Difference In Swimming Speed Research Articles

Insights on the Selection of the Coefficient of Variation to Assess Speed Fluctuation in Swimming.

The aim of this study was to compare swimming speed and speed fluctuations in front crawl between swimmers of different performance levels using discrete variables against statistical parametric mapping (SPM). The sample was composed of 34 male swimmers divided into three groups: (i) group #1-recreational swimmers; (ii) group #2-competitive swimmers aged 12 to 14 years; (iii) group #3-competitive swimmers aged 15 to 17 years. Swimming speed and speed fluctuations (calculated based on four different conditions) were used as discrete variables. Using these discrete variables, ANOVA one-way was used to verify differences between groups, and Bonferroni post-hoc correction for pairwise comparison whenever suitable. SPM (with similar statistical tests) was used to analyze the swimming speed and fluctuation as a continuous variable. Overall, both statistical approaches revealed significant differences (p < 0.001) in swimming speed and speed fluctuations. However, as discrete variables (in four different conditions), the speed fluctuation was not able to detect significant differences between groups #2 and #3. Conversely, SPM was more sensitive and did yield significant differences between these two groups. Therefore, researchers and coaches should be aware that the speed fluctuation as a discrete variable may not identify differences in swimming speed fluctuations when the average value between groups is marginal. On the other hand, SPM was more sensitive in analyzing all groups.

Alteration of shoaling behavior and dysbiosis in the gut of medaka (Oryzias latipes) exposed to 2-μm polystyrene microplastics

There is global concern that microplastics may harm aquatic life. Here, we examined the effects of fine polystyrene microplastics (PS-MPs, 2-μm diameter, 0.1 mg/L, 2.5 × 107 particles/L) on the behavior and the microbiome (linked to brain–gut interaction) of a fish model using medaka, Oryzias latipes. We found that shoaling behavior was reduced in PS-MP-exposed medaka compared with control fish during the exposure period, but it recovered during a depuration period. There was no difference in swimming speed between the PS-MP-exposed and control groups during the exposure period. Analysis of the dominant bacterial population (those comprising ≥1% of the total bacterial population) in the gut of fish showed that exposure to PS-MPs tended to increase the relative abundance of the phylum Fusobacteria and the genus Vibrio. Furthermore, structural-equation modeling of gut bacteria on the basis of machine-learning data estimated strong relationship involved in the reduction of the functional bacterial species of minority (<1% of the total bacterial population) such as the genera Muribaculum (an undefined role), Aquaspirillum (a candidate for nitrate metabolism and magnetotactics), and Clostridium and Phascolarctobacterium (potential producers of short-chain fatty acids, influencing behavior by affecting levels of neurotransmitters) as a group of gut bacteria in association with PS-MP exposure. Our results suggest that fish exposure to fine microplastics may cause dysbiosis and ultimately cause social behavior disorders linked to brain–gut interactions. This effect could be connected to reduction of fish fitness in the ecosystem and reduced fish survival.

Parkinson's disease model in zebrafish using intraperitoneal MPTP injection.

Parkinson's disease (PD) is the second most common neurodegenerative disease that severely affects the quality of life of patients and their family members. Exposure to 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been shown to reflect behavioral, molecular, and proteomic features of PD. This study aimed to assess the protocol for inducing PD following MPTP injection in adult zebrafish. Fish were injected with 100 μg/g of MPTP intraperitoneally once or twice and then assessed on days 1 to 30 post-injection. Between one-time and two-time injections, there was no significant difference in most locomotor parameters, expressions of tyrosine hydroxylase-2 (th2) and dopamine transporter (dat) genes, and dopaminergic neurons (tyrosine hydroxylase positive, TH+ cells) counts. However, caspase-3 levels significantly differed between one- and two-time injections on the day 1 assessment. Over a 30-day period, the parameters showed significant differences in swimming speed, total distance traveled, tyrosine hydroxylase-1 (th1) and dat gene expressions, caspase-3 and glutathione protein levels, and TH+ cell counts. Days 3 and 5 showed the most changes compared to the control. In conclusion, a one-time injection of MPTP with delayed assessment on days 3 to 5 is a good PD model for animal studies.

Effect of operative trauma and multiple propofol anesthesia on neurodevelopment and cognitive function in developmental rats

To investigate the effect of multiple propofol anesthesia and operative trauma on neuroinflammation and cognitive function in development rats and its mechanism. A total of 104 13-day-old neonatal Sprague-Dawley rats were randomly divided into 4 groups with 26 rats in each group: control group was treated with saline q.d for propofol group was treated with propofol q.d for surgery group received abdominal surgery under local anesthesia and then treated with saline q.d for surgery with propofol group received propofol anesthesia plus abdominal surgery under local anesthesia with ropivacaine at d1, then treated with propofol q.d for At d2 of experiment, 13 rats from each group were sacrificed and brain tissue samples were taken, the concentration of TNF-α in hippocampus was detected with ELISA, the expression of caspase-3 and c-fos in hippocampal tissue was determined with immunohistochemical method, the number of apoptotic neurons in hippocampus was examined with TUNEL assay. Morris water maze test was used to examine the cognitive function of the rest rats at the age of 60 d, and the TNF-α concentration, caspase-3, c-fos expressions and the number of apoptotic neurons in hippocampus were also detected. Compared with control group, TNF-α concentration, caspase-3, c-fos expression and the neuroapoptosis in hippocampus increased significantly in other three groups (all <0.05). Compared with surgery group, propofol group and surgery with propofol group showed increased TNF-α level, caspase-3 and c-fos expressions and apoptotic cell numbers (all <0.05), but there was no significant difference between last two groups (all >0.05). Morris water maze test showed that there were no significant differences in swimming speed, escape latency, target quadrant residence time and crossing times among groups (all >0.05). TNF-α level, expressions of caspase-3 and c-fos and apoptotic cell numbers in hippocampus had no significant differences among the 4 adult rats groups (all >0.05). Abdominal surgery and multiple propofol treatment can induce neuroinflammation and neuroapoptosis in hippocampus of neonatal rats, however, which may not cause adverse effects on neurodevelopment and cognitive function when they grown up.

Micromotor-mediated sperm constrictions for improved swimming performance

Sperm-driven micromotors, consisting of a single sperm cell captured in a microcap, utilize the strong propulsion generated by the flagellar beat of motile spermatozoa for locomotion. It enables the movement of such micromotors in biological media, while being steered remotely by means of an external magnetic field. The substantial decrease in swimming speed, caused by the additional hydrodynamic load of the microcap, limits the applicability of sperm-based micromotors. Therefore, to improve the performance of such micromotors, we first investigate the effects of additional cargo on the flagellar beat of spermatozoa. We designed two different kinds of microcaps, which each result in different load responses of the flagellar beat. As an additional design feature, we constrain rotational degrees of freedom of the cell’s motion by modifying the inner cavity of the cap. Particularly, cell rolling is substantially reduced by tightly locking the sperm head inside the microcap. Likewise, cell yawing is decreased by aligning the micromotors under an external static magnetic field. The observed differences in swimming speed of different micromotors are not so much a direct consequence of hydrodynamic effects, but rather stem from changes in flagellar bending waves, hence are an indirect effect. Our work serves as proof-of-principle that the optimal design of microcaps is key for the development of efficient sperm-driven micromotors.Graphic

Processes affecting size of fish schools in agent‐based model

AbstractFish school size varies with several factors, such as environmental conditions, individual size, time of day, and variations between individuals. In this study, we investigate the mean size of fish schools formed in a simple agent‐based model, wherein each individual swims at a fixed speed with the direction modified by interactions with the neighbors. If alignment (tendency to swim in their neighbors' direction) is stronger than cohesion (tendency to swim toward the neighbors), then “marches” are formed, in which individuals swim in the same direction. If alignment is weaker than cohesion, then “circles” are formed, in which individuals chase one another and the entire group moves minimally. We analyzed various processes that control the shape and mean size of the schools. The school's shape is primarily affected by the magnitude of alignment, cohesion, and individual noises. In contrast, the mean size of the group is affected by several factors, including the spatial interaction range, initial configuration, individual differences in swimming speed, and sudden encounters with predators.

Analysis of sex and age differences in performance of young Canadian freestyle swimmers

This study is intended to determine sex and age differences in young Canadian freestyle swimmers aged from ≤10 to 18, for all 6 distances from 50m to 1500m in both short and long course indoor pools. The data set used in the studies is publicly available and categorized into sex/age/course/distance groups during seasons from 2008 to 2019. The sex differences in swimming speed were determined using independent Z-tests (two-sided, unequal SD). The age differences in swimming speed over all ages were analysed using classic one-way ANOVA with subsequent pairwise Tukey-HSD post-hoc tests and Welch’s ANOVA followed by pairwise Games-Howell post-hoc tests. They were then determined using paired two-sample t-tests (two-sided). Young male swimmers outperformed young female swimmers in most groups. Groups with similar performances or no significant differences were in younger age groups (10-year and 11-year). Sex differences increased as age increased, ranging from −0.96% to 13.54%. Sex differences in shorter distances and short course were smaller than in longer distances and long course for ≤12 years and became greater than in longer distances at ≥13 years. Age speed differences decreased as age increased until 17–18-years old, ranging from 12.79% to −0.37%. The performance of female swimmers became stable earlier than that of male swimmers. The age-to-age speed differences of male swimmers were greater than those of female swimmers. These gaps increased from 10–11-year to 13–14-year groups and decreased after that. Age differences in shorter distances and short course were greater than in longer distances and long course. Further studies are required to confirm and extend this research to swimmers at other age groups, in other strokes, and from other countries.

Tracking of algal cells: case study of swimming speed of cold-adapted dinoflagellates

Swimming is a fundamental trait of many protists and optimizes growth and survival. We present an easy to use set-up for filming algal cells using Apocalathium aciculiferum and Borghiella dodgei as case studies; both dinoflagellates are model organisms of psychrophilic dinoflagellates. We filmed at low temperature (4.5°C) using a digital camera directly connected to a microscope and used open-source software to track their movement. We encountered several technical issues that were solved by using specific software settings (scaling, grey scale of images, restrictive particle recognition), and thus we obtained unbiased speed estimates. Borghiella dodgei showed a faster (minimum = 80, maximum = 255, median = 141 µm s−1) swimming speed than A. aciculiferum (minimum = 29, maximum = 134, median = 85 µm s−1). We linked differences in swimming speed to the dinoflagellates’ environmental niche, and suggested that B. dodgei is more adapted to turbulent spring conditions than A. aciculiferum, occurring under ice. The use of a generic digital camera and open-source software makes filming and tracking of plankton movement very affordable. We provided code and detailed instructions to disseminate this type of movement analysis of plankton.

High density polyethylene (HDPE) microplastics impair development and swimming activity of Pacific oyster D-larvae, Crassostrea gigas, depending on particle size

Understanding the effects of plastic debris on marine ecosystems is essential in encouraging decision-makers to take action. The present study investigates the effect of a 24 h experimental exposure to high density polyethylene (HDPE) microplastics (MPs) of different sizes (4–6, 11–13 and 20–25 μm) and at three concentrations (0.1, 1 and 10 mg MP.L−1) on the development and locomotor activity of early stages of Pacific oyster, Crassostrea gigas. The bivalve embryo-larval assay (NF ISO 17244, 2015) was used in this study but with additional toxicity criteria: developmental arrests, abnormal D-larvae, maximum speed and swimming trajectory. Copper (Cu), was used as a positive control. Our results show that smaller MPs (4–6 and 11–13 μm) induced higher rates of malformations and developmental arrests than the larger ones (20–25 μm). In addition, a dose-dependent decrease of maximum swimming speed was observed for larvae exposed to MPs of 4–6 and 11–13 μm. On the other hand, there was no significant difference in swimming speed with the largest MPs size tested (20–25 μm). For all three sizes of MPs, there was a decrease in straight-line swimming trajectories, and an increase in circular trajectories. This abnormal swimming behaviour could affect larvae survival as well as colonization of new habitats.

Effect of N-acetylcysteine on Cognitive Function and Nuclear Factor Erythroid 2 Related Factor 2/Heme Oxygenase-1 Pathway in Mouse Models of Postoperative Cognitive Dysfunction

To investigate the effect of N-acetylcysteine(NAC)on cognitive function and nuclear factor erythroid 2 related factor 2/ heme oxygenase-1(Nrf2/HO-1)pathway in mouse models of postoperative cognitive dysfunction. Methods Fifty-four male C57BL/6J mice(3-4 months old)were randomly divided into control group,surgery group,and surgery+NAC group by block randomization.The intramedullary fixation for left tibial fracture surgery was performed to establish postoperative cognitive dysfunction models.NAC(150 mg/kg)was administered intraperitoneally in group surgery+NAC 30 minutes before and 3 hours,6 hours after surgery,while saline was given in control group and surgery group.Six mice in each group were selected randomly underwent Morris water maze test on the third day after surgery.Animals were sacrificed at the first and third postoperative days,and the hippocampus was harvested.Enzyme-linked immunosorbent assay was used to quantify the levels of interleukin-6(IL-6)and malondialdehyde(MDA)in hippocampus.Western blot and real-time polymerase chain reaction were used to measure the expressions of Nrf2 and HO-1 in hippocampus. Results There was no significant difference in swimming speed among three groups(F=2.135,P=0.114).Compared with control group and surgery+NAC group,the surgery group had prolonged escape latency(P<0.01),reduced platform crossing times(P<0.01),and shortened time spent in the target quadrant(P<0.01).Compared with the control group,the surgery group and the surgery+NAC group had significantly increased levels of IL-6 and MDA in hippocampus at the first postoperative day(all P=0.000).On the third postoperative day,there was no significant difference in the levels of IL-6(P=0.251)and MDA(P=0.103)between control group and surgery+NAC group.The protein expressions of Nrf2 and HO-1 in hippocampus were significantly higher in surgery group and surgery+NAC group than in control group and significantly higher in surgery+NAC group than in surgery group(all P=0.000).The mRNA expressions of Nrf2 and HO-1 in hippocampus were significantly higher in surgery group and surgery+NAC group than in control group and significantly higher in surgery+NAC group than in surgery group (all P=0.000). Conclusions NAC pretreatment may reduce oxidative stress and inflammatory response in hippocampus and improve cognitive function.Such effect may be relate to the activation of Nrf2/HO-1 pathway.

&lt;i&gt;Ginkgo biloba&lt;/i&gt; preparation prevents and treats senile dementia by inhibiting neuro-inflammatory responses

Purpose: To study the effect of Ginkgo biloba preparation on senile dementia and the mechanism of its action. Methods: Sprague Dawley (SD) rat model of chronic cerebral hypoperfusion was produced by vascular occlusion (2-VO). The rats were administered Ginkgo biloba preparation via intra-gastric route 4 h after the operation, and then at 7:30 am every day at a dose of 100 mg/kg per day (0.5 mL/100 g, per day) for 28 days. One group of untreated model rats, and a reference group served as controls. Garcia composite score was used to evaluate the recovery of neurological function in the rats after operation. Morris water maze test was conducted to assess learning and memory abilities. Western blot was used to measure protein expressions of BACE1, TRP1 and RAGE. Serum levels of inflammatory factors IL1, IL6 and TNF were assayed by ELISA. Results: Garcia composite score showed that the neurological function of the SD rats was significantly impaired by the blockage of blood flow to the bilateral common carotid artery. However, neurological function was gradually recovered by treatment with Ginkgo biloba preparation. The escape latency and swimming distance of the rats were significantly shortened, and the number of platform crossings was gradually increased by the Ginkgo biloba preparation. With time, there was no significant difference in swimming speed between the groups. Western blot data showed that expression of BACE1, TRP1 and RAGE gradually decreased. Results from ELISA indicate that with time, Ginkgo biloba preparation decreased the expressions of IL-1, IL-6, and TNF in the reference group. Conclusion: The preventive and therapeutic effects of Ginkgo biloba preparation extract on senile dementia may be related to its inhibition of neuro-inflammatory reaction. Keywords: Alzheimer disease, Neuro-inflammatory reactions, Ginkgo biloba preparation

Amelioration of Prenatal Lead-Induced Learning and Memory Impairments by Methanolic Extract of Zataria Multiflora in Male Rats

Introduction:The current study aimed at evaluating the effects of Zataria Multiflora (ZM) on learning and memory of adult male offspring rats with prenatal lead-exposure.Methods:Pregnant rats in the case group received tap water containing 0.2% lead acetate throughout the gestation period. Control rats had free access to lead-free tap water. Two male offspring (two-month-old, weighing 180–200 g) from each mother were randomly selected and treated with either Z. Multiflora (50, 200, 400, and 800 mg/kg/Intraperitoneally (I.P)/20 day) or saline. Spatial memory of the control, saline, and ZM-treated rats was evaluated by a training trial and probe test using Morris water maze (6–8 rat/group).Results:The obtained results showed memory deficits including increased escape latency, and a greater traveled distance, as well as decrements in the frequency of crossings into target quadrants in prenatally lead-exposed male offspring compared with the controls. ZM treatment (200 mg/kg/i.p) ameliorated the memory deficits in male offspring by increasing the time spent and traveled distance in the trigger zone (P<0.01 vs. saline).There was no significant difference in swimming speed between the groups.Conclusion:The results showed memory deficits in prenatally lead-exposed male offspring. ZM treatment (especially 200 mg/kg) had beneficial effects on cognitive behavior and was indicated as the improvement of lead-induced memory deficits in prenatally lead-exposed male rats. The exact mechanism(s) is not determined yet, but it could be mediated through the anticholinesterase and antioxidant effects and also alterations in Central Nervous System (CNS) and neurotransmission in the central nervous system.

A Sensitive Period for the Development of Motor Function in Rats: A Microgravity Study

Abstract Spaceflight studies offer a unique opportunity to examine the impact of gravity on developing motor skills. Previously, we reported that young rats experiencing microgravity in low Earth orbit (LEO) beginning on postnatal day (P)14 showed impaired swimming, walking, and surface righting after returning to 1 g, with immature motor skills persisting until adulthood. Here, we report on post-flight surface righting and swimming of rats experiencing spaceflight from P7 or P8. Litters with dams were flown aboard a space shuttle Space Transportation System (STS) 9-day (NIH-R3, STS-72) or 16-day mission (Neurolab, STS-90). Flight rats from both missions showed significantly fewer mature, age-appropriate righting tactics after landing compared to ground controls. Flight rats also had a steeper body angle while floating in the water before swimming, started swimming sooner, and swam faster. The effects on surface righting persisted for the duration of behavior tests (6 days [9-day mission] or 23 days [16-day mission]), after landing. Differences in pre-swimming behavior resolved by return day (R)2, and differences in swimming speed and posture resolved by R10. These data suggest that exposure to microgravity at a young age prevents the normal development of surface righting and that the normal development of swimming can recover if animals return from LEO by P16 or P24. These findings lend additional support to the existence of a critical period of development for motor function. However, studies are needed with improved housing during spaceflight to ensure that maternal offspring behavior is not disrupted, as was observed during the Neurolab mission.

Beneficial effects of garlic on learning and memory deficits and brain tissue damages induced by lead exposure during juvenile rat growth is comparable to the effect of ascorbic acid

Objective: The neuroprotective effects of both garlic and ascorbic acid (AA) have been documented. In this study the effects of garlic and ascorbic acid on memory deficits and brain tissue oxidative damages induced by lead exposure was investigated. Methods: The juvenile rats were divided and treated: (1) Control, (2) Lead (lead acetate in drinking water, 8 weeks), (3) Lead – Ascorbic Acid (Lead-AA), (4) Lead – Garlic (100 mg/kg, daily, gavage) (Lead-Gar). Results: In Morris water maze (MWM), the escape latency and traveled path in the Lead group were significantly higher while, the time spent in the target quadrant (Q1) was lower than Control. Both Lead-Gar and Lead-AA groups spent more times in Q1than to lead group. There were no significant differences in swimming speed between the groups. In passive avoidance (PA) test, the time latency for entering the dark compartment by Lead group was lower than Control. Treatment of the animals by AA and garlic significantly increased the time latency. In Lead group, the total thiol concentration in brain tissues was significantly lower while, MDA was higher than Control. Treatment by both garlic and AA increased total thiol concentrations and decreased MDA. Both garlic and AA decreased the lead content of brain tissues. Conclusion: It is suggested that treatment with garlic attenuates the learning and memory impairments due to lead exposure during juvenile rat growth which is comparable to AA. The possible mechanism may be due to its protective effects against brain tissues oxidative damage as well the lowering effects of brain lead content.

Differences in Swimming Speed between Short and Long Course from 50 m to 1,500 m in Elite Female and Male Swiss Freestyle Age Group Swimmers

This study intended (i) to compare the differences in swimming speed between short course and long course and (ii) to investigate differences in swimming speed between age groups in freestyle swimmers competing at national level (Switzerland). Age and swimming speed of 45,888 athletes (22,216 women and 23,672 men) on short course and 46,308 athletes (22,257 women and 24,051 men) on long course competing between 2000 and 2011 were analysed using linear regression analyses and analyses of variance (ANOVA). Swimming speed was faster on short course compared to long course on all distances for both women and men (P ＜ 0.05) except in the women’s 1,500m (P＞0.05). For the distances of 50m, 100m, 200m, 400m, 800m and 1,500m, men completed short course faster by 2.25%, 2.97%, 1.62%, 2.34%, 1.86% and 1.89%, respectively (P＜0.05). For women, the differences between the courses were 3.16%, 2.27%, 2.45%, 1.90%, 2.56% and 5.84%, respectively (P＜0.05). The fastest swimming speeds were achieved in the age group 20-29 years for both women and men on all distances. In summary, (i) freestyle swimming speed was faster on short course than long course except for 1,500m in women and (ii) athletes in age group 20-29 years achieved the fastest swimming speeds on all lengths for both short course and long course.

Altered motility of Caulobacter Crescentus in viscous and viscoelastic media.

BackgroundMotility of flagellated bacteria depends crucially on their organelles such as flagella and pili, as well as physical properties of the external medium, such as viscosity and matrix elasticity. We studied the motility of wild-type and two mutant strains of Caulobacter crescentus swarmer cells in two different types of media: a viscous and hyperosmotic glycerol-growth medium mixture and a viscoelastic growth medium, containing polyethylene glycol or polyethylene oxide of different defined sizes.ResultsFor all three strains in the medium containing glycerol, we found linear drops in percentage of motile cells and decreases in speed of those that remained motile to be inversely proportional to viscosity. The majority of immobilized cells lost viability, evidenced by their membrane leakage. In the viscoelastic media, we found less loss of motility and attenuated decrease of swimming speed at shear viscosity values comparable to the viscous medium. In both types of media, we found more severe loss in percentage of motile cells of wild-type than the mutants without pili, indicating that the interference of pili with flagellated motility is aggravated by increased viscosity. However, we found no difference in swimming speed among all three strains under all test conditions for the cells that remained motile. Finally, the viscoelastic medium caused no significant change in intervals between flagellar motor switches unless the motor stalled.ConclusionHyperosmotic effect causes loss of motility and cell death. Addition of polymers into the cell medium also causes loss of motility due to increased shear viscosity, but the majority of immobilized bacteria remain viable. Both viscous and viscoelastic media alter the motility of flagellated bacteria without affecting the internal regulation of their motor switching behavior.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0322-3) contains supplementary material, which is available to authorized users.

The effect of course length on individual medley swimming performance in national and international athletes.

Effects of course length (25 m versus 50 m) and advances in performance of individual medley swimming were examined for men and women in Swiss national competitions and FINA World Championships during 2000–2011. Linear regression and analysis of variance (ANOVA) were used to analyse 200 m and 400 m race results for 26,081 swims on the Swiss high score list and 382 FINA finalists. Swiss and FINA swimmers of both sexes were, on average, 4.3±3.2% faster on short courses for both race distances. Sex-related differences in swim speed were significantly greater for FINA swimmers competing in short-course events than in long-course events (10.3±0.2% versus 9.7±0.3%, p<0.01), but did not differ for Swiss swimmers (p>0.05). Sex-related differences in swimming speed decreased with increasing race distance for both short- and long-course events for Swiss athletes, and for FINA athletes in long-course events. Performance improved significantly (p<0.05) during 2000–2011 for FINA men competing in either course length and FINA females competing in short-course events, but not for Swiss swimmers. Overall, the results showed that men and women individual medley swimmers, competing at both national and international levels, have faster average swimming speeds on short courses than on long courses, for both 200 m and 400 m distances. FINA athletes demonstrate an improving performance in the vast majority of individual medley events, while performance at national level seems to have reached a plateau during 2000–2011.

Kinematics of swimming and thrust production during powerstroking bouts of the swim frenzy in green turtle hatchlings.

ABSTRACTHatchling sea turtles emerge from nests, crawl down the beach and enter the sea where they typically enter a stereotypical hyperactive swimming frenzy. During this swim the front flippers are moved up and down in a flapping motion and are the primary source of thrust production. I used high-speed video linked with simultaneous measurement of thrust production in tethered hatchlings, along with high-speed video of free swimming hatchlings swimming at different water speeds in a swim flume to investigate the links between kinematics of front flipper movement, thrust production and swimming speed. In particular I tested the hypotheses that (1) increased swimming speed is achieved through an increased stroke rate; (2) force produced per stroke is proportional to stroke amplitude, (3) that forward thrust is produced during both the down and up phases of stroking; and (4) that peak thrust is produced towards the end of the downstroke cycle. Front flipper stroke rate was independent of water speed refuting the hypothesis that swimming speed is increased by increasing stroke rate. Instead differences in swimming speed were caused by a combination of varying flipper amplitude and the proportion of time spent powerstroking. Peak thrust produced per stroke varied within and between bouts of powerstroking, and these peaks in thrust were correlated with both flipper amplitude and flipper angular momentum during the downstroke supporting the hypothesis that stroke force is a function of stroke amplitude. Two distinct thrust production patterns were identified, monophasic in which a single peak in thrust was recorded during the later stages of the downstroke, and biphasic in which a small peak in thrust was recorded at the very end of the upstroke and this followed by a large peak in thrust during the later stages of the downstroke. The biphasic cycle occurs in ∼20% of hatchlings when they first started swimming, but disappeared after one to two hours of swimming. The hypothesis that forward thrust is produced during both the up and down stroke was only supported relatively rarely in hatchlings that exhibited the diphasic cycle, the majority of time forward thrust was only produced during the downstroke phase. The hypothesis that peak forward thrust is produced during the end of the downstroke was supported in both the monophasic and biphasic thrust producing stroke cycles.

Effects of Walnut Polyphenol on Learning and Memory Functions in Hypercholesterolemia Mice

Evidence suggests that dietary walnuts are able to induce improvements in memory and learning functions. In addition, polyphenols have been shown to modulate critical neuronal signalling pathways involved in processes of learning and memory. The aim of our present work was to study the effect of polyphenol extracts from walnut testa (42%) on learning and memory functions in hypercholesterolemia mice based on obesity, hypercholesterolemia and oxidative stress. At the beginning of the experiment, mice were divided into 3 groups, one of them served as normol control group (NCG), the second as hypercholesterolemia control group (HCG), the last as walnut polyphenol-treated group (WTG). After 8 weeks of treatment, we investigated the performance of C57BL/6J mice in Morris water maze test. The results showed that the escape latency was significant increase in HCG, when compared to NCG and WTG. In addition, the number of crossings was significant decrease in HCG, when compared to NCG and WTG (–47.35% and –43.35%, respectively, P < 0.01). The swimming distance was longer in HCG than NCG and WTG [F (2,96) = 44.45, P < 0.001]. However, there was no significant difference in swimming speed among NCG, HCG and WTG [F (2, 96) = 0.167, P > 0.05]. On the other hand, walnut polyphenol (WP) significantly decreased serum total triglycerides, cholesterol and malondialdehyde (MDA) level (–36.31%, –31.48% and –21.51%, respectively, P < 0.01) and increased superoxide dismutase (SOD) activity (+48.39%, P < 0.01). Administration of WP significantly decreased MDA level (–36.86%, P < 0.01) and increased SOD activity (+17.08%, P < 0.01) in brain tissues. In conclusion, walnut polyphenol was able to improve learning and memory functions.

Changes in sex difference in swimming speed in finalists at FINA World Championships and the Olympic Games from 1992 to 2013

BackgroundThis study investigated swimming speeds and sex differences of finalists competing at the Olympic Games (i.e. 624 female and 672 male athletes) and FINA World Championships (i.e. 990 women and 1008 men) between 1992 and 2013.MethodsLinear, non-linear and multi-level regression models were used to investigate changes in swimming speeds and sex differences for champions and finalists.ResultsRegarding finalists in FINA World Championships and Olympic Games, swimming speed increased linearly in both women and men in all disciplines and race distances. Male world champions’ swimming speed remained stable in 200 m butterfly, 400 m, 800 m and 1,500 m freestyle. Considering women, swimming speed remained unchanged in 50 m and 400 m freestyle. In the Olympic Games, swimming speed of male champions remained unchanged in 200 m breaststroke, 50 m, 400 m, 800 m and 1,500 m freestyle. Female Olympic champions’ swimming speed remained stable in 100 m and 200 m backstroke, 100 m butterfly, 200 m individual medley, 50 m and 200 m freestyle. Evaluating sex differences between finalists in FINA World Championships, results showed a linear decrease in 100 m breaststroke and 200 m butterfly and a non-linear increase in 100 m backstroke. In finals at the Olympic Games, the sex difference decreased linearly for 100 m backstroke, 400 m and 800 m freestyle. However, a linear increase for 200 m butterfly can be reported. Considering Olympic and world champions, the sex difference remained stable in all disciplines and race distances.ConclusionSwimming speed of the finalists at the Olympic Games and FINA World Championships increased linearly. The top annual female swimmers increased swimming speed rather at longer race distances (i.e. 800 m and 1,500 m freestyle, 200 m butterfly, and 400 m individual medley), whereas the top annual male swimmers increased it rather at shorter race distances (i.e. 100 m and 200 m freestyle, 100 m butterfly, and 100 m breaststroke). Sex difference in swimming was unchanged in Olympic and world champions. Finalists and champions at the Olympic Games and FINA World Championships reduced the sex difference with increasing race distance.