Effects of different pedalling techniques on muscle fatigue and mechanical efficiency during prolonged cycling

The present study aimed to test the influence of the pedalling technique on the occurrence of muscular fatigue and on the energetic demand during prolonged constant-load cycling exercise. Subjects performed two prolonged (45 min) cycling sessions at constant intensity (75% of maximal aerobic power). In a random order, participants cycled either with their preferred technique (PT) during one session or were helped by a visual force-feedback to modify their pedalling pattern during the other one (FB). Index of pedalling effectiveness was significantly (P<0.05) improved during FB (41.4 ± 5.5%); compared with PT (36.6 ± 4.1%). Prolonged cycling induced a significant reduction of maximal power output, which was greater after PT (-15 ± 9%) than after FB (-7 ± 12%). During steady-state FB, vastus lateralis muscle activity was significantly (P<0.05) reduced, whereas biceps femoris muscles activities increased compared with PT. Gross efficiency (GE) did not significantly differ between the two sessions, except during the first 15 min of exercise (FB: 19.0 ± 1.9% vs PT: 20.2 ± 1.9%). Although changes in muscular coordination pattern with feedback did not seem to influence GE, it could be mainly responsible for the reduction of muscle fatigue after prolonged cycling.

Directional constraints during bimanual coordination: the interplay between intrinsic and extrinsic directions as revealed by head motions

The role of directional compatibility was investigated during the production of in-phase and anti-phase coordination patterns involving both arms as well as the head. Our first aim was to compare the quality of coordination between both arms when symmetrical arm posture manipulations were used to disentangle muscle homology from the mutual direction of limb motions in extrinsic space. Findings revealed that in-phase coordination, characterized by the simultaneous activation of homologous muscle groups, was resistant to posture manipulations. Conversely, during anti-phase coordination, the influence of extrinsic direction became more prevalent whereby isodirectionality in extrinsic space contributed to stabilization of anti-phase coordination patterns. The second aim was to study the effect of periodic head movements upon the assembling of a coordinative synergy among the body segments. The findings demonstrated that the in-phase patterns were hardly affected by directionality of head motion. Conversely, the anti-phase patterns were more vulnerable to the directional influence of head movements, showing less accurate and stable coordination during non-isodirectional than isodirectional head motions. These observations underscore the robust nature of coordination patterns based on muscle homology, even in the absence of symmetric arm positions. Moreover, isodirectional head movements became easily integrated with the overall coordination pattern, whereas head-limb coupling was poor when the head moved anti-directional with the limbs.

Neuromuscular and spatial constraints on bimanual hand-held pendulum oscillations: dissociation or combination?

The present work investigated the effects of spatial and neuromuscular constraints on the mean states and variability of interlimb coordination patterns performed in the para-sagittal plane of motion in a hand-held pendulum oscillation task. Nine right-handed students had to oscillate two pendulums through wrist adduction-abduction movements. Relative movement direction was manipulated by asking participants to perform both isodirectional and non-isodirectional movements. Participants were required to grab the pendulums either with both forearms in the same neutral or supine posture or with one forearm in neutral while the other one was in prone-inversed position. When both forearms were in a similar posture, isodirectional movements were generated predominantly by simultaneous activation of homologous muscle groups whereas non-isodirectional movements mainly resulted from simultaneous activation of non-homologous muscle groups. When forearms were in dissimilar posture, isodirectional movements were generated predominantly by the simultaneous activation of non-homologous muscle groups whereas non-isodirectional movements mainly resulted from simultaneous activation of homologous muscle groups. Standard deviation of relative phase and absolute error of relative phase were analyzed for each forearm posture condition. We hypothesized that neuromuscular and spatial constraints would affect two different aspects of coordination performance, i.e., pattern stability and accuracy, respectively. Comparison of the results obtained for similar and dissimilar postures suggested that changes of pattern stability were mediated by changes in the nature of the muscle activation patterns that gave rise to wrist movement in each condition. On the other hand, the results also showed that movement direction exclusively affected phase shift. The findings are consistent with the conclusion of Park et al. [Park, H., Collins, D. R., & Turvey, M. T. (2001). Dissociation of muscular and spatial constraints on patterns of interlimb coordination. Journal of Experimental Psychology: Human Perception and Performance, 27, 32-47.] that neuromuscular constraints affect variability of relative phase (attractor strength) and spatial constraints affect the shift of relative phase (attractor location).

Symmetry Constraints Mediate the Learning and Transfer of Bimanual Coordination Patterns Across Planes of Motion

The authors investigated whether neuromuscular and directional constraints are dissociable limitations that affect learning and transfer of a bimanual coordination pattern. Participants (N = 9) practiced a 45 degrees muscular relative phasing pattern in the transverse plane over 4 days. The corresponding to-be-learned spatial relative phasing was 225 degrees. Before, during, and following practice, the authors administered probe tests in the sagittal plane to assess transfer of learning. In the probe tests, participants performed various patterns characterized by different muscular and spatial relative phasing (45 degrees, 45 degrees, 45 degrees, 225 degrees, 225 degrees, 45 degrees, and 225 degrees, 225 degrees). The acquisition of the to-be-learned pattern in the transverse plane resulted in spontaneous positive transfer of learning only to coordination patterns having 45 degrees of spatial relative phase, irrespective of muscular phasing. Moreover, transfer occurred in the sagittal plane to coordination patterns that had symmetry properties similar to those of the to-be-learned pattern. The authors conclude that learning and transfer of spatial features of coordination patterns from the transverse to the sagittal plane of motion are mediated by mirror-symmetry constraints.

The coalition of constraints during coordination of the ipsilateral and heterolateral limbs

Previous work on the coordination between the upper and lower limbs has invariably shown that its accuracy/stability is primarily determined by the mutual direction between limbs in extrinsic space and not by muscle relationships. Here we show that muscle grouping does play a critical role in coordination of the arm and leg, in addition to direction. More specifically, the simultaneous activation of isofunctional muscles and/or limb movements proceeding in the same direction, results in more successful performance than the alternated activation of isofunctional muscles and/or movements occurring in different directions. In the absence of isofunctional muscle coupling, the mutual direction between the limbs plays a more prominent role in determining coordinative accuracy. These coordination constraints can largely account for the observed differences between ipsilateral and heterolateral limb coordination. The findings are discussed in view of the coalition of coordination constraints.

Effects of attentional prioritisation on the temporal and spatial components of an interlimb circle-drawing task

This study aimed to examine the effects of directing attention to the spatial dimension of the circle-drawing task on interlimb coordination patterns across limbs. Eighteen participants performed a circle-drawing task involving in-phase and antiphase coordination modes under upper limb, contralateral and ipsilateral limb combinations. Results indicated that (a) coordination pattern stability co-varied with central cost when attentional focus was directed to the spatial dimensions of the interlimb circle-drawing task; (b) attentional focus on the spatial components modified the inherent performance asymmetries between the limbs; (c) finally, attention to the spatial components of the interlimb circle-drawing task modulated movement trajectories and at the same time the stability of temporal coordination.

The effect of visuo-motor transformations on hand-foot coordination: evidence in favor of the incongruency hypothesis

Understanding how multiple constraints contribute to the emergence of coordinated behavior has been the topic of considerable debate in cognitive sciences. The present experiment addressed the issue of the effects of visual motion structures (iso- and non-isodirectionality) on the stability of hand-foot coordination patterns. Visuo-motor transformations--decorrelating the perceived movement direction from the actually generated direction--were applied to both in-phase and anti-phase patterns. Two mutually exclusive hypotheses--the "visual grouping hypothesis" and the "incongruency hypothesis"--were tested. The results indicated that both conditions of transformed visual feedback destabilized the actual performed coordination patterns. Thus, despite the existence of common underlying principles that govern both the perceived motion pattern and the generation of hand-foot coordination patterns, it appeared that perceptual grouping principles were not exploited to monitor the production of coordination. These results strongly suggest that the congruency between the performed pattern and the perceived visual feedback is the primary factor determining the (in)stability of hand-foot coordination patterns.

Interlimb coordination: real constraints and false dichotomies

Despite the recent advances in the field of coordination dynamics addressing the interplay of constraints of different natures in the emergence of human coordination, F. Mechsner (2004) invites us to revive hierarchical and dichotomous thinking b y offering again his exclusive position that coordinated movements are (purely) perceptual-cognitive/psychological in nature. In this comment, the authors address a number of theoretical and methodological issues that might potentially puzzle the readers of Mechsner's article. They contend that the dichotomy proposed by Mechsner (i.e., perceptual-cognitive vs. motor) constitutes a restrictive framework for understanding human coordination.

Interaction of neuromuscular, spatial and visual constraints on hand-foot coordination dynamics

In the present study, we investigated the contributions of motor and perceptual processes to directional constraints as observed during hand-foot coordination. Participants performed cyclical flexion-extension movements of the right hand and foot under two coordination modes: in-phase (isodirectional) and antiphase (non-isodirectional). Those tasks were performed either with full vision or no vision of the limbs. Depending on the position of the forearm (prone or supine), the coordination patterns were performed with similar and dissimilar neuro-muscular coupling with respect to their phylogenetic origin as antigravity muscles. Results showed that the antiphase pattern was more difficult to maintain than the in-phase pattern and that neuro-muscular coupling significantly influenced the coordination dynamics. Moreover, the effect of vision differed as a function of both neuro-muscular coupling and coordination mode. Under dissimilar neuro-muscular coupling, the presence of visual feedback stabilized the in-phase pattern and destabilized the antiphase pattern. In contrast, visual feedback did not influence pattern stability during conditions of similar neuro-muscular coupling. These results shed light on the complex interactions between motor and perceptual (visual) constraints during the production of hand-foot coordination patterns.

Attentional costs of coordinating homologous and non-homologous limbs

This study aimed to examine the attentional demands of coordinating movement patterns across limbs. Eighteen participants performed a circle drawing task involving in-phase and anti-phase coordination modes under homologous, contralateral and ipsilateral limb combinations. Results indicated that: (a) attentional focus further stabilised coordination patterns with a cost at the central level; (b) there was an inverse relationship between stability and probe reaction time (RT) for all coordination patterns, that is the stronger the coupling between the limbs the lower the central cost. Overall, the results support previous research suggesting that attention plays an important role in sustaining coordination pattern stability and that the co-variation between coordination stability and central cost can also be extended to coordination across limbs.

Dynamics of learning and transfer of muscular and spatial relative phase in bimanual coordination: evidence for abstract directional codes

The present study addressed whether the timing of muscle activation and the relative direction of limb movements are dissociable constraints that may affect learning and transfer of bimanual coordination patterns, either independently or in combination. Subjects were assigned to two experimental groups in which the to-be-learned muscular phasing (135 degrees ) was either practiced with 45 degrees (i.e., predominantly isodirectional) or 135 degrees (i.e., predominantly nonisodirectional) of spatial relative phase (RP) across 2 days of practice. Prior to, during, and following practice, probe tests were held in which various relative phasing patterns were administered to assess transfer of learning. Converging evidence was obtained that the relative direction of moving limbs prominently constrained transfer of learning rather than muscular relationships. Acquisition of a specific pattern resulted in spontaneous positive transfer of learning to a new coordination pattern having the same spatial RP but not to a pattern with a different spatial RP, irrespective of muscular phasing relationships. In summary, the present results suggest that learning and transfer of coordination patterns is mediated by abstract directional codes that become part of the memory representation for bimanual coordination.

Interaction of directional, neuromuscular and egocentric constraints on the stability of preferred bimanual coordination patterns

We investigated how the relative direction of limb movements in external space (iso- and non-isodirectionality), muscular constraints (the relative timing of homologous muscle activation) and the egocentric frame of reference (moving simultaneously toward/away the longitudinal axis of the body) contribute to the stability of coordinated movements. In the first experiment, we attempted to determine the respective stability of isodirectional and non-isodirectional movements in between-persons coordination. In a second experiment, we determined the effect of the relative direction in external space, and of muscular constraints, on pattern stability during a within-person bimanual coordination task. In the third experiment we dissociated the effects on pattern stability of the muscular constraints, relative direction and egocentric frame of reference. The results showed that (1) simultaneous activation of homologous muscles resulted in more stable performance than simultaneous activation of non-homologous muscles during within-subject coordination, and that (2) isodirectional movements were more stable than non-isodirectional movements during between-persons coordination, confirming the role of the relative direction of the moving limbs in the stability of bimanual coordination. Moreover, the egocentric constraint was to some extent found distinguishable from the effect of the relative direction of the moving limbs in external space, and from the effect of the relative timing of muscle activation. In summary, the present study showed that relative direction of the moving limbs in external space and muscular constraints may interact either to stabilize or destabilize coordination patterns.

Attentional demands reflect learning-induced alterations of bimanual coordination dynamics

This study aimed to investigate the effects of practice on bimanual coordination dynamics and attentional demands. Participants were asked to perform a dual-task associating a cyclic antiphase bimanual pattern and a discrete reaction time task. A pretest determined each individual critical transition frequency. In the training session, participants practised 120 trials. They were instructed to maintain the antiphase coordination pattern at the critical transition frequency. The training session was interrupted and followed by an intermediate test (after 60 trials) and a post-test (30 min after 120 trials), respectively. A retention test was performed 7 days after the end of the training session. Results showed that: (i) the number of transitions decreased as a consequence of practice; and (ii), subjects were able to maintain the antiphase pattern at a higher frequency than in the pretest. Analysis of the trade-off between relative phase variability and reaction time showed that participants were able to maintain a higher level of stability at the same (intermediate and post-test) or a lower attentional cost (retention test). These findings show that phase transition dynamics and pattern stability can be significantly modified as a result of practice. Changes in the trade-off between pattern stability and cost with learning confirm that the attentional cost incurred by the central nervous system to maintain pattern stability decreased with practice. In line with recent neurobiological studies, the present study provides new insights regarding relationships between brain processes, attentional demands and coordinated behaviour in learning bimanual patterns.

A dynamic pattern analysis of coordination between breathing and rhythmic arm movements in humans

We investigated the behavioral dynamics of human breathing-wrist movement coordination in a 1:1 frequency locking task. A pronation-supination wrist movement and a short trial duration were chosen to limit both mechanical and metabolic constraints on the respiratory system. Subjects voluntarily controlled their breathing rhythm to follow the metronome. We found that pronation-expiration and pronation-inspiration patterns coexisted as the (sole) stable fixed-point attractors of the coordination system. The pronation-expiration pattern was more stable than the pronation-inspiration pattern. Depending on the oscillation frequency, this differential stability gave rise to both absolute and relative coordination. These results show that simple behavioral laws of coordination encapsulate neural coupling dynamics evidenced from experimental research in human beings and animals. They challenge the classical view that such a coupling is not present for all imposed movement frequencies. Rather, relative coordination emerges as a result of the modification of coupling strength with frequency. These results can be accommodated by the asymmetric version of the HKB model of coordination dynamics. Thus, our data suggest that the principles and models of coordination dynamics may be taken as a reference to study the coupling of the motor and physiological subsystems involved in breathing-movement coordination.

A dynamical framework to understand performance trade-offs and interference in dual tasks

This study demonstrated that the dynamic pattern approach may reconcile resource and outcome conflict theories to explain performance in dual tasks. Participants performed a bimanual coordination task and a reaction time task with different conditions of attentional priority. Results showed a trade-off between pattern variability and reaction time when priority was given to the coordination task. Such a trade-off was indicative of resource allocation. An analysis of perturbation in the bimanual coordination revealed interference, a reputed sign of outcome conflict. Moreover, interference diminished substantially when priority was given to the bimanual task. The coexistence of performance trade-off and outcome conflict suggests that these two phenomena are not mutually exclusive. Rather, both may follow from modifying the coupling between the limbs through attention.

Shared dynamics of attentional cost and pattern stability

This paper examines the informational activity devoted by the CNS to couple oscillating limbs in order to sustain and stabilize bimanual coordination patterns. Through a double-task paradigm associating a bimanual coordination task and a reaction time (RT) task, we investigated the relation between the stability of preferred bimanual coordination patterns and the central cost expended by the CNS for their stabilization. Ten participants performed in-phase and anti-phase coordination patterns in a dual task condition (coordination + RT) at several frequencies (0.5, 0.75, 1.0, 1.5, and 2.0 Hz), thereby decreasing the stability of the bimanual patterns. Results showed a U-shaped evolution of pattern stability and attentional cost, as a function of oscillation frequency, exhibiting a minimum value at the same frequency. These findings indicate that central cost and pattern stability covary and may share common, high order dynamics. Moreover, the attentional focus given to the bimanual coordination and the RT task was also manipulated by requiring either shared attention or priority to the coordination task. Such a manipulation led to a tradeoff between pattern stability and RT performance: The more stable the pattern, the more costly it is to stabilize. This suggests that stabilizing a coordination pattern incurs a central cost that depends on its intrinsic stability. Conceptual consequences of these results for understanding the relationship between attention and coordination are drawn, and the mechanisms putatively at work in dual tasks are discussed.

Interplay of biomechanical and neuromuscular constraints on pattern stability and attentional demands in a bimanual coordination task in human subjects

Recent debate has focused upon the issue of whether general principles and laws of movement coordination may be derived without reference to anatomical, mechanical and physiological mechanisms. It has been proposed that self-generated movement involves the interaction of biomechanical and neuromuscular constraints. Biomechanical constraints are usually considered of as arising from the pendular dimensions of the limb or limb segments whereas neuromuscular constraints are commonly associated with nervous and metabolic control processes. The present study aims to investigate the interplay between these two different constraints on bimanual pattern stability and attentional demands. Five subjects were asked to execute an anti-phase coordination pattern (180 degrees of relative phase), while gradually increasing the frequency of oscillation and changing the rotational inertia of the joysticks. Frequency manipulation was expected to affect the neuromuscular constraints. Inertial manipulation was expected to affect biomechanical constraints. Attentional demands, reflecting the central cost associated with the maintenance of the coordination pattern was assessed using a dual-task paradigm. The results showed that: (1) increasing the oscillation frequency altered both coordination dynamics and attentional demands associated with the maintenance of bimanual coordination patterns; (2) manipulation of rotational inertia of the joysticks also altered pattern stability (standard deviation of relative phase) and coordination dynamics (i.e. the number of phase transition and the before transition), but these alterations were not paralleled by a change in attentional demands.

Effects of attention on phase transitions between bimanual coordination patterns: a behavioral and cost analysis in humans

The present study aimed to obtain a behavioral analysis of the effects of attentional focus on the dynamics of phase transitions in bimanual coordination and to evaluate the central cost expended by the central nervous system to maintain and stabilize such coordination patterns before and after the transition. Eight subjects were asked to execute an anti-phase coordination pattern (180 degrees of relative phase), while gradually increasing the frequency of oscillation. The central cost was assessed using a dual-task paradigm associating the bimanual coordination task with a reaction time task. Results showed that: (1) the transition process was significantly altered by focusing attention on the bimanual coordination task; and (2) the cost involved in sustaining the bimanual patterns was determined by their coordination dynamics.

Evidence Supporting the Importance of Peripheral Visual Information for the Directional Control of Aiming Movement

The focus of the present study was on determining whether the high level of directional accuracy found in aiming studies in which the subjects can see their hand in the visual periphery supports the existence of a kinetic visual channel or, rather, the advantage of binocular over monocular vision for movement directional control. The limits of this kinetic visual channel were also explored. The results of the 1st experiment indicated that seeing one's hand in the visual periphery is sufficient to ensure optimal directional aiming accuracy. Further, no differences in aiming accuracy were noted between monocular and binocular vision. These results supported the existence of a visual kinetic channel. In the 2nd experiment, whether this kinetic visual channel would operate with movements slower (55°/s) than those usually used in studies that had proved its existence (over 110°/s) was determined. The results indicated that this visual kinetic channel was operative even at relatively slow movement velocities. Central vision of the hand seemed to be used for on-line directional control of relatively slow movements.

Afferent Information for Motor Control: The Role of Visual Information in Different Portions of the Movement

The question addressed in the present study was whether subjects (N = 24) can use visual information about their hand, in the first half of an aiming movement, to ensure optimal directional accuracy of their aiming movements. Four groups of subjects practiced an aiming task in either a complete vision condition, a no-vision condition, or in a condition in which their hand was visible for the first half [initial vision condition (IV)] or the second half of the movement [final vision condition (FV)]. Following 240 trials of acquisition, all subjects were submitted to a transfer test that consisted of 40 trials performed in a no-vision condition. The results indicated that seeing the hand early in movement did not help subjects to optimize either directional or amplitude accuracy. On the other hand, when subjects viewed their hand closer to the target, movements resulted that were as accurate as those performed under a complete vision condition. In transfer, withdrawing vision did not cause any increase in aiming error for the IV or the no-vision conditions. These results replicated those of Carlton (1981) and extended those of Bard and colleagues (Bard, Hay, & Fleury, 1985) in that they indicated that the kinetic visual channel hypothesized by Paillard (1980; Paillard & Amblard, 1985) appeared to be inoperative beyond 40deg of visual angle.

Combined Effects of Movement Velocity and Duration on Programming Time: Spijkers (1989) Revisited

The goal of the present study was to determine the combined effects of movement velocity and duration on motor programming. Subjects were submitted to a two-choice reaction time task that could be completed by aiming movements differing in the mean velocity at which they were to be produced as well as by their movement time. The results of the present study indicate that, in each pair of responses used, the responses having the higher mean velocity were initiated faster that those having the lower mean velocity. Contrary to Spijkers' (1989) study, the different movement time pairings did not modify the effect of movement velocity on response programming time. Moreover, the same pattern of results was observed whether or not the subjects were permitted to visually guide their ongoing movement. Thus, Spijkers' proposition, that the type of control one may use to guide an aiming movement needs to be determined before movement initiation can take place, was not confirmed.