Physiological Responses and Stroke Variables during Arm Stroke Swimming Using Critical Stroke Rate in Competitive Swimmers.

The current study examined the physiological responses and stroke variables at critical stroke rate (CSR), 105% CSR, and 110% CSR in order to utilize CSR for prescription arm stroke swimming. Nine male national-level collegiate swimmers performed an all-out 200 m and 400 m for determining the CSR. Participants performed three sets of 6 × 100 m (with 10 s of rest between each bout), the stroke rate for each set was enforced at CSR, 105% CSR, and 110% CSR. Mean swimming velocity, heart rate, and rate of perceived exertion were found to increase with each set (p < 0.05). Blood lactate concentration did not differ between the CSR and the 105% CSR (3.3 ± 1.4 vs. 3.5 ± 1.5 mmol/L) but was higher in 110% CSR (5.1 ± 1.6 mmol/L) than in the other two sets (p < 0.05). There was no difference in the stroke rate between all bouts in each set, and the stroke length did not change from the second to sixth bout in each set. This study suggested that training intensity for CSR and 105% CSR correspond to threshold level, and 110% CSR corresponds to high-intensity training level. It was also suggested that training in the CSR−110% CSR range could be performed without regard to SL reduction.

Relationship between Swimming Performance, Biomechanical Variables and the Calculated Predicted 1-RM Push-up in Competitive Swimmers.

One repetition maximum (1RM) push-ups, based upon the load-velocity relationship, are able to predict the maximum upper body strength. The aim of the present study was to examine the relationship between the predicted 1RM push-up based upon the load-velocity relationship and swimming performance and kinematical variables in competitive swimmers. Thirty-three competitive male swimmers (age = 16.46 ± 0.59 years, body mass = 72.82 ± 8.41 kg, body height = 180.56 ± 5.69 cm) performed push-up exercises without a weight vest and with a 10, 20 and 30 kg weight vests. A load-velocity relationship was established as a product of the load and velocity of the push-up per participant, and the equation was used to establish a predicted 1RM. Our findings showed a predicted 1RM push-up of 82.98 ± 9.95 kg. Pearson correlations revealed a nearly perfect relationship between the 1RM push-up and the 25 or 50 m front crawl (r = -0.968, r = -0.955), and between 1RM push-up and the 25 or 50 m front crawl with arms (r = -0.955, r = x0.941). Similarly, our results revealed significant near-perfect correlations between 1RM push-up and kinematical variables (r = 0.93-0.96) except the stroke index, which had a large relationship (r = 0.56). This study suggests that swimming performance and kinematical variables are correlated with the predicted 1RM push-up. The 1RM push-up based upon the load-velocity relationship is a low cost and time-effective alternative for swimmers and coaches to predict maximum upper body strength to optimize swimming performance in short races.

Does a jammer-type racing swimsuit improve sprint performance during maximal front-crawl swimming?

We investigated the effects of jammer-type racing swimsuits (RS) on swimming performance during arm-stroke-only (pull) and whole-body stroke (swim) in 25-m front-crawl with maximal effort. Twelve well-trained male collegiate swimmers wore RS and a conventional swimsuit (CS) and performed three tests: pull, swim, and pull using the system to measure active drag (MAD pull). Swimming velocity and intra-abdominal pressure (IAP) were determined in all tests. Stroke indices during pull and swim and drag-swimming velocity relationship and maximum propulsive power during MAD pull were also determined. Swimming velocities during pull and swim while wearing an RS (1.59 ± 0.13 and 1.77 ± 0.09 m·s-1, respectively) were significantly higher than those wearing a CS (1.57 ± 0.14 and 1.74 ± 0.08 m·s-1, respectively). Stroke length during pull and swim was significantly greater while wearing an RS (1.68 ± 0.12 and 1.83 ± 0.13 m, respectively) than wearing a CS (1.63 ± 0.10 and 1.81 ± 0.13 m, respectively). However, no significant differences were confirmed between the other variables in all tests. In conclusion, swimming performance is improved when wearing an RS compared with a CS.

A Systematic Review and Meta-Analysis: Biomechanical Evaluation of the Effectiveness of Strength and Conditioning Training Programs on Front Crawl Swimming Performance.

The objectives of this systematic review were to summarize and evaluate the effectiveness of strength and conditioning trainings on front crawl swimming, starts and turns performance with relevant biomechanical parameters. Four online databases including PudMed, ESCSOhost, Web of Science and SPORTDiscus were searched according to different combination of keywords. 954 articles were extracted from databases, and ultimately 15 articles were included in this study after removal of duplicate and articles screening according to inclusion and exclusion criteria. Meta-analyses were adopted when appropriate and Egger's regression symmetry was adopted to assess the publication bias and the results were presented with forest plots and funnel plots respectively. Fifteen articles studied the effects of strength and resistance, core, and plyometric trainings. The quality of the investigation was assessed by the checklist developed by Downs and Black. Most of the investigations found out that training programs were beneficial to front crawl sprinting swimming performance, stroke biomechanics, force, and muscle strength. First, strength and resistance trainings and core trainings were effective on sprinting performance enhancement. Second, resistance trainings were found to have positive effects on stroke rate. Plyometric trainings were beneficial to start performance, while there was no sufficient evidence for confirming the positive improvement on turn biomechanical, also overall swimming performance, after weeks of plyometric trainings. Strength and Conditioning trainings are suggested to implement in regular training regime regarding to the positive effects on swimming performance, including starts, turns and front crawl swim, and relevant biomechanical parameters, instead of swimming training only. Further research with higher quality is recommended to conduct and more investigations on the training effects to other stroke styles are also suggested.

Validating Physiological and Biomechanical Parameters during Intermittent Swimming at Speed Corresponding to Lactate Concentration of 4 mmol·L-1.

BACKGROUND: Physiological and biomechanical parameters obtained during testing need validation in a training setting. The purpose of this study was to compare parameters calculated by a 5 × 200-m test with those measured during an intermittent swimming training set performed at constant speed corresponding to blood lactate concentration of 4 mmol∙L-1 (V4). METHODS: Twelve competitive swimmers performed a 5 × 200-m progressively increasing speed front crawl test. Blood lactate concentration (BL) was measured after each 200 m and V4 was calculated by interpolation. Heart rate (HR), rating of perceived exertion (RPE), stroke rate (SR) and stroke length (SL) were determined during each 200 m. Subsequently, BL, HR, SR and SL corresponding to V4 were calculated. A week later, swimmers performed a 5 × 400-m training set at constant speed corresponding to V4 and BL-5×400, HR-5×400, RPE-5×400, SR-5×400, SL-5×400 were measured. RESULTS: BL-5×400 and RPE-5×400 were similar (p > 0.05), while HR-5×400 and SR-5×400 were increased and SL-5×400 was decreased compared to values calculated by the 5 × 200-m test (p < 0.05). CONCLUSION: An intermittent progressively increasing speed swimming test provides physiological information with large interindividual variability. It seems that swimmers adjust their biomechanical parameters to maintain constant speed in an aerobic endurance training set of 5 × 400-m at intensity corresponding to 4 mmol∙L-1.

Upper body kinematic differences between maximum front crawl and backstroke swimming.

The purpose of this study was to investigate why front crawl is faster than backstroke from a kinematic perspective. Three-dimensional kinematics were obtained from one upper-limb cycle of ten male competitive swimmers performing 50 m front crawl and backstroke trials at maximum speed. Swimmers achieved faster centre of mass velocity in front crawl than backstroke (1.70 ±â€¯0.04 vs 1.54 ±â€¯0.06 m·s-1; p < 0.01) with no difference in stroke length (2.00 ±â€¯0.25 vs 2.07 ±â€¯0.17 m·cycle-1), while stroke frequency in front crawl was higher than that in backstroke (51.67 ±â€¯6.38 vs 44.81 ±â€¯4.68 cycles·min-1; p < 0.01). Maximum shoulder roll angle in front crawl was larger than that in backstroke (52.88 ±â€¯4.89 vs 49.73 ±â€¯5.73°; p < 0.05), while swimmers had smaller maximum hip roll in front crawl than backstroke (33.79 ±â€¯6.07 vs 39.83 ±â€¯7.25°; p < 0.05). Absolute duration of the release phase (from the last backward movement to the exit from the water of the wrist) and relative duration of the recovery phase were shorter in front crawl than backstroke (0.07 ±â€¯0.03 vs 0.26 ±â€¯0.08 s; p < 0.01, and 28.69 ±â€¯2.50 vs 33.21 ±â€¯1.43%; p < 0.01, respectively). In conclusion, front crawl is faster than backstroke because of its higher stroke frequency due to the shorter absolute release phase and relative recovery phase durations.

Physiological and Biomechanical Evaluation of a Training Macrocycle in Children Swimmers.

Physiological responses related to 400-m front crawl performance were examined in a 11-week training macrocycle in children 11.6 ± 1.2 years old. Fourteen girls and twenty-nine boys completed a maximum intensity 400-m test, at the beginning (Τ1) and at the end of four weeks of general preparation (Τ2), four weeks of specific preparation (Τ3), and three weeks of the competitive period (Τ4). Blood lactate (La), blood glucose (Glu) and heart rate were measured post effort. Stroke rate (SR), stroke length (SL) and stroke index (SI) were measured during the test. The 400-m time was decreased at T2, T3, and T4 compared to T1 by 4.2 ± 4.9, 7.5 ± 7.0, and 8.6 ± 7.3% (p < 0.05) and at T3 and T4 compared to T2 by 3.1 ± 4.3 and 4.2 ± 4.6%, respectively (p < 0.05). La was not different between tests (p > 0.05) and Glu was decreased at T3 compared to other testing moments (p < 0.05). SR, SL, and SI were higher at T3 and T4 compared to T1 (p < 0.05). SL and SI were also increased at T4 compared to T2 (p < 0.05). Performance changes from T1 to T2 were related to SL and SI changes (r = 0.45 and 0.83, p < 0.05), and subsequent changes between T2 to T3 were related to SR, SI, La, and Glu changes (r = 0.48, 0.68, 0.34, and 0.42, p < 0.05). Performance change from T3 to T4 was related to SL, SI, and La modifications (r = 0.34, 0.70, and 0.53, p < 0.05). Performance gains may be related to various biomechanical or physiological changes according to training macrocycle structure.

Physiological Responses and Swimming Technique During Upper Limb Critical Stroke Rate Training in Competitive Swimmers.

The aim of this study was to examine how arm stroke swimming with critical stroke rate (CSR) control would influence physiological responses and stroke variables in an effort to identify a new swimming training method. Seven well-trained male competitive swimmers (19.9 ± 1.4 years of age) performed maximal 200 and 400 m front crawl swims to determine the CSR and critical swimming velocity (CV), respectively. Thereafter, they were instructed to perform tests with 4 × 400 m swimming bouts at the CSR and CV. The swimming time (CSR test: 278.96 ± 2.70 to 280.87 ± 2.57 s, CV test: 276.17 ± 3.36 to 277.06 ± 3.64 s), heart rate, and rated perceived exertion did not differ significantly between tests for all bouts. Blood lactate concentration after the fourth bout was significantly lower in the CSR test than in the CV test (3.16 ± 1.43 vs. 3.77 ± 1.52 mmol/l, p < 0.05). The stroke rate and stroke length remained stable across bouts in the CSR test, whereas the stroke rate increased with decreased stroke length across bouts in the CV test (p < 0.05). There were significant differences in the stroke rate (39.27 ± 1.22 vs. 41.47 ± 1.22 cycles/min, p < 0.05) and stroke length (2.20 ± 0.07 vs. 2.10 ± 0.04 m/stroke, p < 0.05) between the CSR and CV tests in the fourth bout. These results indicate that the CSR could provide the optimal intensity for improving aerobic capacity during arm stroke swimming, and it may also help stabilize stroke technique.

Cinemática do nado crawl em velocidade sustentada até a exaustão / Kinematics of the front crawl in sustained speed to exhaustion

O objetivo deste estudo foi verificar as respostas da frequência média de ciclos de braçadas (FB) e da distância média percorrida por ciclo de braçada (DC) no nado crawl ao longo de série de natação na intensidade de 95% da velocidade média dos 400 m (V400), até a exaustão. Onze nadadores realizaram 400 m em máxima intensidade para determinação da V400, e, posteriormente, uma série a 95% da V400 (95v) com média de 2,88 ± 1,37 repetições de 400 m e intervalos de 40 s de repouso passivo, quarenta e oito horas após a V400. A duração da série a 95% da V400 foi normalizada a 100%, de modo individual, e posteriormente, foi dividida em cinco momentos (0, 25, 50, 75 e 100%) para a análise de FB e DC, que foram comparadas ao longo da série. Resultados: houve manutenção dos parâmetros cinemáticos apenas entre os momentos 0 e 25%. Ocorreram aumento da FB e diminuição da DC nos últimos momentos (75 e 100%) em comparação aos demais momentos da série 95v. Ao nadar nesta intensidade, que está situada o domínio de intensidade severa, nadadores não são capazes de manter a técnica constante ao longo da duração total da série...(AU)

The objective of this study was to investigate the stroke rate (SR) and the stroke length (SL) responses in front crawl along swimming training series in the intensity of 95% of the average velocity of 400 m (V400) until exhaustion. Eleven swimmers performed 400 m at maximum intensity for determining V400, and subsequently, a series of 95% the V400 (95v) with average 2.88 ± 1.37 trials of 400 m and intervals of 40 s of passive rest, 48 hours after the V400. The duration of the 95V was normalized to 100%, individually, and, later, it was divided into five moments (0, 25, 50, 75, and 100%) for the SR and SL analysis, which were compared over the series. Results: there was maintenance of kinematic parameters only between moments 0 and 25%, The SR increased and the SL decreased in the end of the series (75 and 100%) compared to other moments. When swimming at this intensity, which is situated in severe intensity domain, swimmers are not able to keep constant the technique over the entire duration of the series...(AU)

The Impact of Resistance Training on Swimming Performance: A Systematic Review.

BACKGROUND: The majority of propulsive forces in swimming are produced from the upper body, with strong correlations between upper body strength and sprint performance. There are significant gaps in the literature relating to the impact of resistance training on swimming performance, specifically the transfer to swimming performance. OBJECTIVE: The aims of this systematic literature review are to (1) explore the transfer of resistance-training modalities to swimming performance, and (2) examine the effects of resistance training on technical aspects of swimming. METHODS: Four online databases were searched with the following inclusion criteria: (1) journal articles with outcome measures related to swimming performance, and (2) competitive swimmers participating in a structured resistance-training programme. Exclusion criteria were (1) participants with a mean age <16 years; (2) untrained, novice, masters and paraplegic swimmers; (3) triathletes and waterpolo players; (4) swimmers with injuries or illness; and (5) studies of starts and turns specifically. Data were extracted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the Physiotherapy Evidence Database (PEDro) scale was applied. RESULTS: For optimal transfer, specific, low-volume, high-velocity/force resistance-training programmes are optimal. Stroke length is best achieved through resistance training with low repetitions at a high velocity/force. Resisted swims are the most appropriate training modality for improving stroke rate. CONCLUSION: Future research is needed with respect to the effects of long-term resistance-training interventions on both technical parameters of swimming and overall swimming performance. The results of such work will be highly informative for the scientific community, coaches and athletes.

Comparing para-rowing set-ups on an ergometer using kinematic movement patterns of able-bodied rowers.

While numerous studies have investigated the biomechanics of able-bodied rowing, few studies have been completed with para-rowing set-ups. The purpose of this research was to provide benchmark data for handle kinetics and joint kinematics for able-bodied athletes rowing in para- rowing set-ups on an indoor ergometer. Able-bodied varsity rowers performed maximal trials in three para-rowing set-ups; Legs, Trunk and Arms (LTA), Trunk and Arms (TA) and Arms and Shoulders (AS) rowing. The handle force kinetics of the LTA stroke were comparable to the values for able-bodied literature. Lumbar flexion at the catch, extension at the finish and total range of motion were, however, greater than values in the literature for able-bodied athletes in the LTA set-up. Additionally, rowers in TA and AS set-ups utilised more extreme ranges of motion for lumbar flexion, elbow flexion and shoulder abduction than the LTA set-up. This study provides the first biomechanical values of the para-rowing strokes for researchers, coaches and athletes to use while promoting the safest training programmes possible for para-rowing.

Swimming Stroke Mechanical Efficiency and Physiological Responses of 100-m Backstroke with and without the use of paddles.

The use of swimming aids during training contributes to greater swimming efficiency by the improvement of the swimming specific power of the athlete. The purpose of this study was to compare the swimming stroke technical characteristics and the physiological responses of swimming 100-m backstroke, with and without the use of paddles at maximum and sub-maximum intensities at the same swimming speed. Eight swimmers competing at the national level participated in this study. The measurements took place at 4 different sessions. At every session, each participant swam individually one 100-m backstroke swimming trial with or without paddles at the same speed and two levels of intensity (100% and 85% of maximum speed). The results revealed lower stroke length, greater stroke number and gliding length without the use of swimming paddles at both intensities. Blood lactate concentration (10.03±2.96 vs. 5.85±2.23 mmol/l) and Rating of Perceived Exertion (17.43±2.07 vs. 12±2.82) were greater without the use of swimming paddles only at 100% of maximum speed. Thus, swimming backstroke with paddles compared to unaided swimming, at a similar speed, showed a greater efficiency at maximal but not at sub-maximal intensity.

Wave characteristics in breaststroke technique with and without snorkel use.

The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables.

Kinematic variables and blood Acid-base status in the analysis of collegiate swimmers' anaerobic capacity.

Short duration repeated maximal efforts are often used in swimming training to improve lactate tolerance, which gives swimmers the ability to maintain a high work rate for a longer period of time. The aim of the study was to examine the kinematics of swimming and its relation to the changes in blood acid-base status and potassium level. Seven collegiate swimmers, with at least 6 years of training experience, volunteered to participate in the study. The test consisted of 8 x 25 m front crawl performed with maximum effort. The rest period between repetitions was set to five seconds. Blood samples were taken from the fingertip at rest, after warm-up and in the 3rd minute after completion of the test. The swimming was recorded with a video recorder, for later analysis of time, velocity and technique (stroke index). Based on the swimming velocity results, the obtained curve can be divided into rapid decrease of velocity and relatively stable velocities. The breaking point of repetition in swimming velocity was assumed as the swimming velocity threshold and it was highly correlated with the decrease of the blood acid-base status (pH r=0.82, BE r=0.87, HCO3 (-) r=0.76; p<0.05 in all cases). There was no correlation between stroke index or fatigue index and blood acid-base status. Analysis of the swimming speed in the 8 x 25 m test seems to be helpful in evaluation of lactate tolerance (anaerobic capacity) in collegiate swimmers.

Effects of distance specialization on the backstroke swimming kinematics.

The purpose of the present study was to investigate different biomechanical variables of backstroke technique in swimmers specialized in different distance events, in order to investigate the capacity to modify the timing of the arm stroke when changing the swimming velocity from sub-maximal to maximal. Two 25-m backstroke trials respectively at 70% of maximum velocity (V70) and at 100% of maximum velocity (Vmax) were performed by 9 200-m distance swimmers and 9 50-m distance swimmers. Swimming velocity, stroke length, stroke rate, duration of different phases of the arm stroke and selected kinematic variables were assessed in both cases. In the 50-m distance swimmers, the duration of the propulsive phase at Vmax, expressed as a percentage of the duration of the total underwater arm stroke, increased significantly (p = 0.001) with increasing swimming velocity. Specifically, both the pull and push phases were fundamental in the increase of duration of the propulsive phase. When compared to 200-m specialists, 50-m distance swimmers seem to be more able to modify their arm stroke phases duration when increasing the swimming velocity in backstroke. Key pointsThe 50-m DS are able to find an optimal timing among the stroke phases increasing the duration of the propulsive phase.The 50-m DS, when increasing the swimming velocity, show a more efficient relationship between propulsive and non propulsive phases with respect to the 200-m DS.Both pull and push phases are key factors for increasing the duration of the propulsive phase for the 50-m DS.

Direct Medical Cost of Stroke: Findings from a Tertiary Hospital in Malaysia

This study aimed to estimate cost of in-patient medical care due to stroke in a tertiary hospital in Malaysia. A retrospective analysis of stroke patients admitted to Universiti Kebangsaan Malaysia Medical Centre (UKMMC) between January 2005 and December 2008 were conducted. Cost evaluation was undertaken from the health provider’s perspective using a top-down costing approach. Mean length of stay (LOS) was 6.4 ± 3.1 days and mean cost of care per patient per admission was MYR 3,696.40 ± 1,842.17 or 16% of per capita GDP of the country. Human resources made up the highest cost component (MYR 1,343.90, SD: 669.8 or 36% of the total cost), followed by medications (MYR 867.30, SD:432.40) and laboratory services (MYR 337.90, SD:168.40). LOS and cost of care varied across different stroke severity levels (p<0.01). A regression analysis shown significant influence of stroke severity on cost of care, with the most severe stroke consumed MYR 1,598.10 higher cost than the mild stroke (p<0.001). Cost of medical care during hospital admission due to stroke is substantial. Health promotion and primary prevention activities need to take priority to minimise stroke admission in future.

Relationship between Stroking Parameters and Leg Movement Quantity in 100 Metre Front Crawl.

The objective of this study was to examine the relationship between stroking technique parameters and leg kick quantity in 100 m front crawl swim. Ten New South Wales Sydney Metropolitan swimmers were examined (14.1 ± 1.09 years). The investigation was performed during 100 meter swimming (average speed 1.35 ± .04 [m.s-1]) commencing from water at 50 m outdoor pool. Stroke length (SL), Stroke rate (SR), Swim velocity (SV), Leg Kick Quantity (LKQ) were measured. Arm stroking parameters and LKQ were analysed during segments of the 100m distance. The relationship between SR and LKQ was negative. The correlation between stroke length and leg kick quantity was statistically significant r = .96, and p = .05. Leg Kick quantity influenced stroke length. This study shows that swimming front crawl with a significant leg kick quantity (LKQ) such as a six beat kick, induces a longer stroke length (SL) and therefore improved arm stroke efficiency.

Análise descritiva do desempenho em uma prova de 100 m nado livre feminino baseada em variáveis biomecânicas / Descriptive analysis of performance in the female 100 meters free swimming based on biomechanics variables

Na natação, atualmente, a avaliação do desempenho dos nadadores, apóiam-se em diversas metodologias de observação da competição. As variáveis biomecânicas representam um importante recurso para análise da performance esportiva por serem indicadores da eficiência do nado, com aplicação simples e objetiva. O objetivo deste estudo foi realizar uma análise descritiva do desempenho na prova de 100 metros nado Livre feminino, baseada nas variáveis: comprimento de braçada (CB), frequência de braçada (FB), velocidade de nado (VN), índice de nado (IN), velocidade média escalar (Vm), tempo de saída (Ts) e tempo de virada (Tv), a fim de observar o comportamento e influências na performance. Foram capturadas imagens por uma câmera mini-DV, analisadas por um "software" editor de vídeo. As variáveis CB, VN e IN foram encontradas indiretamente, sem considerar as fases de saída e virada. Ts e Tv foram obtidos através da linha do tempo do software. A análise de dados mostra para atleta 1: CB 2,00 m, FB 0,89 Hz, VN 1,78 m/s e IN 3,56 m²/s; atleta 2: CB 1,82 m, FB 0,97 Hz, VN 1,76 m/s, IN 3,20 m²/s; atleta 3: CB 1,91 m, FB 0,92 Hz, VN 1,75 m/s, IN 3,32 m²/s. Conclui-se que: o desempenho final apresentou comportamentos similares nos três primeiros trechos da prova indicando uma influência semelhante dessas variáveis sobre o desempenho das atletas. No último quarto da prova as variáveis apresentam maior interferência na performance final, sendo este decorrente de uma possível diminuição da eficiência mecânica do nado devido ao aumento do arrasto e redução da força propulsiva.

The performance evaluation of swimmers is based on many methodologies of watching the competition. Biomechanical variables represent an important resource for analyzing the performance of swimmers because they are simple and objective indicators of swimming efficiency. The objective of this research was to observe how biomechanical variables affect swimmers' performance in of the female 100 meters freestyle in order to observe the behavior and influence stroke length (SL), stroke frequency (SF), swimming velocity (SV), swimming index (SI), average speed (AS), time of departure (Td), time of turning (Tt). On swimming performance images were captured using a mini-DV camera, which were subsequently analyzed with the help of a software video editor. The variables SL, SV and SI were indirectly measured, without considering start and turning phases. Td and Tt were obtained through the timeline of the software. Data analysis shows for athlete 1: SL = 2.00 m, SF = 0.89 hz, SV = 1.78 m/s, SI = 3.56 m²/s, athlete 2: SL = 1.82 m, SF = 0,97Hz, SV = 1.76 m/s, SI = 3.20 m²/s, athlete 3: SL = 1.91 m, SF = 0.92 Hz, SV = 1.75 m/s, SI = 3.32 m²/s. We concluded that the final performance presented similar behavior in the first three parts of the race, indicating a similar influence of these variables on the performance of athletes. In the last quarter of the race showed that variables have greater interference in the final performance, this probably due to a possible decrease in mechanical efficiency of swimming due to increase in drag and reduction in propulsive force.

RELATIONSHIP BETWEEN CHANGES OF SWIMMING VELOCITY, STROKE RATE, STROKE LENGTH AND MUSCLE ACTIVITIES IN FRONT CRAWL SWIMMING / 体力科学

The aim of this study was to investigate the relationship between changes in swimming velocity (SV), stroke rate (SR), stroke length (SL) and muscle activities during a 4×50m swimming test to simulate a 200m freestyle race. A total of 20 male collegiate swimmers participated in this study. The electromyography (EMG) signals of 11 muscles, 7 muscles in the upper half of the body and 4 muscles in the lower half, were recorded with surface electrodes. SV, SR and SL were analyzed for each 50m (S1, S2, S3 and S4) from side view recordings of swimmers taken with an underwater camera.SV and SR for S1 were significantly higher than for S2 and S3. SL for S1 was significantly longer than for S3. The averaged EMGs (aEMGs) for S1 were significantly higher than for S2 or for S3 in 5 muscles (flexor carpi ulnaris, biceps brachii, triceps brachii, deltoideus posterior and rectus femoris). There were no significant changes between S3 and S4 in SV, SR, SL and aEMG of all muscles except pectoralis major which showed the highest aEMG in S4. Significant correlations were observed between changes of (Δ) aEMG and ΔSV, especially in upper half muscles (<i>r</i>=0.485-0.939, <i>p</i><0.05).These results suggested that decline in muscle activities of the five muscles mentioned earlier caused a decrease in SV from S1 to S3; and an increase in muscle activity of the pectoralis major led preventing a decline in SV by maintaining the SR in S4.

Índices técnicos correspondentes à velocidade crítica e à máxima velocidade de 30 minutos em nadadores com diferentes níveis de performance aeróbia / Technical indexes corresponding to the critical speed and the maximal speed of 30 minutes in swimmers with different aerobic performance levels

O principal objetivo deste estudo foi verificar o efeito do nível de performance aeróbia na relação entre os índices técnicos correspondentes à velocidade crítica (VC) e à velocidade máxima de 30 minutos (V30) em nadadores. Participaram deste estudo, 23 nadadores do gênero masculino com características antropométricas similares, divididos segundo o nível de performance aeróbia em grupo G1 (maior performance) (n = 13) e G2 (menor performance) (n = 10). Os indivíduos tinham pelo menos quatro anos de experiência no esporte e treinavam um volume semanal de 30.000 a 45.000m. A VC foi determinada através do coeficiente angular da regressão linear entre as distâncias (200 e 400m) e seus respectivos tempos. A V30 foi determinada através da máxima distância realizada em um teste de 30 minutos. Todas as variáveis foram determinadas no nado crawl. A VC foi significantemente maior do que a V30 no grupo G1 (1,30 ± 0,04 vs. 1,23 ± 0,06m.s-1) e no G2 (1,17 ± 0,08 vs. 1,07 ± 0,06m.s-1). As duas variáveis foram maiores no grupo G1. As taxas de braçada correspondentes à VC (TBVC) e à V30 (TBV30) obtidas nos grupos G1 (33,07 ± 4,34 vs. 31,38 ± 4,15 ciclos.min-1) e G2 (35,57 ± 6,52 vs. 33,54 ± 5,89 ciclos.min-1) foram similares entre si. A TBVC foi significantemente menor no grupo 1 do que no grupo 2, enquanto que a TBV30 não foi diferente entre os grupos. Os comprimentos de braçada correspondentes à VC (CBVC) e à V30 (CBV30) foram significantemente maiores no grupo G1 (2,41 ± 0,33 vs. 2,38 ± 0,30m.ciclo-1) do que no G2 (2,04 ± 0,43 vs. 1,97 ± 0,40m.ciclo-1), e similares entre si nos dois grupos. As correlações (r) entre a VC e a V30 e as variáveis técnicas correspondentes às duas velocidades foram significantes em todas as comparações (0,68 a 0,91). Portanto, a relação entre a velocidade e as variáveis técnicas correspondentes à VC e à V30 não é modificada pelo nível de performance aeróbia.

The main objective of this study was to verify the effect of aerobic performance level on the relationship between the technical indexes corresponding to critical speed (CS) and maximal speed of 30 minutes (S30) in swimmers. Participated of this study 23 male swimmers with similar anthropometric characteristics, divided by aerobic performance level in groups G1 (n = 13) and G2 (n = 10). They had at least four years of experience in the modality and a weekly training volume between 30,000 to 45,000 m. The CS was determined through the angular coefficient of the linear regression line between the distances (200 and 400 m) and respective times. The S30 was determined through the maximal distance covered in a 30 minutes test. All variables were determined in front crawl. CS was higher than S30 in G1 (1.30 ± 0.04 vs. 1.23 ± 0.06 m.s-1) and G2 (1.17 ± 0.08 vs. 1.07 ± 0.06 m.s -1). These variables were higher in group G1. The stroke rate corresponding to CS (SRCS) and S30 (SRS30) obtained in group G1 (33.07 ± 4.34 vs. 31.38 ± 4.15 cycles.min-1) and G2 (35.57 ± 6.52 vs. 33.54 ± 5.89 cycles.min-1) were similar. The SRCS was significantly lower in group G1 than G2, while SRS30 was not different between groups. The stroke length corresponding to CS (SLCS) and S30 (SLS30) was significantly higher in group G1 (2.41 ± 0.33 vs. 2.38 ± 0.30 m.cycle-1) than in G2 (2.04 ± 0.43 vs. 1.97 ± 0.40 m.cycle-1), and had similar values in both groups. The correlation (r) between CS and S30 and technical variables corresponding to CS and S30 were significant in all comparisons (0.68 to 0.91). Thus, the relationship between the speed and technical variables corresponding to CS and S30 was not modified by the aerobic performance level.