Exploring in a climbing task during a learning protocol: a complex sense-making process.

In perceptual-motor learning, constant and variable practice conditions have been found to have differential effects on learners' exploratory activity and their ability to transfer their skills to novel environments. However, how learners make sense of these practice conditions during practice remains unclear. This study aimed to analyse learners' experiences of different practice conditions during a climbing learning protocol and to examine how these experiences might further inform learners' exploratory activity. Twelve participants assigned to either 'Constant practice', 'Imposed Novelty', or 'Chosen novelty' groups climbed a 'Control route' (i.e. a route common to all groups) and a 'transfer route' (i.e. a new route) before and after a ten session learning protocol. Descriptions of learners' experiences during previews and climbs were collected using self-confrontation interviews. After identifying general dimensions via a thematic analysis, a hierarchical cluster analysis on these general dimensions allowed the identification of phenomenological clusters (PhC). The distribution of these PhCs was compared between the first and last learning sessions, the control and transfer routes, and the practice condition groups. We identified seven PhCs reflecting learners' meaningful exploratory activity during the previews and climbs. Significant differences in the distribution of these PhCs were found between (i) the first and the last session, (ii) the control and the transfer route and (iii) the Chosen-novelty group and the other two practice groups. These results suggest that exploration is part of a complex sense-making process linked to practice conditions, which can be described by a joint analysis of the intentions, perceptions and actions.

Exploring to learn and learning to explore.

In respect to ecological psychology processes of attunement and calibration, this critical review focusses on how exploratory behaviors may contribute to skilled perception and action, with particular attention to sport. Based on the theoretical insights of Gibson (The senses considered as perceptual systems, Houghton Mifflin, Boston, 1966) and Reed (Encountering the world: Toward an ecological psychology, Oxford University Press, New York, 1996), exploratory and performatory actions have been differentiated in numerous experiments to study the perception of opportunities of action. The distinction between exploratory and performatory actions has informed the study of infant behavior in developmental psychology. In the current article, we highlight limitations with this distinction in the study of sports performers. We propose that a dynamic view of exploratory behavior would reveal how individuals develop exploratory activity that generates information about the fit between environmental properties and action capabilities. In this aim, practitioners should: (1) give learners the opportunity to safely develop exploratory behaviors even when they act outside their action boundary; and (2) guide learners to search for more reliable information to develop exploratory behaviors that would enhance the transfer of skills to various performance contexts.

Arm - Leg coordination profiling during the dolphin kick and the arm pull-out in elite breaststrokers.

In breaststroke races, the dolphin kick could finish before, at the same time, or during the arm pull-out, but it is unclear how swimmers perform this technique. The aim of this study was to investigate whether swimmers glide between the dolphin kick and arm pull-out, favour continuity or even overlap those two phases, as it would impact the active underwater sequence. Fourteen international and national male swimmers performed 100-m breaststroke with all-out effort in a pre-calibrated 25 m swimming pool. A multi-camera system tracked the head of the swimmers. Key points of the active underwater sequence were obtained from notational analysis. A hierarchical cluster analysis identified three coordination profiles. All swimmers started their dolphin kick before the arm pull-out. However, one swimmer started the arm pull-out before the end of the dolphin kick, seven swimmers started the arm pull-out after the end of the dolphin kick, and four swimmers synchronised the beginning of the arm pull-out and the end of the dolphin kick, while two other swimmers mixed two coordination profiles among the start and the three turns. Those different profiles allow achieving similar performance outcome, suggesting individual training regarding the underwater phase.

Metastable attunement and real-life skilled behavior.

In everyday situations, and particularly in some sport and working contexts, humans face an inherently unpredictable and uncertain environment. All sorts of unpredictable and unexpected things happen but typically people are able to skillfully adapt. In this paper, we address two key questions in cognitive science. First, how is an agent able to bring its previously learned skill to bear on a novel situation? Second, how can an agent be both sensitive to the particularity of a given situation, while remaining flexibly poised for many other possibilities for action? We will argue that both the sensitivity to novel situations and the sensitivity to a multiplicity of action possibilities are enabled by the property of skilled agency that we will call metastable attunement. We characterize a skilled agent's flexible interactions with a dynamically changing environment in terms of metastable dynamics in agent-environment systems. What we find in metastability is the realization of two competing tendencies: the tendency of the agent to express their intrinsic dynamics and the tendency to search for new possibilities. Metastably attuned agents are ready to engage with a multiplicity of affordances, allowing for a balance between stability and flexibility. On the one hand, agents are able to exploit affordances they are attuned to, while at the same time being ready to flexibly explore for other affordances. Metastable attunement allows agents to smoothly transition between these possible configurations so as to adapt their behaviour to what the particular situation requires. We go on to describe the role metastability plays in learning of new skills, and in skilful behaviour more generally. Finally, drawing upon work in art, architecture and sports science, we develop a number of perspectives on how to investigate metastable attunement in real life situations.

Influence of stroke rate on coordination and sprint performance in elite male and female swimmers.

This study investigated the effects of gender and the manipulation of the preferred stroke rate on swimming performance and arm coordination in elite front crawl swimmers. Nineteen swimmers performed a dual task, that is, imposed stroke rate and maximal speed. They swam nine 25-m trials at maximal speed twice: one trial at the preferential stroke rate, one trial at maximal stroke rate and seven trials at stroke rates between 41 and 59 cycles/min imposed by an Aquapacer. Stroke rate, arm stroke phases, and arm coordination were computed from an inertial measurement unit on each forearm and one on the sacrum. Time on the 25-m was recorded to assess swimming speed. Results indicated that the error between the imposed and performed stroke rates was lowest at the preferred stroke rate for women. An increase in stroke rate led to an increase in swimming speed and the index of coordination, but these changes could be influenced by the preferred stroke rate. Individual analysis revealed that some swimmers exhibited higher flexibility (larger range of stroke rate) around their preferred stroke rate. This stroke rate flexibility appeared more functional in swimmers who reached higher speeds when swimming at the maximal stroke rate than at the preferred stroke rate.

Action capability constrains visuo-motor complexity during planning and performance in on-sight climbing.

The capability to adapt to changing conditions is crucial for safe and successful performance in physical activities and sports. According to the affordance-based control perspective, individuals act in such a way as to take into account the limits of their capability to act. However, it is not clear how strength interacts with skill in shaping performer-environment interactions. We, therefore, determined whether fingertip strength influences patterns of gaze and climbing behavior on new routes of ever-increasing difficulty. We expected that comparatively weaker climbers would show less complex behavior because of an inability to perceive and act. Stronger climbers would show more complex visuo-motor behavior because more opportunities for action remain, even as route difficulty increases. For very strong climbers the route would not be challenging enough, and less complex patterns suffice. Twenty climbers, ranging from lower grade to elite level participated. Maximum fingertip strength was obtained. Participants previewed and then climbed two separate 3 m long traverses, gradually decreasing in edge depth. Gaze and hip positions were collected for subsequent computation of gaze transition entropy (during preview) and hip displacement entropy (during climbing). Data revealed statistically significant curvilinear relationships between both fingertip strength and gaze transition entropy, and fingertip strength, and hip displacement entropy. Visuo-motor complexity is scaled by how close the individual must act relative to boundaries of what the environment affords and does not afford for action given the individual constraints. Future research should examine in greater detail relationships between action capabilities and functional movement variability.

An enactive approach to appropriation in the instrumented activity of trail running.

The incorporation of external tools during a sports activity can be analyzed through the dynamics of appropriation. In this study, we assumed that appropriation could be documented at both the phenomenological and behavioral scales and aimed to characterize trail runners' interactions with five carrying systems (i.e., backpacks proposing different ways of carrying water) in an ecological setting. The runners ran a 3-km trail running loop, equipped with inertial sensors to quantify both their vertical oscillations and those of the carrying systems. After the trials, phenomenological data were collected in enactive interviews. Results showed that (1) the runners encountered issues related to the carrying system, whose emergence in their experiences while running revealed the interplay between the tool's transparency (i.e., when runners provided no account of the carrying system) and opacity (i.e., when runners mentioned perceptions of disturbing system elements), and (2) when the runners carried the water bottles on the pectoral straps, they felt the system bouncing in an uncomfortable way, especially in the less technical parts of the route. We therefore investigated the low- and high-order parameters of coordination by computing the vertical accelerations and the acceleration couplings between the carrying system and the runners in order to identify coordination modes. The congruence between the runners' experiences and the behavioral data was noted in terms of (1) the system's vertical oscillations (i.e., low-order parameters) and (2) the couplings between the accelerations of the runners and the backpacks (i.e., high-order parameters). Our results demonstrated that the appropriation process was shaped by the interactions between the runners' activity, the environment and the physical properties of the tool. These interactions occurred in fluctuating phases where the runners perceived the carrying systems as more or less incorporated. Our results highlighted how tool incorporation is revealed through changes in its transparency/opacity in the actor's activity.

Predicting volleyball serve-reception at group level.

In a group-serve-reception task, how does serve-reception become effective? We addressed "who" receives/passes the ball, what task-related variables predict action mode selection and whether the action mode selected was associated with reception efficacy. In 182 serve-receptions we tracked the ball and the receivers' heads with two video-cameras to generate 3D world-coordinates reconstructions. We defined receivers' reception-areas based on Voronoi diagrams (VD). Our analyses of the data showed that this approach was accurate in describing "who" receives the serve in 95.05% of the times. To predict action mode selection, we used variables related to: serve kinematics, receiver's movement and on-court positioning, the relation between receiver and his closest partner, and interactions between receiver-ball and receiver-target. Serve's higher initial velocities together with higher maximum height, as well as smaller longitudinal distances between receiver and target increased the chances for the use of the overhand pass. Conversely, decreasing alignment of the receiver with the ball and the target increased the chances of using the underhand-lateral pass. Finally, the use of the underhand-lateral pass was associated with lower quality receptions. Behavioural variability's relevance for serve-reception training is discussed.

Functional Role of Movement and Performance Variability: Adaptation of Front Crawl Swimmers to Competitive Swimming Constraints.

To study the variability in stroking parameters between and within laps and individuals during competitions, we compared and modeled the changes of speed, stroke rate, and stroke length in 32 top-level male and female swimmers over 4 laps (L1-L4) in 200-m freestyle events using video-derived 2-dimensional direct linear transformation. For the whole group, speed was greater in L1, with significant decreases across L2, L3, and L4 (1.80 ± 0.10 vs 1.73 ± 0.08; 1.69 ± 0.09; 1.66 ± 0.09  · s-1, P < .05). This variability was attributed to a decrease in stroke length (L2: 2.43 ± 0.19 vs L4: 2.20 ± 0.13 m, P < .05) and an increase in stroke rate (L2: 42.8 ± 2.6 vs L4: 45.4 ± 2.3 stroke · min-1, P < .05). The coefficient of variation and the biological coefficient of variation in speed were greater for male versus female (3.9 ± 0.7 vs 3.1 ± 0.7; 2.9 ± 1.0 vs 2.6 ± 0.7, P < .05) and higher in L1 versus L2 (3.9 ± 1.3 vs 3.1 ± 0.1; 2.9 ± 0.9 vs 2.3 ± 0.7, P < .05). Intra-lap speed values were best represented by a cubic (n = 38), then linear (n = 37) and quadratic model (n = 8). The cubic fit was more frequent for males (43.8%) than females (15.6%), suggesting greater capacity to generate higher acceleration after the turn. The various stroking parameters managements within lap suggest that each swimmer adapts his/her behavior to the race constraints.

A New Qualitative Typology to Classify Treading Water Movement Patterns.

This study proposes a new qualitative typology that can be used to classify learners treading water into different skill-based categories. To establish the typology, 38 participants were videotaped while treading water and their movement patterns were qualitatively analyzed by two experienced biomechanists. 13 sport science students were then asked to classify eight of the original participants after watching a brief tutorial video about how to use the typology. To examine intra-rater consistency, each participant was presented in a random order three times. Generalizability (G) and Decision (D) studies were performed to estimate the importance variance due to rater, occasion, video and the interactions between them, and to determine the reliability of the raters' answers. A typology of five general classes of coordination was defined amongst the original 38 participants. The G-study showed an accurate and reliable assessment of different pattern type, with a percentage of correct classification of 80.1%, an overall Fleiss' Kappa coefficient K = 0.6, and an overall generalizability φ coefficient of 0.99. This study showed that the new typology proposed to characterize the behaviour of individuals treading water was both accurate and highly reliable. Movement pattern classification using the typology might help practitioners distinguish between different skill-based behaviours and potentially guide instruction of key aquatic survival skills. Key pointsTreading water behavioral adaptation can be classified along two dimensions: the type of force created (drag vs lift), and the frequency of the force impulsesBased on these concepts, 9 behavioral types can be identified, providing the basis for a typologyProvided with macroscopic descriptors (movements of the limb relative to the water, and synchronous vs asynchronous movements), analysts can characterize behavioral type accurately and reliably.

Analysing expertise through data mining: an example based on treading water.

A classification system of treading water based on a conceptual typology was first established and then verified empirically. The typology was established on two concepts: the nature of the forces created within the water and the type of inter-limb coordination used. Thirty-eight participants were videotaped while treading water. Multivariate statistics were used to understand how the different behavioural types related to expertise. Three distinct groups of coordination patterns were adopted during treading water. A support vector machine procedure was used as a confirmatory procedure. The data mining process provides a methodological framework to analyse expertise in sports activities, and in this context suggests that a taxonomy can be established among the numerous coordination solutions that allow humans to create stabilising forces in the water.

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.

Climbing skill and complexity of climbing wall design: assessment of jerk as a novel indicator of performance fluency.

This study investigated a new performance indicator to assess climbing fluency (smoothness of the hip trajectory and orientation of a climber using normalized jerk coefficients) to explore effects of practice and hold design on performance. Eight experienced climbers completed four repetitions of two, 10-m high routes with similar difficulty levels, but varying in hold graspability (holds with one edge vs holds with two edges). An inertial measurement unit was attached to the hips of each climber to collect 3D acceleration and 3D orientation data to compute jerk coefficients. Results showed high correlations (r = .99, P < .05) between the normalized jerk coefficient of hip trajectory and orientation. Results showed higher normalized jerk coefficients for the route with two graspable edges, perhaps due to more complex route finding and action regulation behaviors. This effect decreased with practice. Jerk coefficient of hip trajectory and orientation could be a useful indicator of climbing fluency for coaches as its computation takes into account both spatial and temporal parameters (ie, changes in both climbing trajectory and time to travel this trajectory).

Biomechanical analysis of the swim-start: a review.

This review updates the swim-start state of the art from a biomechanical standpoint. We review the contribution of the swim-start to overall swimming performance, the effects of various swim-start strategies, and skill effects across the range of swim-start strategies identified in the literature. The main objective is to determine the techniques to focus on in swimming training in the contemporary context of the sport. The phases leading to key temporal events of the swim-start, like water entry, require adaptations to the swimmer's chosen technique over the course of a performance; we thus define the swim-start as the moment when preparation for take-off begins to the moment when the swimming pattern begins. A secondary objective is to determine the role of adaptive variability as it emerges during the swim-start. Variability is contextualized as having a functional role and operating across multiple levels of analysis: inter-subject (expert versus non-expert), inter-trial or intra-subject (through repetitions of the same movement), and inter-preference (preferred versus non-preferred technique). Regarding skill effects, we assume that swim-start expertise is distinct from swim stroke expertise. Highly skilled swim-starts are distinguished in terms of several factors: reaction time from the start signal to the impulse on the block, including the control and regulation of foot force and foot orientation during take-off; appropriate amount of glide time before leg kicking commences; effective transition from leg kicking to break-out of full swimming with arm stroking; overall maximal leg and arm propulsion and minimal water resistance; and minimized energy expenditure through streamlined body position. Swimmers who are less expert at the swim-start spend more time in this phase and would benefit from training designed to reduce: (i) the time between reaction to the start signal and impulse on the block, and (ii) the time in transition (i.e., between gliding and leg kicking, and between leg-kicking and full swimming). Key pointsSWIMMERS MEET TWO MAIN CONSTRAINTS DURING THE START MOVEMENT: travelling more distance in the air (to get less resistance) and rotate to enter properly in the water.Swim start is a sum of compromises in all parts of it, and swim-start expertise is distinct from swim stroke expertise corresponding to best ways to manage these compromises.Variability found is contextualized as having a functional role and operating across multiple levels of analysis.

Promoting Exploration During Learning: Effect of Imposed and Self-Controlled Practice Schedules on Learners' Behavioral Flexibility.

Purpose: Enriching learners' motor repertoires in a complex pluri-articular task, such as climbing, could help learners' adaptation to various sets of task constraints. Promoting exploration with variable practice conditions is one solution recurrently proposed. However, recent studies have shown that a too elevated exploration-exploitation ratio during practice could impair learning. A proposed solution is to give learners some control over their practice schedule, which appeared to better respect the individual learning dynamic in comparison to the usual experimenter-imposed practice schedule. Thus, the aim of this study is to investigate whether giving learners the possibility of controlling when to confront to new climbing routes would result in greater flexibility in their motor repertoire compared to giving them an imposed schedule of climbing routes or a constant practice condition. Method: Participants were assigned to either a constant practice group (CPG), an imposed-variability group (IVG) or a self-controlled variability group (SVG) to carry out a climbing task. To assess participants' behavioral flexibility, a scanning procedure was conceived by manipulating the route design and the instructions. Results: Participants showed an initial lack of flexibility as they strongly relied on a single coordination pattern. At posttest and retention, the three groups more frequently used a new hand coordination pattern and more often showed coordination patterns associated with high climbing fluency. Results suggest that the individualized rate of exploration in the self-controlled practice condition may have helped the learners improve their flexibility, whereas forcing exploration did not seem more beneficial than constant practice in this complex pluri-articular task.

The effect of experience on the perception of affordances for aperture crossing in cycling.

To ride successfully and safely, cyclists must perceive and act on the affordances that are available in a given situation. This study investigated whether experience in perceiving and acting with respect to a person-plus-object system would influence whether and how a person choses to cross an aperture of different widths, especially in relation to their maximal action capabilities. We also explore whether the distribution of action modes reflects this effect. We examined the performance (i.e., the probability of successfully crossing the aperture) and the decision (i.e., the probability of attempting to cross the aperture) of 8 experienced cyclists and 16 occasional cyclists in an aperture crossing task. In term of performance, experienced cyclists demonstrated greater ability to cross narrower apertures than occasional cyclists, but there were no such differences when aperture width was scaled to maximal action capabilities. In term of decision, both experienced and occasional cyclists tended to over-estimate their abilities, but the experienced cyclists did so to a greater extent. Our findings indicate that experience improves the ability to perform more complex tasks due to utilizing a wider repertoire of actions, but not necessarily the ability to perceive and actualize (action-scaled) affordances.

Effect of breathing conditions on relationships between impairment, breathing laterality and coordination symmetry in elite para swimmers.

The aim was to investigate the effect of breathing conditions and swimming pace on the relationships between the impairment, the breathing laterality and motor coordination symmetry in elite front crawl Para swimmers. Fifteen elite Para swimmers with unilateral physical impairment or with visual impairment and unilateral breathing preference performed eight 25 m using four breathing conditions (every three strokes, every two strokes on preferred and non-preferred breathing side and apnea) at slow and fast paces in a randomized order. Multicamera video system and five sensors have been used to assess arm and leg stroke phases and to compute symmetry of arm coordination (SIIdC) and of leg kick rate (SIKR). Our findings emphasized motor coordination asymmetry whatever the breathing conditions and swimming paces, highlighting the influence of impairment. Multinomial logistic regression exhibited a high probability for motor coordination asymmetry (SIIdC and SIKR) to be present in categories of Para swimmers with impairment and breathing laterality on the same side, suggesting the joined effect of unilateral impairment and unilateral breathing. Moreover, unilateral physical impairment and breathing laterality could also occur on different sides and generate motor coordination asymmetry on different sides and different levels (arms vs. legs). Finally, visual impairment seems amplify the effect of unilateral breathing on motor coordination asymmetry.

Automatic front-crawl temporal phase detection using adaptive filtering of inertial signals.

This study introduces a novel approach for automatic temporal phase detection and inter-arm coordination estimation in front-crawl swimming using inertial measurement units (IMUs). We examined the validity of our method by comparison against a video-based system. Three waterproofed IMUs (composed of 3D accelerometer, 3D gyroscope) were placed on both forearms and the sacrum of the swimmer. We used two underwater video cameras in side and frontal views as our reference system. Two independent operators performed the video analysis. To test our methodology, seven well-trained swimmers performed three 300 m trials in a 50 m indoor pool. Each trial was in a different coordination mode quantified by the index of coordination. We detected different phases of the arm stroke by employing orientation estimation techniques and a new adaptive change detection algorithm on inertial signals. The difference of 0.2 ± 3.9% between our estimation and video-based system in assessment of the index of coordination was comparable to experienced operators' difference (1.1 ± 3.6%). The 95% limits of agreement of the difference between the two systems in estimation of the temporal phases were always less than 7.9% of the cycle duration. The inertial system offers an automatic easy-to-use system with timely feedback for the study of swimming.

Backstroke technical characterization of 11-13 year-old swimmers.

The aim of this study was to characterize the backstroke swimming technique of 11-13 year-old swimmers when performing at very high intensity. A sample of 114 swimmers was divided into four groups regarding maturational and gender effect, who performed 25- m backstroke swimming at 50-m pace. Using two underwater cameras the general biomechanical parameters (speed, stroke rate, stroke length and stroke index), the arm stroke phases and two indexes of arm coordination (Index of Coordination 1, which characterizes the continuity between propulsive phases of each arm and Index of Coordination 2 that evaluates the simultaneity between the beginning of the pull of one arm and of the recovery of the other arm) were measured. Post- pubertal swimmers achieved higher values of speed (1.06 ± 0.14 and 1.18 ± 0.14 m·s(-1) for pubertal and 1.13 ± 0.14 and 1.24 ± 0.12 m·s(-1) for post-pubertal girl and boy swimmers, respectively), stroke length (1.64 ± 0.26 and 1.68 ± 0.25 m·cycle(-1) for pubertal and 1.79 ± 0.22 and 1.75 ± 0.27 m·cycle(-1) for post-pubertal girls and boys, respectively) and stroke index. Regar-ding genders, male were faster than female swimmers. Boys also showed a higher stroke rate and stroke index than girls, who achieved higher results in the ratio between stroke length and arm span. As it was expected, no hand lag time was noticed in young swimmers. Although no differences were noticed between genders, the Index of Coordination 1 was in catch-up mode (-9.89 ± 3.16 and -10.16 ± 3.60 % for girls and -9.77 ± 2.93 and -10.39 ± 2.44 % for boys pubertal and post-pubertal, respectively) and the Index of Coordination 2 was in superposition mode (1.86 ± 4.39 and 2.25 ± 2.25 % from girls and 1.72 ± 2.62 and 1.95 ± 2.95 % for boys, pubertal and post-pubertal, respectively). Key PointsYoung swimmers adopt the catch-up arm coordina-tion when swimming backstroke.These swimmers present lower stroking parameters then those published for older and higher level swimmers.No hand lag time at the thigh was noticed, meaning that young swimmers perform the final phase of their arm cycle without inducing discontinuity be-tween the propulsive actions of the two arms.

Coordination and stroking parameters in the four swimming techniques: a narrative review.

Swimming performances are multifactorial and primarily include anthropometric, hydrodynamic, bioenergetic and biomechanical factors whose contributions depend on age, gender, swimming distance and swimming stroke. An integrative and multivariate approach to swimming captures the complexity and various pathways of performance, but swimming technique is generally examined through such parameters as stroke index, propelling efficiency, stroke length and stroke rate. The first originality of our narrative review is to present the state of art of the methods to collect and measure inter-limb coordination in the four swimming techniques, with a particular focus on the effect of skill. The second part provides readers with an overview of the current findings on the main factors that influence inter-limb coordination (i.e., swimming speed, drag and the manipulation of stroke rate) following a physical approach.