D Mottet

Publications of D Mottet

• Effects of active vs. passive recovery on repeated rugby-specific exercises.

  Authors: A Jougla, J P Micallef, D Mottet

  Journal of science and medicine in sport / Sports Medicine Australia. 07/2009;

  The aim of this study was to determine the effects of active vs. passive recovery on performance of a rugby-specific intermittent test in rugby union players. Seven male rugby players (20.6+/-0.5The aim of this study was to determine the effects of active vs. passive recovery on performance of a rugby-specific intermittent test in rugby union players. Seven male rugby players (20.6+/-0.5 yrs; 181.9+/-10.0cm; 94.5+/-12.8kg) performed in random order, over two separate sessions, a specific repeated-sprint rugby test, the Narbonne test (6x4 consecutive actions: 1, scrummaging; 2, agility sprinting; 3, tackling; 4, straight sprinting) with 30s of passive or active recovery (running at 50% of maximal aerobic speed). The Narbonne tests were completed before (pre-test) and after (post-test) a 30-min rugby match. During the Narbonne test, scrum forces, agility and sprint times, heart rate and rate of perceived exertion were measured. Scrum forces were lower in active (74.9+/-13.4kg) than in passive recovery (90.4+/-20.9kg), only during the post-test (p<0.05). Fatigue index (%) (p<0.05) and total sprint time (s) (p<0.01) were significantly greater in active than in passive recovery, both during the pre-test (11.5+/-5.7% vs. 6.7+/-4.5% and 18.1+/-1.3s vs. 16.9+/-0.9s) and the post-test (7.3+/-3.3% vs. 4.3+/-1.5% and 18.3+/-1.6s vs. 16.9+/-1.1s). Consequently, the results indicated that passive recovery enabled better performance during the Narbonne test. However, it is obviously impractical to suggest that players should stand still during and following repeated-sprint bouts: the players have to move to ensure they have taken an optimal position.

• Rehabilitation of arm function after stroke. Literature review.

  Authors: L Oujamaa, I Relave, J Froger, D Mottet, J-Y Pelissier

  Annals of physical and rehabilitation medicine. 04/2009;

  INTRODUCTION: In the recent literature we can find many articles dealing with upper extremity rehabilitation in stroke patients. New techniques, still under evaluation, are becoming the practicalINTRODUCTION: In the recent literature we can find many articles dealing with upper extremity rehabilitation in stroke patients. New techniques, still under evaluation, are becoming the practical applications for the concept of post-stroke brain plasticity. METHODS: This literature review focuses on controlled randomized studies, reviews and meta-analyses published in the English language from 2004 to 2008. The research was conducted in MEDLINE with the following keywords: "upper limb", "stroke", "rehabilitation". RESULTS: We reviewed 66 studies. The main therapeutic strategies are: activation of the ipsilesional motor cortex, inhibition of the contralesional motor cortex and modulation of the sensory afferents. Keeping a cortical representation of the upper limb distal extremity could prevent the learned non-use phenomenon. The modulation of sensory afferents is then proposed: distal cutaneous electrostimulation, anesthesia of the healthy limb, mirror therapy, virtual reality. Intensifying the rehabilitation care means increasing the total hours of rehabilitation dedicated to the paretic limb (proprioceptive stimulation and repetitive movements). This specific rehabilitation is facilitated by robot-aided therapy in the active-assisted mode, neuromuscular electrostimulation and bilateral task training. Intensifying the rehabilitation training program significantly improves the arm function outcome when performed during subacute stroke rehabilitation (< six months). Ipsilesional neurostimulation as well as mental practice optimize the effect of repetitive gestures for slight motor impairments. Contralesional neurostimulation or anesthesia of the healthy hand both improve the paretic hand's dexterity via a decrease of the transcallosal inhibition. This pathophysiological mechanism could also explain the positive impact of constraint-induced movement therapy (CI therapy) in an environmental setting for chronic stroke patients. CONCLUSION: To ensure a positive functional outcome, stroke rehabilitation programs are based on task-oriented repetitive training. This literature review shows that exercising the hemiparetic hand and wrist is essential in all stages of a stroke rehabilitation program. New data stemming from neurosciences suggest that ipsilesional corticospinal excitability should be a priority.

• Non-linear analyses of heart rate variability during heavy exercise and recovery in cyclists.

  Authors: J-F Casties, D Mottet, D Le Gallais

  International journal of sports medicine. 11/2006; 27(10):780-5.

  We investigated the time course of RR interval variability during exercise and subsequent 50 minutes of recovery in seven well-trained male cyclists who performed an exercise with 3 successive 8 minWe investigated the time course of RR interval variability during exercise and subsequent 50 minutes of recovery in seven well-trained male cyclists who performed an exercise with 3 successive 8 min stages at 40 %, 70 % and 90 % of their maximal oxygen uptake. The goal of the study was to check whether the decrease in the amplitude of heart rate variability during heavy exercise was accompanied by changes in the chaotic structure of the fluctuations. Heart rate variability was analysed in the temporal and frequency domain using traditional tools and using non-linear methods (Largest Lyapunov Exponent, Detrended Fluctuation Analysis, Minimum Embedding Dimension). When compared to rest, variability at the heaviest exercise intensity was significantly lower (RR: 0.94 +/- 0.22 vs. 0.34 +/- 0.01 ms; SDRR: 0.11 +/- 0.04 vs. 0.01 +/- 0.00 ms) due to a decrease in both LF (2101 +/- 1450 vs. 0.14 +/- 0.09 ms (2) . Hz (-1)) and HF spectral energy (1148 +/- 1126 vs. 7.88 +/- 9.24 ms (2) . Hz (-1)). Non-linear analyses showed that heart rate variability remained chaotic whatever the exercise intensity (the largest Lyapunov exponent was positive at 90 % of the maximal oxygen uptake), with a fractal organisation that tended towards white noise (DFA value close to 0.5) during heavy exercise. During recovery, temporal and spectral variables came back to their rest values within about 30 minutes following an exponential pattern. Non-linear analyses revealed that heartbeat dynamics were disorganised at the beginning of recovery, and involved more regulating systems than at rest, even after 50 minutes of recovery. We concluded that, during heavy exercise, heart rate variability was mainly influenced by other factors than autonomous nervous system, and suggest that mechanical or neurological couplings between the cardiac, locomotor and respiratory systems could play an important part in the observed changes.

• Two-handed performance of a rhythmical fitts task by individuals and dyads.

  Authors: D Mottet, Y Guiard, T Ferrand, R J Bootsma

  Journal of experimental psychology. Human perception and performance. 01/2002; 27(6):1275-86.

  The authors investigated 4 variants of a reciprocal Fitts task in which the pointer was moved to a stationary target, the target was moved to a stationary pointer, or both the pointer and the targetThe authors investigated 4 variants of a reciprocal Fitts task in which the pointer was moved to a stationary target, the target was moved to a stationary pointer, or both the pointer and the target were moved to each other bimanually; the bimanual task was carried out either by a single person or by a dyad. Fitts's law held in all 4 conditions, with only minor parametric changes. The kinematic organization varied with task difficulty but remained invariant in task space (i.e., in the mutual frame of reference of the pointer-target system) whatever the pointing condition. In the bimanual conditions, the 2 effectors were coordinated in antiphase with compensatory variability. The authors suggest that the observed chronometric and kinematic patterns emerge from an interplay between simple harmonic motion and the stabilizing influence of the informational flow generated by the closing of the gap between the pointer and the target interval.

• The dynamics of rhythmical aiming in 2D task space: relation between geometry and kinematics under examination.

  Authors: D Mottet, R J Bootsma

  Human movement science. 07/2001; 20(3):213-41.

  We explored a two-dimensional task space variant of the classical rhythmical Fitts' task in which participants were asked to sequentially cross four targets arranged around the extreme points of theWe explored a two-dimensional task space variant of the classical rhythmical Fitts' task in which participants were asked to sequentially cross four targets arranged around the extreme points of the major axes of an ellipse. Fitts' law was found to adequately describe the changes in movement time with the variations in task difficulty (ID), but the 1/3 power-law relating curvature and tangential velocity of the trajectory did not resist the increase in ID. Kinematic analyses showed that the behavioral adaptation to the ID resulted in an increase in the contribution of non-linear terms to the kinematics along the two axes of task space. Moreover, a limit cycle model (combining Rayleigh damping and Duffing stiffness, as in one-dimensional Fitts' task) captured such a behavior. In such a context, Fitts' law and the 1/3 power law appear as surface relations that emerge from parametric changes in a dynamical structure that captures the nature of Fitts' task.

• The dynamics of human isometric pointing movements under varying accuracy requirements.

  Authors: M Billon, R J Bootsma, D Mottet

  Neuroscience letters. 06/2000; 286(1):49-52.

  The goal of the present study was to explore the relation between speed-accuracy trade-off phenomena and action kinematics in the case of pointing under isometric conditions. Increasing taskThe goal of the present study was to explore the relation between speed-accuracy trade-off phenomena and action kinematics in the case of pointing under isometric conditions. Increasing task difficulty resulted in a linear increase in movement time (as predicted by Fitts' law) and in systematic changes in the spatio-temporal patterning of force production. The observed changes in motion topology were similar to those reported for isotonic tasks and adequately captured by a limit cycle model derived for the latter type of task. These results indicate that, for isometric force control as for isotonic position control, the reasons underlying the emergence of Fitts' law might be sought in dynamic trajectory formation processes.

• The dynamics of goal-directed rhythmical aiming.

  Authors: D Mottet, R J Bootsma

  Biological cybernetics. 05/1999; 80(4):235-45.

  Based on the kinematics of goal-directed aiming movements in a reciprocal Fitts' task, a minimal limit cycle model is proposed that is capable of producing the behavior observed at levels of taskBased on the kinematics of goal-directed aiming movements in a reciprocal Fitts' task, a minimal limit cycle model is proposed that is capable of producing the behavior observed at levels of task difficulty ranging from 3 to 7. From graphical and statistical analyses of the phase planes, Hooke's planes and velocity profiles, we concluded that the minimal terms to be included in the model were (i) a nonlinear damping in the form of a self-sustaining, velocity-driven Rayleigh oscillator and (ii) a nonlinear stiffness in the form of a softening spring Duffing term. The model reproduced the kinematic patterns experimentally observed in rhythmical precision aiming, accounting for 95% of the variance. The coefficients in the model changed in a systematic way when distance and precision constraints were varied, and the meaning of these changes is discussed in the framework of the dynamical patterns approach.

• Trajectory formation and speed-accuracy trade-off in aiming movements.

  Authors: R J Bootsma, D Mottet, F T Zaal

  Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie. 06/1998; 321(5):377-83.

  The trade-off between speed and accuracy and the patterning of movement kinematics have been central issues for theories of human movement for almost a century. In the present contributionThe trade-off between speed and accuracy and the patterning of movement kinematics have been central issues for theories of human movement for almost a century. In the present contribution experimentally obtained kinematics of reciprocal aiming movements, performed under different task conditions, are modelled as resulting from a single non-linear dynamical system whose parameters vary so as to respond to the task demands. Providing a unified account of speed-accuracy trade-off and trajectory formation phenomena, the model offers a theoretical framework in which both discrete and continuous movements, performed along one or more dimensions can be understood.

• Energy cost and stride duration variability at preferred transition gait speed between walking and running.

  Authors: J Brisswalter, D Mottet

  Canadian journal of applied physiology = Revue canadienne de physiologie appliquée. 01/1997; 21(6):471-80.

  The aim of this study was to explore the relationship between energy cost of locomotion and stride duration variability in the region of the walk-run transition speed. Ten subjects participated inThe aim of this study was to explore the relationship between energy cost of locomotion and stride duration variability in the region of the walk-run transition speed. Ten subjects participated in this experiment during four treadmill sessions. The first session was used to habituate subjects to treadmill walking or running. During the second session the treadmill speed was increased from 6 km.h-1 to 10 km.h-1 in steps of 0.2 km.h-1 to determine the freely chosen transition speed between walking and running (ST). The last two sessions consisted of five walks or five runs conducted at five intensities selected to represent respectively ST-1 km.h-1; ST-0.5 km.h-1; ST; ST + 0.5 km.h-1; and ST + 1 km.h-1. Exhaled gases were collected during the last two sessions, and stride duration was continuously recorded. The results indicated a significant increase in stride duration variability before ST for the freely chosen gait condition only. These findings point to an alternative hypothesis to that classically proposed to describe a transition as an energy saving mechanism.

• A note on data smoothing for movement analysis: the relevance of a nonlinear method.

  Authors: D Mottet, B G Bardy, S Athènes

  Journal of motor behavior. 04/1994; 26(1):51-5.

  The goal of this experiment was to test a potentially useful nonlinear method for smoothing noisy position data, which often is encountered in the analysis of data. This algorithm (7RY) uses aThe goal of this experiment was to test a potentially useful nonlinear method for smoothing noisy position data, which often is encountered in the analysis of data. This algorithm (7RY) uses a nonlinear smoothing function and behaves like a low-pass filter, automatically removing aberrant points; it is used prior to differentiation of time series so that usable acceleration information can be obtained. The experimental procedure comprises position data collection along with direct accelerometric data recording. From the position-time data, (a) 7RY and (b) Butterworth algorithms have been used to compute twice-differentiated acceleration curves. The directly recorded acceleration measurements were then compared with the acceleration computed from the original position data. Although the results indicated an overall good fit between the recorded and the calculated acceleration curves, only the nonlinear method led to reliable acceleration curves when aberrant points were present in the position data.

• Fitts' law in two-dimensional task space.

  Authors: D Mottet, R J Bootsma, Y Guiard, M Laurent

  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. 02/1994; 100(1):144-8.

  A traditional continuous Fitts' task may be described as a one-dimensional oscillation between two targets. The combination of two such oscillations along intersecting axes gives rise to aA traditional continuous Fitts' task may be described as a one-dimensional oscillation between two targets. The combination of two such oscillations along intersecting axes gives rise to a two-dimensional aiming task, allowing the study of the speed-accuracy trade-off in two-dimensional task space. In two experiments subjects were asked to draw as many ellipses as possible while passing through four targets, arranged around the extreme points of the two major axes of a model ellipse. In the first experiment, task difficulty was manipulated simultaneously along the two axes of the ellipse. Regardless of ellipse eccentricity and orientation, movement time (MT) was found to depend linearly on Fitts' index of difficulty (ID), which combines between-target distance and target width. In the second experiment, ID was manipulated independently for the short and the long axes of the ellipse. There was a strong linear relation between MT and ID averaged over the two axes, with the two independent measures of task difficulty exerting interactive effects on MT: the higher the ID on one axis, the smaller the effect of the ID on the other. The present results demonstrate that Fitts' law, only examinated so far in one-dimensional aiming tasks, generalises to two-dimensional task space.

• Behind Fitts’ law: kinematic patterns in goal-directed movements

  Authors: R.J. Bootsma, L. Fernandez, D. Mottet

  International Journal of Human-Computer Studies.

  Half a century ago, Paul Fitts first discovered that the time necessary to complete a pointing movement (MT) linearly increases with the amount of information (ID) necessary to specify the targetHalf a century ago, Paul Fitts first discovered that the time necessary to complete a pointing movement (MT) linearly increases with the amount of information (ID) necessary to specify the target width (W) relative to the distance (D). The so-called Fitts’ law states that , with ID being a logarithmic function of the D/W ratio. With the rising importance of pointing in human–computer interaction, Fitts’ law is nowadays an important tool for the quantitative evaluation of user interface design. We show that changes in ID give rise to systematic changes in the kinematics patterns that determine MT, and provide evidence that the observed patterns result from the interplay between basic oscillatory motion and visual control processes. We also emphasize the generality and abstract nature of Fitts’ robust model of human psychomotor behavior, and suggest that some adaptations in the design of the (computer-mediated) coupling of perception and production of movement might improve the efficiency of the interaction.