Congresos y Seminarios

Arellano, R. (2026). The León Lewillie Lecture: The science of swimming in the new AI-driven world. Brazilian Journal of Motor Behavior, 20(2), 33-44.https://doi.org/10.20338/bjmb.v20i2.598[PDF][IAT]

For more than half a century, swimming resisted scientific analysis. When Leon Lewillie opened the first International Symposium on Biomechanics and Medicine in Swimming in Brussels in 1970, he identified the obstacle precisely: a barrier of water had isolated our sport from rigorous measurement. This lecture explores how this barrier became permeable. Starting with Lewillie's balloon-borne electromyograms, it follows the development through Jan Pieter Clarys's five decades of towing-tank and muscle work, which demonstrated that technique rather than body form governs resistance, and on to my own nine editions of this symposium, where the focus shifted from developing instruments to understanding the properties of water itself. The second half turns to the force now reshaping the field: artificial intelligence. Computer vision can already segment races and measure the underwater dolphin kick, while wearable sensors can classify strokes and explainable models can rank the variables behind performance and flag injury risk before it occurs. However, these tools can produce inaccurate results, hide their reasoning and have not read much of our literature. The argument is simple yet demanding: machine learning provides scale and speed, while fluid mechanics provides cause. Only their collaboration — with the scientist firmly in the loop — yields understanding. Fifty-six years after Lewillie, the water still resists; the machine is powerful, yet blind; and the researcher must still ask the right questions and stand by the answers.

Arellano, R., & Ungerechts, B.E. (2026). Beyond the swimming propulsive force: Bridging conventional biomechanics and the energy–momentum continuum. Brazilian Journal of Motor Behavior, 20(2), 109-115.https://doi.org/10.20338/bjmb.v20i2.598[PDF][IAT]

BACKGROUND: Swimming biomechanics still explains propulsion as the hands and feet 'pushing water backwards'. However, years of flow visualisation have revealed a different story. During a cycle, the hand does not propel the body by pushing a compact mass of water. Instead, it continuously modifies the surrounding flow, creating pressure gradients, fluid accelerations and vortical structures. These evolving flow structures redistribute momentum and mechanical energy throughout the surrounding water. Consequently, the hydrodynamic force measured at a particular instant only represents one aspect of the interaction. A complete physical description must also account for the transient storage, convective transport, and dissipation of mechanical energy within the flow field generated by the swimmer. We therefore describe human aquatic propulsion as an energy–momentum continuum, and argue that the force-based and continuum concepts are complementary rather than competing. METHODS: In a conceptual, conference-length format, the case is built in three linked steps — 'Bridging the Gap', 'Decoding the Mechanics of Speed', and 'Beyond Force' — explained in an illustration in each case. The reasoning rests on the Navier–Stokes equations, on global energy and momentum balances, on a Helmholtz decomposition of the flow, and on a BIV–CFD validation chain; derivations are kept to a minimum. RESULTS: The framework redefines the single force value per cycle in terms of power flow (in watts), energy turnover per cycle, momentum transfer and work cycles. It explains why the Strouhal number determines which mechanism dominates in each body segment, yielding quantities that can be used by coaches and equipment designers. CONCLUSIONS: 'Beyond force' means thinking past it by putting energy, momentum and vortices at the centre, while keeping what kinematics has already taught us.

Santillana-Camargo, D.N., Ruiz-Navarro, J.J., Morales-Ortíz, E., & Arellano, R. (2026). 3D trajectory analysis of the front-crawl stroke: A pilot study [Abstract]. Brazilian Journal of Motor Behavior, 20(2), 133.https://doi.org/10.20338/bjmb.v20i2.598[PDF][IAT]

The use of programming tools in swimming biomechanical analysis has become increasingly relevant due to the need for accessible cost-effective, and accurate evaluation methods. These tools allow coaches, swimmers, and technical staff to perform detailed underwater analyses without relying on expensive or complex systems. Therefore, the aim of this study was to develop a methodological protocol for analyzing front-crawl biomechanics using programming tools and specialized software such as Kwon3D and MATLAB. Three female student swimmers from the Faculty of Sport Sciences at the University of Granada (22±1 years, 1.66±0.03 m of height, 61.17±3.21 kg of body mass, 31.5±1.1 s 50 m front-crawl time) voluntarily participated in a resisted swimming test. Each swimmer completed 20 m trials under four loading conditions (0, 1, 3, and 5 kg) applied using the 1080 Sprint 2. Data were collected in a 5×2 m underwater recording area starting at the 10 m line. Four GoPro HERO9 cameras were used for motion capture. A right wrist-mounted tracker was attached to each participant to facilitate motion tracking. Movement data were processed using Kwon3D software to extract 3D coordinates (X, Y, and Z axes). Subsequently, a custom MATLAB script was developed to analyze the data, compute average trajectory curves for each axis, and compare the unloaded condition with the resisted conditions. As a result, the average trajectories were calculated across the three swimmers for each axis and load condition. A margin of ±0.05% of the maximum and minimum values was registered along the trajectories. The developed protocol through the integration of programming tools enabled a systematic analysis of front-crawl biomechanics using Kwon3D and MATLAB, facilitating efficient data processing and contributing to a better understanding of the kinematic changes that occur during semi-tethered swimming. Future studies should include larger sample sizes and compare a wider range of loading conditions to further validate and expand these findings.

Ruiz-Navarro, J.J., Febles-Castro, A., Gay, A., López-Belmonte, Ó., Morales-Ortíz, E., López-Contreras, G., & Arellano, R. (2026). Relationship between selected load-velocity profile variables and underwater undulatory swimming performance. Brazilian Journal of Motor Behavior, 20(2), 433-438.https://doi.org/10.20338/bjmb.v20i2.598[PDF][IAT]

BACKGROUND: Load-velocity profiling (LVP) using semi-tethered devices is a validated methodology for quantifying force and velocity capabilities in surface swimming, yet its application to underwater undulatory swimming (UUS) remains unexplored. This study aimed to characterize the LV profile during UUS, investigate the relationship between the LV profile and UUS performance and anthropometrics, and examine sex-based differences. METHODS: Thirty-three competitive swimmers (21 males, 12 females) performed a LV profile test. Individual LV profiles were constructed via linear regression of each trial and the theoretical maximum velocity (V0), the theoretical maximum load (L0), and the slope of the regression line (Slope) were calculated. Anthropometric measurements included height, arm span, body mass, sitting height, body length, biacromial and biiliocristal breadths, and derived indices. RESULTS: High linearity was confirmed for the LV profile (R² = 0.987 ± 0.015, males; 0.981 ± 0.023, females). Except for Slope in males, the LV profile-derived variables were largely to nearly perfectly correlated with UUS performance in both sexes (p<0.05). Body mass showed moderate association with L0 (r = 0.39) and Slope (r = 0.42) in males and no other significant association between anthropometrics and performance was observed (p>0.05). Males exhibited higher V₀ (1.58 ± 0.17 vs. 1.39 ± 0.14 m·s⁻¹, p<0.01) and L₀ (7.99 ± 2.38 vs. 5.76 ± 1.02 kg, p<0.01). Females showed steeper load-velocity Slopes (–0.21 ± 0.05 vs. –0.25 ± 0.03, p<0.05). CONCLUSIONS: LV profile methodology is applicable to UUS assessment, with limited direct influence of anthropometric factors and clear differences between sexes.

Febles-Castro, A., Rodríguez-Fernández, A., Ruiz-Navarro, J.J., Marcé Gil, J., & Arellano, R. (2026). Exploratory validation of temporal and event-based metrics from Triton 2 unit in swimmers with and without disability. Brazilian Journal of Motor Behavior, 20(2), 489-495.https://doi.org/10.20338/bjmb.v20i2.598[PDF][IAT]

BACKGROUND: Wearable inertial sensors are increasingly used to monitor swimming performance; however, evidence regarding their validity remains limited and inconsistent, particularly in Para swimmers, whose alterations in coordination, symmetry and propulsion may challenge head-mounted inertial event detection. This study aimed to provide a preliminary evaluation of the validity and agreement of the Triton 2 Unit system (triaxial accelerometer, gyroscope and magnetometer) against video-based analysis in swimmers with and without disabilities. METHODS: Four male and two female competitive swimmers (three without disabilities and three Paralympic swimmers) performed a structured training protocol under controlled conditions. Performance metrics derived from the head-worn inertial sensor were compared with a video-based reference. Variables analysed included lap time, mean stroke rate, number of strokes, underwater time, and turn time. Agreement and accuracy were assessed using median bias, interquartile range (IQR), median absolute percentage error (MdAPE), Lin's concordance correlation coefficient (ρc), and non-parametric 95% limits of agreement. RESULTS: In swimmers without disabilities, Triton showed high agreement for lap time (ρc = 0.968), stroke rate (ρc = 0.962), and number of strokes (ρc = 0.955), with low relative errors. Moderate agreement was observed for underwater time (ρc = 0.829), while turn time showed poor agreement (ρc = 0.228). In Para swimmers, agreement was generally lower and more variable, with wider limits of agreement across all variables. Lap time (ρc = 0.869) and stroke rate (ρc = 0.822) showed the highest consistency, whereas underwater time, number of strokes, and turn time showed reduced agreement. In one swimmer with severe impairment (S5), the device failed to correctly identify lap structure, leading to invalid outputs. CONCLUSIONS: Triton 2 Unit provides acceptable accuracy for selected metrics in swimmers without disabilities under ecological conditions. In Para swimmers, increased variability and occasional detection failures limit its applicability, particularly for event-based variables and severe impairments.

Arellano, R. (2024). Is ChatGPT a tool for swimming scientists and swimming coaches. En S. S. Marek Rejman (Ed.), Science In Swimming VIII (1.ª ed., Vol. 1, pp. 9-19). Wroclaw, Polonia: Wydawnictwo Akademii Wychowania Fizycznego im Polskich Olimpijczyków we Wrocławiu.

Capítulo de libro. Reflexión sobre el uso de modelos conversacionales de IA como apoyo a la investigación y al entrenamiento en natación.

Arellano, R. (2025). Smarter Swimming with AI: Using Neural Networks to Improve Swimmers' Technique and Performance. International Conference for Swimming Coaches, organizado por European Aquatics, Varsovia, Polonia. 19 a 21 de septiembre.

Conferencia invitada. Aplicación de redes neuronales al análisis técnico y al rendimiento en natación competitiva.