A number of studies have analyzed various indices of the final position variability in order to provide insight into different levels of neuromotor processing during reaching movements. Yet the possible effects of movement kinematics on variability have often been neglected. The present study was designed to test the effects of movement direction and curvature on the pattern of movement variable errors. Subjects performed series of reaching movements over the same distance and into the same target. However, due either to changes in starting position or to applied obstacles, the movements were performed in different directions or along the trajectories of different curvatures. The pattern of movement variable errors was assessed by means of the principal component analysis applied on the 2-D scatter of movement final positions. The orientation of these ellipses demonstrated changes associated with changes in both movement direction and curvature. However, neither movement direction nor movement curvature affected movement variable errors assessed by area of the ellipses. Therefore it was concluded that the end-point variability depends partly, but not exclusively, on movement kinematics.
Slobodan Jaric, Charli Tortoza, Ismael F.C. Fatarelli and Gil L. Almeida
Kreg G. Gruben, Lynn M. Rogers, Matthew W. Schmidt and Liming Tan
The force that healthy humans generated against a fixed pedal was measured and compared with that predicted by four models. The participants (n = 11) were seated on a stationary bicycle and performed brief pushing efforts against an instrumented pedal with the crank fixed. Pushes were performed to 10 force magnitude targets and at 12 crank angles. The increasing magnitude portion of the sagittal-plane force path for each push effort was fitted with a line to determine the direction of the muscle component of the foot force. Those directions varied systematically with the position of the pedal (crank angle) such that the force path lines intersected a common region superior and slightly anterior to the hip. The ability of four models to predict force path direction was tested. All four models captured the general variation of direction with pedal position. Two of the models provided the best performance. One was a musculoskeletal model consisting of nine muscles with parameters adjusted to provide the best possible ft. The other model was derived from (a) observations that the lines-of-action of the muscle component of foot force tended to intersect in a common region near the hip, and (b) the corresponding need for foot force to intersect the center-of-mass during walking. Thus, this model predicted force direction at each pedal position as that of a line intersecting the pedal pivot and a common point located near the hip (divergent point). The results suggest that the control strategy employed in this seated pushing task reflects the extensive experience of the leg in directing force appropriately to maintain upright posture and that relative muscle strengths have adapted to that pattern of typical activation.
Kreg G. Gruben, Lynn M. Rogers and Matthew W. Schmidt
Control of the force exerted by the foot on the ground is critical to human locomotion. During running on a treadmill and pushing against a fixed pedal, humans increased foot force in a linear manner in sagittal plane force space. However, for pushes against a moving pedal, force output was linear for some participants but slightly curved for others. A primary difference between the static and dynamic pedaling studies was that the dynamic study required participants to push with varying peak effort levels, whereas a constant peak effort level was used for the fixed pedal pushes. The present study evaluated the possibility that force direction varied with level of effort. Seated humans pushed against a fixed pedal to a series of force magnitude targets. The force direction varied systematically with effort level consistent with the force path curvature observed for dynamic pedaling.
Filippo Dolci, Andrew E. Kilding, Tania Spiteri, Paola Chivers, Ben Piggott, Andrew Maiorana and Nicolas H. Hart
nature. 3 Indeed, soccer players commonly change activity every 3.5 seconds, 4 performing more than 600 accelerations and decelerations per match and changing direction up to 700 times, mostly over angles up to 180°. 5 To overcome such testing limitations, the assessment of movement economy when
Davide Ferioli, Ermanno Rampinini, Andrea Bosio, Antonio La Torre and Nicola A. Maffiuletti
Basketball is a physically demanding team sport characterized by frequent high-intensity phases 1 during which neuromuscular factors are heavily taxed. 2 Players are frequently asked to quickly accelerate, decelerate, and change direction during basketball games. 1 Specifically, time
Rachael D. Seidler
Visuomotor adaptive processes were examined by testing transfer of adaptation between similar conditions. Participants made manual aiming movements with a joystick to hit targets on a computer screen, with real-time feedback display of their movement. They adapted to three different rotations of the display in a sequential fashion, with a return to baseline display conditions between rotations. Adaptation was better when participants had prior adaptive experiences. When performance was assessed using direction error (calculated at the time of peak velocity) and initial endpoint error (error before any overt corrective actions), transfer was greater when the final rotation reflected an addition of previously experienced rotations (adaptation order 30° rotation, 15°, 45°) than when it was a subtraction of previously experienced conditions (adaptation order 45° rotation, 15°, 30°). Transfer was equal regardless of adaptation order when performance was assessed with final endpoint error (error following any discrete, corrective actions). These results imply the existence of multiple independent processes in visuomotor adaptation.
Guillaume Martinent and Claude Ferrand
The purpose of this study was to explore the directional interpretation process of discrete emotions experienced by table tennis players during competitive matches by adopting a naturalistic qualitative video-assisted approach. Thirty self-confrontation interviews were conducted with 11 national table tennis players (2 or 3 matches per participants). Nine discrete emotions were identified through the inductive analyses of the participants' transcriptions: anger, anxiety, discouragement, disappointment, disgust, joy, serenity, relief, and hope. Inductive analyses revealed the emergence of 4 categories and 13 themes among the 9 discrete emotions: positive direction (increased concentration, increased motivation, increased confidence, positive sensations, and adaptive behaviors), negative direction (decreased concentration, decreased motivation, too confident, decreased confidence, negative sensations, and maladaptive behaviors), neutral direction (take more risk and take less risk), and no perceived influence on own performance. Results are discussed in terms of current research on directional interpretation and emotions in sport.
Yuji Matsuda, Yoshihisa Sakurai, Keita Akashi and Yasuyuki Kubo
In swimming, horizontal velocity fluctuations in the whole-body center of mass (CoM) are related to the energy cost. 1 , 2 Furthermore, variations in the CoM velocity, maximal and minimal CoM velocities in swimming direction during a stroke cycle, are related to the swimming performance. 2 , 3
Masakazu Matsuoka, Hiroshi Kunimura and Koichi Hiraoka
on advanced information (prediction) of a forthcoming perturbation. The advanced information about the time and direction of the perturbation is critical to prepare the postural response. The displacement of the center of pressure during postural perturbation in stance was smaller when humans could
Conall F. Murtagh, Christopher Nulty, Jos Vanrenterghem, Andrew O’Boyle, Ryland Morgans, Barry Drust and Robert M. Erskine
independent lower-limb power qualities in soccer players. 3 However, no attempt has been made to investigate the neuromuscular factors underpinning direction-specific (soccer associated) CMJ performance. Such information could be used to inform the neuromuscular factors that should be considered when