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PubMed1995

Developmental exposure to ozone induces subtle changes in swimming navigation of adult mice.

Following exposure to ozone (O3, 0.6 ppm) from the beginning of neonatal life until weaning, adult CD-1 mice were tested in swimming navigation, a sensitive indicator for hippocampal damage. Control mice received a sham exposure. All mice were tested at 12-13 weeks of age for their ability to find a submerged platform in a fixed location (acquisition: 18 trials, six trials per day) and for capacity to re-orient towards a new platform position (reversal: 12 trials, six trials per day). Exposure to O3 did not produce any significant impairment of swimming navigation during the acquisition phase while it slightly increased the swimming paths during the last day of the reversal phase. Mice exposed to O3 showed a slightly but significantly higher swimming speed during all the days, which was unrelated to differences in body weight and to navigational performances. Moreover, mice exposed to O3 (with the exception of one animal) had a strong tendency to make turns to the left while the controls, independent of sex, preferred clockwise turns. Data are discussed with respect to possible implications with early CNS and immune alteration leading to behavioral asymmetries at adulthood.

Animals↗
PubMed2004

Impact of PCB mixture (Aroclor 1254) and TBT and a mixture of both on swimming behavior, body growth and enzymatic biotransformation activities (GST) of young carp (Cyprinus carpio).

The sensitivity of carp to chronical stress due to single and combined mixtures (each 50%) of TBT and PCB was evaluated under laboratory conditions. And concluded, mixed exposures were partially more or less toxic than single ones. Xenobiotic stress led to both decreased mean daily swimming speed and an increased mean swimming speed during darkness. Also a decreased preferred swimming depth (nearer to the surface) during nighttime was observed. We found approximately synergistic effects of TBT and PCB in swimming behavior of carp exposed to those mixtures. PCB did not affect the body growth significantly, TBT-stress led to a decreased body growth and the exposure to PCB-TBT mixture caused an approximately additive decrease of body growth. Measurement of biotransformation potential measured as GST enzyme activity showed both increasing or decreasing activity levels after exposure to single and mixture chemical combinations (approximately additive, antagonistic and synergistic). Nevertheless, we had to conclude that all methods tested were useful to screen subacute effects of single as well as mixed xenobiotic chemicals on carp, which is the prerequisite for an investigation of samples taken from the environment.

Animals↗
PubMed2006

New insights into the vascular mechanisms underlying the beneficial effect of swimming training on the endothelial vasodilator function in apolipoprotein E-deficient mice.

The antiatherogenic role of exercise is poorly understood. We examined the swimming exercise-induced vascular mechanisms which enhance the endothelial vasodilator function in apoE(-/-) mice. Male apoE(-/-) mice treated for 9 weeks with a lipid-rich diet were divided into two groups: the exercise group (apoE(-/-) X), which underwent a 9-week swimming protocol (50 min/day; 5days/week) and the sedentary group (apoE(-/-) S). C57BL/6 mice were used as the control group. Atherosclerotic lesions in the aortic roots were significantly reduced in apoE(-/-) X compared to apoE(-/-) S. Relaxation to acetylcholine was improved in apoE(-/-) X as compared to apoE(-/-) S and control mice with E(max) and pD(2) values significantly higher. pD(2) values in response to papaverine were higher in apoE(-/-) X than in the other groups. Relaxation in response to A23187 and DEA-NONOate were similar. These findings suggest that swimming training may increase the sensitivity of relaxation to acetylcholine, which in turn activates acetylcholine-mediated signaling pathways leading to increased NO bioactivity. Swimming may also prolong the signaling actions of NO by stimulating the sensitivity of vascular smooth muscle cells to cyclic nucleotides. These appear to be the key mechanisms underlying the improvement of the NO-cGMP pathway in exercised apoE(-/-) mice.

Acetylcholine↗
PubMed2005

Endocrine and immunological correlates of behaviorally identified swim stress resilient and vulnerable rats.

Animal models of stress-induced depression have identified a bimodal reactivity to stress, namely 'resilience' and 'vulnerability.' Possible corresponding differences in endocrine and immunological responses between these groups have not been delineated. Male Sprague-Dawley rats were divided into three groups: stress (n=25), confined controls (n=7), and home cage controls (n=7). Stress rats were exposed to 80, 5-s inescapable cold water swim trials (15 degrees C). Twenty-four hours later, the stress rats were tested on an instrumental swim escape test (SET) but now they had access to an omnidirectional lever that terminated the stress. Immediately after the SET, trunk blood was collected to assay for serum corticosterone (CORT), and spleens were removed and natural killer cell activity (NKCA) and concanavalin A (CON-A) induced lymphocyte proliferation determined. Subjects in the stress treatment group were divided into distinct 'resilient' and 'vulnerable' categories by a median split for average escape latencies across the last 25 trials of the SET. Stress rats secreted more CORT than controls and vulnerable rats secreted greater levels than resilient rats. NKCA was greatest in control rats, and was decreased in the stress rats although the resilient and the vulnerable groups did not differ. Conversely, CON-A-induced lymphocyte proliferation was greatest in stress rats, vulnerable rats exhibiting more proliferation than resilient rats, but both were greater than both control groups. Stress animals were hypothermic throughout the swim stress procedures but exhibited a stress-induced fever following the initial swim trials. The observed differences may have important predictive and theoretical utility for vulnerable and resilient profiles.

Adaptation, Psychological↗
PubMed2006

Role of amygdala MAPK activation on immobility behavior of forced swim rats.

The role of amygdala mitogen-activated protein kinase (MAPK) in rats during a forced swim test was investigated. The variation of amygdala MAPK level was studied in control rats and early-life maternally deprived rats. A forced swim test was carried out to estimate the immobility level. The data showed that the immobility time of rats that received maternal deprivation in early life was longer than that of control rats and Western blot analysis also showed that the amygdala phospho-MAPK level in maternally deprived rats was almost two times higher than in control rats. Intra-amygdala infusion of PD098059 or U0126, MEK inhibitors, suppressed immobility behavior during the forced swim test in both rats. Western blot analysis also showed that the amygdala MAPK activities in both rats infused with MEK inhibitors were also suppressed in parallel with expression of immobility behavior. The suppressed MAPK activities as well as the restoration of immobility time returned to the original level 48 h later. These results suggest that amygdala MAPK activation might play a role in the regulation of immobility behavior in rats during the forced swim test. Moreover, it could provide a hint that amygdala MAPK activation might be involved in the formation of depression-like behavior.

Amygdala↗
PubMed2006

The depressive-like behaviors are correlated with decreased phosphorylation of mitogen-activated protein kinases in rat brain following chronic forced swim stress.

In the present study, 40 Sprague-Dawley rats were divided into forced swim stress group and controls, with 20 rats in each group (10 for behavioral tests, 10 for protein detection). The forced swim stress group received swim stress for 14 consecutive days, and the controls were stress-free. After stress, 20 rats were tested for behavioral observation using body weight gain, open field, elevated plus-maze and saccharin preference test, and 20 rats were decapitated for protein detection. The extracellular signal-regulated kinase (Erk) and phospho-Erk (P-Erk) in the hippocampus and prefrontal cortex were determined using western blot. It was found that the body weight gain of stressed animals during the 7 stressed days and the 14 stressed days was significantly decreased compared to that of controls. Stressed animals spent less time in open arms and longer time in closed arms. The stressed animals demonstrated decreased locomotor activity and increased grooming in open field. The saccharin solution intake and the ratio of saccharin solution intake to total liquid intake were both decreased in the stressed group. Stressed animals showed decreased P-Erk2 and decreased ratio of P-Erk2 to total Erk2 in the hippocampus and prefrontal cortex, but their Erk1/2 was increased in the prefrontal cortex with no change in hippocampus. The saccharin solution intake positively correlated with the P-Erk2 in the hippocampus and negatively correlated with the Erk2 in the prefrontal cortex. In conclusion, chronic forced swim stress was a good animal model of depression, and it induced depressive-like behavior and decreased P-Erk2 in the hippocampus and prefrontal cortex in rats. The depressive-like behaviors were correlated with decreased phosphorylation of Erk, which suggested that the dysfunction of Erk activity might be one of biological mechanisms underlying depression induced by stress.

Animals↗
PubMed2004

Swim posture of mice does not affect performance in the water maze.

We quantified swim postures of mice in relation to their cognitive performance. After training in a water maze, young (5-6 months) and aged (14-16 months) female apolipoprotein E-knockout (apoE0/0) mice and wild type controls were video taped while swimming. Subsequently, angles of body points with the water surface were calculated. Mice with a more horizontal swim posture (young and aged apoE0/0, aged wild type mice) also showed an increased body weight. However, swim posture was not related to cognitive performance.

Aging↗
PubMed2005

Combined effects of pulp and paper effluent, dehydroabietic acid, and hypoxia on swimming performance, metabolism, and hematology of rainbow trout.

Experiments were conducted to examine the effects of a thermomechanical (TMP)/bleached kraft pulp and paper mill effluent (BKME), dehydroabietic acid (DHAA), hypoxia, and combinations of hypoxia and effluent on juvenile rainbow trout. In the first two experiments, trout were exposed for 4 weeks to 0%, 10%, 30%, and 70% TMP/BKME or 0, 35, 110, and 250 microgL(-1) DHAA, respectively. Endpoints of those dose-response studies included critical swimming speed, oxygen consumption, and hematology. Reduced swimming performance was found for fish exposed to 70% TMP/BKME. Moderate increases in mean cell hemoglobin concentration at 70% TMP/BKME and blood glucose at 30% and 70% TMP/BKME were also seen. The opposite trend for glucose was found for DHAA-exposed fish, where a slight decrease in glucose was seen at 110 and 250 microgL(-1) DHAA. The third experiment examined the effects of 15% v/v TMP/BKME exposure at 2.5 and 5.0 mgL(-1) dissolved oxygen (DO) for 4 weeks. This experiment found no effect of low DO on swimming ability. An interactive effect between DO and effluent exposure was seen only on hematocrit, where effluent caused an increase in hematocrit at 5 mgL(-1) and a decrease at 2.5 mgL(-1) DO. Effluent exposure in this experiment resulted in a greater number of smaller red blood cells. The current study demonstrated physiological effects in rainbow trout exposed to varying concentrations (15-70% v/v) of a TMP/BKME and no substantial effects of DHAA exposure. With the exception of the reduced swimming performance in fish exposed to TMP/BKME, the observed effects are considered relatively small in magnitude but are occurring at concentrations of effluent that occur in the receiving environment.

Abietanes↗
PubMed2006

Caffeic acid attenuates the decrease in cortical BDNF mRNA expression induced by exposure to forced swimming stress in mice.

We previously reported that caffeic acid produces antidepressive-like effects in the forced swimming test in mice, an animal model of depression. Increased evidence suggests that brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family that has high affinity for the tyrosine kinase receptor B (TrkB), plays an important role in the pathophysiology and treatment of depression. The present study examined whether caffeic acid affects the expression levels of BDNF and TrkB mRNA in brain regions of mice subjected to a forced swimming test. Caffeic acid (4 mg/kg, i.p.) reduced the duration of immobility of mice in the forced swimming test. The levels of BDNF mRNA in the frontal cortex as well as TrkB mRNA in the amygdala were significantly decreased after the forced swimming test, and the former reduction was significantly inhibited by caffeic acid (4 mg/kg, i.p.). Caffeic acid (4 mg/kg, i.p.) did not modify the levels of BDNF and TrkB mRNA in brain regions of naive mice. These results suggest that caffeic acid can attenuate the down-regulation of BDNF transcription that results from stressful conditions.

Animals↗
PubMed2006

Prevention of pro-depressant effect of L-arginine in the forced swim test by NG-nitro-L-arginine and [1H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one].

Previous studies have shown that l-arginine, the precursor of nitric oxide, has a dual effect (antidepressant and pro-depressant) in the forced swim test. The aim of the present study was to investigate whether nitric oxide-cGMP pathway was involved in this dual effect. Porsolt swim test was conducted to resemble the symptomatology of major depressive disorder. An open field locomotor activity test was also used. L-arginine exerted a U-shape effect in the forced swim test: doses of 30, 100, 300, and 1000 mg/kg caused no alteration, statistically significant reduction, no alteration, and non-significant enhancement, respectively. Neither N(G)-nitro-L-arginine (NNA) nor [1H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one] (ODQ) at doses of 3 mg/kg was found to be effective in the forced swim test, whereas 10 mg/kg ODQ significantly reduced the immobility time. In the presence of NNA, the antidepressant and pro-depressant effects of L-arginine disappeared, however, only the pro-depressant component of l-arginine effect was prevented by ODQ (3 and 10 mg/kg). Saline, the solvent of L-arginine and NNA, and dimethyl sulfoxide (15% in saline), the solvent of ODQ, had no effect on the duration of immobility. None of the drugs or solvents used in the present study had any effect on locomotor activity over the dose range applied. The results show that L-arginine exerts its paradoxical effects by producing nitric oxide and that cGMP seems to have a role only in the pro-depressant component.

Animals↗
PubMed2006

Behavioral depression in the swim test causes a biphasic, long-lasting change in accumbens acetylcholine release, with partial compensation by acetylcholinesterase and muscarinic-1 receptors.

The nucleus accumbens may play a role in acquisition and expression of behavioral depression as measured using the inescapable swim test. Previous work shows that a local injection of a cholinergic muscarinic-1 receptor agonist increases immobility and a specific muscarinic-1 antagonist acts as an antidepressant-like drug by increasing swimming escape efforts. The present study used microdialysis to monitor extracellular acetylcholine levels in the accumbens, fluorescent labeled toxins to monitor changes in acetylcholinesterase and muscarinic-1 receptors, and semiquantitative-polymerase chain reaction to detect changes in gene expression for the muscarinic-1 receptor. Microdialysis showed that acetylcholine levels did not change while an animal was swimming; however, a significant transient decrease occurred when the rat was returned to the dialysis cage, followed by a long-lasting increase that reached a maximum three hours after the test. Acetylcholine levels stayed high even 24 h after the initial test as evidenced by a significant elevation in basal level prior to the second swim. This increase in neurotransmitter may have been partially compensated by a significant increase in the degradative enzyme, acetylcholinesterase, and by a decrease in muscarinic-1 receptors and their gene expression. These results further demonstrate the importance of accumbens cholinergic function in the appearance of a depression-like state.

Acetylcholine↗
PubMed2003

Involvement of tachykinin NK1 receptor in the behavioral and immunological responses to swimming stress in mice.

This study investigated the influence of a selective tachykinin NK(1) receptor antagonist FK888 on the performance of mice in the elevated plus-maze test and on peripheral blood count after central treatment with substance P (SP) compared to animals submitted to a swim stress session. Percentage of time spent on open arms was significantly reduced by SP treatment as well as the percentage of entries into open arms and the number of head-dipping, indicating an anxiogenic-like profile of action to SP, as previously described. Nevertheless, SP did not affect the peripheral blood counting. The swim stress also promoted a marked reduction in the exploration of the open arms of the plus-maze as well as in the number of leukocytes, most notably lymphocytes. FK888 alone showed the reverse effect, i.e. an anxiolytic-like profile, increasing the frequency of entries and the time spent in the open arms, but did not affect the blood parameters used as an index of the immune system activity. Nevertheless, FK888 (100 pmol) inhibited the anxiogenic-like profile of SP and swimming stress and also prevented the effect promoted by the swimming stress on the immunological parameters, i.e., the reduction in the number of peripheral leukocytes. These findings are discussed in terms of the interaction between the CNS and the immune system and the involvement of the tachykininergic system.

Animals↗
PubMedDate not supplied

Effects of dizocilpine (MK-801) on circling behavior, swimming activity, and place preference in zebrafish (Danio rerio).

Glutamate transmission plays an important role in many behavioral systems, including motor activity, learning, and memory. The noncompetitive NMDA receptor antagonist (+)MK-801 has been shown to increase motor activity and impair learning and memory in a variety of tasks in rats, mice, and other species. In an attempt to characterize the effects of MK-801 on motor activity and cognitive performance in an emerging neurobehavioral model, the zebrafish (Danio rerio), we examined the effects of MK-801 on circling behavior, swimming activity, and latency to enter, as well as preference for, an enriched chamber (EC). In Experiment 1, the effects of a 37-min acute exposure to (+)MK-801 (0, 2.0, and 20.0 microM) on circling behavior were measured in a round observation chamber. (+)MK-801 was observed to increase circling behavior in a dose-dependent manner. In the second experiment, fish were treated with 0, 2, 20, or 200 microM (+)MK-801 for 1 h, and swimming activity was measured in a rectangular observation chamber for 60 min following dosing. The lowest dose of (+)MK-801 decreased swimming activity. In the third experiment, fish were treated with either 0 or 20 microM (+)MK-801 for 1 h each day over four consecutive days. The fish were tested in a modified T-maze to assess both latency to enter, and preference for, an EC 24, 27, and 48 h after the last treatment. The results showed that untreated fish exhibited a preference for the EC at the 27- and 48-h trials, but (+)MK-801-treated fish did not exhibit a preference for the EC at any trial. No significant reduction in latency to enter the chamber was found for either treated or control fish. Together, the results of these experiments suggest that NMDA receptor antagonism (1) increases circling behavior, (2) alters swimming activity, and (3) impairs place preference. These findings lend further support for the usefulness of the zebrafish for assessing the acute and chronic exposure effects of water-soluble compounds on motor and cognitive functions.

Animals↗
PubMedDate not supplied

Developmental chlorpyrifos effects on hatchling zebrafish swimming behavior.

Chlorpyrifos (CPF), a widely used organophosphate insecticide and potent acetylcholinesterase inhibitor, interferes with neurobehavioral development. Rat models have been key in demonstrating that developmental CPF exposure causes learning deficits and locomotor activity alterations, which persist into adulthood. Complementary nonmammalian models can be useful in determining the neurodevelopmental mechanisms underlying these persisting behavioral effects. Zebrafish (Danio rerio) with their clear chorion and extensive developmental information base provide an excellent model for assessment of molecular processes of toxicant-impacted neurodevelopment. We have developed methods for assessing spatial discrimination learning in adult zebrafish and have documented persisting effects of developmental CPF exposure on swimming activity and learning after low and high doses of CPF (10 and 100 ng/ml) administered to zebrafish embryos on Days 1-5 postfertilization (pf). In the current study, we developed methods for behavioral assessment of CPF exposure on swimming activity in newly hatched zebrafish. An equal area segmented annular grid (concentric circles divided into quadrants through the diameter) was made in a 16-mm diameter cylinder. The test area was placed on a heating device secured to an Olympus SZH10 dissecting scope stage. Zebrafish embryos were exposed to 10 ng/ml CPF, 100 ng/ml CPF, or vehicle control (25 microl/ml DMSO) (n=8-10/treatment group). Each treatment group was kept in a total volume of 25 ml of egg water (60 mg/ml Instant Ocean) including DMSO with or without CPF mixed to above dilutions in an incubator set at 28.5 degrees C. CPF dilutions or vehicle were changed daily with exposure ending on Day 5 pf. Testing of larval zebrafish was performed on Days 6 and 9 pf. The fish were placed in the test cylinder with 1.5 ml of egg H(2)O (28.5 degrees C). After a 2-min acclimation period, the swimming activity of the fish was measured for a 3-min testing session. The 100 ng/ml CPF dose caused significant slowing of swimming activity on Days 6 and 9 pf and had persisting effects of impairing spatial discrimination and decreasing response latency in adulthood. Developmental exposure to 10 ng/ml of CPF did not cause a significant change in locomotor activity during the period soon after hatching. CPF exposure during early development caused clear behavioral impairments detectable during the posthatching period. In a previous study, we found that early developmental CPF exposure caused behavioral alterations in zebrafish, which lasted throughout adulthood. The molecular mechanisms by which early developmental CPF exposure produces these behavioral impairments expressed in adulthood can now be studied in the zebrafish model.

Animals↗
PubMed2004

Antidepressant-like effects of the acute and chronic administration of nicotine in the rat forced swimming test and its interaction with fluoxetine [correction of flouxetine].

An antidepressant action of nicotine (NIC) has recently been suggested. Flouxetine, a selective serotonin reuptake inhibitor, is currently the most widely used antidepressant. In the present study, we analyzed the effects of the administration of NIC, fluoxetine (FLX), and the combination of both drugs given acutely, subchronically, and chronically as well as 7 days after chronic administration of these drugs on the forced swim test. Results showed that NIC induced a significant reduction of the time in immobility during the forced swim test (antidepressant effect), with a concomitant increase in swimming activity (serotonergic activation), after acute administration. These effects remain the same after subchronic and chronic administration. FLX failed to induce any effect after acute administration but did induce a significant decrease of immobility and an increase of swimming after subchronic administration. The effect of the chronic administration was significantly larger compared to subchronic administration. The combination of both drugs induced a larger effect than that observed after a single administration but only after subchronic treatment. No effect was observed after the end of the 7-day treatments. Data suggest that NIC has an antidepressant action that is expressed faster than FLX but remains the same later. Thus, cholinergic-serotonergic interactions could play an important role in the treatment of depression.

Animals↗
PubMed2005

Alterations in GABAergic function following forced swimming stress.

Forced swimming induces alterations in the GABA brain concentration and could change the sensitivity of the GABA/benzodiazepine receptor-chloride ionophore complex to benzodiazepines. This change in sensitivity could be explained by the allopregnanolone release that takes place during stress. The current study was carried out to determine whether forced swimming is able to modify the anti-anxiety effect of diazepam and to explore the possible relation of this change to allopregnanolone, the GABA concentration or/and the GABA/benzodiazepine receptor density. Unstressed and stressed mice, injected with the vehicle or diazepam, were evaluated in the exploratory behavior test. Diazepam induced clear anxiolytic actions at all doses in unstressed animals, but such an effect was not observed in stressed animals. The injection of allopregnanolone 24 h before the anxiety test blocked the effect of this benzodiazepine. Forced swimming decreased GABA concentrations in the hippocampus and the thalamus-hypothalamus region, besides decreasing the [(3)H]flunitrazepam labeling in both the hypothalamus and amygdala. These results show that forced swimming abolishes the anti-anxiety effect of diazepam.

Animals↗
PubMed2006

A new automated and high-throughput system for analysis of the forced swim test in mice based on magnetic field changes.

INTRODUCTION: MicroAct (Neuroscience, Tokyo, Japan) was originally developed as a new system for an automated analysis of scratching behaviors in mice. This system is based on the detection of electric current in the coils according to the movement of the magnets implanted in the hind paws. We applied and improved this system to establish an automated analysis system of forced swimming behaviors in mice, which is used as an animal model of depression. METHODS: One day before the test, male CD-1 mice were attached with a wire ring to their hind paws under inhalation anesthesia. After attaching a small magnet to both of the wire rings, each animal was placed for 6 min in a glass cylinder filled with water, which is surrounded by a coil. The swimming behaviors of the mouse were analyzed for the measurement of duration of immobility, a major marker of depression in rodents, by the detection system (MicroAct). The duration of immobility was also determined by manual measurement using the swimming behavior-recorded videotapes produced at the same time as the automated analysis. RESULTS: The difference of the duration of immobility between naïve mice and mice with the rings was not significant. The dose-response effect of imipramine (tricyclic antidepressant, 0, 7.5, 15, 30 and 60 mg/kg, p.o.) on the duration of immobility in the last 4-min of the 6-min testing period determined by MicroAct was similar to that assessed by the manual measurement. These data from the two different methods were significantly correlated (r=0.8805). Moreover, throughput of the automated analysis was 15 times more efficient than that of the manual analysis. DISCUSSION: These results suggest that the automated analysis system of forced swimming of mice using MicroAct can be used as a high-throughput method to examine antidepressive activity of a compound with objectivity and reliability.

Animals↗
PubMed2006

The role of hind limb flexor muscles during swimming in the toad, Bufo marinus.

Most work examining muscle function during anuran locomotion has focused largely on the roles of major hind limb extensors during jumping and swimming. Nevertheless, the recovery phase of anuran locomotion likely plays a critical role in locomotor performance, especially in the aquatic environment, where flexing limbs can increase drag on the swimming animal. In this study, I use kinematic and electromyographic analyses to explore the roles of four anatomical flexor muscles in the hind limb of Bufo marinus during swimming: m. iliacus externus, a hip flexor; mm. iliofibularis and semitendinosus, knee flexors; and m. tibialis anticus longus, an ankle flexor. Two general questions are addressed: (1) What role, if any, do these flexors play during limb extension? and (2) How do limb flexors control limb flexion? Musculus iliacus externus exhibits a large burst of EMG activity early in limb extension and shows low levels of activity during recovery. Both m. iliofibularis and m. semitendinosus are biphasically active, with relatively short but intense bursts during limb extension followed by longer and typically weaker secondary bursts during recovery. Musculus tibialis anticus longus becomes active mid way through recovery and remains active through the start of extension in the next stroke. In conclusion, flexors at all three joints exhibit some activity during limb extension, indicating that they play a role in mediating limb movements during propulsion. Further, recovery is controlled by a complex pattern of flexor activation timing, but muscle intensities are generally lower, suggesting relatively low force requirements during this phase of swimming.

Animals↗