The key kinematic determinants of undulatory underwater swimming at maximal velocity

The optimisation of undulatory underwater swimming is highly important in competitive swimming performance. Nineteen kinematic variables were identified from previous research undertaken to assess undulatory underwater swimming performance. The purpose of the present study was to determine which kinematic variables were key to the production of maximal undulatory underwater swimming velocity. Kinematic data at maximal undulatory underwater swimming velocity were collected from 17 skilled swimmers. A series of separate backward-elimination analysis of covariance models was produced with cycle frequency and cycle length as dependent variables (DVs) and participant as a fixed factor, as including cycle frequency and cycle length would explain 100% of the maximal swimming velocity variance. The covariates identified in the cycle-frequency and cycle-length models were used to form the saturated model for maximal swimming velocity. The final parsimonious model identified three covariates (maximal knee joint angular velocity, maximal ankle angular velocity and knee range of movement) as determinants of the variance in maximal swimming velocity (adjusted-r² = 0.929). However, when participant was removed as a fixed factor there was a large reduction in explained variance (adjusted r² = 0.397) and only maximal knee joint angular velocity continued to contribute significantly, highlighting its importance to the production of maximal swimming velocity. The reduction in explained variance suggests an emphasis on inter-individual differences in undulatory underwater swimming technique and/or anthropometry. Future research should examine the efficacy of other anthropometric, kinematic and coordination variables to better understand the production of maximal swimming velocity and consider the importance of individual undulatory underwater swimming techniques when interpreting the data.     

Relationships between kinematics and undulatory underwater swimming performance

Undulatory underwater swimming (UUS) is one of the major skills contributing to performance in competitive swimming. UUS has two phases– the upbeat is performed by hip extension and knee flexion, and the downbeat is the converse action. The purpose of this study was to determine which kinematic variables of the upbeat and downbeat are associated with prone UUS performance in an elite sample. Ten elite participants were filmed performing three prone 20 m UUS trials. Seven landmarks were manually digitised to calculate eighteen kinematic variables, plus the performance variable– horizontal centre of mass velocity (V_COM). Mean V_COM was significantly correlated with body wave velocity (upbeat r = 0.81, downbeat r = 0.72), vertical toe velocity (upbeat r = 0.71, downbeat r = 0.86), phase duration (upbeat r = ?0.79), peak hip angular velocity (upbeat r = 0.73) and mean knee angular velocity (upbeat r = ?0.63), all significant at P < 0.05. A multiple stepwise regression model explained 78% of variance in mean V_COM. Peak toe velocity explained 72% of the variance, and mean body wave velocity explained an additional 6%. Elite swimmers should strive for a high peak toe velocity and a fast caudal transfer of momentum to optimise underwater undulatory swimming performance.     

Unsteady flow phenomena in human undulatory swimming: a numerical approach

The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition.     

A theoretical and experimental analysis of diver technique in underwater fin swimming

This research was theoretical and experimental, with an objective of a better understanding of the physics of fin swimming. The theoretical work followed Lighthill’s slender body theory (1960). Video measurements were made on underwater fin swimmers swimming in an annular pool (58.6 m in circumference). This study considers only SCUBA divers. Five male swimmers swam at five speeds between 0.4 m/s-0.8 m/s. Skilled divers consumed less oxygen and had lower kick frequencies at each speed. The skilled divers adhered to the requirements of the theory, but not the unskilled. Specifically, the fin’s trailing edge (TE) lateral velocity was greater than the relative velocity of the water at the TE (requirement 1); which is the most forgiving. The second requirement is more stringent, and requires the TE lateral velocity and the relative velocity of the water at the TE to be of the same sign. Violating the first requirement sometimes causes a change in the instantaneous thrust’s direction. Violating the second requirement almost always produced instantaneous thrust in the opposite direction than the diver’s desired swimming direction. This study found that the Lighthill model can be used to describe diver fin swimming, which was optimised when the diver met the two requirements required for efficient thrust.     

A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming

We present a new method that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick. The focus of the current work is to model this particular stroke in all its complexity with minimal ad-hoc assumptions or simplifications. Simulations of one female and one male swimmer (both at about 1.7 m beneath the water surface) at velocities of 0.95 and 1.31 m/s and Strouhal numbers of 1.21 and 1.06 respectively are presented. Vorticity and fluid velocity profiles in the wake are examined in detail for both swimmers. A three-dimensional vortex ring is clearly identified in the wake for one of the cases and a two-dimensional slice through the ring corroborates previous experiments of Miwa et al. (2006). We also find that most of the thrust is produced by the feet and in both cases the down-kick produces much larger thrust than the up-kick.     

Pacing in lane-based head-to-head competitions: A systematic review on swimming

ABSTRACT

Athletes’ energy distribution over a race (e.g. pacing behaviour) varies across different sports. Swimming is a head-to-head sport with unique characteristics, such as propulsion through water, a multitude of swimming stroke types and lane-based racing. The aim of this paper was to review the existing literature on pacing behaviour in swimming. According to PRISMA guidelines, 279 articles were extracted using the PubMed and Web of Science databases. After the exclusion process was conducted, 16 studies remained. The findings of these studies indicate that pacing behaviour is influenced by the race distance and stroke type. Pacing behaviours in swimming and time-trial sports share numerous common characteristics. This commonality can most likely be attributed to the lane-based racing set-up. The low efficiency of swimming resulting from propulsion through the water induces a rapid accumulation of blood lactate, prompting a change in swimmers’ biomechanical characteristics, with the goal of minimising changes in velocity throughout the race. Although the literature on youth swimmers is scarce, youth swimmers demonstrate more variable pacing profiles and have more difficulty in selecting the most beneficial energy distribution.     

Wearable inertial sensors in swimming motion analysis: a systematic review

The use of contemporary technology is widely recognised as a key tool for enhancing competitive performance in swimming. Video analysis is traditionally used by coaches to acquire reliable biomechanical data about swimming performance; however, this approach requires a huge computational effort, thus introducing a delay in providing quantitative information. Inertial and magnetic sensors, including accelerometers, gyroscopes and magnetometers, have been recently introduced to assess the biomechanics of swimming performance. Research in this field has attracted a great deal of interest in the last decade due to the gradual improvement of the performance of sensors and the decreasing cost of miniaturised wearable devices. With the aim of describing the state of the art of current developments in this area, a systematic review of the existing methods was performed using the following databases: PubMed, ISI Web of Knowledge, IEEE Xplore, Google Scholar, Scopus and Science Direct. Twenty-seven articles published in indexed journals and conference proceedings, focusing on the biomechanical analysis of swimming by means of inertial sensors were reviewed. The articles were categorised according to sensor’s specification, anatomical sites where the sensors were attached, experimental design and applications for the analysis of swimming performance. Results indicate that inertial sensors are reliable tools for swimming biomechanical analyses.     

Analysis of swimming performance: perceptions and practices of US-based swimming coaches

In elite swimming, a broad range of methods are used to assess performance, inform coaching practices and monitor athletic progression. The aim of this paper was to examine the performance analysis practices of swimming coaches and to explore the reasons behind the decisions that coaches take when analysing performance. Survey data were analysed from 298 Level 3 competitive swimming coaches (245 male, 53 female) based in the United States. Results were compiled to provide a generalised picture of practices and perceptions and to examine key emerging themes. It was found that a disparity exists between the importance swim coaches place on biomechanical analysis of swimming performance and the types of analyses that are actually conducted. Video-based methods are most frequently employed, with over 70% of coaches using these methods at least monthly, with analyses being mainly qualitative in nature rather than quantitative. Barriers to the more widespread use of quantitative biomechanical analysis in elite swimming environments were explored. Constraints include time, cost and availability of resources, but other factors such as sources of information on swimming performance and analysis and control over service provision are also discussed, with particular emphasis on video-based methods and emerging sensor-based technologies.     

The effect of inspiratory muscle fatigue on acid-base status and performance during race-paced middle-distance swimming

The aim of this study was to investigate the effect of pre-induced inspiratory muscle fatigue (IMF) on race-paced swimming and acid-base status. Twenty-one collegiate swimmers performed two discontinuous 400-m race-paced swims on separate days, with (IMF trial) and without (control trial) pre-induced IMF. Swimming characteristics, inspiratory and expiratory mouth pressures, and blood parameters were recorded. IMF and expiratory muscle fatigue (P < 0.05) were evident after both trials and swimming time was slower (P < 0.05) from 150-m following IMF inducement. Pre-induced IMF increased pH before the swim (P < 0.01) and reduced bicarbonate (P < 0.05) and the pressure of carbon dioxide (PCO₂) (P < 0.05). pH (P < 0.05), bicarbonate (P < 0.01) and PCO₂ (P < 0.05) were lower during swimming in the IMF trial. Blood lactate was similar before both trials (P > 0.05) but was higher (P < 0.01) in the IMF trial after swimming. Pre-induced IMF induced respiratory alkalosis, reduced bicarbonate buffering capacity and slowed swimming speed. Pre-induced and propulsion-induced IMF reflected metabolic acidosis arising from dual role breathing and propulsion muscle fatigue.     

Bilateral inter-arm coordination in freestyle swimming: Effect of skill level and swimming speed

The aim of this study was to examine the influence of level of skill and swimming speed on inter-limb coordination of freestyle swimming movements. Five elite (2 males, 3 females; age 18.9?±?1.0 years, height 1.71?±?0.04?m, body mass 62.1?±?7.0?kg) and seven novice (age 22.0?±?2.0 years, height 1.77?±?0.04?m, body mass 74.8?±?9.0?kg) swimmers swam a sprint and a self-paced 25?m freestyle trial. The swimming trials were recorded by four digital cameras operating at 50 Hz. The digitized frames underwent a three-dimensional direct linear transformation to yield the three-dimensional endpoint kinematic trajectories. The spatio-temporal relationship between the upper limbs was quantified by means of the peak amplitude and time lag of the cross-correlation function between the right and left arm's endpoint trajectories. A strong anti-phase coupling between the two arms, as confirmed by peak amplitudes greater than 0.8, was noted for both groups and swimming speeds. Significantly higher (P <?0.05) peak amplitudes were observed for the sprint compared with self-paced swimming. No significant differences in the strength of inter-limb coupling were noted between the elite and novice swimmers (P >?0.05). Time lags were very close to 0?ms and did not differ between groups or swimming speeds. We conclude that in freestyle swimming, the intrinsic anti-phase (180° phase difference) inter-limb relationship is strongly preserved despite the physically powerful environmental influence of the water and this “preferred” pattern is not affected by level of skill. In contrast, increasing movement speed results in stronger inter-limb coupling that is closer to the anti-phase inter-limb relationship.     

An unacceptable status quo: A sport development case study of swimming and drownings

This case study illustrates the complexity of sport development decision-making and specifically highlights the public health concern of drowning disparities in the United States. Using sport development research to demonstrate the linkage between empirical study and practice, students must consider various factors for the most effective approach to attract and retain participants involved in a local swimming program. The parks and recreation department director, Bob Shell, is tasked with determining the best program structure based on the sets of sport development proposals he received from a member of the management staff. To further ensure students are presented with a realistic scenario, this case offers a combination of fictional and real life events from an innovative swimming program in Memphis, Tennessee. Students must critically evaluate not only sport development practices and the merits of the swimming program, but other organizational partnerships that may be formed in the community. Therefore, students are placed in a decision-making role that is common to managers in many sport contexts beyond swimming. This case study is appropriate for both undergraduate and graduate sport management courses, with specific application to sport development, policy and governance, strategic management, and recreation or leisure topics.     

近三届世锦赛男子自由泳优秀运动员的速度、划频、划幅变化特征

通过对2001、2003和2005年世锦赛男子自由泳项目前8名运动员比赛技术数据进行分析和比较，了解当今世界男子自由泳项目优秀运动员速度、划频、划幅的变化特征，并对男子自由泳运动员最佳划频和划幅组合特征进行探讨。结果发现：（1）短距离运动员划频明显高于中长距离运动员；中长距离项目运动员划幅增长也明显高于短距离项目运动员。（2）最高游速下，运动员的划频和划幅达到或接近最高水平。（3）男子自由泳运动员理想划频和划幅会随着个人特点和项目距离特点变化而变化。（4）个人理想的划频和划幅组合应保持有效划频和有效划幅的组合。（5）在疲劳状态下，仍能继续保持良好的划频和划幅是取得好成绩的关键。     

A battery of strength tests for evidence-based classification in Para swimming

This study examined the validity of isometric strength tests for evidence-based classification in Para swimming. Thirty non-disabled participants and forty-two Para swimmers with physical impairment completed an isometric strength test battery designed to explain activity limitation in the freestyle discipline. Measures pertaining to dominant and non-dominant limb strength and symmetry were derived from four strength tests that were found to be reliable in a cohort of non-disabled participants (ICC = 0.85–0.97; CV = 6.4–9.1%). Para swimmers had lower scores in strength tests compared with non-disabled participants (d = 0.14–1.00) and the strength test battery successfully classified 95% of Para swimmers with physical impairment using random forest algorithm. Most of the strength measures had low to moderate correlations (r = 0.32 to 0.53; p ≤ 0.05) with maximal freestyle swim speed in Para swimmers. Although, fewer correlations were found when Para swimmers with hypertonia or impaired muscle power were analysed independently, highlighting the impairment-specific nature of activity limitation in Para swimming. Collectively, the strength test battery has utility in Para swimming classification to infer loss of strength in Para swimmers, guide minimum eligibility criteria, and to define the impact that strength impairment has on Para swimming performance.     

The biomechanics of soccer: A review

Abstract

The purpose of this investigation was to determine whether combining two mental preparation strategies would be more effective in enhancing performances than a single strategy. Subjects (n = 40) practiced on a basketball free throw task (20 shots) using one of the following mental preparation strategies: (a) imagery, (b) relaxation, (c) relaxation plus imagery, (d) placebo control. To simulate game conditions, subjects were allowed only 10 s in which to use their mental preparation strategy. After the practice session, subjects shot 20 test free throws using their designated technique. Results indicated a significant main effect with the imagery group performing significantly better than the placebo control group although there were no specific differences between the three experimental groups. The results are discussed in terms of potential variables mediating the effectiveness of imagery in enhancing sport performance, and future directions for research are offered.     

Biomechanics of Tai Chi: A review

Tai Chi Chuan is a favourite form of exercise throughout the world and has drawn increasing research interest from international scientists. Biomechanical research into Tai Chi has grown substantially and has provided evidence of the beneficial effects of Tai Chi exercise on health, fitness, and prevention of falls. This paper reviews studies that have explored the biomechanical aspects of Tai Chi, such as balance, kinematics, kinetics, strength, and neuromuscular activities.     

Golf-related injuries: A systematic review

Abstract

A review was undertaken to assess the prevalence of musculoskeletal injuries in golf and to stimulate the discussion on possible injury mechanisms. The main conclusion of most published studies is that although professional and amateur golfers show a similar anatomical distribution of injuries by body segment, differences tend to be seen in the ranking of injury occurrence by anatomical site. This could be due to many things, including the player's handicap, age, golf swing biomechanics, and training or playing habits. The impact of golf injuries deserves special attention due to the interaction of the nature of the injury, practice routines, amount of practice, handicap, and frequency of activity. Individual differences and clinical and coaching procedures deserve investigation. Other epidemiological information should be regarded as insufficient with respect to a full understanding of injury mechanisms, which can give us a better insight into the evolutionary nature of the injury. Also, a better understanding of golf swing mechanisms and individual neuromuscular aspects can help explain why some individuals are more injury-prone than others.     

广东省全运会游泳项目竞技实力的研究

以亚项群和各项目为基本单位,以第8—11届全运会为背景,对广东省全运会游泳项目竞技特征进行全面分析,结果显示：在第8—11届全运会竞技中,体能主导类的速度性项群为广东省全运会游泳项目上的传统优势项群,耐力性项群为广东省全运会游泳项目上的弱势项群;广东省竞技实力特征为优势项目单一;提示广东省游泳队应按各项群和项目竞技特征进行合理资源配置。     

Science and medicine of rowing: A review

The biology and medicine of rowing are briefly reviewed. Effort in a 2000 -m race is about 70% aerobic. Because the boat (and in some instances a cox) must be propelled, successful competitors are very tall, with a large lean mass and aerobic power. Large hearts may lead to erroneous diagnoses of a cardiomyopathy. Large respiratory minute volumes must be developed by chest muscles that are also involved in rowing. The vital capacity is typically large, and breathing becomes entrained. Expiration cannot be slowed relative to inspiration (as normally occurs at high rates of ventilation) and the limiting flow velocity may be reached, with the potential for airway collapse. Performance is strongly related to the power output at the ‘anaerobic threshold’, and lactate measures provide a guide to an appropriate intensity of endurance training. Peak blood lactate levels are higher in males (commonly 11–19 mmol·l -1 and occasionally as high as 25 mmol·l -1) than in females (9–11 mmol·l -1), probably because males have a greater muscle mass in relation to blood volume. The skeletal muscles are predominantly slow twitch in type, developing an unusual force and power at low contraction velocities. Many rowers have a suboptimal diet, eating excessive amounts of fat. Lightweight rowers also have problems of weight cycling. Aerobic power and muscle endurance often change by 10% over the season, but such fluctuations can be largely avoided by a well-designed winter training programme. Injuries include back and knee problems, tenosynovitis of the wrist and, since the introduction of large blades, fractures of the costae.     

Science of rugby league football: A review

The purpose of this paper is to provide a comprehensive review of the science of rugby league football at all levels of competition (i.e. junior, amateur, semi-professional, professional), with special reference to all discipline-specific scientific research performed in rugby league (i.e. physiological, psychological, injury epidemiology, strength and conditioning, performance analysis). Rugby league football is played at junior and senior levels in several countries worldwide. A rugby league team consists of 13 players (6 forwards and 7 backs). The game is played over two 30?–?40 min halves (depending on the standard of competition) separated by a 10?min rest interval. Several studies have documented the physiological capacities and injury rates of rugby league players. More recently, studies have investigated the physiological demands of competition. Interestingly, the physiological capacities of players, the incidence of injury and the physiological demands of competition all increase as the playing standard is increased. Mean blood lactate concentrations of 5.2, 7.2 and 9.1?mmol?·?l^?1 have been reported during competition for amateur, semi-professional and professional rugby league players respectively. Mean heart rates of 152 beats?·?min^?1 (78% of maximal heart rate), 166 beats?·?min^?1 (84% of maximal heart rate) and 172 beats?·?min^?1 (93% of maximal heart rate) have been recorded for amateur, semi-professional and junior elite rugby league players respectively. Skill-based conditioning games have been used to develop the skill and fitness of rugby league players, with mean heart rate and blood lactate responses during these activities almost identical to those obtained during competition. In addition, recent studies have shown that most training injuries are sustained in traditional conditioning activities that involve no skill component (i.e. running without the ball), whereas the incidence of injuries while participating in skill-based conditioning games is low. Collaborative research among the various sport science disciplines is required to identify strategies to reduce the incidence of injury and enhance the performance of rugby league players. An understanding of the movement patterns and physiological demands of different positions at all standards of competition would allow the development of strength and conditioning programmes to meet the precise requirements of these positions. Finally, studies investigating the impact of improvements in physiological capacities (including the effect of different strength and conditioning programmes) on rugby league playing performance are warranted.