performance, and endurance in terms of blood lactate. A concomitant increase in Mn-superoxide dismutase (Mn-SOD) activity and reduced malondialdehyde in the left ventricle (LV) and right ventricle (RV) were evident. Lipofuscin was higher in the LV compared to RV. Our results reflect the minimization of free radical generation through appropriate exercise protocols. Our findings on improved blood lipid profile could be related to lower free radicals, which would otherwise oxidize LDLs. Further, swim training when initiated in the young and middle age for as low as 20 min/day at 2% intensity improves the Mn-SOD in the LV and RV. However, the adaptive response of the LV was weaker when compared to the RV, more so in the middle aged.

Adaptation, Physiological↗
PubMed1997

Heart rate and plasma lactate responses during submerged swimming and trained diving in California sea lions, Zalophus californianus.

California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20-50 bpm, and demonstrated that otariid diving heart rates were at or below resting heart rate. Venous blood samples were collected after submerged swimming periods of 1-3 min. Plasma lactate began to increase only after 2.3-min submersions. This rise in lactate and our inability to train sea lions to dive or swim submerged for periods longer than 3 min lead us to conclude that an aerobic limit had been reached. Due to the similarity of heart rate responses and swimming velocities recorded during submerged swimming and trained diving, this 2.3-min limit should approximate the aerobic dive limit in these 40-kg sea lions. Total body O2 stores, based on measurements of blood and muscle O2 stores in these animals, and prior lung O2 store analyses, were 37-43 ml O2 kg-1. The aerobic dive limit, calculated with these O2 stores and prior measurements of at-sea metabolic rates of sea lions, is 1.8-2 min, similar to that measured by the change in post-submersion lactate concentration.

Animals↗
PubMed2002

Determinants of the energy cost of front-crawl swimming in children.

The aim of the present study was to define the determinants of the energy cost of swimming (Cs) in children. Eleven healthy children [mean (SD) age: 12.42 (0.53) years] who practised 7.5-8.5 h x week(-1) volunteered to take part in this study. Anthropometric dimensions such as height (H), body mass (BM), hydrostatic lift (HL) and body surface area (SA) were measured. Forty-eight hours later when maximal oxygen consumption (VO(2max)) had been measured during 400 m of front-crawl swimming, Cs was measured over 200 m for three submaximal swimming speeds (0.9, 1.0 and 1.1 m x s(-1)). Oxygen consumption (Douglas bag method), stroke frequency (SF) and stroke length (SL) were calculated during the last 50 m of each 200 m. The mean (SD) VO(2max) of the young swimmers was 2.19 (0.38) l x min(-1) at a maximal aerobic velocity of 1.19 (0.03) m x s(-1). The values of for Cs at 0.9 m x s(-1), 1.0 m x s(-1) and 1.1 m x s(-1) were 29.27 (3.13) ml x m(-1), 30.25 (3.68) ml x m(-1) and 32.91 (3.59) ml x m(-1), respectively. There was a significant increase in Cs with increasing swim speed. In addition, SF increased with velocity when SL remained constant. The values for SF at 0.9 m x s(-1), 1.0 m x s(-1) and 1.1 m x s(-1) were 31.28 (4.36) strokes x min(-1), 34.10 (5.09) strokes x min(-1) and 38.31 (5.90) strokes x min(-1), respectively. No significant correlation was obtained between Cs and the anthropometric or stroking parameters. It was concluded that for young swimmers, anthropometric characteristics, SF and SL are not good predictors of Cs in front-crawl swimming, and that further studies are needed to explore the influence of underwater torque on Cs in prepubertal children.

Anthropometry↗
PubMed2006

Respiratory muscle training improves swimming endurance in divers.

Respiratory muscles can fatigue during prolonged and maximal exercise, thus reducing performance. The respiratory system is challenged during underwater exercise due to increased hydrostatic pressure and breathing resistance. The purpose of this study was to determine if two different respiratory muscle training protocols enhance respiratory function and swimming performance in divers. Thirty male subjects (23.4 +/- 4.3 years) participated. They were randomized to a placebo (PRMT), endurance (ERMT), or resistance respiratory muscle training (RRMT) protocol. Training sessions were 30 min/day, 5 days/week, for 4 weeks. PRMT consisted of 10-s breath-holds once/minute, ERMT consisted of isocapnic hyperpnea, and RRMT consisted of a vital capacity maneuver against 50 cm H(2)O resistance every 30 s. The PRMT group had no significant changes in any measured variable. Underwater and surface endurance swim time to exhaustion significantly increased after RRMT (66%, P < 0.001; 33%, P = 0.003) and ERMT (26%, P = 0.038; 38%, P < 0.001). Breathing frequency (f (b)) during the underwater endurance swim decreased in RRMT (23%, P = 0.034) and tidal volume (V (T)) increased in both the RRMT (12%, P = 0.004) and ERMT (7%, P = 0.027) groups. Respiratory endurance increased in ERMT (216.7%) and RRMT (30.7%). Maximal inspiratory and expiratory pressures increased following RRMT (12%, P = 0.015, and 15%, P = 0.011, respectively). Results from this study indicate that respiratory muscle fatigue is a limiting factor for underwater swimming performance, and that targeted respiratory muscle training (RRMT > ERMT) improves respiratory muscle and underwater swimming performance.

Adult↗
PubMed2003

From swimming to walking: a single basic network for two different behaviors.

In this paper we consider the hypothesis that the spinal locomotor network controlling trunk movements has remained essentially unchanged during the evolutionary transition from aquatic to terrestrial locomotion. The wider repertoire of axial motor patterns expressed by amphibians would then be explained by the influence from separate limb pattern generators, added during this evolution. This study is based on EMG data recorded in vivo from epaxial musculature in the newt Pleurodeles waltl during unrestrained swimming and walking, and on a simplified model of the lamprey spinal pattern generator for swimming. Using computer simulations, we have examined the output generated by the lamprey model network for different input drives. Two distinct inputs were identified which reproduced the main features of the swimming and walking motor patterns in the newt. The swimming pattern is generated when the network receives tonic excitation with local intensity gradients near the neck and girdle regions. To produce the walking pattern, the network must receive (in addition to a tonic excitation at the girdles) a phasic drive which is out of phase in the neck and tail regions in relation to the middle part of the body. To fit the symmetry of the walking pattern, however, the intersegmental connectivity of the network had to be modified by reversing the direction of the crossed inhibitory pathways in the rostral part of the spinal cord. This study suggests that the input drive required for the generation of the distinct walking pattern could, at least partly, be attributed to mechanosensory feedback received by the network directly from the intraspinal stretch-receptor system. Indeed, the input drive required resembles the pattern of activity of stretch receptors sensing the lateral bending of the trunk, as expressed during walking in urodeles. Moreover, our results indicate that a nonuniform distribution of these stretch receptors along the trunk can explain the discontinuities exhibited in the swimming pattern of the newt. Thus, separate limb pattern generators can influence the original network controlling axial movements not only through a direct coupling at the central level but also via a mechanical coupling between trunk and limbs, which in turn influences the sensory signals sent back to the network. Taken together, our findings support the hypothesis of a phylogenetic conservatism of the spinal locomotor networks generating axial motor patterns from agnathans to amphibians.

Animals↗
PubMed1986

Differential effects of striatal injections of dopaminergic, cholinergic and GABAergic drugs upon swimming behavior of rats.

The present study provides a detailed report about similarities and dissimilarities between the effects of neostriatally applied dopaminergic (apomorphine, 250-300 ng; haloperidol, 250-500 ng), cholinergic (carbachol, 50-100 ng; scopolamine, 200-500 ng), and GABAergic (muscimol, 1-2 ng; bicuculline, 5-35 ng) drugs upon swimming of rats. The used swimming test consisted of 4 parts: (a) open-field test for analyzing drug-induced changes in normal behavior; (b) 'swimming without escape' test for analyzing drug-induced changes in the ability to switch from one type of behavior to another; (c) 'swimming with escape' test for analyzing drug-induced changes in the ability to switch from ongoing swimming behavior to climbing behavior by allowing the rats to escape via a rope; and (d) 'rope' test for analyzing drug-induced changes in the kind of contact behaviors needed to switch to the latter climbing behavior. In the open-field test the drugs produced neither abnormal behavior nor motor disturbances, which prevented the display of normal behavior in the remaining tests. Both apomorphine and carbachol produced identical effects in all tests. Muscimol produced overall effects which were not only opposite to those of apomorphine and carbachol, but also comparable to those of scopolamine. All effects elicited by apomorphine, carbachol and muscimol were antagonized by their corresponding antagonists: haloperidol, scopolamine and bicuculline respectively, whereas the effects of the latter were suppressed by their corresponding agonists. These data globally show that dopamine and acetylcholine act in the same direction but opposite to that of GABA as far as it concerns the regions investigated. The finding that haloperidol injected into the GABA target area produced effects which were not only similar to those of haloperidol injected into the dopamine target area, but also dissimilar to those of muscimol and bicuculline injected into the GABA target area, shows that the effects were drug-specific rather than region-specific. Though 3 distinct cholinergic regions were investigated, cholinergic-specific effects could only be elicited from one region, suggesting that the neostriatum is heterogeneous in this respect. Finally, well-delineated dissimilarities between haloperidol-, scopolamine-, and muscimol-treated rats were found in the rope test. These data show that behavior-relevant information transmitted by GABAergic drugs surmounted that transmitted by cholinergic drugs which, in turn, surmounted behavior-relevant information transmitted by dopaminergic drugs.

Acetylcholine↗
PubMed1987

Long-lasting effects of chronic chlorimipramine treatment of rats on exploratory activity on a hole-board, and on immobility in the forced swimming test.

The study concerned the effects of acute and chronic clomipramine administration to male rats on exploratory activity in a novel environment (hole-board) and on immobility in the forced swimming test. Acute clomipramine administration did not alter either exploratory activity on a hole-board as measured 3 or 20 h after drug administration, or immobility in the forced swimming test as measured 20 h after drug administration. Approximately 20 h after the last injection of clomipramine, the rats chronically treated with the drug showed reduced exploratory activity on the hole-board. In contrast, chronic clomipramine treatment significantly increased the activity in the forced swimming test. The effects of the drug on exploratory and forced swimming activities persisted for 14 days after the cessation of clomipramine administration. These data indicate that chronic clomipramine administration exerted profound and long-lasting effects on central nervous system function. The long-lasting action of the drug on behaviour in the forced swimming test might explain the long-term beneficial effect of antidepressant drugs in counteracting behavioral depression.

Animals↗
PubMed1989

The effect of swimming activity on bone architecture in growing rats.

The effect of non-habitual physical activity on bone architecture in the rat humeral shaft was examined. Two groups of rats were trained to swim for 1 h a day, for 20 weeks, at two training levels. The control group consisted of sedentary rats. Parameters of cross-sectional bone morphology (cross-section areas, principal area moments of inertia and their ratio) were used to evaluate the response of bone architecture to mechanical loading. The strength of bone was assessed by measuring the ultimate compressive force and stress. The cortical cross-section area and principal moments of inertia were found to be significantly higher in the swimming groups than in the controls. Examination of the ratio between the major and minor moments of inertia revealed a pronounced change in the shape of the bone cross-section which became more rounded following swimming training. The ultimate compressive force was significantly higher in the swimming rats while the changes in ultimate stress were not significant. Our results indicate a gain of bone strength due to increased periosteal apposition and modified bone tissue distribution. The marked changes in bone morphology are attributed to the different nature of the forces and moments exerted on the humerus during swimming compared to those prevailing during normal locomotion.

Adaptation, Physiological↗
PubMed1991

Effect of propelling surface size on the mechanics and energetics of front crawl swimming.

In swimming the propulsive force is generated by giving a velocity change to masses of water. In this process energy is transferred from the swimmer to the water, which cannot be used to propel the swimmer. Theoretical considerations indicated that an increase of the propelling surface size should lead to a reduced loss of energy to the water. Thus, in this study, the effect of artificially enlarging the propelling surface of the hand was examined. The effect was examined in terms of the propelling efficiency during front crawl swimming using the arms alone. The legs were floated with a small buoy as previously described (Toussaint et al., J. appl. Physiol. 65, 2506-2512, 1988a). In ten competitive swimmers (six male, four female) the rate of energy expenditure (power input, Pi), power output (Po), work per stroke cycle (As), distance per stroke cycle (d), work per unit distance (Ad), and propelling efficiency (ep) were determined at various swimming speeds once with and once swimming without paddles. At the same average velocity the effect of swimming with paddles was to reduce Pi, Po, and Ad by 6, 7.6, and 7.5% respectively, but to increase ep and As by 7.8 and 7%. The increase in distance per stroke cycle and the decrease in stroke cycle frequency matched the predicted values based on the theoretical considerations in which the actual increase in propelling surface size was taken into account.

Arm↗
PubMed1982

A swimming test for assessing effects of drugs upon motor performance in the guinea-pig (Cavia porcellus).

A swimming test was developed to provide a method for assessing gross motor behaviour in the guinea-pig (Cavia porcellus). The simplicity of the procedure enables a large number of animals to be tested in a short time. Learning was not required of the animals, thereby simplifying the interpretation of the effects of drugs. Control animals were highly motivated to complete the task and the variability in swimming times was small. The acetylcholinesterase inhibitor sarin significantly increased swimming time in a dose-related manner and did not affect "turning behaviour" during the swim. Alcohol, diazepam and amphetamine increased swimming time but only in the larger doses tested. Diazepam also increased turning behaviour. The suitability of the test for measuring effects of drugs upon gross motor behaviour in the guinea-pig is discussed.

Acetylcholinesterase↗
PubMed1984

Task-dependent rate of recovery from hemilabyrinthectomy: an analysis of swimming and locomotor performances.

Guinea pigs were hemilabyrinthectomized or hemicerebellectomized and repeatedly tested on a swimming task and in the open field. Initially, hemilabyrinthectomized animals showed impaired swimming behavior which improved over time: within 21-25 days after the vestibular damage, the animals were able to swim around the tank with coordinated motor patterns. Only a slight tendency to turn towards the lesion side continued to be displayed. Hemicerebellectomized guinea pigs were significantly less impaired in their swimming ability since the very first test session. Both groups of animals showed similar recovery time courses in their open field activity. The data demonstrate a task-dependence in the rate of recovery following a unilateral labyrinthectomy and a substantial contribution by the labyrinth to swimming function.

Adaptation, Physiological↗
PubMed1990

Neonatal chronic stress induces subsensitivity to chronic stress in adult rats. I. Effects on forced swim behavior and endocrine responses.

An influence of early stimulation on sensitivity to acute stress in adulthood has been reported. The purpose of the present work was to determine the effect of exposure of male and female rats to three models of chronic stress (unpredictable stress, cold stress and handling) from day 2 to day 15 of life on behavioral and endocrine sensitivity to chronic stresses in adulthood. The chronic stresses applied in adulthood were a model of intermittent cold stress (daily 30-min sessions at -20 degrees C for 15 days) and the Katz's model of unpredictable chronic stress (15 days). Forced swim behavior and serum concentration of the stress-sensitive hormones, corticosterone and prolactin, were chosen to investigate stress sensitivity. It was found that all neonatal treatments stimulated body weight gain, did not cause infant mortality and did not affect forced swim behavior as adult. The repetitive exposure to cold stress in adulthood did not cause major impairment of forced swim behavior and did not affect basal levels of serum corticosterone and prolactin in either control or experimental rats. These findings support the view that repeated stressors can induce behavioral and endocrine adaptation in rats. The neonatal treatments did not affect this characteristic. The exposure of control rats to the unpredictable stress model severely impaired forced swim behavior and increased basal levels of serum corticosterone and prolactin. This observation conforms to the view that standard laboratory rats cannot adapt to unpredictable chronic stress. This has been reported to cause a behavioral depression syndrome comprising forced swim deficit and endocrine alterations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Methods for measurement of energy expenditure and substrate concentrations in swimming rats.

A measuring system is described for the determination of oxygen consumption (Vo2) and carbon dioxide production (Vco2) in swimming rats. Vo2 and Vco2 were measured by means of an O2-analyzer (Ametek S3A) and a mass spectrometer (Balzers QMG 511), respectively, combined with a gas flow meter. The measurements were made in a 5-1 metabolic chamber on top of a swimming pool in which a water flow of 0.22 m/s was maintained. The rats were fitted with an indwelling catheter with its tip at the entrance of the right atrium for the repeated determination of energy substrate and hormone concentrations, before, during, and after swimming. The inaccuracy of the Vo2 and Vco2 measurements was 0.18% and 0.31% of the reading, respectively; the imprecision was 2.15% and 2.59%. This high accuracy and precision of the system was attained by measuring room air for 20 s after each 100 s of measuring air from the metabolic chamber, and by using demineralized water in the swimming pool. Vo2 during steady-state swimming was 1.89 +/- 0.06 mmol/kg.min (ca. 60% Vo2max), indicating moderate exercise. Respiratory quotient (RQ), during steady-state exercise, was 0.80 +/- 0.01. Vo2 and RQ resulted in rates for carbohydrate and fat utilization of 15.6 +/- 0.8 and 15.1 +/- 0.7 mg/kg.min, respectively.

Animals↗
PubMed1996

Swimming training improves brown-adipose-tissue activity in young and old mice.

The impairment of brown adipose tissue (BAT) thermogenic activity with aging has been well documented. The current study investigated the effect of swimming training on BAT activity in 2-month-old (young) and 26-month-old (old) male mice. The trained mice underwent a 6-week swimming program (1 h/day, 5 days/week) in water at 35-36 degrees C. Compared with young sedentary mice, the BAT-to-body mass ratio was markedly smaller in old sedentary mice, accompanied by the decreased amount of protein, whereas there was no significant difference in uncoupling protein (UCP) content, UCP mRNA expression, or guanosine 5'-diphosphate (GDP) binding (an index of UCP activity) between young and old mice. Meanwhile, the swimming training definitely increased BAT mass and its protein content in both the young and old mice, suggesting hypertrophy and hyperplasia. In addition, after the swimming training, the amounts of protein, UCP antigen, and GDP binding in the mitochondria recovered from BAT of both mice increased significantly as compared with the respective sedentary groups, while the expression of UCP mRNA did not vary substantially. These findings suggest that, irrespective of age, swimming training enhances the thermogenic activity and capacity in BAT of mice.

Adipose Tissue, Brown↗
PubMed1990

Bright light blocks the capacity of inescapable swim stress to supersensitize a central muscarinic mechanism.

Clinical and basic researchers have proposed that muscarinic cholinergic mechanisms mediate some effects of chronic stress. Chronic inescapable (forced) swim stress depletes brain biogenic amines and is used to produce learned helplessness in rats. Behavioral and biochemical characteristics of animals in the state of learned helplessness lead some investigators to believe this condition provides a useful animal model of depression. Inescapable swim stress also produces supersensitivity to the hypothermic effect of the muscarinic agonist oxotremorine in the rat. The authors previously demonstrated that bright light potently induces subsensitivity of a central muscarinic mechanism involved in the regulation of core temperature under a variety of circumstances. They now report using a repeated measures design that inescapable swim stress of five days duration produces supersensitivity to oxotremorine (increase in thermic response of 405%). This supersensitivity is reversed within five days by treatment with bright light, despite continuation of daily swim stress. Daily inescapable swim stress was continued beyond cessation of treatment with bright light. Five days later, supersensitivity to the hypothermic effect of oxotremorine was once again evident.

Animals↗
PubMed1990

Chronic swim stress enhances the motoric inhibiting effects of a muscarinic agonist.

The authors previously demonstrated that chronic inescapable swim stress and footshock increase the capacity of a fixed dose of a muscarinic agonist to produce hypothermia in the rat. This project was designed to determine whether chronic inescapable swim stress in cold water would render a low dose of a muscarinic agonist, devoid of an effect on motor behavior in the naive rat (i.e., prior to subjection to the course of swim stress), an inhibitor of mobility. The study involved two groups of rats, an experimental group which received arecoline and a control group which received saline five minutes prior to being placed in an open field. Number of crossings, the dependent variable, was measured in both groups before and after a 14-day course of twice daily inescapable swim stress of 10 minutes duration at 12 degrees C. The arecoline-treated group, as hypothesized, exhibited a significantly greater reduction in number of crossings than the saline-treated groups following the course of swim stress.

Animals↗
PubMed1993

Effect of alpha 2-adrenergic drugs on REM sleep deprivation-induced increase in swimming activity.

Effects of alpha 2-adrenergic agents on rapid eye movement sleep (REMs) deprivation-induced anti-immobility effect in the forced swimming test (FST) were investigated. Mice were deprived of REMs for 24-72 h by a small pedestal method. Animals that were either group housed or socially isolated during the same period as REMs deprivation were used as the control groups. REMs deprivation for 48 and 72 but not 24 h significantly increased swimming activity without increasing locomotor activity. Clonidine HCl (30-300 micrograms/kg, IP), an alpha 2-adrenoceptor agonist, dose-dependently increased swimming activity in group-housed, isolated, and REMs-deprived mice, but the effective doses of clonidine in REMs-deprived mice were lower than those in group-housed or isolated animals. Yohimbine HCl (5 mg/kg, IP), an alpha 2-adrenoceptor antagonist, blocked the clonidine (300 micrograms/kg)- but not the REMs deprivation-induced increase in swimming activity. These results suggest that REMs deprivation enhances the sensitivity of the alpha 2-adrenoceptor and that the increase in swimming activity by REMs deprivation may be mediated by other neuronal mechanisms rather than the alpha 2-adrenoceptor.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1994

Effect of changes in swimming area on results of "behavioral despair test".

Our previous observations have revealed that the total time spent in immobility and time to reach complete immobility (latency) vary with the diameter of the cylindric chamber where mice are forced to swim in the behavioral despair test. Therefore, we investigated the effect of changing the test conditions of the original Porsolt test. Mice were forced to swim for 15 min in chambers with 10 cm (original diameter of the Porsolt's forced swimming chamber), 20, 30, and 50 cm diameter in 20 cm deep water. Total time spent in spells of immobility during the observation period from third to sixth (inclusive) minutes and time to reach complete immobility were measured. In addition, a possible correlation between the rotatory locomotor activity of mice during swimming as assessed by the number of tours per minute and effect of antidepressant drugs on it was investigated. Total duration of spells of immobility was shorter and the latency was longer in tests carried out in chambers with 10 cm diameter. Increasing the diameter of the cylinders made it possible to distinguish the antidepressant drugs from caffeine, anticholinergics, and antihistaminics, which gave a false positive response in 10 cm diameter cylinders, but not in cylinders with larger diameters. Increasing the diameter of the chambers to 20 and 30 cm also allowed to study the selective effect of the antidepressants, namely, the rotatory locomotor activity during swimming. The extension of the test period to 15 min increased the reliability of the measurement of the time to reach complete immobility.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗