Swimming Start Research Articles

Does jumping conducted before the swimming start elicit underwater enhancement?

The effects of pre-activation exercises on undulatory underwater swimming (UUS) have not been studied. This research aimed to: 1) assess the effects of a jumping-exercise strategy upon UUS performance and kinematics variables; 2) test the different effects on males and females, and; 3) to explore if stronger participants exhibit greater post-activation performance enhancement (PAPE). Ninety-two age-group national level swimmers randomly assigned into control (17 males and 18 females) and experimental groups (27 males and 30 females) took part in a cross-sectional study designed to test two maximal 15-m UUS performance efforts. The experimental group performed four maximal tuck jumps before the first or the second UUS effort. Performance and kinematics variables were analyzed using instantaneous velocity data via speedometer. Maximal lower-limbs force was obtained during a countermovement jump through a linear-encoder. Two-way repeated measures ANOVA test and linear regression analysis were used to explore variable interactions between baseline and PAPE, and the association between the PAPE response and strength of the swimmers, respectively. Despite trends toward improvements in push-off velocity (Δ = 1.33%; d = 0.12), the results did not show enhancements nor deterioration in UUS performance and kinematics after the tuck jumps. No specific PAPE responses modulated by sex or by the strength level of the swimmers were observed for this age-group (p < 0.05). Four tuck jump repetitions executed prior to diving could be insufficient to acutely enhance UUS performance. The fact that the exercise performed during warm-up was a body-weight based exercise, was possibly not enough to evoke PAPE.

Does the Back Plate Position Influence Swimming Start Temporal Characteristics?

The current study examined the back plate position impact on the block phase movement pattern and total starting performance with a distinction for sex. Thirty-eight swimmers performed starts changing the back plate position (preferred position, one position forward and one position backward), with the data being assessed using a 3D dynamometric central and a video camera. In males, the 15 m start time was 0.1 s shorter for the preferred position compared with the backward position (p < 0.05). Regardless of the back plate positioning, the swimmers spent a similar time on the block. A more forward position of the back plate postponed the rear foot take-off and consequently reduced the front foot stand duration. A back plate position effect was revealed for those variables with a larger effect size in males whereas in females, a change of about two positions was needed to reach a significance level. Probably due to the specification of physical domains, a greater impact on the changes introduced was noted for males. Therefore, whilst searching for the optimal starting position, adjustments to the back plate placement might affect a greater number of males than females. To reinforce the starting optimization during the training process and its monitoring, the effect of personal preference toward the starting block setting was also considered.

From decision to action: Detailed modelling of frog tadpoles reveals neuronal mechanisms of decision-making and reproduces unpredictable swimming movements in response to sensory signals.

How does the brain process sensory stimuli, and decide whether to initiate locomotor behaviour? To investigate this question we develop two whole body computer models of a tadpole. The "Central Nervous System" (CNS) model uses evidence from whole-cell recording to define 2300 neurons in 12 classes to study how sensory signals from the skin initiate and stop swimming. In response to skin stimulation, it generates realistic sensory pathway spiking and shows how hindbrain sensory memory populations on each side can compete to initiate reticulospinal neuron firing and start swimming. The 3-D "Virtual Tadpole" (VT) biomechanical model with realistic muscle innervation, body flexion, body-water interaction, and movement is then used to evaluate if motor nerve outputs from the CNS model can produce swimming-like movements in a volume of "water". We find that the whole tadpole VT model generates reliable and realistic swimming. Combining these two models opens new perspectives for experiments.

Swimming start model and determination of the optimal breakout position

ABSTRACT While many parameters contribute to swimming start performance, a few have been proven to affect the overall start performance more significantly than others; these include take-off velocity, flight time, entry water distance, time underwater during descent and ascent, and free-swimming velocity. This study aims to analyse the influential trajectory of these key parameters on the overall start performance, particularly focusing on determining the optimal breakout point. Ten national-level swimmers participated in this study, which combined kinematics and statistical analysis to propose a novel start model that can be used to explore the influential trajectory of key parameters on the overall start performance and assess the effect of some training factors for performance improvement. Further, this study investigated the optimal breakout position via a mathematical model. This is the first study to provide a solution to determine this parameter. The solution is verified to be practical through trial data, and the overall start performance is improved by 0.71–3.29%, depending on the swimmer’s current level. Therefore, the results can be used as a reference for swimming start training and improvement.

Effects of wearing a customized bite-aligning mouthguard on powerful actions in highly trained swimmers

Background/objectivesThe potential advantages of wearing customized bite-aligning mouthguards on several performance parameters such as muscular strength, power and reaction time have been reported. Literature shows that the concurrent activation potentiation phenomenon, elicited by a powered and balanced jaw clenching, can provide athletes with several neuromuscular advantages. The aim of the present study was to investigate the acute effects of jaw clenching while wearing a customized bite-aligning mouthguard on swimming start, countermovement jump and swim bench test, in contrast to two other conditions: non-jaw clenching and jaw clenching without mouthguard. MethodsA randomized, repeated measure within study design was used to compare the condition effect on eight highly trained elite male and female swimmers. ResultsStatistical analysis revealed a significant increase in the countermovement jump height (p = 0.041) when comparing the use of mouthguards with the non-jaw condition. In the swim bench, a significant greater time to peak force (p = 0.049) was found when comparing the use of mouthguards with the jaw condition. Although, non-significant effects, small differences were found in the start reaction time and 15-m freestyle swimming when comparing the use of mouthguards with the non-jaw condition. ConclusionThis study demonstrated that wearing customized, bite-aligning mouthguards had an ergogenic effect on specific measures of vertical jump and swim bench test, whereas non-meaningful but small differences were found in swimming start.

Which variables may affect underwater glide performance after a swimming start?

ABSTRACT The underwater phase is perhaps the most important phase of the swimming start. To improve performance during the underwater phase, it is necessary to improve our understanding of the key variables affecting this phase. The main aim of this study was to identify key kinematic variables that are associated with the performance of an underwater glide of a swimming start, when performed at streamlined position without underwater undulatory swimming. Sixteen experienced swimmers performed 48 track starts and 20 kinematic variables were analysed. A multiple linear regression analysis was carried out to explore the relationship between glide performance (defined as glide distance) and the variables that may affect glide performance. Four variables in the regression model were identified as good predictors of glide distance: flight distance; average velocity between 5 m and 10 m; and maximum depth of the hip. The results of the present study help improve our understanding of underwater glide optimisation and could potentially facilitate improvement of overall start performance.

Infant swimming: a contribution to children’s health

Nowadays, infant swimming is a rather relevant topic. Swimming has a beneficial effect on the child’s body as a whole, strengthening its nervous system and improving sleep, appetite, and adaptive capacity, as well as stimulating metabolism.Aim. To study infant swimming as a progressive direction in improving child health from birth to 3 years old. The objective was to study the importance of infant swimming, consider its main techniques, highlight indications and contraindications, conduct and analyze a survey among parents on this topic. Early start of swimming significantly improves the child’s health, or reduces the current health problems. The skill of independent swimming is not the main goal. The main goal is effective hardening, strengthening immunity and health, correcting identified abnormalities and stimulating proper development.The division of the education period of infants into stages is conditional and depends on the individual characteristics of a child. It is important to observe the basic hardening principles: consistency and graduality.Also, we conducted a survey of parents to study and understand their opinions on teaching swimming. Relevant conclusions were drawn from the results. The relevance of this topic and the need for more active promotion of infant swimming is evidenced by the fact that 69% of parents surveyed consider it necessary to provide home courses on infant swimming. Also, 84% spoke in favor of the need to open specialized centers for teaching swimming for children from birth to 3 years old.

Longitudinal tracking of body composition, lower limb force-time characteristics and swimming start performance in high performance swimmers

This study aimed to (1) track changes in body composition, lower body force-time characteristics, and swim start performance over a competitive season, and (2) investigate the intra-individual associations between changes in body composition and lower body force-time characteristics to swim start performance in five high performance swimmers (three males, two females). Over a ∼12-month period, body composition, lower body force-time characteristics and swim start performance were assessed at three time points via DXA scan, squat jump and swim start performance test (start times to 5 and 15 m and several kinematic and kinetic outputs). Throughout a competitive season of concurrent swimming and dry-land resistance training, improvements in lower body lean mass and squat jump force-time characteristics were observed. However, changes in start times varied between athletes. Total body and lower body lean mass both displayed large negative correlations with the time spent in the entry and propulsive underwater phases ( r = –0.57 to –0.66), along with a large positive correlations with glide time ( r = 0.56–0.53). Additionally, lower body lean mass exhibited large to very large positive correlations with the flight phase ( r = 0.70–0.73). Overall, these findings provide some insight into the potential magnitude of change in body composition, lower body force-time characteristics and swim start performance in high performance swimmers within a season. The large to very large correlations between increased lower body lean mass and SJ force-time metrics to improvements in aspects of start performance may provide useful information to coaches and sports scientists.

What Goes Wrong during Early Development of Artificially Reproduced European Eel Anguilla anguilla? Clues from the Larval Transcriptome and Gene Expression Patterns

Simple SummaryClosing the life cycle of the European eel in captivity is urgently needed to gain perspective for the commercial production of juvenile glass eels. Larvae are produced weekly at our facilities, but large variations in larval mortality are observed during the first week after hatching. Although much effort has been devoted to investigating ways to prevent early larval mortality, it remains unclear what the causes are. The aim of this study was to perform a transcriptomic study on European eel larvae in order to identify genes and physiological pathways that are differentially regulated in the comparison of larvae from batches that did not survive for longer than three days vs. larvae from batches that survived for at least a week up to 22 days after hatching (non-viable vs. viable larvae). In contrast to earlier published studies on European eel, we conclude that larvae exhibit immune competency. Non-viable larvae initiated an inflammatory and host protection immune response and tried to maintain osmoregulatory homeostasis. As a perspective, microbial control and salinity reduction might benefit eel larvae in terms of lower mortality and improved development by lowering the costs of immune functioning and osmoregulation.In eels, large variations in larval mortality exist, which would impede the viable production of juvenile glass eels in captivity. The transcriptome of European eel larvae was investigated to identify physiological pathways and genes that show differential regulation between non-viable vs. viable larvae. Expression of genes involved in inflammation and host protection was higher, suggesting that non-viable larvae suffered from microbial infection. Expression of genes involved in osmoregulation was also higher, implying that non-viable larvae tried to maintain homeostasis by strong osmoregulatory adaptation. Expression of genes involved in myogenesis, neural, and sensory development was reduced in the non-viable larvae. Expression of the major histocompatibility complex class-I (mhc1) gene, M-protein (myom2), the dopamine 2B receptor (d2br), the melatonin receptor (mtr1), and heat-shock protein beta-1 (hspb1) showed strong differential regulation and was therefore studied in 1, 8, and 15 days post-hatch (dph) larvae by RT-PCR to comprehend the roles of these genes during ontogeny. Expression patterning of these genes indicated the start of active swimming (8 dph) and feed searching behavior (15 dph) and confirmed immunocompetence immediately after hatching. This study revealed useful insights for improving larval survival by microbial control and salinity reduction.

Kinematic analysis of above- and underwater swim start phases of male swimmers aged 16–18 years

IntroductionSwim start technique analysis is usually conducted in elite swimmers or only limited to above-water phases. The aim of the study was to analyse kinematic parameters of above- and underwater kick start phases among young male swimmers.Material and methodsThe study group comprised male swimmers (FINA points per 100-m freestyle: 525 ± 84). The subjects performer a 15-m front crawl with kick start. The trials were recorded above and below water with 3 recording devices synchronized with the starting signal. Kinematic analysis by using 2 models (above- and underwater) of body was done. On the basis of time to cover 15 m, 2 groups were distinguished: quickly (FS) and slowly (SS) performing the swim start.ResultsFS and SS demonstrated differences (p &lt; 0.05) regarding hip joint height at starting signal (1.56 ± 0.05 m vs. 1.45 ± 0.05 m), push-off angle (23.89 ± 6.50° vs. 35.12 ± 3.43°), hip joint angle upon completing push-off (163.83 ± 8.37° vs. 149.73 ± 9.93°), and horizontal velocity during flight (3.70 ± 0.35 m/s vs. 3.24 ± 0.22 m/s), submersion (4.88 ± 0.09 m/s vs. 4.36 ± 0.22 m/s), and glide phase (3.40 ± 0.17 m/s vs. 2.99 ± 0.29 m/s).ConclusionsThe obtained results indicate that position on the block significantly influences the movement course in consecutive phases. Young competitors should aim towards elevated hip positioning, allowing to maximize horizontal velocity during the flight, submersion, and glide phases.

Differences in the key parameters of the individual versus relay swimming starts

ABSTRACT The purpose of the present study was twofold: (i) to compare the kinematic characteristics of individual and relay swimming starts; and (ii) to relate the kinematic variables to 5 m performance for both starts. Twelve elite-level swimmers performed 2 × 25 m at maximal effort (one with an individual and one with a relay start randomly). Two-dimensional direct linear transformation algorithms were used to calculate swimmers’ centre of mass (CM) kinematics during each subphase. The results indicated moderate to much faster 5 m, 10 m 15 and 15 m times (29.4, 10.7 and 6.5%) for relay than individual starts as well as the differences at specific parameters, but no differences in take-off horizontal velocity between start techniques. Large correlations to performance times were found in block time, horizontal take-off velocity, take-off velocity and entry angle (r = 0.77 to 0.83) 20 for individual start, but in changeover time, take-off height and entry distance (r = 0.69 to 0.90) for relay start. Differences on swim start regulations between individual and relay events were in line with different key parameters related to start performances in each event. This should be considered by swimmers and coaches when addressing the starting improvement.

On-block mechanistic determinants of start performance in high performance swimmers

ABSTRACT This study aimed to 1) identify what starting block outcome kinetics have the greatest relationship to 15 m start time; 2) investigate key mechanistic determinants of the block phase and how these forces are sequenced. One hundred and fifty-two high-level competitive swimmers were included in the study. Linear mixed modelling identified four on-block outcome kinetic variables (work, average power, horizontal take-off velocity (HTOV), and average acceleration) as having a very large relationship (R2 = 0.79–0.83) to 15 m start time, with average power having the most substantial impact. On-block force sequencing started with the rear leg, followed by upper limb grab forces and the front leg. Further exploration of underlying determinants was performed for average power and HTOV of the centre of mass. Multiple linear regression identified grab resultant peak force, rear resultant average force, front horizontal peak force, and resultant peak force as significant predictors of average power (R2 = 0.88). HTOV was predicted using the same variables, apart from the inclusion of rear horizontal peak force instead of rear resultant average force (R2 = 0.73). These findings may influence how strength and conditioning and skill acquisition interventions are designed to improve swim start performance.

Pushing up or pushing out-an initial investigation into horizontal- versus vertical-force training on swimming start performance: a pilot study.

BackgroundThe block phase in the swimming start requires a quick reaction to the starting signal and a large take-off velocity that is primarily horizontal in direction. Due to the principle of specificity of training, there is a potential benefit of performing a greater proportion of horizontal force production exercises in a swimmers’ dry-land resistance training sessions. Therefore, the purpose of this pilot study was to provide an insight into the effects of a horizontal- (HF) vs vertical-force (VF) training intervention on swim start performance.MethodsEleven competitive swimmers (six males (age 20.9 ± 1.8 years, body mass 77.3 ± 9.7 kg, height 1.78 ± 0.05 m) and five females (age 21.4 ± 2.0 years, body mass 67.5 ± 7.4 kg, height 1.69 ± 0.05 m)) completed 2 weekly sessions of either a horizontal- or vertical-force focused resistance training programme for 8 weeks. Squat jump force-time characteristics and swim start kinetic and kinematic parameters were collected pre- and post-intervention.ResultsAcross the study duration, the swimmers completed an average of nine swimming sessions per week with an average weekly swim volume of 45.5 ± 17.7 km (HF group) and 53 ± 20.0 km (VF group), but little practice of the swim start per week (n = 9). Within-group analyses indicated a significant increase in predicted one repetition maximum (1RM) hip thrust strength in the HF group, as well as significant increases in grab resultant peak force but reductions in resultant peak force of the block phase for the VF group. No significant between-group differences in predicted 1RM hip thrust and back squat strength, squat jump force-time and swim start performance measures were observed after 8 weeks of training. Significant correlations in the change scores of five block kinetic variables to time to 5 m were observed, whereby increased block kinetic outputs were associated with a reduced time to 5 m. This may be indicative of individual responses to the different training programmes.DiscussionThe results of this current study have been unable to determine whether a horizontal- or vertical-force training programme enhances swim start performance after an 8-week training intervention. Some reasons for the lack of within and between group effects may reflect the large volume of concurrent training and the relative lack of any deliberate practice of the swim start. Larger samples and longer training duration may be required to determine whether significant differences occur between these training approaches. Such research should also look to investigate how a reduction in the concurrent training loads and/or an increase in the deliberate practice of the swim start may influence the potential changes in swim start performance.

Proposal of a Conditioning Activity Model on Sprint Swimming Performance.

This study aimed to propose a conditioning activity (CA) model to stimulate improvement on neuromuscular responses, mechanical parameters and for the 50-m freestyle swimming. Thirteen male swimmers (19 ± 3 years and performances of 77% in relation to World Championship records) performed four CA protocols followed by a maximum performance in the 50-m freestyle. In the first protocol (P1) swimmers performed a standard warm-up (∼15 min); in the second protocol (P2) lunges (3 × 85% of the one-repetition maximum); in the third (P3) pull-ups (3 maximum repetitions) and box jumps 40 cm high and 60 cm deep (1 × 5 with 10% of the corporal weight); and in the fourth protocol (P4) a combination of exercises from the second and third protocols. CA protocols had no effect on the standard warm-up. However, P2 performance (27.01 ± 1.25 s) was similar to P1 (27.01 ± 1.18 s) and presented higher positive effects in mechanical parameters for the swim start performance in comparison to other protocols, contributing to improvements in the 50-m freestyle. In addition, turnaround time also had a negative effect, mainly in P3 (3.12 ± 0.28 s), signaling the improvement of this variable in all protocols (P1: 3.30 ± 0.38 s; P2: 3.17 ± 0.30 s; P4: 3.17 ± 0.34 s). P2 (after: 80 ± 11%; before: 82.7 ± 9.9%) and P3 (after: 82.7 ± 9.9%; before: 85.1 ± 9.7%) presented a possible positive effect on the percentage of voluntary activation in relation to P1 (after: 79.3 ± 10.7%; before: 76.3 ± 12%). In conclusion, the proposed conditioning activity protocols were not efficient for performance improvement in the 50-m freestyle compared to the standard model and seem to specifically influence each phase of the event.

Musculoskeletal Injuries in Master Swimmers: A National Survey in Turkey.

BackgroundThis study aimed to determine the frequency of musculoskeletal injuries in master swimmers in Turkey.MethodsA questionnaire was formed and distributed to all master swimmers registered with the Turkish Swimming Federation. The collected data included age, sex, the age to start swimming (SAS), weekly training time (WTT), weekly training distance (WTD), any painful episode that lasted more than 10 days in any of the body regions within last one year, any confirmed diagnosis of musculoskeletal disease by a physician, and history of musculoskeletal surgical operation. The descriptive data were presented, and multiple comparisons were made according to demographic characteristics.ResultsThere were 88 male swimmers with a mean age of 47.1±13.2 years (range, 26-89 years). Of the 88 athletes, 27 (30.7%) had no pain in daily activities, and 61 (69.3%) reported pain in at least one region, with a total of 118 pain zones reported. The shoulder was the most common painful body region (n:37, 42.0%), followed by the lower back (n: 24, 27.3%), neck (n: 19, 21.6%), back (n:12, 13.6%), and knee (n:9, 10.2%). The mean age, SAS, WTT, WTD, and distribution of stroke preference were similar in subjects with or without reported pain and diagnosis (p>0.005). Any painful body region and diagnosis were equally distributed in all swimming styles (p>0.05). The most common surgeries were lumbar disc disease (16.7%) and meniscectomy (16.7%).ConclusionCompared to the findings in the current literature, master swimmers do not have as many musculoskeletal problems as their younger counterparts. The problems seen in master swimmers are lower but similar to those in competitive elite swimmers. From the musculoskeletal health perspective, swimming is safe for the master age group. Swimming can be safely offered to elderly patients who underwent even musculoskeletal surgery.

The prediction of swim start performance based on squat jump force-time characteristics.

BackgroundDepending on the stroke and distances of the events, swim starts have been estimated to account for 0.8% to 26.1% of the overall race time, with the latter representing the percentage in a 50 m sprint front crawl event (Cossor & Mason, 2001). However, it is still somewhat unclear what are the key physiological characteristics underpinning swim start performance. The primary aim of this study was to develop a multiple regression model to determine key lower body force-time predictors using the squat jump for swim start performance as assessed by time to 5 m and 15 m in national and international level swimmers. A secondary aim was to determine if any differences exist between males and females in jump performance predictors for swim start performance.MethodsA total of 38 males (age 21 ± 3.1 years, height 1.83 ± 0.08 m, body mass 76.7 ± 10.2 kg) and 34 females (age 20.1 ± 3.2 years, height 1.73 ± 0.06 m, body mass 64.8 ± 8.4 kg) who had competed at either an elite (n = 31) or national level (n = 41) participated in this study. All tests were performed on the same day, with participants performing three bodyweight squat jumps on a force platform, followed by three swim starts using their main swimming stroke. Swim start performance was quantified via time to 5 m and 15 m using an instrumented starting block.ResultsStepwise multiple linear regression with quadratic fitting identified concentric impulse and concentric impulse2 as statistically significant predictors for time to 5 m (R2 = 0.659) in males. With time to 15 m, concentric impulse, age and concentric impulse2 were statistically significant predictors for males (R2 = 0.807). A minimum concentric impulse of 200–230 N.s appears required for faster times to 5 m and 15 m, with any additional impulse production not being associated with a reduction in swim start times for most male swimmers. Concentric impulse, Reactive strength index modified and concentric mean power were identified as statistically significant predictors for female swimmers to time to 5 m (R2 = 0.689). Variables that were statistically significant predictors of time to 15 m in females were concentric impulse, body mass, concentric rate of power development and Reactive strength index modified (R2 = 0.841).DiscussionThe results of this study highlight the importance of lower body power and strength for swim start performance, although being able to produce greater than 200 or 230 N.s concentric impulse in squat jump did not necessarily increase swim start performance over 5 m and 15 m, respectively. Swimmers who can already generate greater levels of concentric impulse may benefit more from improving their rate of force development and/or technical aspects of the swim start performance. The sex-related differences in key force-time predictors suggest that male and female swimmers may require individualised strength and conditioning programs and regular monitoring of performance.

Protocolización de la post-activación potenciación estimulada en natación y su relación con la fuerza relativa

Objetivo: Este estudio experimentó un protocolo de post-activación potenciación estimulada en 16 nadadores de competición.&#x0D; Método: En primer lugar, se aplicaron ejercicios de acondicionamiento para extremidades superiores e inferiores y se exploraron los efectos producidos tras 5, 8, 12 y 20 minutos de descanso en un test que implicaba tres saltos verticales y tres flexiones explosivas. En una sesión posterior, se aplicaron ejercicios de acondicionamiento específico en ambas extremidades proporcionando el mismo tiempo de descanso que había inducido los mejores resultados en la evaluación exploratoria (8 min), y sus efectos se evaluaron en una prueba de natación sprint (50 m). Finalmente, también se obtuvo el índice de fuerza relativa de los participantes y se estudió su relación con el rendimiento.&#x0D; Resultados: Las variables relacionadas con la salida de natación mejoraron. La velocidad en el despegue fue mayor debido al incremento de las fuerzas desarrolladas en el poyete. El tiempo de nado en la prueba de 50-m se mantuvo igual a la situación estándar aunque la velocidad fue mayor en los primeros metros.&#x0D; Conclusiones: Los sujetos con mayor índice de fuerza obtuvieron mejores resultados y reaccionaron mejor a la post-activación potenciación estimulada posiblemente porque sus efectos son más efectivos en las fibras tipo II y estas, son más comunes en sujetos entrenados.

Effect of front leg extension timing during kick-start on swimming start performance

Effect of front leg extension timing during kick-start on swimming start performance

Is 3 Weeks of Exercise Enough to Change Blood Pressure and Cardiac Redox State in Hypertensive Rats?

Abstract The investigation was aimed to evaluate the effects of 3-weeks swimming exercise on blood pressure and redox status in high-salt-induced hypertensive rats. Male Wistar albino rats (n=40, 6 weeks old) were divided into 4 groups: 1. hypertensive rats that swam for 3 weeks; 2. sedentary hypertensive control rats; 3. normotensive rats that swam for 3 weeks; 4. sedentary normotensive control rats. Hypertensive animals were on high concentrated sodium (8% NaCl) solution for 4 weeks (period of induction of hypertension). After sacrificing, hearts were isolated and perfused according to Langendorff technique at gradually increased coronary per-fusion pressure from 40–120 cmH2O. The oxidative stress markers were determined in coronary venous effluent: the index of lipid peroxidation (measured as TBARS), nitrites (NO2 −), superoxide anion radical (O2 −) and hydrogen peroxide (H2O2). Swimming did not lead to significant changes in levels of TBARS, NO2 −, O2 − in any of compared groups while levels of H2O2 were significantly higher in swimming hyper-tensive group comparing to swimming normotensive group at coronary perfusion pressure of 80–120 cmH2O. Our results indicate that the short-term swimming start to reduce blood pressure. In addition it seems that this type of swimming duration does not promote cardiac oxidative stress damages.

Swimming Performance to 25 Meters Backstroke Depends on Selected Factors of Explosive Strength of Lower Limbs

Summary The aim of our work was to analyze the partial shares of selected factors of explosive strength of lower limbs on the overall explanation of swimming performance to the 25 meters backstroke. 29 students of Physical Education took part in our research and completed 6 tests. These tests were realized on a dry-land and in the water and they consisted of swimming performance to 25 meters backstroke, swimming start speed to 4 meters, vertical jump with and without arm-swing, maximum and average velocity of take-off performance on dry land under the backstroke start conditions. The obtained data are described by descriptive statistics and all parameters were entered to the correlation analysis for their dependence evaluation. By the analysis, we found that all tests significantly correlated with each other (p &lt; 0.01; p &lt; 0.05) except for the start to 4 meters test and Tendo velocity average test. For the evaluation of factors that determine the swimming performance to 25 meters backstroke, we use the regression analysis of parameters where the regression model was reflected as statistically significant (R2 = 0.479 %; SEE = 3.396 %). Partial shares of individual tests, except for tests of maximal and average velocity on a dryland, showed up as statistically significant (p &lt; 0.05; p &lt; 0.01), with the highest share of swimming start to 4 meters performance (p &lt; 0.01; r = 0.686). We used the regression step analysis in which we decrease the indicators to the three main factors of the strength of lower limbs model, which influence the swimming performance to the 25 meters backstroke significantly with large effect (R2 = 0.4787 %; f2 = 0.9183; F = 7.652; p &lt; 0.01). Again, the highest and statistically significant (p &lt; 0.01) share on the explanation of swimming performance had the start to 4 meters with 43.33 % percentage share. Besides the swimming start, the Countermovement Jump test was statistically significant too (p &lt; 0.05) and statistically insignificant was test of maximum velocity on a dry-land. By this study we can evaluate how individual factors of strength of lower limbs influence the swimming performance and for the future it is necessary to complete them with the other factors for the better creation of the appropriate swimming training program.