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PubMed1998

Swimming capacity of mice is increased by oral administration of a nonpungent capsaicin analog, stearoyl vanillylamide.

Intravenous injection of stearoyl vanillylamide (C18-VA), a nonpungent capsaicin (CAP) analog, enhances adrenaline secretion significantly and as effectively as CAP in rats. Because swimming capacity was enhanced by CAP in mice due to CAP-induced adrenal catecholamine secretion, we investigated the effects of oral administration of C18-VA on swimming capacity using an adjustable-current water pool. Male Std ddY 6-wk-old mice were fed a commercial diet for this study and one group was orally administered C18-VA via a stomach tube. Treated mice were able to swim longer before exhaustion than the control mice (62.9 +/- 5.6 vs. 49.6 +/- 7. 0 min, P < 0.05). The swimming capacity of two groups administered C18-VA (0.02 and 0.033 mmol/kg) was significantly greater than that of those administered vehicle alone, (P < 0.05). Substance P concentration in cerebrospinal fluid, which is involved in pain transmission and is the first direct measure of pungency, was not affected by C18-VA administration. In an experiment examining the effects of C18-VA on serum adrenaline concentration, adrenaline was significantly greater in C18-VA treated mice than in controls at 2-h post-dose (C18-VA group, 26.09 +/- 2.82; control group 13.29 +/- 0. 96 microg/L, P < 0.01). In a separate study free fatty acids in serum were elevated in treated mice at 2-h post-dose (P < 0.01). While serum glucose concentration was not affected. These results suggest that C18-VA increased swimming capacity of mice via adrenaline release, independent of pungency. In addition, the present study suggests the usefulness of its application to humans.

Animals↗
PubMed1997

Regional and fiber-type percentages and sizes in the hamster diaphragm after swim training.

BACKGROUND AND PURPOSE: The purpose of this study was to determine the effect of a swimming endurance training program on changes in percentages and sizes of fiber types in different regions of the hamster diaphragm. METHODS: Adult male golden Syrian hamsters were randomly assigned to a control group (n = 9) or a swimming group (n = 10). Hamsters in the swimming group swam for 80 minutes per session, 5 days per week, for 13 weeks. Fiber-type percentages and sizes were determined for the costal region and for the abdominal and thoracic surfaces of the crural region of the diaphragm from cross sections processed for myofibrillar adenosine triphosphatase. RESULTS: Muscle fibers in the thoracic surface of the crural region were smaller in the swimming group than in the control group. Fiber-type percentages in the diaphragm, however, were not different between groups. CONCLUSION AND DISCUSSION: Swim training may have improved the endurance of the thoracic/crural region by decreasing cross-sectional area and thus decreasing the distance for oxygen to diffuse to the internal regions of the muscle fibers.

Adenosine Triphosphatases↗
PubMed1991

The development of swimming rhythmicity in post-embryonic Xenopus laevis.

The post-embryonic development of 'fictive' swimming in immobilized Xenopus laevis tadpoles has been examined during the first day of larval life. In Xenopus embryos (stage 37-38; Nieuwkoop & Faber 1956), the rhythmic ventral root activity underlying swimming occurs as single brief (ca. 7 ms) compound impulses on each cycle. However, by stage 42 (about 24 h after hatching), ventral root discharge consists of bursts lasting around 20 ms per cycle. In addition to increased burst duration in each cycle of larval swimming, the range of cycle periods within an episode increases, although mean period values (ca. 70-80 ms) remain similar to those of the younger animal. Consequently, motoneurons at developmental stage 42 are active during swimming for a greater percentage (ca. 25%) of cycle time than at stage 37-38 (ca. 10%). Developmental stage 40 (ca. 12 h post-hatching) is an intermediate stage in rhythm development. Ventral root discharge varies from bursts of 10-20 ms at the start of an episode to embryonic (ca. 7 ms) spikes at the end of an episode. Furthermore, discharge varies from bursts of activity in rostral segments of stage 40 larvae to 7 ms spikes more caudally, as in embryos. The data thus suggest that Xenopus swimming rhythmicity develops relatively rapidly, along a rostrocaudal gradient, and may involve acquisition of multiple spiking in spinal neurons.

Animals↗
PubMed2003

The turn of the sword: length increases male swimming costs in swordtails.

Sexual selection via female mate choice can result in the evolution of elaborate male traits that incur substantial costs for males. Despite increased interest in how female mating preferences contribute to the evolution of male traits, few studies have directly quantified the locomotor costs of such traits. A sexually selected trait that could affect movement costs is the sword exhibited by male swordtail fishes: while longer swords may increase male mating success, they could negatively affect the hydrodynamic aspects of swimming activities. Here, we examine the energetic costs of the sword in Xiphophorus montezumae by experimentally manipulating sword length and measuring male aerobic metabolism during two types of activity, routine swimming and courtship swimming. Direct measurements of oxygen consumption indicate that males with longer swords expend more energy than males with shortened swords during both types of swimming. In addition, the sword increases the cost of male courtship. Thus, while sexual selection via female choice favours long swords, males with longer swords experience higher metabolic costs during swimming, suggesting that sexual and natural selection have opposing effects on sword evolution. This study demonstrates a hydrodynamic cost of a sexually selected trait. In addition, this study discriminates between the cost of a sexually selected trait used in courtship and other courtship costs.

Animals↗
PubMed2000

Predisposed to adapt? Clade-level differences in characters affecting swimming performance in damselflies.

Previous studies have shown that two or three lineages of Enallagma damselflies, which historically co-existed with fish, recently invaded and adapted to living with large dragonfly predators in fishless waters. In adapting to live with these new predators, lineages shifted behaviorally to using swimming as an evasive tactic against attacking predators, evolved morphological features that made them faster swimmers, and evolved biochemical features to increase refueling strenuous activities like swimming. However, these habitat shifts have occurred in only one of the two primary clades within the genus in North America. Here, I show that clade-level differences exist among species in the ancestral, fish-lake habitat that should make habitat shifts easier to accomplish in the clade in which they have occurred. Specifically, fish-lake species in the clade in which habitat shifts occurred have much higher propensities to swim in the laboratory, swim faster when they do swim, and have higher mass-specific activities for arginine kinase than do species in the other primary clade, in which no extant species are found in fishless waters. These results are discussed in the context of the dynamics of founder events and the potential implications for community structure.

Adaptation, Physiological↗
PubMed2001

Evolution of intrinsic growth and energy acquisition rates. I. Trade-offs with swimming performance in Menidia menidia.

Latitudinal populations of the Atlantic silverside, Menidia menidia, show substantial genetic variation in rates of energy acquistion and allocation. Reared in common environments, silversides from northern latitudes consume more food, grow faster and more efficiently, store more energy, and produce greater quantities of eggs than their southern conspecifics. The persistence of seemingly inferior southern genotypes in the face of ostensibly superior northern genotypes suggest that there are hidden evolutionary trade-offs associated with these elevated acquisition and allocation rates. We tested the hypothesis that rapid growth and high levels of food consumption trade-off against locomotory performance in M. menidia. We compared both aerobic (prolonged and endurance) and anaerobic (burst) swimming capacities between intrinsically fast-growing fish from the north (Nova Scotia, NS) and intrinsically slow-growing fish from the south (South Carolina, SC) and between growth-manipulated phenotypes within each population. We also compared swimming speeds and endurance between fasted and recently fed fish within populations. Maximum prolonged and burst swimming speeds of NS fish were significantly lower than those of SC fish, and swimming speeds of fast-growing phenotypes were lower than those of slow-growing phenotypes within populations. Fed fish had lower burst speeds and less endurance than fasted fish from the same population. Thus, high rates of growth and the consumption of large meals clearly diminish swimming performance, which likely increases vulnerability to predation and decreases survival and relative fitness. The submaximal growth rate of southern M. menidia appears to be adaptive, resulting from balancing selection on rates of somatic growth.

Aging↗
PubMed2004

The evolution of larval morphology and swimming performance in ascidians.

The complexity of organismal function challenges our ability to understand the evolution of animal locomotion. To meet this challenge, we used a combination of biomechanics, phylogenetic comparative analyses, and theoretical morphology to examine evolutionary changes in body shape and how those changes affected swimming performance in ascidian larvae. Results of phylogenetic comparative analyses suggest that coloniality evolved at least three times among ascidians and that colonial species have a convergent larval morphology characterized by a large trunk volume and shorter tail length in proportion to the trunk. To explore the functional significance of this evolutionary change, we first verified the accuracy of a mathematical model of swimming biomechanics in a solitary (C. intestinalis) and a colonial (D. occidentalis) species and then ran numerous simulations of the model that varied in tail length and trunk volume. The results of these simulations were used to construct landscapes of speed and cost of transport predictions within a trunk volume/tail length morphospace. Our results suggest that the reduction of proportionate tail length in colonial species resulted in improved energetic economy of swimming. The increase in the size of larvae with the origin of coloniality facilitated faster swimming with negligible energetic cost, but may have required a reduction in adult fecundity. Therefore, the evolution of ascidians appears to be influenced by a trade-off between the fecundity of the adult stage and the swimming performance of larvae.

Animals↗
PubMed1995

Dissociation between behavioral and hormonal responses to the forced swim stress in lactating rats.

Retention of immobility in the Porsolt forced swim test is believed to be dependent upon glucocorticoid secretion in male rats. Because lactating females exhibit increased basal glucocorticoid secretion and blunted stress responses, we tested the hypothesis that lactation-induced changes in adrenal glucocorticoid and in circulating estrogen and progesterone levels would improve retention and/or acquisition of immobility. Immobility was recorded during 3 intervals of 5 min on day 1 (acquisition) and one 5 min interval 24 h later (retention). Blood samples were collected before the swim test and at various times after the onset of stress for plasma ACTH and corticosterone (B) determinations. Male rats (young=200 g, old=325 g) were compared to virgin females (V) and to lactating females in early (day 8-10, EL) and late (day 17-19, LL) lactation. Adrenalectomy (ADX) and ovariectomy (OVX) were performed 5 and 10 days prior to testing, respectively. All animals acquired immobility at the end of the 15 min swim on day 1, but only the young male group exhibited a significant retention of immobility on day 2. Total immobility was higher in males than females (V) although basal and stress-induced ACTH and B secretion were comparable on both testing days. Lactational status did not affect immobility in either the acquisition or retention phases. However, stress-induced ACTH secretion was greatly diminished in intact and ADX lactating females (EL and LL) compared to virgins (LL < EL < virgin), demonstrating a clear dissociation between behavioral and neuroendocrine responses. Following ADX, immobility in the retention phase was either decreased in males or increased in lactating females. Finally, OVX decreased immobility in both lactating (EL) and virgin females without significantly altering the magnitude of the ACTH and B responses to stress. In summary, our results demonstrated both sex-related and lactation-related differences in the behavioral and endocrine responses to he forced swim test of Porsolt. Although retention of the immobile response is thought to involve glucocorticoids and/or opioids secreted during the first testing session, we did not find evidence for a direct relationship between basal or stress-induced total corticosterone secretion, the magnitude of ACTH response to stress and behavioral scores in the retention period. However, experimental variables such as body weight, sex and water depth could significantly modify the outcome of behavioral testing and question the validity of glucocorticoid-mediated retention processes. Since the effect of ADX was reversed in lactating females compared to male rats, we hypothesize that glucocorticoid sensitivity of cognitive processes controlling behavioral reactivity is different from that controlling hypothalamic-adrenocortical function. Our results also demonstrated a clear dissociation between behavioral and neuroendocrine responses to the swim test, in particular during lactation. In early and late lactation, blunted responsiveness to stress was not caused by enhanced glucocorticoid feedback but might result from modifications in the inhibitory and/or stimulatory inputs to hypothalamic neurons controlling adrenocortical activity.

Adrenalectomy↗
PubMed1993

Unusual responses of nocturnal pineal melatonin synthesis and secretion to swimming: attempts to define mechanisms.

The effect of swimming at night on rat pineal melatonin synthesis was compared with that of light exposure at night. Rats were forced to swim at 0030 hr (lights out at 2000 hr) and sacrificed by decapitation 15 and 30 min later, immediately after swimming. Other groups of animals were exposed to white light (650 muW/cm2) for 15 and 30 min at same time. Swimming caused a rapid and highly significant drop in the melatonin content in the pineal gland; however, the activity of N-acetyltransferase (NAT), the supposed rate limiting enzyme in the melatonin production, was not changed. Despite the drop in pineal melatonin levels, serum concentrations of the indole remained elevated in the rats that swam. In contrast, melatonin levels in the pineal and serum of light exposed rats fell precipitously, accompanied by a significant suppression of NAT activity. Since we anticipated that the strenuous exercise associated with swimming may induce release of artrial natriuretic peptide (ANP) from the heart, which in turn could cause the release of pineal melatonin, in a second study we injected physiological saline intravenously to stretch the cardiac muscle and release ANP. Three milliliters of normal saline was injected during the day into the jugular vein of anesthetized rats that were pretreated with isoproterenol to stimulate pineal melatonin production. Animals were killed 15 min after the saline injection, and pineal NAT activity and pineal melatonin levels were measured. The saline injections caused no alteration in the elevated levels of either NAT or melatonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Alpha-adrenoceptor involvement in swim stress-induced antinociception in the mouse.

Three different intensities of swim stress produced stress-induced antinociception (SIA) in mice which was assessed either by the reduction in the number of abdominal constrictions produced by acetic acid or by an increase in reaction time on a hot-plate. The involvement of alpha-adrenoceptors in the three models of SIA was investigated using selective antagonists. SIA produced by the mild stress of a 30 s warm water swim was attenuated by idazoxan (0.5-1 mg kg-1), and by yohimbine at a dose (1 mg kg-1) which reduced antinociception produced by clonidine (12.5-50 micrograms kg-1). Indoramin (1-2 mg kg-1) did not affect this model of SIA, but reversed phenylephrine induced inhibition of the constrictions. A 3 min room temperature swim increased reaction times on the hot-plate and this naloxone-sensitive SIA was reduced significantly by prazosin (1-2 mg kg-1), idazoxan (0.5-1 mg kg-1) and yohimbine (0.5-1 mg kg-1) but enhanced by clonidine (0.5 mg kg-1) and noradrenaline (NA) (10 micrograms i.c.v.). Mice treated with 6-hydroxydopamine (60 + 60 micrograms i.c.v.) were hypersensitive to the hot-plate and did not develop SIA. Levels of noradrenaline in the brain (minus the cerebellum) were decreased after the room temperature swim SIA. The most severe stress of a cold water swim produced SIA on the hot-plate which was initially naloxone-insensitive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1984

Excitatory amino acid receptors in Xenopus embryo spinal cord and their role in the activation of swimming.

Bath application of N-methyl-D-aspartate (NMDA), kainate or quisqualate to Xenopus embryos depolarized spinal cord motoneurones and reduced their input resistance in both normal salines and salines containing 20 mM-Mn2+ and 0.5 mM-Ca2+, or 2 X 10(-6) M-tetrodotoxin. This suggests that motoneurones possess all three types of excitatory amino acid receptor. These receptors have similar specificities to excitatory amino acid antagonists as those occurring in adult frog and cat spinal cords. Application of 30-40 microM-NMDA or 5-6.5 microM-kainate to the medium bathing spinalized embryos can cause a sustained patterned motor output similar to that of swimming evoked by natural stimulation of intact animals. At these concentrations NMDA and kainate depolarized motoneurones by 19.0 +/- 1.80 (mean +/- S.E. of mean) and 18.0 +/- 2.00 mV respectively and decreased their input resistance by 23.0 +/- 2.82% and 24.0 +/- 3.46%. These changes are similar to those associated with the tonic excitation which motoneurones receive during naturally evoked swimming. Bath application of 5-8 microM-quisqualate to spinal embryos can also cause a sustained motor output. However, this was different to that evoked by NMDA and kainate and was inappropriate for swimming. When applied to intact animals during swimming both 2-3 mM-cis-2,3-piperidine dicarboxylic acid (PDA) and 0.5 mM-gamma-D-glutamylglycine (DGG) selectively blocked the tonic excitation of motoneurones and in doing so abolished the motor output of the spinal cord. 50-200 microM-2-amino-5-phosphonovaleric acid reduced the tonic excitation but to a lesser extent than either PDA or DGG. The tonic excitation of motoneurones which occurs during swimming therefore appears to be mediated via an endogenous excitatory amino acid transmitter which acts on NMDA and kainate receptors.

Animals↗
PubMed1988

Function of identified motoneurones and co-ordination of primary and secondary motor systems during zebra fish swimming.

1. The activity of the two classes of motoneurones, primary and secondary, which innervate myotomal muscle fibres in the zebra fish, was monitored with electromyographic and intracellular techniques. 2. Simultaneous EMG and intracellular recordings from muscle fibres showed that the activity of the two motor systems and of individual primary motoneurones can be distinguished by recording EMG spikes during swimming. 3. Measurements of EMG spikes demonstrated that primary and secondary motoneurones are co-ordinately activated over a wide range of conditions during normal swimming. 4. During swimming the primary motoneurones within a given segment are usually co-activated although they sometimes fire independently. 5. When different primary motoneurones within a given segment are co-activated, they fire nearly synchronously. 6. We conclude that the primary motoneurones are used principally, although not exclusively, during fast swimming, struggling and the startle response, whereas secondary motoneurones function primarily during slower swimming.

Action Potentials↗
PubMed1970

Crayfish swimming: alternating motor output and giant fiber activity.

Many workers have suggested that the crayfish giant fibers trigger swimming movements or tail flips during escape responses. Recordings from intact animals show that this is often not the case; both swimming and single tail flips can occur in the absence of giant fiber activity. Swimming movements and tail flips are coordinated by neural mechanisms not involving the giant fibers. When giant fibers are active, they may trigger the first flexion in a swimming sequence, initiate a single tail flip, or synchronize the muscular activity in the several segments of the abdomen, but they are not a necessary part of the neural oscillator which drives swimming.

Action Potentials↗
PubMed1986

Swimming experiences and abilities of nine year olds.

As part of a longitudinal study of children, 941 mothers were asked to report on their childrens' swimming experiences and abilities. At age nine, twenty-nine per cent of the children could swim only a few strokes or not at all. A disproportionate number of children who could swim more than a few strokes came from high socio-economic backgrounds, from families where one or more of the parents could swim, and which scored higher on an index of active recreational orientation. There were no significant sex differences in swimming ability. There were 97 incidents reported where a child had been in difficulties while in water and had to be rescued. The importance of collecting data on such incidents is discussed.

Child↗
PubMed2006

Influence of water immersion, water gymnastics and swimming on cardiac output in patients with heart failure.

BACKGROUND: Whole-body water immersion leads to a significant shift of blood from the periphery to the intrathoracic circulation, followed by an increase in central venous pressure and heart volume. In patients with severely reduced left ventricular function, this hydrostatically induced volume shift might overstrain the cardiovascular adaptive mechanisms and lead to cardiac decompensation. AIM: To assess the haemodynamic response to water immersion, gymnastics and swimming in patients with chronic heart failure (CHF). METHODS: 10 patients with compensated CHF (62.9 (6.3) years, ejection fraction 31.5% (4.1%), peak oxygen consumption (Vo(2)) 19.4 (2.8) ml/kg/min), 10 patients with coronary artery disease (CAD) but preserved left ventricular function (57.2 (5.6) years, ejection fraction 63.9% (5.5%), peak Vo(2) 28 (6.3) ml/kg/min), and 10 healthy controls (32.8 (7.2) years, peak Vo(2) 45.6 (6) ml/kg/min) were examined. Haemodynamic response to thermoneutral (32 degrees C) water immersion and exercise was measured using a non-invasive foreign gas rebreathing method during stepwise water immersion, water gymnastics and swimming. RESULTS: Water immersion up to the chest increased cardiac index by 19% in controls, by 21% in patients with CAD and by 16% in patients with CHF. Although some patients with CHF showed a decrease of stroke volume during immersion, all subjects were able to increase cardiac index (by 87% in healthy subjects, by 77% in patients with CAD and by 53% in patients with CHF). Vo(2) during swimming was 9.7 (3.3) ml/kg/min in patients with CHF, 12.4 (3.5) ml/kg/min in patients with CAD and 13.9 (4) ml/kg/min in controls. CONCLUSIONS: Patients with severely reduced left ventricular function but stable clinical conditions and a minimal peak Vo(2) of at least 15 ml/kg/min during a symptom-limited exercise stress test tolerate water immersion and swimming in thermoneutral water well. Although cardiac index and Vo(2) are lower than in patients with CAD with preserved left ventricular function and controls, these patients are able to increase cardiac index adequately during water immersion and swimming.

Adult↗
PubMed2003

Assessing the health impact of local amenities: a qualitative study of contrasting experiences of local swimming pool and leisure provision in two areas of Glasgow.

STUDY OBJECTIVE: To assess the health impacts of local public swimming pool and leisure provision. DESIGN: Retrospective qualitative study using focus groups. Reports from two areas with contrasting experience of provision of a public swimming pool (opening and closure) were compared within the context of general reports about health and neighbourhood. SETTING: Two deprived neighbourhoods in south Glasgow. PARTICIPANTS: Local adult residents of mixed ages, accessed through local community groups. MAIN RESULTS: In both areas the swimming pool was reported as an important amenity that was linked to health and wellbeing. However, few residents reported regular use of the pool for physical activity. Use of the pool facility for social contact was directly linked to reports of relief of stress and isolation, and improved mental health. Pool closure was one in a series of amenity closures and area decline and was used to represent other area changes. Health impacts were strongly linked to the pool closure. The pool opening was associated with local area regeneration, similar but less prominent links between swimming pool provision and health were reported. Health benefits of social contact were diffuse and linked to other local amenities as well as the new pool facility. CONCLUSIONS: Although theoretically linked to increased physical activity, the health benefits conveyed by the swimming pool may be more closely linked to the facilitation of social contact, and a supervised facility for young children. The use of qualitative work to investigate area based change provides rich contextual data to strengthen and explain the reported health impacts.

Adult↗
PubMed2005

VO2 responses to intermittent swimming sets at velocity associated with VO2max.

While the physiological adaptations following endurance training are relatively well understood, in swimming there is a dearth of knowledge regarding the metabolic responses to interval training (IT). The hypothesis tested predicted that two different endurance swimming IT sets would induce differences in the total time the subjects swam at a high percentage of maximal oxygen consumption (VO(2)max). Ten trained triathletes underwent an incremental test to exhaustion in swimming so that the swimming velocity associated with VO(2)max (vVO(2)max) could be determined. This was followed by a maximal 400-m test and two intermittent sets at vVO(2)max: (a) 16 x 50 m with 15-s rest (IT(50)); (b) 8 x 100 m with 30-s rest (IT(100)). The times sustained above 95% VO(2)max (68.50 +/- 62.69 vs. 145.01 +/- 165.91 sec) and 95% HRmax (146.67 +/- 131.99 vs. 169.78 +/- 203.45 sec, p = 0.54) did not differ between IT(50) and IT(100)(values are mean +/- SD). In conclusion, swimming IT sets of equal time duration at vVO(2)max but of differing work-interval durations led to slightly different VO(2)and HR responses. The time spent above 95% of VO(2)max was twice as long in IT(100) as in IT (50), and a large variability between mean VO(2)and HR values was also observed.

Adaptation, Physiological↗
PubMed1982

Response of blood pressure and cardiac myosin polymorphism to swimming training in the spontaneously hypertensive rat.

Cardiac muscle can adapt to different functional demands, as evidenced by polymorphism of myosin. Pressure load in spontaneously hypertensive rats induced a shift of the myosin isoenzymes towards myosin V3 (18% V1, 27% V2, 55% V3) relative to normotensive Wistar rats (49% V1, 29% V2, 22% V3). A swimming routine with Wistar rats resulted in a shift towards myosin V1 (72% V1, 18% V2, 10% V3). The training effect is not restricted to normotensive rats, since spontaneously hypertensive rats subjected to the same swimming routine exhibited a myosin isoenzyme pattern (38% V1, 31% V2, 31% V3) approaching that of the sedentary Wistar rats. Swimming training can, therefore, prevent the myosin isoenzyme redistribution towards myosin V3 found in sedentary spontaneously hypertensive rats. Furthermore, systolic blood pressure was significantly reduced (130 +/- 8 mmHg (1 mmHg = 133.322 Pa) ) in the swim-trained compared with the sedentary spontaneously hypertensive rats (157 +/- 12 mmHg). The training-induced changes in myosin polymorphism and systolic blood pressure are, at least partially, attributed to substantially normalized sympathetic activity. The functional relevance of swimming training in the spontaneously hypertensive rat is seen in the increased potential of coping with situations requiring fast contraction which may occur during sudden physical exertion or emotional stress.

Animals↗