Swimming biomechanics: an editorial

Swimming Sports Biomechanics is a branch of Sports Biomechanics that deals with the analysis of swimming motions with the goal of optimising performance and minimising injuries in aquatic sports. Research in the area started many years ago, in the beginning of the twentieth century (Cureton, 1930; Du Bois-Reymond, 1927; Karpovich, 1933; Rork & Hellebrandt, 1937). Over time, this field of scientific research was relevantly catalysed by the Biomechanics and Medicine in Swimming (BMS) international symposium every four years since 1970. The proceedings books of these events are freely available (https://www.iat.uni-leipzig.de/datenbanken/iks/bms/) and constitute a very relevant repository of specific knowledge.

Traditionally, BMS literature includes contributions from leading swimming scientists focused on the different modalities of ‘Aquatic Sports’ and touching also different fields of knowledge, like sports biomechanics, physiology, medicine, etc. (Barbosa et al., 2010; Vilas-Boas, 2010). Indeed, the Fédération Internationale de Natation (FINA, https://www.fina.org/swimming) includes several ‘swimming’ modalities, as swimming itself (sometimes called ‘pure swimming’ by some national federations—please note that in this issue we prefer to use the expression to refer to the strict action of swimming, without the influence of starts and turns), performed both in a swimming pool or in Open Water, Artistic Swimming, Water Polo, Springboard Diving and Platform Diving. Swimming is also a decisive part of another sport, governed by another federation: Triathlon. Furthermore, it is possible to recognise other sports practiced in the water that rely, more or less, on specific swimming locomotion abilities: Fin Swimming, Deep Diving, Life-Saving Swimming and Underwater Hockey, among others.

Unfortunately, it seems that scientific literature in most of these specific aquatic sport disciplines is scarce compared to the sport of ‘swimming’ and that most of the corpus of knowledge in those specific aquatic sport disciplines is anchored in swimming science which is underpinned by a common set of scientific principles pertaining to producing movement in the water or in the interface between water and air. Consequently, we focused this Special Issue predominantly on competitive pool swimming. However, we decided to include also contributions on Artistic Swimming and Water Polo, not only for stimulating scientific research on other aquatic sports but also because the specific knowledge provided can complement existing knowledge of how hydrodynamic forces are generated.

Although swimming is among the most practiced sports across the world (https://sportsbrief.com/facts/top-listicles/16715-revealed-top-15-popular-sports-world-2022/; accessed in June 2022), scientific literature on the sport accounted for only about 6% of the total sport science literature (Costa & Barbosa, 2018) published between 2013 and 2017. By soliciting and compiling key papers for this Sports Biomechanics special issue, we aimed to motivate other researchers to work in the field, thereby further stimulating the growth in quality and quantity of published scientific research on swimming.

Competitive Swimming Biomechanics is commonly divided into the Biomechanics of Starts, Pure Swimming and Turning. We have tried to preserve this taxonomy and used it to select the papers to be included. Consequently, we have contributions focused on the starts (ventral and dorsal), the turns and pure swimming. Here, particular emphasis was given to the Biomechanics of Drag and Propulsion, as the main dynamic determinants of water locomotion. We mixed invited and freely submitted contributions to enable a balanced coverage of the biomechanical aspects of competitive swimming. Furthermore, researchers in different topics were assembled as contributing authors of each invited paper. Consequently, the volume represents a unique compilation of the latest scientific knowledge accumulated cooperatively by many of the world’s leading swimming researchers.

The first paper is an invited paper from Sanders, Takagi and Vilas-Boas that, for the first time, tries to assess, in the perspective of the researcher, the relevance for the practitioner of scientific research outcomes on swimming biomechanics. Relevant research on starts, turns, swimming and swimming to finish the 100-m freestyle event were reviewed in an attempt to quantify how a highly competitive swimmer might achieve additional improvements in performance towards podium levels. The conclusion was stunning: a total improvement of almost 7% of the world record (WR) could be achieved by applying recent research findings.

Indeed, it is expected that coaches and swimmers may be apply new knowledge on generating propulsion and minimising resistive drag. These are the topics of the second and third articles authored by Takagi et al. and Sacilotto et al., respectively. Given that both propulsion and drag are expected to be influenced by torso twist and body position changes, two further papers are presented. The first, authored by Andersen et al., deals with the role of torso muscles on torso twist and postural stability during front crawl swimming at different paces. The second compared buoyancy torque between the two currently used alternating-stroke techniques: front crawl and backstroke. Indeed, dynamic buoyancy torque may be decisive for propulsion and drag, as distinct from torques produced by other hydrodynamic forces. These forces and torques are linked to the coordination and stroking parameters of swimming techniques explored by Seifert and Carmigniani.

The start plays a decisive role in determining the result of a swimming events and offers a strong potential for performance improvement. This vindicates the inclusion of three papers on starts. The first is an invited systematic review from de Jesus et al. synthetising the state of the art on the effect of back-plate and wedge on the ventral and dorsal starts. A paper from Shepherd et al. outlines the effect of body position and velocity at toe off, in both genders, on start performance. The sequel to the gliding phase, namely the breakout phase, and its repercussions on subsequent swimming actions were considered by Stosic et al.

The biomechanics of turning actions is also covered in this issue of Sports Biomechanics. Kinematic and kinetics of the tumble turn performed by elite female swimmers are studied by Hellard et al., and a comparison of four different variants of the backstroke to breaststroke turn in age-group swimmers is presented by Chainok et al.

Race analysis developments are also provided by Gonjo and Olstad, including time-series velocity data, allowing for a better discrimination of exertion time effects on performance capacity during breaststroke events. For many years, race analysis at major competitions has been conducted. Its importance is manifest in the increasing trend of including a ‘Biomechanics Analyst’ to accompany national teams. Consequently, we invited a number of national team analysts (Barbosa et al.) to elaborate their role, both during training and competition.

As referred beforehand, this Special Issue has focused on competitive pool swimming. However, in the interest of contributing to a better understanding of the mechanisms of propulsion in water, we close with two selected papers: one on kinematics and kinetics underpinning the identification of different eggbeater techniques in Water Polo (Eisuke et al.) and another on propulsion in Artistic Swimming sculling actions (Homma et al.).

As Editors of this Special Issue, we are very happy about the receptivity of the swimming biomechanics community to our call and proud of compiling a state-of-the-art, balanced, stimulating and thought-provoking volume of scientific reading on the topic.

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