Search

The present study investigated swimmers’ performances on the starting and turning segments between individual and relay races. A total number of 72 race performances of the same swimmers in both relay 4 × 100 m finals (freestyle, medley, and mixed freestyle) and individual 100 m finals or semi-finals (butterfly, breaststroke, and freestyle) from the LEN European Swimming Championships were compared with repeated measures MANOVA. Swimmers performed 5–7% faster starts in the relay than in the corresponding individual events, despite no differences in the flight phase and a lower performance (shorter distances and slower velocities) on the underwater start section. The 15 m turn times were slower in the butterfly relay races although no specific differences in the underwater parameters were observed. These results suggest that specific training of the starting and turning segments should be performed under relay conditions to optimise pacing and performance in the underwater sections.

In swimming relay races, various start techniques are performed by swimmers, but it remains unclear which technique leads to a better start performance. Therefore, the purpose of the present study was to compare the kinematic characteristics of different relay start techniques with the new starting block Omega OSB11. Eleven international youth swimmers were filmed during 1) no step with parallel feet, 2) no step with separated feet and 3) one-step starts and their centre of mass kinematics calculated with 2D-DLT algorithms. Results indicate that differences between techniques were detected in the spatiotemporal parameters of the block and aerial start phases (e.g., initial and take-off positions, entry height, preparation and changeover times) and in selected parameters of the underwater phase (e.g., emersion time and distance, underwater time and distance). However, no statistical effects were found in 5 m, 10 m and 15 m start times, nor in horizontal take-off velocity, despite an observed trend for the one-step start to be superior to the non-step techniques. These results suggest that differences between relay techniques could rely more on the swimmer’s body posture (angular kinematics) on the block, flight and underwater phases than on the centre of mass linear kinematics.

The aim of this study was to analyse the quadriceps-hamstring coactivation in the lunge and Bulgarian squat exercises. A cross-sectional study design was applied to seventeen healthy professional football players. Muscular activity was measured using wireless surface electromyography (sEMG). The Maximum Voluntary Isometric Contraction was used to normalize the data. The muscle activation of each muscle belly was significantly different between the two exercises (F4.24=28.076, p<.001, partial ƞ2 =.72). Activity in individual muscles varied in both the lunge (F4,24=49.315, p<.001,partial ƞ2 =.89), and the Bulgarian squat (F4,24=28,076, p<.001,partial ƞ2 =.82). The results showed no significant differences between the preferred and non-preferred legs of the participants (p>.05). In both the lunge and the Bulgarian squat, a significantly greater activation of the vastus medialis (VM) and the vastus lateralis (VL) muscles were found compared to the rectus femoris (RF) and biceps femoris (BF) and semitendinosus (ST). Muscles showed a greater activation during the Bulgarian squat compared to the lunge, but the hamstrings to quadriceps ratio was similar in both exercises (p>.05). The present work shows that the Bulgarian Squat exercise produces greater muscle activation than the Lunge exercise, whereas in both exercises there is a similar pattern of muscle activation. No differences were found between legs. If one wants to work specifically on strength development, the Bulgarian Squat would be a better option, as would be the case if one were to focus on synergistic work on the quadriceps and hamstrings, as the Bulgarian Squat exercise shows a higher H:Q ratio.

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.

The aims of the present study were twofold: 1) to measure inter-limb asymmetries from a battery of fitness tests in youth soccer players and, 2) determine the association between asymmetry and measures of athletic performance. Sixteen elite youth soccer players (14.7 ± 0.2 years) performed a single leg Abalakov test (ABK), change of direction (COD) test over 10 m (5 + 5) and 20 m (10 + 10), and an iso-inertial power test. Subjects also performed 10 m, 20 m and 30 m sprints and a bilateral countermovement jump (CMJ), which were correlated with all ABK, COD and iso-inertial asymmetry scores. A one-way repeated measures ANOVA showed significant differences between inter-limb asymmetry scores across multiple tests (p < 0.05), with the iso-inertial power test presenting the greatest magnitude of asymmetry, while individual data highlighted substantially greater inter-individual differences in each test. Pearson’s r correlations showed no significant relationships (p > 0.05) between the different inter-limb asymmetry scores, and between asymmetry scores and athletic performance. These findings show the test-specific nature of asymmetries in youth soccer players, with the iso-inertial power test being the most sensitive in detecting asymmetry. Moreover, the results obtained suggest that inherent asymmetry in young soccer players did not negatively impact their performance.

Despite the increasing importance of the underwater segment of start and turns in competition and its positive influence on the subsequent surface swimming, there is no evidence on how the transition from underwater to surface swimming should be performed. Therefore, the aim of the present study was to examine the role of segmental, kinematic and coordinative parameters on the swimming velocity during the pre-transition and transition phases. 30 national male swimmers performed 4 x 25 m (one each stroke) from a push start at maximum velocity while recorded from a lateral view by two sequential cameras (50 Hz), and their kinematic and coordinative swimming parameters were calculated by means of two-dimensional direct linear transformation (DLT) algorithms. Unlike pre-transition, backward regression analysis of transition significantly predicted swimming velocity in all strokes except breaststroke (R2 ranging from 0.263 in front crawl to 0.364 in butterfly). The inter-limb coordination was a predictor in butterfly stroke (p=0.006) whereas the body depth and inclination were predictors in the alternate strokes [front crawl (p=0.05) and backstroke (p=0.04)]. These results suggest that the body position and coordinative swimming parameters (apart from kicking or stroking rate and length) have an important influence on the transition performance, which depends on the swimming strokes.

Despite the existence of literature on the athletics hurdles event, no previous studies have examined the kinematic behavior of athletes during the race. The aims of the present research were (1) to compare the spatiotemporal parameters of elite and high-level hurdlers (men and women) in the approach run, hurdles-unit and run-in phases and (2) to relate these parameters to the 60 m end race results. Split times, step lengths, step widths, step times, contact times and flight times were calculated for the 60 m hurdlers (n = 110) who participated in the 44th Spanish Indoor Championship and in the 12th IAAF World Indoor Championship. Both men and women elite-level hurdlers obtained shorter split times than high-level hurdlers in the approach run (δ 0.14 ± 0.01 and 0.18 ± 0.02 s, respectively), the hurdles-unit (δ 0.11 ± 0.01 and 0.13 ± 0.01 s, respectively) and the run-in (δ 0.10 ± 0.01 and 0.20 ± 0.02 s, respectively) race phases. Elite-level men athletes also presented lower step lengths in the approach run phase (δ 0.01 ± 0.00 m), greater take-off distances (δ 0.10 ± 0.03 m) and shorter landing distances (δ 0.17 ± 0.05 m) than high-level athletes, although elite-level women hurdlers only showed longer landing step length (δ 0.07 ± 0.02 m) than high-level athletes. Finally, in the run-in phase, elite-level hurdlers had longer step lengths than high-level hurdlers (men: δ 0.09 ± 0.03 m; women: δ 0.11 ± 0.03 m). Step times, contact times and flight times were also different between both levels of performance in most of the race phases. Correlational analysis with the race result showed large (r > 0.5), very large (r > 0.7), or nearly perfect (r > 0.9) relationships for most of the mentioned kinematic parameters. These results indicate that elite-level athletes were faster than high-level in the three phases of the 60 m hurdles event, specifically in some new spatiotemporal parameters (e.g. step length in the run-in phase) as well as others already studied. Accordingly

Despite literature on the pacing strategies of endurance sports, there is an existing lack of knowledge about the swimmers’ tactical decisions in the open water races. The aims of the present research were (1) to compare the pacing profiles and tactical strategies of successful elite open water swimmers (men and women) in the 5-km, 10-km, and 25-km races and (2) to relate these pacing strategies to the end race results. Intermediate split times, positions and gaps with leaders of the first ten swimmers classified in the 2017 FINA World Swimming Championships races were collected from the public domain and were related to the finishing positions. Overall swimming velocities of the 5-km races were faster than the 10-km (δ 0.03 ± 0.03 m/s) and the 25-km (δ 0.14 ± 0.01 m/s) events with male swimmers achieving relatively faster mean velocities than females in the 5-km (δ 0.12 ± 0.01 m/s) compared to the 25-km (δ 0.08 ± 0.01 m/s) events. Medallist swimmers achieved moderate faster overall velocities than finalists in the 25-km races (0.01 ± 0.01 m/s) only. Inter-level differences were detected in selected splits for each race distance. Pacing profiles presented lap to lap velocity improvements in the 5-km and men’s 10-km races (from +0.02 ± 0.00 to +0.11 ± 0.01 m/s) but also mid-race decreases in the women’s 10-km and on the 25-km races. Successful swimmers were located in the leading positions of the 5-km races but at mid-group in the first part of the 10-km and 25-km races, with time gaps with leaders of 15–20 s. Faster lap swimming velocities, mid-race leading positions and shorter time-gaps were only related to the finishing positions in the last lap of the 10-km and in the three last laps of the 25-km events, but also in the first lap of the women’s 5-km race. Despite different mid-race positioning, successful open water swimmers typically presented negative pacing profiles, a consistent control of mid-race gaps with leaders (15–20 s maximum) and great spurts (4–6% f

BACKGROUND: Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury. METHODS: Forty-five professional players (males: N.=19, previously injured players=4, age=21.16±2.00 years; females: N.=19, previously injured players =10, age= 22.15±4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases. RESULTS: A shorter backswing (20.20±3.49% vs. 25.64±4.57%), and differences in knee flexion angle (58±10º vs. 72±14º) and hip flexion velocity (8±0 rad/s vs. 10±2 rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50±0.84 m/s vs. 4.10±0.45 m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern. CONCLUSIONS: Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.

According to the literature, the risk of developing iliotibial band syndrome (ITBS) is related to the running technique of each runner. The purpose of this study was to investigate whether differences exist in the running technique of runners with ITBS and healthy runners. The sample was composed of 60 recreational runners (30 healthy runners and 30 with ITBS). A 3D kinematic analysis was performed to measure 3D joint angles of the lower limb. Reaction forces in the stance phase of running were also determined. Runners in the ITBS group exhibited significantly lower contact time, knee valgus, peak knee flexion and hip rotation. Of note, gender-based differences were observed. No differences were found between groups in hip adduction angle, tibial internal rotation and foot kinematics. The runners with current ITBS showed an altered kinematic profile. Male and female runners with ITBS showed different alterations in running kinematics. These results suggest that gender should be considered when investigating the biomechanical etiology of ITBS.

Purpose: To (1) compare the pacing strategies of different-level open-water swimmers during the 10-km race of the FINA 2015 Swimming World Championships and (2) relate these pacing strategies to the race performance. Methods: Final and intermediate split times, as well as intermediate race positions, from the 10-km race participants (69 men and 51 women) were collected from the public domain and were divided into 5 groups (G1–G5) depending on their finishing positions. Results: Medalists and finalists (G1 and G2, respectively) presented an even pacing profile with swimming velocities similar to those of the less successful swimmers (G3–G5) on the initial and middle stages of the race but a 1.5–3% increase in swimming velocity in the last quarter of the race. This acceleration toward the end of the race, or “end spurt,” was largely related to the race performance and was not observed in the G3 and G4 (even-paced profile) or G5 (positive pacing profile) groups. Intermediate race positions and lap rankings were negatively related to finishing position, indicating a delayed positioning of the most successful swimmers at 25%, 50%, and 75% of race distance. Conclusions: The adoption of a conservative starting strategy by open-water swimmers with a negative pacing profile and delayed partial positioning seems to increase the chances of overall race success, as it allows a fast end spurt that is closely related to successful finishing race positions.

In the present research, we examined the effect of the starting and turning performances on the subsequent swimming parameters by (1) comparing the starting and turning velocities with the swimming parameters on the emersion and mid-pool segments and (2) by relating the individual behaviour of swimmers during the start and turns with subsequent behaviour on each swimming lap. One hundred and twelve 100 m performances on the FINA 2013 World Swimming Championships were analysed by an image-processing system (InThePool 2.0®). At the point of the start emersion, the swimming parameters of the 100-m elite swimmers were substantially greater than the mid-pool parameters, except on the breaststroke races. On the other hand, no diminution in the swimming parameters was observed between the turn emersion and the mid-pool swimming, except on the butterfly and backstroke male races. Changes on the surface swimming kinematics were not generally related to the starting or turning parameters, although male swimmers who develop faster starts seem to achieve faster velocities at emersion. Race analysts should be aware of a transfer of momentum when swimmers emerge from underwater with implications on the subsequent swimming kinematics, especially for male swimmers who employ underwater undulatory techniques.

The main objectives of the present research were (1) to examine the relationships between the distances travelled underwater during the start and turn segments with swimming race performance at the elite level and (2) to determine if the individualised-distance start and turn parameters affect the overall race performance. The race parameters of the 100 and 200 m events during 2013 World Championships were measured by an innovative image-processing system (InThePool® 2.0). Overall, 100 m race times were largely related to faster start velocities in men's breaststroke and freestyle events. Conversely, overall, 200 m race times were largely related to longer starting distances in the women's butterfly events, to longer turn distances in men's and women's backstroke and women's butterfly events and to shorter turn distances in women's freestyle events. Changes on the start or turn velocities could represent moderate time improvements in most of the 100 m events, whereas modifications on the start or turn distances (especially in the last turn) could provide elite swimmers with time improvements of practical importance on the 200 m events. The evaluation of races by individualised-distance parameters should be provided to elite swimmers in order to decide the most appropriate race segment configuration for each event.

El objetivo de este estudio, ha sido revisar la bibliografía sobre la lesión de isquiotibiales desde un punto de vista biomecánico. METODOLOGÍA. Las bases de datos utilizadas fueron Medline, Scopus y SportsDiscuss. RESULTADOS Y DISCUSIÓN. Muchos estudios prospectivos han demostrado que el principal factor de riesgo es haber tenido la lesión previamente. Sin embargo, las causas primarias de la lesión en fútbol son desconocidas. Una falta de flexibilidad ha sido uno de los principales factores de riesgo pero existen controversias en los resultados de la literatura. Desequilibrio de la fuerza isocinética es un factor de riego pero la participación de cada músculo por separado durante la flexo-extensión de rodilla en fútbol no ha sido considerado en los estudios. Mientras que la sincronización de los músculos lumbopélvicos parece ser clave para entender el riesgo de lesión, no se ha desarrollado investigación al respecto. CONCLUSIONES. Por tanto, son necesarios más estudios prospectivos y nuevos procedimientos como el escaner dinámico, la electromiografía de superficie o el análisis dinámico inverso. El análisis de gestos más específicos del fútbol es necesario. Gestores, entrenadores, preparadores físicos, fisioterapeutas, médicos deportivos e investigadores deberían trabajar juntos para mejorar los sistemas de prevención y de recuperación de la lesión. ---------- ABSTRACT---------- The aim has been to review the literature about the risk factors of hamstring injury in soccer from a biomechanical point of view. METHODOLOGY. Data bases of bibliography references were Medline, Scopus and SportDiscuss. RESULTS AND DISCUSSION. Many prospective studies have shown that the previous injury is the greatest risk factor of sustaining the injury. However the primary causes of the injury are unclear in soccer. A lack of hamstring flexibility has been one of the main injury risk factors with controversies on the results. Imbalance of isokinetic force is a risk factor but electrical

El objetivo del presente estudio fue analizar el comportamiento de la pelvis en hombres y mujeres, en el plano frontal, y relacionarlo con el movimiento del centro de gravedad y la cadera durante el ciclo de la marcha. Se solicitó a 33 hombres y 29 mujeres caminar a velocidad libremente seleccionada. Se grabaron tres ciclos a cada sujeto utilizando el sistema Vicon de captura de movimiento, y 19 marcadores reflectantes colocados en puntos anatómicos. Los resultados mostraron que los hombres realizaban mayor amplitud de movimiento lateral del centro de gravedad que las mujeres, mientras que las mujeres mostraron mayor amplitud de basculación lateral de la pelvis que los hombres. Además, las mujeres mostraron mayor aducción de cadera en la amortiguación (p<0.001). Hombres y mujeres seleccionan estrategias diferentes para realizar el cambio de peso durante la marcha normal, los hombres mueven el tronco lateralmente, y, por el contrario, las mujeres realizan más basculación lateral de la pelvis combinada con una mayor aducción de cadera. El conocimiento de estas estrategias podría aplicarse a la evaluación, diferenciada por sexo, de las compensaciones producidas durante el proceso de rehabilitación, en planes de reentrenamiento, o en el abordaje del déficit de equilibrio y prevención de caídas.

The aim of this study was to investigate the effects of different swimming race constraints on the evolution of turn parameters. One hundred and fifty-eight national and regional level 200-m (meters) male swimming performances were video-analyzed using the individualized-distance model in the Open Comunidad de Madrid tournament. Turn (p < .001, ES = 0.36) and underwater distances (p < .001, ES = 0.38) as well as turn velocity (p < .001, ES = 0.69) significantly dropped throughout the race, although stroke velocity and underwater velocity were maintained in the last lap of the race (p > .05). Higher expertise swimmers obtained faster average velocities and longer distances in all the turn phases (p < .001, ES = 0.59), except the approach distance. In addition, national level swimmers showed the ability to maintain most of the turn parameters throughout the race, which assisted them in improving average velocity at the end of races. Therefore, the variations in the turning movements of a swimming race were expertise-related and focused on optimizing average velocity. Turning skills should be included in the swimming race action plan.

The aim of this study was to compare the race characteristics of the start and turn segments of national and regional level swimmers. In the study, 100 and 200-m events were analysed during the finals session of the Open Comunidad de Madrid (Spain) tournament. The “individualized-distance” method with two-dimensional direct linear transformation algorithm was used to perform race analyses. National level swimmers obtained faster velocities in all race segments and stroke comparisons,although significant inter-level differences in start velocity were only obtained in half (8 out of 16) of the analysed events. Higher level swimmers also travelled for longer start and turn distances but only in the race segments where the gain of speed was high. This was observed in the turn segments, in the backstroke and butterfly strokes and during the 200-m breaststroke event, but not in any of the freestyle events. Time improvements due to the appropriate extension of the underwater subsections appeared to be critical for the end race result and should be carefully evaluated by the “individualized-distance” method.

biomecanica de la natación

biomecanica de la natación