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This study aims to identify stroke regulation profiles and tipping-points in stroke regulation timing during international open water races according to performance level. Twelve elite or world-class swimmers were analysed during 18 international races. Stroke rate and jerk cost were computed cycle-to-cycle using an Inertial Measurement Unit and regulations profiles fitted using polynomials. We performed two-ways mixed-ANOVA to compare stroke kinematics among race segments and performance groups (G1 -fastest- to G3 -slowest-). Swimmers displayed specific regulation profiles (i.e., J-shape with end-spurt, J-shape without end-spurt and reverse L-shape for stroke rate and U-shape, reverse J-shape and reverse L-shape for jerk cost, for respectively G1, G2 and G3) with significant effect of race segment on stroke kinematics for G1 and G2. We highlighted tipping-points in stroke regulations profiles (TP1 and TP2) at respectively 30% and 75% of the race with greater magnitude in G1 than G2. TP1 reflects the end of a stroke economy period (0–30%) and TP2 the end of a progressive increase in stroke kinematics (30–75%) towards end-spurt (75–100%). Open water races follow a high-grading dynamics requiring biomechanical regulations along the race. Targeting stroke rate reserve and management of stroke smoothness should be considered during training of open water swimmers. [ABSTRACT FROM AUTHOR]

This study presents a deep learning model devoted to the analysis of swimming using a single Inertial Measurement Unit (IMU) attached to the sacrum. Gyroscope and accelerometer data were collected from 35 swimmers with various expertise levels during a protocol including the four swimming techniques. The proposed methodology took high inter- and intra-swimmer variability into account and was set up for the purpose of predicting eight swimming classes (the four swimming techniques, rest, wallpush, underwater, and turns) at four swimming velocities ranging from low to maximal. The overall F1-score of classification reached 0.96 with a temporal precision of 0.02 s. Lap times were directly computed from the classifier thanks to a high temporal precision and validated against a video gold standard. The mean absolute percentage error (MAPE) for this model against the video was 1.15%, 1%, and 4.07%, respectively, for starting lap times, middle lap times, and ending lap times. This model is a first step toward a powerful training assistant able to analyze swimmers with various levels of expertise in the context of in situ training monitoring. [ABSTRACT FROM AUTHOR]

The present study aimed to examine the effects of Spirulina supplementation on anthropometrical measurements and physical performance in elite rugby players. Twenty-two elite male Rugby Union players (21–36 years old) volunteered to participate in this study. They were randomly assigned to a Spirulina group (SPI: n = 11), or a placebo group (PLA: n = 11) in a double-blind design. Subjects were supplemented with Spirulina platensis (5.7 g/d) or placebo (isoproteic and caloric) for 7 weeks. At baseline (W0) and after 7 weeks of supplementation (W7), the same anthropometric measurements and physical performance test battery were performed. These tests included isokinetic leg strength and power, vertical jump, speed, and aerobic fitness assessment. For anthropometric data, the fat mass percentage was significantly reduced in both groups without significant difference between groups. While both groups exhibited significant improvements for Squat Jump (SJ), Countermovement Jump (CMJ), and 10- and 30-m sprints between W0 and W7, higher percentage improvements with the SPI group did not reach significance. Neither training alone (PLA) nor training associated with Spirulina supplementation affected leg maximal strength and power or aerobic fitness. Seven weeks of Spirulina supplementation in elite rugby players did not improve body composition or substantially increase physical performance. We only observed a non-significant small advantage in vertical jump and sprint performance in the SPI group. Based on the data from this study, Spirulina supplementation has modest effects in elite rugby players during the competitive phase. Further studies are required to verify Spirulina supplementation effects among athletes of different sports, ages, genders, and athletic levels with longer durations and higher dosages. [ABSTRACT FROM AUTHOR]

Lunge motion is one of the fundamental attacks used in modern fencing, asking for a high level of coordination, speed and accuracy to be efficient. The aim of the current paper was the assessment of fencer’s performance and response time in lunge attacks under uncertain conditions. For this study, an innovative fencing lunge simulator was designed. The performance of 11 regional to national-level fencers performing lunges in Fixed, Moving and Uncertain conditions was assessed. The results highlighted notably that i) Accuracy and success decreased significantly in Moving and Uncertain conditions with regard to Fixed ones ii) Movement and Reaction times were also affected by the experimental conditions iii) Different fencer profiles were distinguishable among subjects. In conclusion, the hypothesis that fencers may privilege an adaptation to the attack conditions and preserve accuracy instead of privileging quickness was supported by the results. Such simulators may be further used to analyze in more detail the motor control strategies of fencers through the measure and processing of biomechanical quantities and a wider range of fencing levels. It has also a great potential to be used as training device to improve fencer’s performance to adapt his attack to controlled opponent’s motion. [ABSTRACT FROM AUTHOR]

This study investigated the influence of an incremental exercise on bilateral asymmetry through the spatio-temporal evolution of 3D joint angular displacement, using the Normalized Symmetry Index (NSI) and cross-correlation methods. Twelve professional cyclists performed an incremental test to exhaustion, during which motion capture was used. Results revealed a decrease in range of motion between the first and last stages for twelve of the eighteen joint rotations, with the highest impact observed for right hip flexion/extension (61.8 ± 4.7° to 58.8 ± 4.1°, p < 0.05, ES = 0.68). For both stages, significant bilateral differences greater than 10° were observed for hip and knee flexion/extension (p < 0.05, ES>0.90) and ankle and hip internal/external rotation (p < 0.05, ES>0.25). Cross-correlation displayed the lowest pattern similarities for hip abduction/adduction and the highest similarities for knee flexion/ extension, ankle plantarflexion/dorsiflexion and hip internal/external rotation. The cross-correlation method showed that the right leg was mostly ahead of time with respect to the left leg, a trend that was accentuated with power output increase. Instantaneous NSI fluctuated up to 18% throughout the pedalling cycle, with different behaviour between the power and recovery phases. This study demonstrated the workload effects on side-to-side joint angular pattern similarity. [ABSTRACT FROM AUTHOR]

Keywords: Maximal joint torque; isokinetic dynamometer; torque-angle-velocity relationship; knee; muscle mechanics EN Maximal joint torque isokinetic dynamometer torque-angle-velocity relationship knee muscle mechanics S286 S288 3 01/29/21 20191002 NES 191002 1. Model evaluation Root mean square errors (RMSE) between modelled and experimental knee flexion/extension torques were computed for each JTAR models and for each combination of JTAR and JTVR models. Maximal joint torque, isokinetic dynamometer, torque-angle-velocity relationship, knee, muscle mechanics. [Extracted from the article]

This study aims to profile biomechanical abilities during sprint front crawl by identifying technical stroke characteristics, in light of performance level. Ninety-one recreational to world-class swimmers equipped with a sacrum-worn IMU performed 25 m all-out. Intra and inter-cyclic 3D kinematical variabilities were clustered using a functional double partition model. Clusters were analysed according to (1) swimming technique using continuous visualisation and discrete features (standard deviation and jerk cost) and (2) performance regarding speed and competition calibre using respectively one-way ANOVA and Chi-squared test as well as Gamma statistics. Swimmers displayed specific technical profiles of intra-cyclic (smoothy and jerky) and inter-cyclic stroke regulation (low, moderate and high repeatability) significantly discriminated by speed (p < 0.001, η2 = 0.62) and performance calibre (p < 0.001, V = 0.53). We showed that combining high levels of both kinds of variability (jerky + low repeatability) are associated with highest speed (1.86 ± 0.12 m/s) and competition calibre (ℽ = 0.75, p < 0.001). It highlights the crucial importance of variabilities combination. Technical skills might be driven by a specific alignment of stroke pattern and its associated dispersion according to the task constraints. This data-driven approach can assist eyes-based technical evaluation. Targeting the development of an explosive swimming style with a high level of body stability should be considered during training of sprinters. [ABSTRACT FROM AUTHOR]

This paper presents a novel sensor-to-segment calibration procedure for inertial sensor-based knee joint kinematics analysis during cycling. This procedure was designed to be feasible in-field, autonomously, and without any external operator or device. It combines a static standing up posture and a pedaling task. The main goal of this study was to assess the accuracy of the new sensor-to-segment calibration method (denoted as the 'cycling' method) by calculating errors in terms of body-segment orientations and 3D knee joint angles using inertial measurement unit (IMU)-based and optoelectronic-based motion capture. To do so, 14 participants were evaluated during pedaling motion at a workload of 100 W, which enabled comparisons of the cycling method with conventional calibration methods commonly employed in gait analysis. The accuracy of the cycling method was comparable to that of other methods concerning the knee flexion/extension angle, and did not exceed 3.8°. However, the cycling method presented the smallest errors for knee internal/external rotation (6.65 ± 1.94°) and abduction/adduction (5.92 ± 2.85°). This study demonstrated that a calibration method based on the completion of a pedaling task combined with a standing posture significantly improved the accuracy of 3D knee joint angle measurement when applied to cycling analysis. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to explore training and testing practices from Strength & Conditioning (S&C) coaches who manage groups of high-level French swimmers in elite training centers. The transfer of abilities from dry-land to in situ condition was also investigated., Methods: 24 French S&C coaches completed a survey via an online platform. Frequency analyses were made for quantitative and qualitative responses, the level of significance set for this study was p  ≤ 0.05., Results: Core stability, Strength & Power were the three most targeted qualities. Core strengthening in all its forms, Bench Press & Squat were the three most prescribed exercises. 79% of S&C coaches adapted exercises according to different parameters. Most of the coaches indicated that dry-land S&C sessions were preferentially placed before in-water sessions. Very varied exercises were used in-water to make the transfer from dry-land more effective. 87% of participants monitored the training load and 38% assessed the force and velocity parameters for some S&C exercises., Discussion: Dry-land training practices of S&C coaches were mostly in line with scientific recommendations. In the light of results of the questionnaire, it would appear that testing procedures might be a key issue for transferring qualities from dry-land to in situ ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Raineteau, Pla, Bideau, Bideau and Nicolas.)

This article focuses on the design of a sensor system for a non-planar surface, in particular a cylindrical shape, such as a kayak paddle. The main objective is to develop a piezoresistive sensor system to measure the pressure exerted by the hand on the shaft. The study begins with static characterization of the sensors, including dispersion analysis to assess their sensitivity, linearity and measurement range. A calibration process is carried out using a dedicated test bench, and an inverse viscoelastic model is used to establish an accurate relationship between the measured resistance and the corresponding pressure. The sensor system is connected to a data acquisition board equipped with an analog-to-digital converter (ADC) that enables the direct conversion of analog data into digital resistance values. Furthermore, Bluetooth Low Energy (BLE) wireless communication is employed to facilitate data transfer to a computer, enabling a detailed pressure mapping of the kayak paddle and real-time data collection. The calibrated sensors are then tested and validated on the kayak paddle, facilitating the mapping of pressure zones on the paddle surface. This mapping provides information for locating areas of high pressure exertion during kayaker movements.

Introduction: Improving swimming performance involves assessments of biomechanical variables of the stroke, and it can be achieved using semi-tethered swimming tests. The aim of this study was thus to investigate the associations between load-velocity (L-V) profiles, from a semi-tethered swimming protocol and race variables in the 100 m and 200 m freestyle events., Methods: Eight swimmers completed a L-V profiling protocol consisting of four sprints (25 m, 25 m, 20 m, 15 m) against increasing loads (0.1, 2.0, 4.0, 6.0 kg respectively) with complete recovery between repetitions (>5 min). The L-V linear regression was used to estimate maximal velocity (V0) and body mass normalized load (rL0). Race variables such as clean swimming speed (V), stroke rate (SR), distance per cycle (SL) and stroke index (SI) were assessed from video analysis of 100 m and 200 m freestyle events taking place 3-4 days after the L-V protocol., Results: L-V results showed high levels of speed (mean ± SD: 1.87 ± 0.04 m/s) and heavy maximal relative loads (mean ± SD: 38.5 ± 6.51 as % of body mass). Swimmers also achieved high-level performances in the 100 m (mean ± SD time: 51.95 ± 0.75 s) and the 200 m (mean ± SD time: 113.85 ± 2.67 s). For the 100 m events, the maximal relative load showed strong correlation with performance ( r  = 0.63) whereas trivial correlation was observed for the 200 m events ( r  = 0.12). SR on the 100 m and the 200 m also showed very strong association with rL0 ( r  = 0.83) and a strong association with V0 ( r  = 0.68) respectively., Conclusion: The relationships between L-V variables and race variables depend on the distance of the event. However, L-V variables seem to be less related to SR and SL evolutions for the 100 m than in the 200 m event. Moreover, L-V profiles tend to be more related to the 100 m than 200 m freestyle performance. L-V profile should be interpreted taking into consideration the specific physiological and biomechanical constraints of the main events of the swimmer., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Raineteau, Nicolas, Bideau, Bideau and Pla.)

This study aimed to quantify the influence of an increase in power output (PO) on joint kinematics and electromyographic (EMG) activity during an incremental test to exhaustion for a population of professional cyclists. The hip flexion/extension and internal/external rotation as well as knee abduction/adduction ranges of motion were significantly decreased at 100% of the maximal aerobic power (MAP). EMG analysis revealed a significant increase in the root mean square (RMS) for all muscles from 70% of the MAP. Gastrocnemius muscles [lateralis gastrocnemius ( GasL ) and medialis gastrocnemius ( GasM )] were the less affected by the increase of PO. Cross-correlation method showed a significant increase in the lag angle values for VM in the last stage compared to the first stage, meaning that the onset of the activation started earlier during the pedaling cycle. Statistical Parametric Mapping (SPM) demonstrated that from 70% MAP, biceps femoris ( BF ), tibialis anterior ( TA ), gluteus maximus ( GM ), and rectus femoris ( RF ) yielded larger ranges of the crank cycle on which the level of recruitment was significantly increased. This study revealed specific muscular and kinematic coordination for professional cyclists in response to PO increase., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Pouliquen, Nicolas, Bideau and Bideau.)