BODY WAVE CHARACTERISTICS AND VARIABILITY OF AN INTERNATIONAL AND A REGIONAL LEVEL SWIMMER IN 50 M BUTTERFLY SWIMMING

The purpose of this study was to compare body wave characteristics between butterfly swimmers with different competitive levels as a case study. An international and a regional level swimmer performed a 50 m butterfly with their maximum effort, and their one stroke cycle velocity, stroke frequency, stroke length, and the vertical coordinate of the shoulder, hip, knee, and ankle joint were quantified for each stroke. The vertical coordinate data were analysed by a Fourier analysis to establish the amplitude, phase angle, contribution to the total signal of harmonic with one maxima/minima (due to one arm stroke motion in a cycle: H1) and two maxima/minima (related to two kicks in a cycle: H2). The velocity of each harmonic travelling caudally between shoulder and hip, hip and knee, and knee and ankle was also obtained. The international swimmer was faster by 23% with 17% longer stroke length and 6% higher stroke frequency than the regional swimmer. The international swimmer was also characterised by lower inter-stroke variability in the amplitude, contribution, and wave velocity of H1 and H2, suggesting that the international swimmer has a more stable rhythm and coordination between the upper and lower body compared with the regional swimmer. The international swimmer had a larger contribution of H1 to the vertical shoulder motion than the regional swimmer, meaning that the kick motion of the international swimmer originates from a more cephalic part of the body compared with the regional swimmer. The international swimmer generated the shoulder H1 rhythm for one stroke cycle at the end of the preceding cycle whereas the regional swimmer produced the shoulder H1 rhythm at the beginning of each cycle, which might be a reason for the higher stroke frequency of the international swimmer compared with the regional swimmer

Comparison of biomechanical and physiological characteristics between front crawl and back crawl

Front crawl (FC) and back crawl (BC) are similar in terms of having alternating contributions of the arms combined with a six beat kick. However, the reason for the faster swimming times of FC than BC has not yet been established. There have been several studies in which the energy expenditure (Ė) of FC and BC were investigated. However, few researchers have compared Ė between the strokes. Also, although there have been some studies for FC using 3D motion analysis, few researchers have applied 3D motion analysis for BC. There have also been some studies in which the relationship between isokinetic torque produced on an isokinetic dynamometer and FC performance has been investigated, however, the relationship between isokinetic torque and BC performance is unclear. Therefore, the aim of this study was to determine why FC is faster than BC by investigating physiological and biomechanical differences between FC and BC. Ten Portuguese male national level swimmers were recruited for this study. Three studies were conducted to achieve the aim. In the first study, Ė of FC and BC at the same testing speed below the anaerobic threshold were investigated by measuring swimmers’ oxygen uptake. Kinematic variables of FC and BC below the anaerobic threshold were also measured by 3D motion analysis in the first study. In the second study, 3D motion kinematics of FC and BC at the same selected speeds were investigated. In the third study, kinematic differences between FC and BC at the same exercise intensities, and correlations between the kinematics and isokinetic muscular torques of the swimmer in FC and BC and their differences were assessed. Below the anaerobic threshold, Ė of the swimmers in BC was significantly greater than that in FC at the same speed although there were no differences in stroke frequency (SF), stroke length (SL) and stroke index (SI). Swimmers also had significantly higher Froude efficiency (ηF) in FC than in BC. Differences in several kinematic variables (range of motion of the foot, duration of non-propulsive phases, and intra-cycle velocity variation) suggested that swimmers expended greater energy in BC than in FC. Differences in other kinematic variables (body roll angle, hand speed/acceleration, yaw angle fluctuation, centre of mass displacement, and hand/foot displacements) suggested the possibility of resistive impulse being larger in BC than in FC during the stroke cycle. Thus, FC is more economical and efficient than BC because swimmers lose less energy to the water during the non-propulsive phase, and possibly have smaller resistive impulse in FC than in BC at speeds below the anaerobic threshold. At the same selected speeds above the anaerobic threshold, ηF in BC was significantly lower than that in FC, which was due to faster mean 3D hand speed during the stroke cycle in BC than in FC. The faster mean hand speed in BC than in FC was due to the faster 3D hand speed during the pull phase, and longer relative duration of the release and above-water phases in BC than in FC. SI was also larger in FC than in BC, which was due to longer SL in FC than in BC. The longer SL in FC than in BC was due to the longer duration of propulsive phases and probably smaller resistive impulse during the stroke cycle in FC than in BC. At the same selected exercise intensities, FC was faster than BC because of higher SF. The higher SF in FC than in BC was due to the longer duration of the above-water phase in BC than in FC, longer hand path distance during non-propulsive phases in BC than in FC, earlier timing of the hand entry in relation to the underwater phase of the other hand in FC than in BC. SF in both FC and BC was significantly correlated with shoulder adduction isokinetic torque of the swimmers, however, the effect of shoulder isokinetic torque on the difference in swimming performance between FC and BC required further investigation. In conclusion, FC is faster than BC because swimmers can achieve higher SF in FC than in BC, and FC is more economical and efficient than in BC with indirect evidence that resistive force are greater in BC than in FC

Reliability of Three-Dimensional Angular Kinematics and Kinetics of Swimming Derived from Digitized Video

The purpose of this study was to explore the reliability of estimating three-dimensional (3D) angular kinematics and kinetics of a swimmer derived from digitized video. Two high-level front crawl swimmers and one high level backstroke swimmer were recorded by four underwater and two above water video cameras. One of the front crawl swimmers was digitized at 50 fields per second with a window for smoothing by a 4(th) order Butterworth digital filter extending 10 fields beyond the start and finish of the stroke cycle (FC1), while the other front crawl (FC2) and backstroke (BS) swimmer were digitized at 25 frames per second with the window extending five frames beyond the start and finish of the stroke cycle. Each camera view of one stroke cycle was digitized five times yielding five independent 3D data sets from which whole body centre of mass (CM) yaw, pitch, roll, and torques were derived together with wrist and ankle moment arms with respect to an inertial reference system with origin at the CM. Coefficients of repeatability ranging from r = 0.93 to r = 0.99 indicated that both digitising sampling rates and extrapolation methods are sufficiently reliable to identify real differences in net torque production. This will enable the sources of rotations about the three axes to be explained in future research. Errors in angular kinematics and displacements of the wrist and ankles relative to range of motion were small for all but the ankles in the X (swimming) direction for FC2 who had a very vigorous kick. To avoid large errors when digitising the ankles of swimmers with vigorous kicks it is recommended that a marker on the shank could be used to calculate the ankle position based on the known displacements between knee, shank, and ankle markers

Race Analysis in Competitive Swimming: A Narrative Review.

Researchers have quantified swimming races for several decades to provide objective information on race strategy and characteristics. The purpose of the present review was to summarize knowledge established in the literature and current issues in swimming race analysis. A systematic search of the literature for the current narrative review was conducted in September 2020 using Web of Science, SPORTDiscus (via EBSCO), and PubMed. After examining 321 studies, 22 articles were included in the current review. Most studies divided the race into the start, clean swimming, turn, and/or finish segments; however, the definition of each segment varied, especially for the turn. Ideal definitions for the start and turn-out seemed to differ depending on the stroke styles and swimmers' level. Many studies have focused on either 100 m or 200 m events with the four strokes (butterfly, backstroke, breaststroke, and freestyle). Contrastingly, there were few or no studies for 50 m, long-distance, individual medley, and relay events. The number of studies examining races for short course, junior and Paralympic swimmers were also very limited. Future studies should focus on those with limited evidence as well as race analysis outside competitions in which detailed kinematic and physiological analyses are possible

Start and Turn Performances of Competitive Swimmers in Sprint Butterfly Swimming.

The purposes of this study were to establish relationships between selected underwater kinematics and the starting and turning performances and to quantify kinematic differences between these segments in sprint butterfly swimming. Fourteen male swimmers performed 50 m maximal butterfly swimming in a short course pre-calibrated pool. The entire race was filmed by a multi-camera system, which quantified the forward head displacement and velocity (vxhead ) throughout the race with a sampling frequency of 50 Hz. The time taken between 0-15 m (T0-15 ) and 25-35 m (T25-35 ) as well as 16 kinematic variables were acquired from the data provided by the system and manual video processing for further analysis. The mean underwater velocity (UW-vxmean ) was related to both T0-15 and T25-35 (r = -0.70 and -0.95, respectively; p < 0.01). UW-vxmean was positively correlated with vxhead during the first kick (r = 0.84, p < 0.001) in the start segment and with vxhead during the last kick in the turn segment (r = 0.68, p < 0.01), but other kinematic variables such as kick frequency, body angle, deceleration during kicks (Deckick ), and glide time were not related to UW-vxmean . Swimmers had larger vxhead at the beginning of the segment and during the first kick in the start than in turn segment (p < 0.001). However, vxhead during the last kick was similar due to the larger Deckick (p < 0.05) in the start than in turn segment. The underwater time was similar between the segments despite a longer underwater distance (p < 0.01) and a larger kick count and frequency (p < 0.01) in the start than turn segment. In conclusion, UW-vxmean is an important factor for start and turn performances, but swimmers select individual kinematic strategies to achieve a large UW-vxmean . Results also highlighted the importance of the different parts within the underwater segment in each segment

Magnitude of maximum shoulder and hip roll angles in back crawl at different swimming speeds.

The purpose of this study was to identify the characteristics of maximum shoulder and hip roll angles in back crawl at different swimming speeds. Ten male elite swimmers performed back crawl at four different swimming speeds. The swimming trials were filmed by a total of six digital video cameras and three-dimensional coordinates of swimmer's anatomical landmarks were calculated using the three-dimensional direct linear transform. The data were input to a MATLAB programme to calculate linear and angular kinematics. Among the four speed trials, maximum shoulder and hip roll angles were unchanged, and maximum shoulder roll angle was significantly larger than maximum hip roll angle in all trials. In conclusion, the swimming speed does not affect swimmer's shoulder and hip roll angles in back crawl swimming

LOAD-VELOCITY SLOPE CAN BE AN INDICATOR OF THE ACTIVE DRAG IN FRONT CRAWL SWIMMING

The purpose of this study was to investigate the relationship between swimming load-velocity slope and the active drag (Da) in front crawl. 19 female and 22 male swimmers were recruited and performed three 25 m front crawl sprints with different external loads (1, 3, 5 kg for females and 1, 5, and 9 kg for males) assigned by a robotic resistance device. The mean swimming velocity was plotted against the external load to establish the load-velocity profile for each swimmer. Da was obtained by the velocity perturbation method. The relationship between the load-velocity slope and Da was assessed using the Pearson correlation coefficient, which showed a very large correlation (r = 0.84, p \u3c 0.001) and an extremely large correlation (r = 0.93, p \u3c 0.01) for female and male swimmers, respectively, indicating that the load-velocity slope is an indicator of Da in front crawl swimming

THE RELATIONSHIP BETWEEN BACKSTROKE SWIMMING SPRINT PERFORMANCE AND LOAD-VELOCITY PROFILES

The study investigated relationships between backstroke sprint swimming performance and variables extracted from load-velocity profiles. Thirteen male swimmers performed 50 m backstroke and semi-tethered swimming with three progressive external loads. From 50 m backstroke, race time (T50m) swimming velocity (v50m), stroke length and frequency were obtained. From semi-tethered swimming, maximum load (L0) and velocity (v0), slope and L0 normalized to body mass (rL0) were computed. Large to very large significant relationships were found between v50m and all variables derived from the load-velocity profiling. Similar relationships were found between T50m and v0, L0 and slope, but not with rL0 (r = -0.530, p = 0.062). These findings indicate that load-velocity profiling is a practical method to predict and assess sprint backstroke performance and swimming velocity, and to assess propulsive force production and velocity capabilities related to backstroke sprint performance

Differences in limb coordination in polyrhythmic production among water polo players, artistic swimmers and drummers.

This study compares polyrhythmic production ability between water polo players (WPs), artistic swimmers (ASs) and drummers (Ds), to assess how their differing experiences in coordinating complex inter-limb activity with music affected this ability. Eight ASs, eight WPs and eight Ds participated. They were asked to perform finger and foot taps in a single-rhythm task (every 750 ms) and two polyrhythmic tasks (finger and foot taps at 750 and 500 ms, respectively, and vice versa). The percentage of correct response cycles (PCRC), subjective difficulty scores were collected and analysed using a two-way mixed analysis of variance (ANOVA) and coefficients of variation of the inter-tap interval (CVITI) were collected and analysed using a three-way mixed analysis of variance (ANOVA). The three groups showed no statistically significant differences in the single-rhythm task. However, on polyrhythmic tasks, the WPs were significantly outperformed by the other two groups in PCRC and CVITI. These results suggest that the experience of coordinating limbs with music has positive impacts on polyrhythmic production ability. They also imply that ASs and Ds have similar polyrhythmic production ability despite the apparent differences in task complexity in their daily training and performances

The effect of experience in movement coordination with music on polyrhythmic production: Comparison between artistic swimmers and water polo players during eggbeater kick performance.

The aim of this study was to compare artistic swimmers (ASs) and water polo players (WPs) in their polyrhythmic production ability and entrainment between arm and leg motion frequency. Nine ASs and nine WPs participated in the study. First, we assessed the natural eggbeater kick frequency of each participant without any additional motion for 20 s. We then required the participants to perform a circular arm movement in synchronization with two sequences of metronome rhythms (either 100%, 80% and 120% or100%, 120% and 80% of their natural eggbeater kick frequency) while maintaining their natural eggbeater kick frequency. All tasks were repeated three times. The participants' performances were recorded by a motion capture system synchronized with the metronome. A two-way mixed-design ANOVA was performed on the coefficient of variation of natural eggbeater kick frequency obtained from the first task to confirm the consistency of participants' kicking motion. In the second task, a three-way mixed-design ANOVA was performed on the average frequency of the arm and leg motions to assess the entrainment between the two. In the first task, there were no significant main effects and interaction between group and trial in the coefficient of variation of eggbeater kick frequency, suggesting that both WPs and ASs maintained their natural eggbeater kick frequency equally consistently. In the second task, however, WPs were not able to maintain their natural eggbeater kick frequency when they were required to do circular arm movements at 120% tempo (p < .01). On the other hand, ASs successfully maintained their natural eggbeater kick frequency with all metronome rhythms, suggesting that they have a better polyrhythmic production ability than WPs