Intracyclic Velocity Research Articles

Biomechanical characterization of swimmers with physical disabilities

The evaluation of swimming technique is one of the main aspects to be considered in any training program, with biomechanics being an important source of knowledge. It was our objective to characterize the biomechanical parameters (SL and SF) relating them to the swimming velocity (v) at different intensities and to analyze within each swimming stroke cycle the intra-cyclic velocity variation (IVV) in a group of motor disabled swimmers. Eight disabled male swimmers (25.83 ± 2.93 years old, 72.45 ± 9.26 kg body mass and 1.79 ± 0.11 m of height) of the following functional classes: S6 (n = 1), S8 (n = 2) and S9 (n = 5) participated in this study. Swimmers were evaluated in the kinematic parameters v, stroke frequency (SF) and stroke length (SL) along with an incremental protocol of 6 x 200 m in the the crawl stroke. Data were registered in each step at the distances of 100 and 175 m. With increasing velocity, the mean values of SL decreased while the mean values of SF increased. To achieve higher swimming velocities, swimmers compensated the lack of the propulsive segment increasing SF to increase swimming speed. For the mean values of IVV at 100m distance, a decrease between the first and second levels, followed by a tendency to stabilize from the 2nd to the 6th level is presented. For the 175 m distance, there was a decrease in IVV with an increase in swimming velocity. Stroke frequency is directly related to the magnitude of IVV, which directly influences swimming performance.

Concentration effect on the nonlinear measures of dense polyethylene oxide solutions under large amplitude oscillatory shear

In this paper, we study the nonlinear viscoelastic response of concentrated polyethylene oxide solutions under large amplitude oscillatory shear (LAOS). We investigate the concentration effect as a function of strain and shear rate by using nondimensional elastic and viscous Lissajous–Bowditch plots. We also employ the mitlaos software to calculate the intracycle nonlinear viscoelasticity parameters. We find that the transition to nonlinear behavior occurs at lower strain values as the polymer concentration increases. For the higher concentration and at large strain amplitudes, the intracycle elastic stress component is almost zero to a large extent of the oscillation cycle and thus strain-independent. The corresponding stress decomposition in the shear rate domain shows a significant shear rate dependence, with a self-intersection of the total stress curve. By increasing the oscillation frequency and, correspondingly, the shear rate, by one order of magnitude, the intercycle nonlinear behavior does not qualitatively change. The spatiotemporal velocity profiles are obtained using a custom-made particle image velocimetry system. Interestingly, we record nonlinear velocity profiles at approximately 300% strain along with significant wall slip for both oscillation frequencies. The intracycle velocity data close to the stationary plate reveal strong nonlinear velocity waveforms. The results of this study suggest that the number of entanglements per chain is responsible for the strain thinning or thickening behavior in LAOS.

Differences in kinematics and energy cost between front crawl and backstroke below the anaerobic threshold.

The purpose of this study was to determine kinematic and energetic differences between front crawl and backstroke performed at the same aerobic speeds. Ten male competitive swimmers performed front crawl and backstroke at a pre-determined sub-anaerobic threshold speed to assess energy cost (through oxygen uptake measurement) and kinematics (using three-dimensional videography to determine stroke frequency and length, intra-cycle velocity fluctuation, three-dimensional wrist and ankle speeds, and vertical and lateral ankle range of motion). For detailed kinematic analysis, resultant displacement, the duration, and three-dimensional speed of the wrist during the entry, pull, push, and release phases were also investigated. There were no differences in stroke frequency/length and intra-cycle velocity fluctuation between the swimming techniques, however, swimmers had lower energy cost in front crawl than in backstroke (0.77 ± 0.08 vs 0.91 ± 0.12 kJm-1, p < 0.01). Slower three-dimensional wrist and ankle speeds under the water (1.29 ± 0.10 vs 1.55 ± 0.10 and 0.80 ± 0.16 vs 0.97 ± 0.13ms-1, both p < 0.01) and smaller ankle vertical range of motion (0.36 ± 0.06 vs 0.47 ± 0.07m, p < 0.01) in front crawl than in backstroke were also observed, which indirectly suggested higher propulsive efficiency in front crawl. Front crawl is less costly than backstroke, and limbs motion in front crawl is more effective than in backstroke.

Intracyclic Velocity Variation of the Center of Mass and Hip in Breaststroke Swimming With Maximal Intensity.

Gourgoulis, V, Koulexidis, S, Gketzenis, P, and Tzouras, G. Intra-cyclic velocity variation of the center of mass and hip in breaststroke swimming with maximal intensity. J Strength Cond Res 32(3): 830-840, 2018-The aim of the study was to compare the center of mass (CM) and hip (HIP) intracyclic velocity variation in breaststroke swimming using 3-dimensional kinematic analysis. Nine male breaststrokes, of moderate performance level, swam 25-m breaststroke with maximal intensity, and their movements were recorded, both under and above the water surface, using 8 digital cameras. Their CM and HIP velocities and their intracyclic variations were estimated after manual digitization of 28 selected points on the body in a complete arm and leg breaststroke cycle. Paired sample t-tests or Wilcoxon tests, when the assumption of normality was broken, were used for statistical analyses. In both, CM and HIP velocity-time curves, the results revealed a similar pattern of 2 clear peaks associated with the leg and arm propulsive phases and 2 minimal velocities that corresponded to the arm and leg recovery phase and the lag time between the leg and arm propulsive phases, respectively. However, despite this similar general pattern, the HIP minimum resultant velocity was significantly lower, whereas its maximal value was significantly greater, than the corresponding CM values. Consequently, the HIP intracyclic swimming velocity fluctuation significantly overestimates the actual variation of the swimmer's velocity in breaststroke swimming.

Intracyclic Variation of Force and Swimming Performance.

In front-crawl swimming, the upper limbs perform alternating movements with the aim of achieving a continuous application of force in the water, leading to lower intracyclic velocity variation (dv). This parameter has been identified as a crucial criterion for swimmers' evaluation. To examine the assessment of intracyclic force variation (dF) and to analyze its relationship with dv and swimming performance. A total of 22 high-level male swimmers performed a maximal-effort 50-m front-crawl time trial and a 30-s maximal-effort fully tethered swimming test, which were randomly assigned. Instantaneous velocity was obtained by a speedometer and force by a strain-gauge system. Similarity was observed between the tests, with dF attaining much higher magnitudes than dv (P < .001; d = 8.89). There were no differences in stroke rate or in physiological responses between tethered and free swimming, with a high level of agreement for the stroke rate and blood lactate increase. Swimming velocity presented a strong negative linear relationship with dF (r = -.826, P < .001) and a moderate negative nonlinear relationship with dv (r = .734, P < .01). With the addition of the maximum impulse to dF, multiple-regression analysis explained 83% of the free-swimming performance. Assessing dF is a promising approach for evaluating a swimmer's performance. From the experiments, this new parameter showed that swimmers with higher dF also present higher dv, leading to a decrease in performance.

Pacing the phasing of leg and arm movements in breaststroke swimming to minimize intra-cyclic velocity fluctuations.

In swimming propelling efficiency is partly determined by intra-cyclic velocity fluctuations. The higher these fluctuations are at a given average swimming velocity, the less efficient is the propulsion. This study explored whether the leg-arm coordination (i.e. phase relation ϕ) within the breaststroke cycle can be influenced with acoustic pacing, and whether the so induced changes are accompanied by changes in intra-cyclic velocity fluctuations. Twenty-six participants were asked to couple their propulsive leg and arm movements to a double-tone metronome beat and to keep their average swimming velocity constant over trials. The metronome imposed five different phase relations ϕi (90, 135, 180, 225 and 270°) of leg-arm coordination. Swimmers adjusted their technique under the influence of the metronome, but failed to comply to the velocity requirement for ϕ = 90 and 135°. For imposed ϕ = 180, 225 and 270°, the intra-cyclic velocity fluctuations increased with increasing ϕ, while average swimming velocity did not differ. This suggests that acoustic pacing may be used to adjust ϕ and thereby performance of breaststroke swimming given the dependence of propelling efficiency on ϕ.

Reproducibility and repeatability of intracyclic velocity variation in front crawl swimming from manual and semi-automatic measurement

PurposeIntracyclic velocity variation is an important kinematic parameter to evaluate swimming performance. It can be estimated by a fixed point at the swimmer’s hip. The aim of the study was to determine the reproducibility and repeatability of active light markers to measure intracyclic velocity variation in swimming.MethodsReproducibility and repeatability were tested by image measurement, by five manual digitizing processes and five sessions of automatic tracking of a LED marker set in a swimmer’s hip. The procedures were evaluated by the intraclass correlation coefficient, and the agreement between the methods was evaluated with Bland-Altman plots. The reproducibility was excellent in both procedures.ResultsThe repeatability of manual digitalization ranged between satisfactory to excellent, while the repeatability of automatic tracking was excellent. In addition, the Bland-Altman plots displayed a good agreement between manual and automatic measure­ments. The automatic tracking was 27% faster than manual digitization.ConclusionsActive markers are promising to evaluate the intracyclic velocity variation of swimmers, with a faster response than the common manual processing.

The Effect of Intensity on 3-Dimensional Kinematics and Coordination in Front-Crawl Swimming.

Coaches are often challenged to optimize swimmers' technique at different training and competition intensities, but 3-dimensional (3D) analysis has not been conducted for a wide range of training zones. To analyze front-crawl 3D kinematics and interlimb coordination from low to severe swimming intensities. Ten male swimmers performed a 200-m front crawl at 7 incrementally increasing paces until exhaustion (0.05-m/s increments and 30-s intervals), with images from 2 cycles in each step (at the 25- and 175-m laps) being recorded by 2 surface and 4 underwater video cameras. Metabolic anaerobic threshold (AnT) was also assessed using the lactate-concentration-velocity curve-modeling method. Stroke frequency increased, stroke length decreased, hand and foot speed increased, and the index of interlimb coordination increased (within a catch-up mode) from low to severe intensities (P ≤ .05) and within the 200-m steps performed above the AnT (at or closer to the 4th step; P ≤ .05). Concurrently, intracyclic velocity variations and propelling efficiency remained similar between and within swimming intensities (P > .05). Swimming intensity has a significant impact on swimmers' segmental kinematics and interlimb coordination, with modifications being more evident after the point when AnT is reached. As competitive swimming events are conducted at high intensities (in which anaerobic metabolism becomes more prevalent), coaches should implement specific training series that lead swimmers to adapt their technique to the task constraints that exist in nonhomeostatic race conditions.

О новой группе пространственных аппаратов с мешалкой

The four ways to intensify the mixing process was proposed and developed, implemented in devices with a stirrer according to the type of working units movement: the operating shaft moves with intracyclic angular velocity, the shaft performs a complex spatial movement, the working units was made in the form of 3,4 and 5 mobile units, with two and more working shafts with different motion laws. Nine new classification groups of devices with a stirrer with a lot of variants in each group were created. The devices have a high degree of intensification of mixing liquid and hard-mixing agricultural materials.&#x0D;

A Simplified Upper-Body Model to Improve the External Validity of Wheelchair Simulators

During overground wheelchair propulsion, upper-body (UB) movement causes intracycle velocity variations that are neglected by current wheelchair simulators. This could affect the external validity of wheelchair propulsion on simulators. In this study, we investigated ways to incorporate these dynamics into the dynamic model (DM) reproduced by wheelchair simulators. We aimed to maximize the DM accuracy and minimize the number of required inputs. First, two DMs were presented: Model RL represented propulsion on a typical roller-based wheelchair simulator and model UB represented overground propulsion, modeling the UB as five rigid bodies. Then, three new DMs were presented: Model trunk (TR), model upper arm (UA), and model forearm (FA); these models simplified model UB by estimating the UB kinematics based on the acceleration of only one segment. For all DMs, wheelchair velocity prediction was tested overground at a self-selected velocity among 19 experienced manual wheelchair users with a spinal cord injury. UB kinematics was reconstructed based on personalized kinematic patterns recorded on a wheelchair simulator. Models UB and UA were the most accurate: they reduced the root-mean-square intracycle velocity prediction error from 0.044 m/s (RL) to 0.026 m/s (UB) and 0.024 m/s (UA), and reduced the velocity peak time prediction error from $-$ 27.7% (RL) to 1.7% (UB) and $-$ 7.3% (UA). Implementing model UA instead of model RL on a wheelchair simulator may improve the external validity of wheelchair propulsion on a simulator.

Front-crawl stroke descriptors variability assessment for skill characterisation

ABSTRACTThe goal of this article is to characterise front-crawl swimming skill based on variability pattern of technique descriptors. Nine national level and nine recreational swimmers performed three 300 m trials in a 50 m outdoor pool, at 70%, 80% and 90% of their front-crawl 400 m personal best time. Using wearable inertial measurement units (IMUs) and validated algorithms we assessed the variability of technique descriptors at each arm cycle (139 ± 17 per trial). We calculated the duration of pull, push and non-propulsive phases, index of coordination (IdC), stroke length, stroke rate and intra-cyclic velocity variation. To track intra-trial technique variability, we calculated the Cauchy index to quantify the stability of multidimensional technique descriptors in space–time. Skilled swimmers, having access to divers motor solutions, achieved significantly higher velocities at similar intensities and similar IdC (P < 0.01) with more stable motor pattern (smaller Cauchy index). Besides, the similarity of intra-cyclic velocity variation at different intensities denotes that skilled swimmers used a wider dynamic range of velocity. We also introduced cycle velocity variation as a new metric of propulsive pattern repeatability and showed cycle velocity variation changes is correlated to the Cauchy index (rx,y = 0.72, P < 0.01). These findings indicate that IdC can be used as a predictor of performance only when swimmers of homogeneous expertise level are studied and suggest the scrutiny of both intra-cyclic velocity variation and cycle velocity variation as a requisite to study the motor adaptations of the swimmer in facing new constraints.

Non-circular chainring improves aerobic cycling performance in non-cyclists

Non-circular chainrings alter the crank velocity profile over a pedalling cycle. The aim of this study was to investigate the effect of this altered crank velocity profile on the aerobic performance compared to a circular chainring (CC). Ten male non-cyclists performed two incremental maximal tests at 80 rpm on a cycle ergometer: one with a circular (Shimano) and the other with a non-circular chainring Osymetric® (Somovedi), at least 50 h apart. Each test started with a workload of 100 W lasting 3 min. During the first 12 min, the workload was increased by 30 W every 3 min. Thereafter, the workload was increased by 30 W every 2 min until exhaustion. The power output, the intra-cycle crank angular velocity and the physiological parameters were monitored continuously, averaged over the last 30 s of each increment and at exhaustion, and compared for the two chainrings. Results showed a higher maximal aerobic power attained with the non-circular chainring (362.6 ± 37.9 vs. 338.8 ± 32.6 W, p < .001; moderate effect), which could be explained by a significantly lower energy expenditure during the first increment at 100 W. It could be hypothesised that the use of the non-circular chainring allowed saving a small part of energy expenditure throughout the test, allowing the exhaustion of the subject at a higher increment for a similar maximal energy expenditure, in comparison with a CC. Although this improvement is obtained only for non-cyclists, it allowed highlighting the link between cycling equipment modifying the pedalling motion and physiological responses.

Front Crawl Sprint Performance: A Cluster Analysis of Biomechanics, Energetics, Coordinative, and Anthropometric Determinants in Young Swimmers.

The aim of this study was to evaluate the determinants of front crawl sprint performance of young swimmers using a cluster analysis. 103 swimmers, aged 11- to 13-years old, performed 25-m front crawl swimming at 50-m pace, recorded by two underwater cameras. Swimmers analysis included biomechanics, energetics, coordinative, and anthropometric characteristics. The organization of subjects in meaningful clusters, originated three groups (1.52 ± 0.16, 1.47 ± 0.17 and 1.40 ± 0.15 m/s, for Clusters 1, 2 and 3, respectively) with differences in velocity between Cluster 1 and 2 compared with Cluster 3 (p = .003). Anthropometric variables were the most determinants for clusters solution. Stroke length and stroke index were also considered relevant. In addition, differences between Cluster 1 and the others were also found for critical velocity, stroke rate and intracycle velocity variation (p < .05). It can be concluded that anthropometrics, technique and energetics (swimming efficiency) are determinant domains to young swimmers sprint performance.

Intracycle Velocity Fluctuations during the 200 m swimming of the steady pace breaststroke

Intracycle Velocity Fluctuations during the 200 m swimming of the steady pace breaststroke

Intracyclic velocity variation and arm coordination for different skilled swimmers in the front crawl.

The aim of this study was to examine whether the intracyclic velocity variation (IVV) was lower in elite swimmers than in beginner swimmers at various velocities, and whether differences may be related to arm coordination. Seven elite and nine beginner male swimmers swam front crawl at four different swimming velocities (maximal velocity, 75%, 85%, and 95% of maximal swimming velocity). The index of arm coordination (IDC) was calculated as the lag time between the propulsive phases of each arm. IVV was determined from the coefficient of variation of horizontal velocity within one stroke cycle. IVV for elite swimmers was significantly lower (26%) than that for beginner swimmers at all swimming velocities (p<0.01, 7.28 1.25% vs. 9.80 1.70%, respectively). In contrast, the IDC was similar between elite and beginner swimmers. These data suggest that IVV is a strong predictor of the skill level for front crawl, and that elite swimmers have techniques to decrease IVV. However, the IDC does not contribute to IVV differences between elite and beginner swimmers.

Coordination pattern adaptability: energy cost of degenerate behaviors.

This study investigated behavioral adaptability, which could be defined as a blend between stability and flexibility of the limbs movement and their inter-limb coordination, when individuals received informational constraints. Seven expert breaststroke swimmers performed three 200-m in breaststroke at constant submaximal intensity. Each trial was performed randomly in a different coordination pattern: ‘freely-chosen’, ‘maximal glide’ and ‘minimal glide’. Two underwater and four aerial cameras enabled 3D movement analysis in order to assess elbow and knee angles, elbow-knee pair coordination, intra-cyclic velocity variations of the center of mass, stroke rate and stroke length and inter-limb coordination. The energy cost of locomotion was calculated from gas exchanges and blood lactate concentration. The results showed significantly higher glide, intra-cyclic velocity variations and energy cost under ‘maximal glide’ compared to ‘freely-chosen’ instructional conditions, as well as higher reorganization of limb movement and inter-limb coordination (p<0.05). In the ‘minimal glide’ condition, the swimmers did not show significantly shorter glide and lower energy cost, but they exhibited significantly lower deceleration of the center of mass, as well as modified limb movement and inter-limb coordination (p<0.05). These results highlight that a variety of structural adaptations can functionally satisfy the task-goal.

Natatometer. Real-Time Intra-Cycle Velocity Data for Swimming Stroke Correction

109 дистанции 5 км. Юные спортсмены, генетически предрасположенные к скоростно-силовым нагрузкам, на дистанциях 3 и 5 км не смогли показать высокие результаты. Возможно, более успешно они будут выступать на спринтерских дистанциях в старшем возрасте. Для юных спортсменов 13-14 лет необходимо использовать дифференцированный подход. Выбор оптимальной методики подготовки в лыжных гонках с акцентом развития физических качеств (скоростно-силовых, выносливости или универсальных) необходимо осуществлять с помощью современных технологий. ЛИТЕРАТУРА

Backstroke Intra-Cycle Velocity Fluctuations In Unilateral Arm Amputee Swimmers

Backstroke Intra-Cycle Velocity Fluctuations In Unilateral Arm Amputee Swimmers

Assessment of Fatigue Thresholds in 50-m All-Out Swimming

It is essential to determine swimmers' anaerobic potential and better plan training, understanding physiological effects of the fatigue. To study changes in the characteristics of the intracyclic velocity variation during an all-out 50-m swim and to observe differences in speed and stroking parameters between these changes. 28 competitive swimmers performed a 50-m front-crawl all-out test while attached to a speedometer. The velocity-time (v[t]) curve off all stroke cycles was analyzed per individual using a routine that included a wavelet procedure, allowing the determination of the fatigue thresholds that divide effort in time intervals. One or 2 fatigue thresholds were observed at individual level on the v(t) curve. In males, when 1 fatigue threshold was identified, the mean velocity and the stroke index dropped (P < .05) in the second time interval (1.7 ± 0.0 vs 1.6 ± 0.0 m/s and 3.0 ± 0.2 vs 2.8 ± 0.3 m/s, respectively). When 2 fatigue thresholds were identified, the mean velocity of the first time interval was higher than that of the third time interval (P < .05), for both male (1.7 ± 0.0 vs 1.6 ± 0.1 m/s) and female (1.5 ± 0.1 vs 1.3 ± 0.1 m/s) swimmers. One or 2 fatigue thresholds were found in the intracyclic velocity-variation patterns. Concurrently, changes in velocity and stroke parameters were also observed between time intervals. This information could allow coaches to obtain new insights into delaying the degenerative effects of fatigue and maintain stable stroke-cycle characteristics over a 50-m event.

Do Qualitative Changes in Interlimb Coordination Lead to Effectiveness of Aquatic Locomotion Rather Than Efficiency?

This study compared interlimb coordination and indicators of swim efficiency and effectiveness between expert and recreational breaststroke swimmers. Arm-leg coordination of 8 expert and 10 recreational swimmers at two different paces, slow and sprint, were compared using relative phase between elbow and knee. For each participant, knee and elbow angles were assessed using a 3-dimensional video analysis system with four below and two above cameras. During each phase of the cycle, indicators of swim efficiency (intracyclic velocity variations) and effectiveness (horizontal distance, velocity peaks, acceleration peaks) were calculated. Two coordination patterns emerged between expert and recreational swimmers, with significant differences in the relative phase at the beginning of a cycle (-172.4° for experts and -106.6° for recreational swimmers) and the maximum value of relative phase (9.1° for experts and 45.9° for recreational swimmers; all P<.05). Experts' coordination was associated with higher swim effectiveness (higher acceleration peak: 2.4 m/s2 for experts and 1.6 m/s2 for recreational swimmers) and higher distance covered by the center of mass during each phase of the cycle (all P<.05). This study emphasized how experts coordinate arms and legs to achieve effective behavior, therefore exhibiting flexibility, mainly in the timing of the glide phase, to adapt to different speed.