Improve Swimming Performance Research Articles

International Swimming League: Do Successive Events Lead to Improve Swimming Performance?

To quantify the impact of successive competitions on swimming performance in world-class swimmers. An entire data set of all events swum during a new competition named the International Swimming League was collected. A Bayesian linear mixed model has been proposed to evaluate whether a progression could be observed during the International Swimming League's successive competitions and to quantify this effect according to event, age, and gender. An overall progression of 0.0005 (0.0001 to 0.0010)m/s/d was observed. The daily mean progression (ie,faster performance) was twice as high for men as for women (0.0008 [0.00 to 0.0014] vs 0.0003 [-0.0003 to 0.0009]m·s-1). A tendency toward higher progression for middle distances (200 and 400m) and for swimmers of a higher caliber (above 850 FINA [Fédération Internationale de Natation] points) was also observed. Swimmers between 23 and 26years of age seemed to improve their swimming speed more in comparison with the other swimmers. This new league format, which involves several competitions in a row, seems to allow for an enhancement in swimming performance. Coaches and their support staff can now adapt their periodization plan in order to promote competition participation.

Different patterns of chronic hypoxia lead to hierarchical adaptive mechanisms in goldfish metabolism.

Some hypoxia-tolerant species, such as goldfish, experience intermittent and severe hypoxia in their natural habitat, causing them to develop multiple physiological adaptations. However, in fish, the metabolic impact of regular hypoxic exposure on swimming performance in normoxia is less well understood. Therefore, we experimentally tested whether chronic exposure to constant (30 days at 10% air saturation) or intermittent hypoxia (3 h in normoxia and 21 h in hypoxia, 5 days a week) would result in similar metabolic and swimming performance benefits after reoxygenation. Moreover, half of the normoxic and intermittent hypoxic fish were put on a 20-day normoxic training regime. After these treatments, metabolic rate (standard and maximum metabolic rates: SMR and MMR) and swimming performance [critical swimming speed (Ucrit) and cost of transport (COT)] were assessed. In addition, enzyme activities [citrate synthase (CS), cytochrome c oxidase (COX) and lactate dehydrogenase (LDH)] and mitochondrial respiration were examined in red muscle fibres. We found that acclimation to constant hypoxia resulted in (1) metabolic suppression (-45% SMR and -27% MMR), (2) increased anaerobic capacity (+117% LDH), (3) improved swimming performance (+80% Ucrit, -71% COT) and (4) no changes at the mitochondrial level. Conversely, the enhancement of swimming performance was reduced following acclimation to intermittent hypoxia (+45% Ucrit, -41% COT), with a 55% decrease in aerobic scope, despite a significant increase in oxidative metabolism (+201% COX, +49% CS). This study demonstrates that constant hypoxia leads to the greatest benefit in swimming performance and that mitochondrial metabolic adjustments only provide minor help in coping with hypoxia.

Does Rest Period After Warming Up Have an Effect on Swimming Performance?

The purpose of this study is to evaluate the effects of different rest periods after the warm-up (WU) done before a swimming performance.Eighteen licensed male swimmers in Samsun's swimming clubs who have been at least three years in active swimming and training with a minimum of 4 days a week; voluntarily participated in this study. After doing land and water WU, athletes rested 10 min, 20 min, 30 min or 40 min (on different days) before swimming performance. The swimming performance values of the athletes were measured at distances of 50m or 400 m. Each athlete had the test within eight separate days (resting 10 min, 20 min, 30 min or 40 min), with a total of 4 times 50 m and 4 times 400 m. The measurements were carried out at the Olympic swimming pool of Ondokuz Mayıs Univer-sity. Statistical analysis of the collected data was done using the Friedman test and Wilcoxon sign rank test.Findings show that post-WU rest periods of 10 min, 20 min, 30 min and 40 min, did not have any significant effect on the 50 m swimming performance values of the athletes(p> 0.05), while, a statistically significant effect (p 0.05), while it seemed to affect the HR values after 400 m distance (p<0.05).Rest periods post-WU do not affect the 50 m swimming performance. However, 40 minutes rest time post-WU enhances the 400 m swimming performance. Concurrently, a higher performance after a 40 min rest period results in higher HR values after a 400 m swimming. In conclusion, we conclude that post-WU rest time does not affect the 50 m and 400 m freestyle swimming performance. However, at 400 m swimming distances, increasing the rest time post-WU improves swimming performance.

Effect of Additional Buoyancy Swimsuits on Performance of Competitive Swimmers

Background: When in water, the Centers of Buoyancy (CoB) and Mass (CoM) of the human body are positioned cranially and caudally, respectively. With increasing distance between these centers, the sinking torque of the lower limbs increases, with a subsequent decrease in swimming performance due to increased drag. Objective: To clarify the effect of additional buoyancy swimsuits on swimming performance. Methods: The subjects were eight competitive male swimmers of mean ±SD age 21±2 years. Swimming performance was compared between Conventional (CS) and Additional Buoyancy Swimsuits (ABS). CoM and CoB were identified on land and in water, respectively, with the swimmers maintaining a horizontal posture. CoM was measured by the reaction board method. CoB was calculated as the force exerted in the vertical direction accompanied by changes in inspiratory volume. Swimming velocity and Blood Lactate (BL) concentration value during 200 m front crawl in trials at four different speeds (curve test) were recorded as swimming performance. Results: No significant difference in inspiratory volume was observed between CS and ABS (small effect size, d=0.28). The distance between CoM and CoB was significantly shorter for CS than ABS (p &lt; 0.001; large effect size, d=1.08). Both swimming velocity at BL of 4 mmol·L-1 and maximal effort were significantly faster for ABS (p &lt; 0.042; 0.008), with large effect size (d=0.91; 0.98). However, there was no significant difference in maximal BL between CS and ABS (small effect size, d=0.37). Conclusion: ABS improves swimming performance by streamlining the horizontal posture.

What Is the Optimal Strength Training Load to Improve Swimming Performance? A Randomized Trial of Male Competitive Swimmers.

This study aimed to compare the effectiveness of high, moderate, and low resistance training volume-load of maximum strength training on muscle strength and swimming performance in competitive swimmers. Thirty-three male swimmers were randomly allocated to high (age = 16.5 ± 0.30 years), moderate (age = 16.1 ± 0.32 years) and a low resistance training volume-load group (age = 15.9 ± 0.31). This study was carried out in mid-season (January to March). Pre and post strength (e.g., repetition maximum [1RM] leg extension and bench press tests), swimming (25, 50 m front-crawl), start (speed, time, distance) and turn (time of turn) performance tests were conducted. Our findings revealed a large main effect of time for 1RM bench press: d = 1.38; 1RM leg extension: d = 1.55, and for 25 (d = 1.12), and 50 m (d = 1.97) front-crawl, similarly for start and turn performance (d = 1.28–1.46). However, no significant Group × Time interactions were shown in all strength swimming performances, start and turn tests (p > 0.05). In conclusion, low training loads have been shown to elicit the same results as moderate, and high training loads protocol. Therefore, this study shows evidence that the addition of low training volume-loads as a regular part of a maximal strength training regime will elicit improvements in strength and swimming performance.

Assessment and Prediction of Swimming Performance Using the SWOLF Index

ABSTRACT In this paper, we report on the use of the swim golf (SWOLF) index as a method for assessing and predicting swimming performance. The SWOLF index is the sum of the number of arm strokes and the time needed to cover a certain distance. A reduction of the SWOLF index means improved swimming performance since a decrease of this index reflects higher technical ability and/or higher swimming speed. A total of 188 freshmen university students in Movement Sciences (59 girls, 129 boys, mean age 19 years), enrolled in an 11-lesson crawl unit, participated in this study. Front crawl was taught by a certified teacher using direct instruction (8 lessons) and peer learning (2 lessons), aiming to improve performance and skill analysis. Before and after the crawl unit, students’ SWOLF index was calculated during a 50-meter sprint test. Results demonstrated a significant decrease of the SWOLF index for both female (p < .001, d = 0.88) and male (p < .001, d = 0.54) students from pretest to posttest. Based on these results, SWOLF-charts were produced visualizing expected learning outcomes based on performance level at course entry. To conclude, the SWOLF index is a promising tool for assessing swimming performance. In addition, SWOLF index percentiles can be used to predict and target individual swimming performance after well-defined educational interventions. Future work could investigate the generalizability and applicability of the SWOLF index to assess and predict swimming performance in a variety of settings.

Closer Appendage Spacing Augments Metachronal Swimming Speed by Promoting Tip Vortex Interactions.

Numerous species of aquatic invertebrates, including crustaceans, swim by oscillating multiple closely spaced appendages. The coordinated, out-of-phase motion of these appendages, known as "metachronal paddling," has been well-established to improve swimming performance relative to synchronous paddling. Invertebrates employing this propulsion strategy cover a wide range of body sizes and shapes, but the ratio of appendage spacing (G) to the appendage length (L) has been reported to lie in a comparatively narrow range of 0.2 < G/L ≤ 0.65. The functional role of G/L on metachronal swimming performance is unknown. We hypothesized that for a given Reynolds number and stroke amplitude, hydrodynamic interactions promoted by metachronal stroke kinematics with small G/L can increase forward swimming speed. We used a dynamically scaled self-propelling robot to comparatively examine swimming performance and wake development of metachronal and synchronous paddling under varying G/L, phase lag, and stroke amplitude. G/L was varied from 0.4 to 1.5, with the expectation that when G/L is large, there should be no performance difference between metachronal and synchronous paddling due to a lack of interaction between vortices that form on the appendages. Metachronal stroking at nonzero phase lag with G/L in the biological range produced faster swimming speeds than synchronous stroking. As G/L increased and as stroke amplitude decreased, the influence of phase lag on the swimming speed of the robot was reduced. For smaller G/L, vortex interactions between adjacent appendages generated a horizontally oriented wake and increased momentum fluxes relative to larger G/L, which contributed to increasing swimming speed. We find that while metachronal motion augments swimming performance for closely spaced appendages (G/L <1), moderately spaced appendages (1.0 ≤ G/L ≤ 1.5) can benefit from the metachronal motion only when the stroke amplitude is large.

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

Numerical study on the effects of a semi-free and non-uniform flexible filament in different vortex streets

The variable flexibility of a fish body is believed to play a significant role in improving swimming performance. To explore the effect of non-uniform flexibility on the motion performance of fish under biologically relevant conditions, we set up three different flexible distribution modes for a semi-free filament and compared the motion performance of different flexible distribution modes through numerical simulations. The filament is located in the wake of the front flapping foil; it can swing adaptively in the lateral direction according to the flow situation of the surrounding fluid and finally reach a stable position. The results show that the motion state of the filament will alter with a change in the flexibility of the filament, from moving in the vortex street to moving on the side of the vortex street. In the Benard-von Karman (BvK) vortex streets, the drag coefficient of the filament increases as the flexibility of the filament increases, and the value of the drag coefficient is at a minimum when the flexibility of the filament increases linearly along the length of the filament. Further investigation indicates that at 85%–90% of the filament length (starting from the leading edge), the flexibility of the filament begins to increase significantly, and the filament can obtain its best propulsion performance. The results of this work provide new insights into the role of non-uniform flexibility during the process of fish movement and provide a valuable reference for the design of bionic underwater vehicles.

EFFECTS OF INDIVIDUALIZED TRAINING AND RESPIRATORY MUSCLE TRAINING IN IMPROVING SWIMMING PERFORMANCE AMONG COLLEGIATE SWIMMERS - AN EXPERIMENTAL STUDY

Previous researches have been conducted to determine the types of training to improve swimming performance. Nevertheless, no study has been done on the individualized training approach among swimmers. Hence, this study aimed (i) to examine the effects of respiratory muscle training on swimming performance (ii) to examine the effects of combined respiratory muscle training with individualized training on swimming performance, and (iii) to compare the differences between the isolated respiratory muscle training, combined intervention of respiratory muscle training with individualized training and usual training on swimming performance. For this, 45 collegiate swimmers with no previous injuries and swims regularly for at least 1 hour per week participated in the study. Participants were randomly assigned into three groups; Group A: Respiratory muscle training and Individualized Training, Group B: Respiratory muscle training alone, and Group C: Usual training session. The difference within the groups after four weeks of the intervention was analyzed using Paired T-test, while the differences between intervention groups were analyzed using repeated measure two-way ANOVA. Both the intervention groups (Group A and B) showed significant improvement after four weeks of intervention, whereas in group comparison, Group A showed tremendous improvement in swimming performance (F (17,238) = 8.385, p&lt;0.05, np2 = 0.375). Thus, the current study has proven that the combination of respiratory muscle training with individualized training could further enhance the swimming performance in terms of heart rate, Vo2 max, stroke volume, perceived exertion, and SWOLF score. Future studies on athletic swimmers with a larger sample size are recommended to further examine the individualized training approach.

Does sports-specific training improve measures of impairment developed for para sport classification? A multiple-baseline, single-case experiment

ABSTRACT Conceptually, sports-specific training should not influence measures of impairment used to classify Para athletes. This study evaluated the extent to which measures of strength, range of movement and coordination developed for Para swimming classification changed in response to a performance-focused swimming programme. A five-phase multiple-baseline, single-case experimental research design was utilized. Three participants with cerebral palsy and high support needs completed the 64-week study, which included two 16-week performance-focused swimming training blocks. Swimming speed, isometric shoulder extension strength, shoulder flexion range of movement and upper limb coordination were monitored throughout. Interrupted Time-Series Simulation Method analysis demonstrated large, significant changes in swimming speed (m/s) during the first (d = 2.17; 95% CI 0.45–3.88; p = 0.01) and second (d = 2.59; 95% CI 1.66–3.52; p = 0.00) training blocks. In contrast, changes in strength, range of movement and coordination were predominantly trivial and non-significant. This was the first study to investigate training responsiveness of measures developed for Para sport classification. Results indicate that despite significantly improved swimming performance, impairment measures remained relatively stable, and therefore these measures of impairment may be valid for the purposes of Para swimming classification. Further research is required in elite athletes, different sports and different impairment types.

Temperature surpasses the effects of velocity and turbulence on swimming performance of two invasive non-native fish species.

Global climate change continues to impact fish habitat quality and biodiversity, especially in regard to the dynamics of invasive non-native species. Using individual aquaria and an open channel flume, this study evaluated the effects of water temperature, flow velocity and turbulence interactions on swimming performance of two lentic, invasive non-native fish in the UK, pumpkinseed (Lepomis gibbosus) and topmouth gudgeon (Pseudorasbora parva). Burst and sustained swimming tests were conducted at 15, 20 and 25°C. Acoustic Doppler velocimetry was used to measure the flume hydrodynamic flow characteristics. Both L. gibbosus and P. parva occupied the near-bed regions of the flume, conserving energy and seeking refuge in the low mean velocities flow areas despite the relatively elevated turbulent fluctuations, a behaviour which depended on temperature. Burst swimming performance and sustained swimming increased by up to 53% as temperature increased from 15 to 20°C and 71% between 15 and 25°C. Furthermore, fish test area occupancy was dependent on thermal conditions, as well as on time-averaged velocities and turbulent fluctuations. This study suggests that invasive species can benefit from the raised temperatures predicted under climate change forecasts by improving swimming performance in flowing water potentially facilitating their further dispersal and subsequent establishment in lotic environments.

Plasmalogens improve swimming performance by modulating the expression of genes involved in amino acid and lipid metabolism, oxidative stress, and ferroptosis in an Alzheimer's disease zebrafish model.

Plasmalogens (PLs) are critical to human health. Studies have reported a link between the downregulation of PLs levels and cognitive impairments in patients with Alzheimer's disease (AD). However, the underlying mechanisms remain to be clarified. In the present study, an AlCl3-induced AD zebrafish model was established, and the model was used to elucidate the neuroprotective effects of PLs on AD by analysing the transcriptional profiles of zebrafish in the control, AD model, AD_PL, and PL groups. Chronic AlCl3 exposure caused swimming performance impairments in the zebrafish, yet PLs supplementation could improve the dyskinesia recovery rate in the AD zebrafish model. Through transcriptional profiling, a total of 5413 statistically significant differentially expressed genes (DEGs) were identified among the groups. In addition to the DEGs involved in amino acid metabolism, we found that the genes related to iron homeostasis, lipid peroxidation, and oxidative stress, all of which contribute to ferroptosis, were dramatically altered among different groups. These results suggest that seafood-derived PLs, in addition to their role in eliminating oxidative stress, can improve the swimming performance in AlCl3-exposed zebrafish partly by suppressing neuronal ferroptosis and accelerating synaptic transmission at the transcriptional level. This study provides evidence for PLs to be developed as a functional food supplement to relieve AD symptoms.

Adaptation of a mouse Doppler echocardiograph system for assessing cardiac function and thermal performance in a juvenile salmonid.

Measures of cardiac performance are pertinent to the study of thermal physiology and exercise in teleosts, particularly as they pertain to migration success. Increased heart rate, stroke volume and cardiac output have previously been linked to improved swimming performance and increased upper thermal tolerance in anadromous salmonids. To assess thermal performance in fishes, it has become commonplace to measure the response of maximum heart rate to warming using electrocardiograms. However, electrocardiograms do not provide insight into the hemodynamic characteristics of heart function that can impact whole-animal performance. Doppler echocardiography is a popular tool used to examine live animal processes, including real-time cardiac function. This method allows for nonsurgical measurements of blood flow velocity through the heart and has been used to detect abnormalities in cardiovascular function, particularly in mammals. Here, we show how a mouse Doppler echocardiograph system can be adapted for use in a juvenile salmonid over a range of temperatures and timeframes. Using this compact, noninvasive system, we measured maximum heart rate, atrioventricular (AV) blood flow velocity, the early flow-atrial flow ratio and stroke distance in juvenile Atlantic salmon (Salmo salar) during acute warming. Using histologically determined measures of AV valve area, we show how stroke distance measurements obtained with this system can be used to calculate ventricular inflow volume and approximate cardiac output. Further, we show how this Doppler system can be used to determine cardiorespiratory thresholds for thermal performance, which are increasingly being used to predict the consequences that warming water temperatures will have on migratory fishes.

Acoustic radiation forces on magnetically actuated helical swimmers

Artificial microswimmers have gained significant attention recently for use in biomedical applications, such as drug delivery, and microfluidic applications, such as mixing. The small scale of the swimmers requires external actuation mechanisms, such as magnetic fields. Acoustic actuation, due to its biocompatible nature, can be used alongside magnetic fields to improve swimming performance. Several experimental studies have already shown the propulsion of both non-helical and helical swimmers with acoustic fields. Here, we present a simple model to evaluate the acoustic radiation force on helices. The methodology can be applied to solve for the force on other complicated structures as well, reducing the high computational cost required with other methods, such as the finite-element method. The approach is coupled with a resistive force theory-based model of slender magnetized helices to evaluate the complete three-dimensional trajectories of the swimmers under acoustic and magnetic fields. Traveling waves are shown to reduce swimmer wobbling significantly while also generating a significant push. Standing waves, on the other hand, are observed to place the swimmer in a unique position and orientation, which can be exploited for accurate positioning or micro-mixing.

The effects of plyometric jump training on jump and sport-specific performances in prepubertal female swimmers

Background/objectiveDry land-training (e.g., plyometric jump training) can be a useful mean to improve swimming performance. This study examined the effects of an 8-week plyometric jump training (PJT) program on jump and sport-specific performances in prepubertal female swimmers. MethodsTwenty-two girls were randomly assigned to either a plyometric jump training group (PJTG; n = 12, age: 10.01 ± 0.57 years, maturity-offset = -1.50 ± 0.50, body mass = 36.39 ± 6.32 kg, body height = 146.90 ± 7.62 cm, body mass index = 16.50 ± 1.73 kg/m2) or an active control (CG; n = 10, age: 10.50 ± 0.28 years, maturity-offset = -1.34 ± 0.51, body mass = 38.41 ± 9.42 kg, body height = 143.60 ± 5.05 cm, body mass index = 18.48 ± 3.77 kg/m2). Pre- and post-training, tests were conducted for the assessment of muscle power (e.g., countermovement-jump [CMJ], standing-long-jump [SLJ]). Sport-specific-performances were tested using the timed 25 and 50-m front crawl with a diving-start, timed 25-m front crawl without push-off from the wall (25-m WP), and a timed 25-m kick without push-off from the wall (25-m KWP). ResultsFindings showed a significant main effect of time for the CMJ (d = 0.78), the SLJ (d = 0.91), 25-m front crawl test (d = 2.5), and the 25-m-KWP (d = 1.38) test. Significant group × time interactions were found for CMJ, SLJ, 25-m front crawl, 50-m front crawl, 25-m KWP, and 25-m WP test (d = 0.29–1.63) in favor of PJTG (d = 1.34–3.50). No significant pre-post changes were found for CG (p > 0.05). ConclusionIn sum, PJT is effective in improving muscle power and sport-specific performances in prepubertal swimmers. Therefore, PJT should be included from an early start into the regular training program of swimmers.

Improved aerobic and anaerobic swimming performance after exercise training and detraining in Schizothorax wangchiachii: Implications for fisheries releases

Swimming performance (aerobic and anaerobic) is often used to predict the ability of fish to adapt and survive. Fish raised in captivity are typically poor swimmers and have lower survival rates than wild conspecifics when released into the natural environment. We investigated the potential for exercise training to enhance the swimming performance of Schizothorax wangchiachii held in captivity. Juvenile fish (mean body mass 1.40 ± 0.13 g, mean body length 4.36 ± 0.24 cm) were trained under five different regimes [3 cm·s−1 control group (C), 10 cm·s−1 for 6 (L6) and 12 h (L12) per day and 20 cm·s−1 for 6 (H6) and 12 h (H12) per day] for 30 days and then detrained for 20 days (i.e. no training). Aerobic (i.e. critical swimming speed, Ucrit), anaerobic swimming performance (i.e. endurance time at 1.2 or 1.5 Ucrit), and morphological parameters were measured at the beginning (T0), after 30 days of exercise training (T30) and after 20 days of detraining (DT20). Aerobic exercise training significantly improved the Ucrit, endurance time at 1.2 and 1.5 Ucrit of juvenile S. wangchiachii (P < .05). After 20 days of detraining, both the aerobic and anaerobic swimming performance of the H6 and H12 groups declined and no longer differed from the control group indicating a failure to maintain improved swimming performance, whereas improved swimming performance was maintained in L6 and L12 groups. No significant difference in swimming performance was found between 6 and 12 hours training at 10 cm·s−1. Thus, exercise at close to 10 cm·s−1 for 6 h per day for 30 days or a longer time periods prior to release appears to be a suitable regime for swimming performance enhancement, potentially increasing survivability of released S. wangchiachii in wild.

The Ground Effect in Anguilliform Swimming.

Some anguilliform swimmers such as eels and lampreys swim near the ground, which has been hypothesized to have hydrodynamic benefits. To investigate whether swimming near ground has hydrodynamics benefits, two large-eddy simulations of a self-propelled anguilliform swimmer are carried out—one swimming far away from the ground (free swimming) and the other near the ground, that is, midline at of fish length (L) from the ground creating a gap of . Simulations are carried out under similar conditions with both fish starting from rest in a quiescent flow and reaching steady swimming (constant average speed). The numerical results show that both swimmers have similar speed, power consumption, efficiency, and wake structure during steady swimming. This indicates that swimming near the ground with a gap larger than does not improve the swimming performance of anguilliform swimmers when there is no incoming flow, that is, the interaction of the wake with the ground does not improve swimming performance. When there is incoming flow, however, swimming near the ground may help because the flow has lower velocities near the ground.

Freezing ovarian fluid does not alter how it affects fish sperm swimming performance: creating a cryptic female choice 'spice rack' for use in split-ejaculate experimentation.

Cryptic female choice is often mediated chemically in external fertilizers by ovarian fluid (OF), which can change sperm swimming performance and bias paternity under sperm competition. Assessing cryptic female choice is hindered by the necessity of using fresh gametes and the short time window available to obtain diverse samples from wild animals. Using split-ejaculate experimental designs and samples from lake trout, brown trout and Atlantic salmon, we evaluated whether freezing OF alters the way in which it modifies sperm swimming. Sperm had improved swimming performance in the presence of OF over plain water, and the effect did not depend on whether the OF had previously been frozen. Freezing OF does not seem to alter the way it influences sperm. This allows the researcher to create a 'spice rack' of OF samples that can be used in studies on cryptic female choice, and opens up the possibility to compare animals mating under large spatial and temporal variability.

Effects of temperature and viscosity on miracidial and cercarial movement of Schistosoma mansoni: ramifications for disease transmission

Parasites with complex life cycles can be susceptible to temperature shifts associated with seasonal changes, especially as free-living larvae that depend on a fixed energy reserve to survive outside the host. The life cycle of Schistosoma, a trematode genus containing some species that cause human schistosomiasis, has free-living, aquatic miracidial and cercarial larval stages that swim using cilia or a forked tail, respectively. The small size of these swimmers (150–350 µm) dictates that their propulsion is dominated by viscous forces. Given that viscosity inhibits the swimming ability of small organisms and is inversely correlated with temperature, changes in temperature should affect the ability of free-living larval stages to swim and locate a host. By recording miracidial and cercarial movement of Schistosoma mansoni using a high-speed camera and manipulating temperature and viscosity independently, we assessed the role each factor plays in the swimming mechanics of the parasite. We found a positive effect of temperature and a negative effect of viscosity on miracidial and cercarial speed. Reynolds numbers, which describe the ratio of inertial to viscous forces exerted on an aquatic organism, were <1 across treatments. Q10 values were <2 when comparing viscosity treatments at 20 °C and 30 °C, further supporting the influence of viscosity on miracidial and cercarial speed. Given that both larval stages have limited energy reserves and infection takes considerable energy, successful transmission depends on both speed and lifespan. We coupled our speed data with mortality measurements across temperatures and discovered that the theoretical maximum distance travelled increased with temperature and decreased with viscosity for both larval stages. Thus, our results suggest that S. mansoni transmission is high during warm times of the year, partly due to improved swimming performance of the free-living larval stages, and that increases in temperature variation associated with climate change might further increase transmission.