KINESIOLOGICAL FACTORS DETERMINING THE HEIGHT ACHIEVED DURING FLIGHT IN A SPRINGBOARD DIVE

INTRODUCTION: Vertical velocity of the center of mass (COM) and body orientation described by joint angles at the instant of take-off have been suggested as among the most important factors contributing to maximum height of a dive after take-off from a spring-board (Miller, 1980; Sanders & Wilson,1988; Miller & Munro,1984). The present study examined several kinematic and kinetic variables proposed in the literature as potential predictors of diving performance and incorporated them in a model that used multiple regression techniques to predict those variables most directly related to the maximum height achieved during a springboard dive. A secondary purpose of the study was to identify those variables that distinguish between the forward and backward group of dives using techniques of analysis of variance. METHODS: Four (4) divers were filmed using high-speed cinematography (100Hz) while performing simple dives (½ somersault) from the 1m. spring-board. At the same time, the reaction forces between the diver’s foot and the board were recorded (500 Hz) by placing four (4) strain gauges beneath the surface of the board. Nine (9) dives from the four (4) groups were analyzed in total, and kinematic and dynamic variables were derived from the digitized film. RESULTS: The analysis confirmed that almost 90% of the variance in maximum height was explained by the vertical velocity of the COM and the amount of the board’s downward deflection at the instant of take-off. The amount of hip flexion for the forward dives and knee flexion for the backward dives were also highly correlated with the height of the dive. On the other hand, the angle of take-off and the board’s vertical velocity were not significant predictors of height. Forward and backward dives were significantly different (

Posture and gaze tracking of a vertically moving target reveals age-related constraints in visuo-motor coupling

Previously we have demonstrated that the effect of aging on posture and gaze active tracking of a visual target moving in the horizontal direction is dependent on target’s complexity. In this study, we asked whether a similar phenomenon is present when tracking a visual target moving with varying complexity in the vertical direction. Ten young (22.98 ± 2.9 years) and 10 older adults (72.45 ± 4.72 years) tracked for 120 s, a visual target moving vertically by shifting their bodyweight in the anterior-posterior direction. Three target motions were tested: a simple periodic (sine wave), a more complex (Lorenz attractor) and an ultra-complex random (Surrogated Lorenz attractor) pattern. Cross-spectral analysis revealed lower sway-target coherence as a function of age, regardless of target motion’s complexity. This age effect was significant for the sway-target gain but not for the phase index. Gaze-target analysis revealed age related differences only when tracking the more complex targets. Regardless of age, tracking of the complex target was associated with lower cross Approximate Entropy. It is concluded that tracking of visual targets oscillating in the vertical direction reveals age related constraints that are independent of visual motion’s complexity. These constraints are evident in the spatial and not temporal aspects of visuo-motor coupling, which suggests the presence of neuromuscular deficiencies in controlling visually guided postural sway in the anterior-posterior direction

Age induced modifications in the persistency of voluntary sway when actively tracking the complex motion of a visual target

Movement persistency, reflected in systematic cycle to cycle fluctuations of a rhythmical task such as walking or voluntary sway, is compromised with increasing age, making older adults more susceptible to falls. In the present study, we tested whether it is possible to improve rhythmic voluntary sway persistency in old age by actively tracking the complex (i.e. persistent) motion of a visual target. Twenty healthy young and 20 older adults performed 132 cycles of anterior-posterior sway under two conditions: a) self-paced sway and b) sway while tracking the vertical motion of a complex visual target. The persistency of sway cycle amplitude and duration, detected from the center of pressure displacement, was quantified using the Fractal exponent α. We also recorded body kinematics in order to assess the intersegmental coordination that was quantified in the Mean Absolute Relative Phase (MARP) and the Deviation Phase (DPh) between the trunk and the lower limbs. In self-paced sway, older adults showed a lower persistency of cycle duration and a higher MARP and DPh between the trunk and the lower limbs compared to young adults. Tracking the complex visual target motion increased the persistency of cycle amplitude, in young but not in older adults, when compared to the self-paced sway while it decreased the persistency of cycle duration in both groups. The relative phase measures showed a moderate to strong relationship with the persistency of cycle amplitude and duration when older adults swayed in their self-pace. These findings suggest older adults cannot exploit active tracking of the complex visual motion cue to improve voluntary sway persistency. This could be related to the less stable and out of phase intersegmental coordination characterizing rhythmic voluntary sway in old age

Aging affects postural tracking of complex visual motion cues

Postural tracking of visual motion cues improves perception–action coupling in aging, yet the nature of the visual cues to be tracked is critical for the efficacy of such a paradigm. We investigated how well healthy older (72.45 ± 4.72 years) and young (22.98 ± 2.9 years) adults can follow with their gaze and posture horizontally moving visual target cues of different degree of complexity. Participants tracked continuously for 120 s the motion of a visual target (dot) that oscillated in three different patterns: a simple periodic (simulated by a sine), a more complex (simulated by the Lorenz attractor that is deterministic displaying mathematical chaos) and an ultra-complex random (simulated by surrogating the Lorenz attractor) pattern. The degree of coupling between performance (posture and gaze) and the target motion was quantified in the spectral coherence, gain, phase and cross-approximate entropy (cross-ApEn) between signals. Sway–target coherence decreased as a function of target complexity and was lower for the older compared to the young participants when tracking the chaotic target. On the other hand, gaze–target coherence was not affected by either target complexity or age. Yet, a lower cross-ApEn value when tracking the chaotic stimulus motion revealed a more synchronous gaze–target relationship for both age groups. Results suggest limitations in online visuo-motor processing of complex motion cues and a less efficient exploitation of the body sway dynamics with age. Complex visual motion cues may provide a suitable training stimulus to improve visuo-motor integration and restore sway variability in older adults

Swaying to the complex motion of a visual target affects postural sway variability

Background Voluntary shifting body weight in the anteroposterior direction is an important element of daily life activities, such as rising from a chair or initiating a step. In order to accommodate the daily-life challenges of such tasks, voluntary postural sway needs to be flexible and variable. Research question In this study we asked how whole-body tracking of a complex visual target motion with the concurrent provision of feedback modulates the variability of voluntary sway. Methods Twenty young adults (age: 27.10 ± 9.15years, height: 170.73 ± 9.40 cm, mass: 62.84 ± 11.48 kg) performed 132 cycles of voluntary antero-posterior sway, on a force platform, under two conditions: a) self-paced sway and b) swaying while tracking the complex motion of a visual target. Magnitude and temporal structure of variability of postural sway were investigated with the Coefficient of Variance (CoV) and the fractal exponent α, respectively. This analysis was performed for sway cycle duration, amplitude and velocity. The cross-correlation function between the target and sway cycle parameters was computed as a measure of visuo-postural coupling. Results The CoV of sway cycle amplitude, duration and velocity increased during active tracking of the complex target. Fractal exponent α increased for sway cycle amplitude but decreased for cycle duration and remained unchanged for sway velocity. The cross-correlation function revealed a consistent peak at lag+1 indicating an asynchrony between the target and sway cycle duration, while the peak cross-correlation for cycle amplitude was noted at lag 0. Significance Swaying to the complex motion of a visual target improves the variability of sway cycle amplitude, at the cost of cycle duration. This is associated with a more synchronous spatial than temporal coupling to the visual target motion. This knowledge could inform the design of postural tracking paradigms as appropriate exercise interventions, for improving voluntary sway in populations with reduced limits of stability (i.e. older adults)

Power flow analysis as a method to document coordination disabilities observed in Parkinson's disease

The purpose of the present study was to establish the use of the power flow analysis and the subsequent phase breakdown of the movement pattern as an objective and reliable tool to document in detail movement disabilities observed in Parkinson's disease. Movement was reflected in a series of functional phases responsible for detailed muscle function around the joint as the result of the kinematic output.The results revealed the importance of the power flow analysis as a sensitive tool for describing coordination disabilities. Similar muscle phenomena were reflected through the functional movement phases of both ability groups. However, the variability in the number of phases increased as a function of the task complexity. The statistical comparison of selected kinematic and dynamic parameters revealed significantly higher peaks for the able-bodied movement profiles. The analysis also demonstrated that the movement deficiencies observed in Parkinson's Disease cannot simply be attributed to the pure force production by the joint musculature. It seems that there is also a problem in managing and organizing the active and passive forces acting at the joint. (Abstract shortened by UMI.

Patterns of interlimb coordination during asymmetrical reaching movements

The present study investigated the patterns of interlimb organization during the concurrent performance of asymmetrical reaching movements. The inherent tendency towards interlimb synchronization often constrains activities requiring the two limbs to move over different distances or at different movement speeds. The study of bimanual coordination has shown that the amount of interlimb interference during bilateral performance of asymmetrical actions, is regulated according to the magnitude characteristics of the variable used to introduce the asymmetry between the limbs. The purpose of the present study was to examine the relationship between the degree of interlimb decoupling and the magnitude of the asymmetry between the limbs. Asymmetry was systematically manipulated by scaling the magnitude of the interlimb difference in final target distance, during bimanual performance of reaching movements. The degree of interlimb decoupling was reflected in the movement time, muscle activity onset and joint torque relationship between the limbs.Decoupling of the asymmetrical limb movements was effected by an earlier onset of the antagonist muscles in the constrained limb which scaled the amount of muscle torque production and therefore the stiffness of the limb during the acceleration phase of the movement. Thus, the movement amplitude differentiation was achieved by an initial accelarative impulse attributed to the differential control of the muscle torque production at each joint. On the other hand, the interactive forces played a secondary role in the degree of decoupling process. Overall, the degree of decoupling scaled according to the magnitude of the interlimb difference in distance; the greater the asymmetry, the greater the differentiation between the limbs. However, systematic variations of the interlimb asymmetry in distance gave rise to a wide variety of individual decoupling trends. Bimanual practice of the asymmetrical reaching tasks did not result in the development of more independent limb movements. The results of the present study have implications to human factor design and ergonomics

The influence of a rythmical-motor activity program on the development of fundamental motor skills in pre-school children

Influence d'un programme d'activités rythmiques musicales (séance de 45 minutes 3 fois par semaine pendant 8 semaines) sur le développement moteur de fillettes de 4-6 ans : schéma corporel, équilibration statique et dynamique, roulade avant, saut vertical, sautillement, course, frappe du ballon avec le pied, etc

Center of Pressure Feedback Modulates the Entrainment of Voluntary Sway to the Motion of a Visual Target

Visually guided weight shifting is widely employed in balance rehabilitation, but the underlying visuo-motor integration process leading to balance improvement is still unclear. In this study, we investigated the role of center of pressure (CoP) feedback on the entrainment of active voluntary sway to a moving visual target and on sway’s dynamic stability as a function of target predictability. Fifteen young and healthy adult volunteers (height 175 ± 7 cm, body mass 69 ± 12 kg, age 32 ± 5 years) tracked a vertically moving visual target by shifting their body weight antero-posteriorly under two target motion and feedback conditions, namely, predictable and less predictable target motion, with or without visual CoP feedback. Results revealed lower coherence, less gain, and longer phase lag when tracking the less predictable compared to the predictable target motion. Feedback did not affect CoP-target coherence, but feedback removal resulted in greater target overshooting and a shorter phase lag when tracking the less predictable target. These adaptations did not affect the dynamic stability of voluntary sway. It was concluded that CoP feedback improves spatial perception at the cost of time delays, particularly when tracking a less predictable moving target.Peer Reviewe