Arm-leg Coordination Research Articles

Intra- and inter-individual variability in the underwater pull-out technique in 200 m breaststroke turns.

The purpose of the present study was to investigate the intra- and inter-individual variability in arm-leg coordination during the underwater phase of the turn segment in 200 m breaststroke. Thirteen male swimmers were recruited and performed a 200 m breaststroke in a pre-calibrated 25 m pool. Sub-phases during the underwater segment were obtained using a notational analysis, and the mean velocity, displacement and duration during each sub-phase were obtained. A hierarchical cluster analysis (HCA) was performed using the analysed variables in all phases to identify inter-individual variability and random intra-individual variability. In addition, a linear mixed model (LMM: lap as a fixed effect and the participant as a random effect) was conducted to investigate systematic intra-individual variability. HCA identified three coordination patterns that were distinguished by the timing of the dolphin kick relative to the arm pull-out and the duration of the glide with arms at the side. All swimmers except one performed the arm pull-out after the dolphin kick. Nine swimmers maintained one coordination pattern, but other swimmers switched their coordination during the trial, particularly by shortening the duration of the glide with arms at the side. LMM showed a linear decrease (from the first to the last turn) in the time gap between the end of the dolphin kick and the start of the arm pull-out (a glide with the streamlined body position; F = 9.64, p = 0.034) and the glide duration with the arms at the side (F = 11.66, p = 0.015). In conclusion, both inter- and intra-individual variabilities during the underwater phase were evident in 200 m breaststroke turns, which were categorised into three patterns based on the timing of the dolphin kick and the duration of glides.

Arm–leg coordination during the underwater pull-out sequence in the 50, 100 and 200 m breaststroke start

ObjectivesTo investigate the arm–leg coordination from different perspectives of motor control during the underwater start sequence to understand whether differences exist between the three competitive breaststroke swimming events. DesignCross-sectional study. MethodsForty-one breaststroke races (with race times relative to the world record): 50-meter (n = 14, 87.6%), 100-meter (n = 14, 88.5%) and 200-meter (n = 13, 85.4%) were recorded. A race analysis system tracked the two-dimensional displacement of the head. Key points from the underwater start sequence were obtained from notational analysis in order to compute seven time-gaps and four phases to assess the arm–leg coordination and timing of the dolphin kick. A one-way ANOVA with Bonferroni post-hoc correction was used to assess differences between the time gaps and phases for the three events. ResultsDifferences between the three events were found for total underwater glide, and the first (T0) and second (T1) major glide phase. No differences between the events were found in relative duration and distance for the time gaps related to arm–leg coordination (T1–3, T4, T6) and timing of the dolphin kick (T4–5) during the underwater start sequence. ConclusionsThe arm–leg coordination and timing of the dolphin kick showed no difference between the events, but the total underwater glide duration was longer in both the 100- and 200-meter compared with the 50-meter start. This shows that swimmers did not change the complex inter-limb coordination between the competitive events, but only modified the least complex movement, gliding, to adapt to the swimming speed of the respective events.

Visual cues two-steps ahead are adequate to grasp an object while walking without compromising stability.

In our prior studies, participants walked and grasped a dowel using an anticipatory mode of control. However, it is unknown how this combined task would change in a less predictable environment. We investigated the online control aspects involved in the combined task of walking and grasping under different coordination patterns between upper- and lower-limbs in young adults. Fifteen young adults walked and grasped a dowel under several experimental conditions combining the instant of visual cue appearance and coordination pattern of upper and lower limbs used to grasp the dowel. Visual cues provided two steps ahead or earlier were enough for executing the combined task of walking and prehension appropriately. Visual cues provided within this window impacted both walking stability and the execution of the prehension movement. Although an ipsilateral arm-leg coordination pattern increased mediolateral stability, a contralateral pattern significantly decreased mediolateral center of mass stability when the visual cue appeared one-step before grasping the object. These results imply that acquiring information to plan the combined task of walking and reaching for an object two steps ahead allows the maintenance of the general movement characteristics present when the decision to reach out for the object is defined two or more steps ahead. These results indicate that the prehension movement is initiated well before heel contact on that side when given sufficient planning time, but that a disruption of the natural arm-leg coordination dynamics emerges to accomplish the task when the cue is provided one step before the object.

Muscle Synergies and Coherence Networks Reflect Different Modes of Coordination During Walking.

When walking speed is increased, the frequency ratio between the arm and leg swing switches spontaneously from 2:1 to 1:1. We examined whether these switches are accompanied by changes in functional connectivity between multiple muscles. Subjects walked on a treadmill with their arms swinging along their body while kinematics and surface electromyography (EMG) of 26 bilateral muscles across the body were recorded. Walking speed was varied from very slow to normal. We decomposed EMG envelopes and intermuscular coherence spectra using non-negative matrix factorization (NMF), and the resulting modes were combined into multiplex networks and analyzed for their community structure. We found five relevant muscle synergies that significantly differed in activation patterns between 1:1 and 2:1 arm-leg coordination and the transition period between them. The corresponding multiplex network contained a single module indicating pronounced muscle co-activation patterns across the whole body during a gait cycle. NMF of the coherence spectra distinguished three EMG frequency bands: 4–8, 8–22, and 22–60 Hz. The community structure of the multiplex network revealed four modules, which clustered functional and anatomical linked muscles across modes of coordination. Intermuscular coherence at 4–22 Hz between upper and lower body and within the legs was particularly pronounced for 1:1 arm-leg coordination and was diminished when switching between modes of coordination. These findings suggest that the stability of arm-leg coordination is associated with modulations in long-distant neuromuscular connectivity.

Between exploitation and exploration of motor behaviours: unpacking the constraints-led approach to foster nonlinear learning in physical education

ABSTRACTIntroduction: The constraints-led approach (CLA) and more generally a complex systems perspective on motor learning emphasizes the role of perceptual-motor exploration during learning in order to ensure the acquisition of a highly individualized, adapted and adaptable movement pattern. Recent studies have shown that human beings have a strong tendency to exploit already stable patterns rather than looking for new potentially more efficient patterns. In order to shape the amount of exploration, we implemented two learning designs based on a CLA where constraints were used to limit the boundaries of the perceptual-motor workspace of the learners. We sought to highlight how practitioners can play with the perceptual motor workspace boundaries in order to (i) promote the use of exploratory behaviours and (ii) guide the learner towards task-relevant functional areas.Method: For the experiment, twenty-four beginners in breaststroke swimming were allocated to three groups of learning: a control group receiving only the goal of the learning, an analogy group receiving the goal of learning accompanied by an analogy about ‘how to perform’, a pacer group receiving information on the goal of learning and the use of a metronome to continuously push them to ‘perform better’. Based on their assigned group, each learner then followed a learning protocol of 16 sessions with a 10*25 m swimming distance per session with the goal of increasing the stroke length for a fixed swimming speed. Both performance (i.e. stroke length) and motor behaviour (i.e. arm-leg coordination) were collected for each session. The arm-leg coordination patterns were computed by the continuous relative phase between knee and elbow angles. Thereafter, a cluster analysis was performed on the coordination in order to get a qualitative label for every cycle performed during the entire process of learning. Based on the use of cluster analysis, an exploration/exploitation ratio was calculated and the increase in performance was determined based on the increase in stroke length.Results and Discussion: With reference to the exploration/exploitation ratio, our results showed that additional temporary constraints-led learners to increase both the nature of their exploration and also the quantity of their exploration. In the meantime, the three groups showed an equivalent final performance enhancement. The aim of manipulating the constraints was not only to push the learner out of his comfort zone, but also to provide relevant information about ‘where’ to explore during learning. For this purpose, the use of analogy appeared as the most relevant constraint to encourage the emergence of efficient behaviour. Interestingly the impact of the analogy was modified by adding the metronome, showing an interaction effect of both constraints. The group using the metronome exhibited different behaviours as compared to the analogy group and showed an increase in exploration during learning compared to the control group. However, although the metronome constantly pushed the learner to improve performance, it did not actually lead to a better improvement of performance when compared to the analogy group. The simple assumption that the constraints forced the learner to explore therefore does not seem a mandatory condition to promote an exploratory learning. Rather, the qualitative nature of the constraint seems the most relevant characteristic that can be manipulated to promote an exploratory learning by guiding the learner within the perceptual motor workspace.

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact.

Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free) arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating) arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries (“quadrupedal” arm-leg coordination) during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and coordinate steps during walking.

Early manifestation of arm-leg coordination during stepping on a surface in human neonates.

The accomplishment of mature locomotor movements relies upon the integrated coordination of the lower and upper limbs and the trunk. Human adults normally swing their arms and a quadrupedal limb coordination persists during bipedal walking despite a strong corticospinal control of the upper extremities that allows to uncouple this connection during voluntary activities. Here we investigated arm-leg coordination during stepping responses on a surface in human neonates. In eight neonates, we found the overt presence of alternating arm-leg oscillations, the arms moving up and down in alternation with ipsilateral lower limb movements. These neonates moved the diagonal limbs together, and the peak of the arm-to-trunk angle (i.e., maximum vertical excursion of the arm) occurred around the end of the ipsilateral stance phase, as it occurs during typical adult walking. Although episodes of arm-leg coordination were sporadic in our sample of neonates, their presence provides significant evidence for a neural coupling between the upper and lower limbs during early ontogenesis of locomotion in humans.

Changes in kinematics and arm–leg coordination during a 100-m breaststroke swim

ABSTRACTThe purpose of this study was to compare arm–leg coordination and kinematics during 100 m breaststroke in 26 (8 female; 18 male) specialist breaststroke swimmers. Laps were recorded using three 50-Hz underwater cameras. Heart rate and blood lactate were measured pre- and post-swim. Arm–leg coordination was defined using coordination phases describing continuity between recovery and propulsive phases of upper and lower limbs: coordination phase 1 (time between end of leg kick and start of the arm pull phases); and coordination phase 2 (time between end of arm pull and start of leg kick phases). Duration of stroke phases, coordination phases, swim velocity, stroke length (SL), stroke rate (SR) and stroke index (SI) were analysed during the last three strokes of each lap that were unaffected by turning or finishing. Significant changes in velocity, SI and SL (P < 0.05) were found between laps. Both sexes showed significant increase (P < 0.05) in heart rate and blood lactate pre- to post-swim. Males had significantly (P < 0.01) faster swim velocities resulting from longer SLs (P = 0.016) with no difference in SR (P = 0.064). Sex differences in kinematic parameters can be explained by anthropometric differences providing males with increased propelling efficiency.

Kinematic Analysis of Butterfly Swimming

This study aimed to examine the relative phase of the arm and leg movements and the percentage of each of the 4 arm movement phases at three race paces of the butterfly swimming between two levels of swimmers based on the temporal analysis. Eight elite male swimmers and eight club level college male swimmers participated in the study. Two underwater high-speed cameras (200Hz) were set in the transverse and sagittal plane under the water and synchronized to capture one cycle of butterfly stroke movement. The kinematics data were digitized and calculated with the Kwon 3D software. The continuous relative phase was calculated using the normalized time series of the angular displacement and angular velocity of the shoulder and knee joints angles. Macroscopically, one cycle of the arm-leg coordination pattern can be observed between two levels at three race paces in butterfly stroke: a consistent relationship (2:1) exists between two dolphin kicks and one arm stroke in butterfly swimming. The continuous relative phase analyses showed that, in the beginning of the stroke-catch phase, the continuous relative phase was from anti-phase (-180°) to in-phase (50°). For the pull phase, the in-phase relation (±50°) remained unchanged throughout the stage. During the push phase, the relative phase gradually increased toward anti-phase (180°). The percentage of catch, pull, push, and recovery phases were not evenly distributed across one cycle of the butterfly stroke. Especially in elite group, there is a trend of decreasing the percentage of catch phase. In conclusion, these results provide useful information for swimmers as well as coaches to examine the swimming movement of the butterfly stroke.

Neurobiological degeneracy: Supporting stability, flexibility and pluripotentiality in complex motor skill

This paper investigated neurobiological degeneracy of the motor system that emerged as a function of levels of environmental constraint. Fourteen participants performed a breaststroke-swimming task that required them to develop a specific biomechanically expert pattern and in turn provide the basis for a suitable task vehicle to study the functional role of movement variability. Inter-limb coordination was defined based on the computation of continuous relative phase between elbow and knee oscillators. Unsupervised cluster analysis on arm–leg coordination revealed the existence of different patterns of coordination when participants achieved the same task goal under different levels of environmental constraints (i.e. different amounts of forward resistances). In addition, clusters differed in terms of higher order derivatives (e.g., joint angular velocity, joint amplitude), suggesting an effective role for degeneracy in learning by allowing the exploration of the key relationships between motor organization and interacting constraints. There is evidence to suggest that neurobiological degeneracy supports the potential for motor re-organization to enhance motor learning.

Virtual reality game-based therapy for treatment of postural and co-ordination abnormalities secondary to TBI: A pilot study

Primary objective: The study objective was to test the efficacy of game-based virtual reality (VR) therapy as a mean of correcting postural and co-ordination abnormalities in individuals with traumatic brain injury (TBI). Therapy was done with interactive customized VR games and scenarios, utilizing an Xbox Kinect sensor.Research design: The study was a pilot project using the structure of a phase II clinical trial.Methods and procedures: Fifteen participants with mild-to-moderate chronic TBI-related balance and motor co-ordination impairments participated in 15 sessions, each lasting ∼50–55 minutes, scheduled 2–3 times a week over 5–6 consecutive weeks. Participants were evaluated at baseline, immediately after the final session and in a 1-month follow-up with a battery of clinical tests (measuring postural stability, gait and co-ordination) and movement performance parameters. Movement parameters included arm–leg co-ordination, dynamic stability and arm precision, calculated from kinematic data recorded with Xbox Kinect sensor.Results: Following therapy, most participants improved their static and dynamic postural stability, gait and arm movements. These effects persisted over the retention interval.Conclusions: Results will be used to improve the VR program, with the goal of producing a cost-effective, accessible and easy to individualize therapeutic approach. The pilot data will be used for designing a larger scale clinical trial.

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.

Flexible Kinesthetic Distance Perception: When Do Your Arms Tell You How Far You Have Walked?

ABSTRACT Given the flexible organization of locomotion evidenced in the many ways the limbs can be coordinated, the authors explored the potentially correspondingly flexible organization of nonvisual (kinesthetic) distance perception. As kinesthetic distance perception is known to be affected by how the limbs are coordinated, the authors probed the potential perceptual contribution of the arms during locomotion by manipulating arm–leg coordination patterns in blind-walked distance-matching tasks. Whereas manipulation of arm–leg coordination for walking with free-swinging arms had no observable perceptual consequences, comparable manipulation for walking with hiking poles did affect distance matching. These results suggest that under conditions in which the arms act to propel the body (e.g., crawling or stair-climbing) a person's nonvisual sense of movement is conveyed in the coordinated actions of all four limbs.

Intentions, Perceptions and Actions Constrain Functional Intra- and Inter-Individual Variability in the Acquisition of Expertise in Individual Sports

Expertise in sport results from the adaptation of behavoirbehavoir to interacting constraints, individually per-ceived and encountered. With this emphasis on intentionality, perception and action to constrain behavoirbehavoir, the role of movement pattern stability, functional intra-individual and inter-individual performance variability is paramount. Here we illustrate these ideas with reference to two individual performance environments: ice climbing and breaststroke swimming. In ice climbing, compared to beginners, expert climbers exhibited greater levels of variability in upper- and lower-limb coordination patterns, exploring a larger range of limb positions and movement types (ice tool swinging, ice hole hooking). Ice fall properties contain affordances that induced variable motor coordination patterns in expert climbers, whereas learners used a basic and functionally stable motor organization to achieve their main goal of maintaining body equilibrium with respect to gravity. In swimming, while learners organized their limbs to advance in the water, their main intention was to balance, float, breathe, and perceive information. For these reasons they typically adopted one stable (in-phase) mode of arm-leg coordination whatever the swim speed. In contrast, experts harnessed available environmental and organismic constraints (strength, flexibility relative to aquatic resistance and the Archimedes principle) to satisfy a key performance constraint (swim fast). To achieve this aim, they varied the arm-leg coordination mode within a stroke cycle and swim speed. Together these data illustrate how functional performance in sport is predicated on the intertwined rela-tionship between intentions, actions and perceptions of each individual, requiring a blend of stable and variable movement patterns to satisfy changing task constraints.

Coordination between upper- and lower-limb movements is different during overground and treadmill walking

Locomotion studies employ either treadmill (TW) or overground walking (OW), considering that differences between them are negligible. The present study tests this notion by comparing coordination between upper- and lower-limb movements in healthy individuals during OW and TW at matched speeds. Results indicated that TW induced a higher cadence, which highly influenced interlimb coordination, in terms of frequency coupling and relative phase between arm and thigh motion. At low speed, the 2:1 pattern (double arm swing per stride) displayed lower incidence in TW compared to OW, and this was correlated with a lower sagittal acceleration at the shoulders, at twice the stride frequency, in the former condition. The low occurrence of the 2:1 coupling in TW, moreover, was correlated to a preferential adoption of a cadence exceeding 80% of the arm's resonant frequency, whereas higher incidence of this pattern in OW involved a preferential cadence below the 80% threshold. Results indicated also that the relative phase between arm and ipsilateral thigh swinging was smaller in TW, in relation to an earlier occurrence of maximum thigh extension, shortened stance phase, and increased cadence. These findings suggest that arm-leg coordination is different in OW and TW, and that difference can be mainly ascribed to condition-specific setting of central mechanisms for scaling stride frequency, for controlling dynamic axial posture (sagittal shoulder acceleration), and, possibly, for maintaining inter-limb synchrony. Awareness of a different "motor set" in TW and OW is critical if data from the two paradigms are used in physiological and patho-physiological studies.

The coordination of upper and lower limb movements during gait in healthy and stroke individuals

Human walking involves coordinated movements of all four limbs. The benefits of incorporating arm movements in gait rehabilitation are not known and difficult to investigate in patient populations with poor balance and reduced walking capacity. This study assessed the effect of supported (SUP) versus unsupported (UNSUP) arm movements on the coordination patterns present during walking in individuals with and without a stroke. Ten high functioning stroke subjects and 10 healthy subjects walked on a treadmill while swinging their arms naturally, and while holding onto handles that were either fixed in place or allowed to slide along horizontal handrails. Full-body kinematics were recorded, and arm–leg coordination was quantified using relative phase index, mean relative phase, and cross-correlation of hip and shoulder angle time series. No differences were observed in any measures of coordination between healthy and stroke subjects, indicating that the ability to coordinate arm and leg movements during walking remains preserved in high functioning stroke individuals. Coordination patterns were also unaffected by the use of sliding handrails, suggesting that this paradigm may be a suitable surrogate for natural arm movements if individuals are unable to walk without an external support. Stroke subjects were able to perform arm movements at a faster walking speed when using the handles than they were able to achieve without the handles, indicating that this paradigm may be useful in encouraging arm movements during gait rehabilitation.

Arm–leg coordination in recreational and competitive breaststroke swimmers

The aims of this study were to assess the durations of the different arm and leg stroke phases (propulsion, glide, and recovery) and the temporal arm–leg gaps between 12 competitive and 12 recreational breaststroke swimmers. The mean ages and best times for a 50-m breaststroke were, respectively, (recreational: 16.9±1.6y; 49.55±3.38s; competitive: 16.2±1.5y; 33.85±1.96s). Each swimmer was required to swim 2×25-m breaststroke at two different paces (slow and sprint) while being videotaped by two underwater cameras (frontal and lateral views). At the same given speed, recreational swimmers used no glide phase which increased the relative contribution of their recovery and propulsive phases. This was mainly caused by the superposition of their leg extension and the second part of their arm recovery, indicating a technique with no glide time between the arm recovery and the leg extension. In terms of phase duration, the recreational swimmers spent more time in arm recovery and in propulsive phases. Furthermore, it was observed that for a comparable increase of swimming speed (recreational: 23.3%, competitive: 22.6%), competitors switched from a glide to an overlapped coordination while recreational swimmers adopted an overlapped technique whatever the swimming speed. As a result, the relative time spent in propulsive phases did not change in the recreational group, but increased by 27.2% in the competitive one. In a swimming developmental program, particular emphasis should be put on arm–leg coordination drills, when considering the breaststroke.

Differences in spatial-temporal parameters and arm–leg coordination in butterfly stroke as a function of race pace, skill and gender

Spatial-temporal parameters (velocity, stroke rate, stroke length) and arm–leg coordination in the butterfly stroke were studied as a function of race pace, skill (due to technical level, age, and experience) and gender. Forty swimmers (ten elite men, ten elite women, ten less-skilled men, and ten less-skilled women) performed the butterfly stroke at four velocities corresponding to the appropriate paces for the 400-m, 200-m, 100-m, and 50-m, respectively. Arm and leg stroke phases were identified by video analysis and used to calculate four time gaps (T1: the time difference between the start of the arms’ catch phase and the start of the legs’ downward phase of the first leg kick; T2: the time difference between the start of the arms’ pull phase and the start of the legs’ upward phase of the first leg kick; T3: the time difference between the start of the arms’ push phase and the start of the legs’ downward phase of the second leg kick; and T4: the time difference between the start of the arms’ recovery and the start of the legs’ upward phase of the second leg kick) and the total time gap (TTG), i.e., the sum of the four discrete time gaps. These values described the changing coupling of arm to leg actions over an entire stroke cycle. A significant race pace effect indicated that the synchronization between the key motor points of the arms and legs, which determine the starts and ends of the arm and leg stroke phases, increased with pace for all participants. A significant skill effect indicated that the elite swimmers had greater velocity, stroke length, and stroke rate and stronger synchronization of the arm and leg stroke phases than the less-skilled swimmers, due to smaller T2 and T3 and greater T1. A significant gender effect revealed greater velocity and stroke length for the men, and smaller T1 for the less-skilled women. These time gap differences between skill levels were related to the capacity of elite swimmers to assume a more streamlined position of trunk, head and upper limbs during leg actions, adopt a shorter glide and higher stroke rate to overcome great forward resistance, and generate higher forces and use better technique during the arm pull. Thus, coaches are advised to begin monitoring arm–leg coordination earlier in swimmers’ careers to ensure that they attain their highest possible skill levels.

Arm-Leg Coordination in Flat Breaststroke: A Comparative Study Between Elite and Non-Elite Swimmers

The aim of this study was to compare the arm-leg coordination in flat breaststroke among four groups of swimmers (elite males, elite females and non-elite males, non-elite females) of two different competitive levels. Using a velocity-video system, both forward acceleration and deceleration phases of the hip were first identified. Based on these phases, four temporal gaps indicated the time duration between arm and leg actions throughout three race paces (200, 100, and 50 m). For both groups, a velocity increase was combined with an increase of stroke rate, a decrease of stroke length, and an increase of the propulsive phases and a decrease of the glide phases. However, when the relative duration of one stroke cycle was considered, the elite swimmers had significant shorter time of the glide phase than lower competitive level swimmers (18.80 % vs. 31.04 % for females and 11.89 % vs. 19.60 % for males) combined with a longer stroke length (respectively 2.05 m vs. 1.73 m and 2.03 m vs. 1.82 m). Furthermore, the temporal gaps of the elite swimmers showed a greater continuity in the arm and leg actions, which indicates a better timing than non-elite swimmers. It was concluded that elite breaststroke swimmers are able to optimise their propulsion by reducing their glide phase and using a more continuous timing between arm and leg coordination.

Evaluation of arm-leg coordination in flat breaststroke.

This study proposes a new method to evaluate arm-leg coordination in flat breaststroke. Five arm and leg stroke phases were defined with a velocity-video system. Five time gaps quantified the time between arm and leg actions during three paces of a race (200 m, 100 m and 50 m) in 16 top level swimmers. Based on these time gaps, effective glide, effective propulsion, effective leg insweep and effective recovery were used to identify the different stroke phases of the body. A faster pace corresponded to increased stroke rate, decreased stroke length, increased propulsive phases, shorter glide phases, and a shorter T1 time gap, which measured the effective body glide. The top level swimmers showed short time gaps (T2, T3, T4, measuring the timing of arm-leg recoveries), which reflected the continuity in arm and leg actions. The measurement of these time gaps thus provides a pertinent evaluation of swimmers' skill in adapting their arm-leg coordination to biomechanical constraints.