In the current study, we examined whether coupling influences resulting from unintended afference-based phase entrainment are affected by movement amplitude as such or by the amplitude relation between the limbs. We assessed entrainment strength by studying how passive movements of the contralateral hand influenced unimanual coordination with a metronome. Results showed that amplitude as such did not affect entrainment strength, whereas the amplitude relation between the hands did. Larger amplitudes of the passive hand relative to the active hand resulted in stronger entrainment. This dependence on relative amplitude implies that entrainment strength is not only based on the intensity of afferent signals generated in the entraining limb but also on the susceptibility of the entrained limb to these signals.
Betteco J. de Boer, C. (Lieke) E. Peper, Arne Ridderikhoff and Peter J. Beek
Ida Maria Bosga-Stork, Jurjen Bosga and Ruud G.J. Meulenbroek
This longitudinal study examined the movement efficiency of typically developing children between 7 and 9 years of age by scrutinizing their movement amplitudes and frequencies as they settled into a loop-writing task in which both parameters were prescribed. It was hypothesized that during the first three grades at primary school children would show increasing efficiency in exploiting the inverse relationship between movement amplitude and frequency when adjusting their movement errors. Whereas a clear developmental trend showed increasing efficiency with respect to the way in which the primary school children met the amplitude constraints, a more variable pattern was found for the age-dependent adjustments to the frequency requirements. At the level of parameter-error corrections from one cycle to the next, a marginal developmental trend was observed. Results are discussed in terms of contrasting effects between educational targets and movement-efficiency principles.
Ronald G. Marteniuk, Chris J. Ivens and Christopher P. Bertram
A pointing task was performed both while subjects stood beside and while subjects walked past targets that involved differing movement amplitudes and differing sizes. The hand kinematics were considered relative both to a fixed frame of reference in the movement environment (end effector kinematics) and to the subject's body (kinematics of the hand alone). From the former view, there were few differences between standing and walking versions of the task, indicating similarity of the kinematics of the hand. However, when the hand was considered alone, marked differences in the kinematics and spatial trajectories between standing and walking were achieved. Furthermore, kinematic analyses of the trunk showed that subjects used differing amounts of both flexion-extension and rotation movements at the waist depending on whether they were standing or walking as well as on the constraints imposed by target width and movement amplitude. The present results demonstrate the existence of motor equivalence in a combined upper and lower extremity task and that this motor equivalence is a control strategy to cope with increasing task demands. Given the complexity involved in controlling the arm, the torso, and the legs (during locomotion), the movements involved in the present tasks appear to be planned and controlled by considering the whole body as a single unit.
Semyon Slobounov, Robert Simon, Richard Tutwiler and Matthew Rearick
The question regarding the invariant movement properties the central nervous system may organize to accomplish different motor task demands as reflected in EEG remains unsolved. Surprisingly, no systematic electrocortical research in humans has related movement preparation with different movement distance, although this area has been widely investigated in the field of motor control. This study examined whether the amplitude of discrete wrist movements influences the various EEG components both in time and frequency domains. Time-domain averaging techniques and Morlet wavelet transforms of EEG single trials were applied in order to extract three components [BP(0), Nl, and LPS] of movement related potentials (MRP) and to quantify changes in oscillatory activity of the movement-induced EEG waveforms accompanying 20, 40, and 60° unilateral wrist flexion movements. The experimental manipulations induced systematic changes in BP(0) and Nl amplitude along the midline (Fz, Cz, and Pz) with 20° movement showing the most negativity and 60° the least. The dominant energy within a 30-50 frequency cluster from bilateral precentral (C3, Cz, C4), frontal (F3, Fz, F4), and parietal (P3, Pz, P4) areas with maximum at vertex (Cz) also appeared to be sensitive to movement amplitude with the least power observed during 60° wrist flexion. This suggests that movement amplitude may be a controllable variable that is highly related with task-specific cortical activation primarily at frontocentral areas as reflected in EEG.
Neil E. Fowler and Adrian Lees
The aim of this study was to compare the kinetic and kinematic characteristics of plyometric drop-jump and pendulum exercises. Exercises were filmed (100 Hz) from the sagittal view and manually digitized; the data were smoothed and differentiated using cross-validated quintic splines. Ground reaction force data were sampled using a Kistler force platform sampling at 500 Hz. Differences between movement amplitudes and coordination strategies were assessed using t tests and conjugate cross-correlations. Pendulum exercises involved a greater range of motion at the ankle and knee but less motion at the hip joint than drop-jumps. Although different in absolute terms, the exercises used a similar coordination strategy. Drop-jumps resulted in greater peak vertical ground reaction forces than the pendulum exercises although the latter involved a greater net impulse. The similarity between the movement patterns for the two modes of exercise led to the conclusion that pendulum exercises offer a training stimulus similar to that of drop-jumps.
Mireille Bonnard, Jean Pailhous and Frédéric Danion
The intentional on-line adaptive capabilities of human movements during continuous variation in gravitational force were investigated. Subjects performed rhythmic forearm movements in the gravitational plane during parabolic flight maneuvers that induced a continuous change from 1.8 G to 0 G over a period of 2.3 s. During the initial plateau of hypergravity, subjects produced movements at two frequencies, with and without space constraints. Afterward, they were faced with the drop in gravity, during which they were instructed either to let the movement evolve freely while maintaining the initial frequency (time-constrained task) or to intentionally maintain the frequency, amplitude, and forearm center of oscillation (time/space-constrained task). The results showed (a) a reduced angle for the forearm center of oscillation and maintenance of movement amplitude in the time-constrained task, (b) a change from an in-phase to an out-of-phase biceps/triceps activation pattern regardless of the task, and (c) an earlier occurrence of this change in the time/space-constrained task, impeding the spontaneous forearm rise. These results are discussed in the perspective of the λ model.
Jürgen Konczak, Kai Brommann and Karl Theodor Kalveram
Knowledge of how stiffness, damping, and the equilibrium position of specific limbs change during voluntary motion is important for understanding basic strategies of neuromotor control. Presented here is an algorithm for identifying time-dependent changes in joint stiffness, damping, and equilibrium position of the human forearm. The procedure requires data from only a single trial. The method relies neither on an analysis of the resonant frequency of the arm nor on the presence of an external bias force. Its validity was tested with a simulated forward model of the human forearm. Using the parameter estimations as forward model input, the angular kinematics (model output) were reconstructed and compared to the empirically measured data. Identification of mechanical impedance is based on a least-squares solution of the model equation. As a regularization technique and to improve the temporal resolution of the identification process, a moving temporal window with a variable width was imposed. The method's performance was tested by (a) identifying a priori known hypothetical time-series of stiffness, damping, and equilibrium position, and (b) determining impedance parameters from recorded single-joint forearm movements during a hold and a goal-directed movement task. The method reliably reconstructed the original angular kinematics of the artificial and human data with an average positional error of less than 0.05 rad for movement amplitudes of up to 0.9 rad, and did not yield hypermetric trajectories like previous procedures not accounting for damping.
-Kuang Wu * 10 2013 17 4 382 398 10.1123/mcj.17.4.382 Phase Entrainment Strength Scales With Movement Amplitude Disparity Betteco J. de Boer * C. (Lieke) E. Peper * Arne Ridderikhoff * Peter J. Beek * 10 2013 17 4 399 411 10.1123/mcj.17.4.399 The Effect of Transcranial Direct Current Stimulation on
Andressa Busch Rocha Pereira and Renato Moraes
groups. Figure 1 —(a) Sequence of experimental protocol events and illustration of the fatigue protocol. (b) Movement amplitude of the heel marker on the vertical axis during the cycles of a participant’s fatigue protocol. (c) Mean values and standard error of the mean of the movement amplitude of the
Marlowe Pecora, Luc Tremblay and Matthew Heath
Plamondon & Alimi, 1997 ), movement times (MTs) adhere to Fitts’ ( 1954 ) equation asserting that a task’s index of difficulty (ID Fitts : represented in bits of information) is reflected by ID Fitts = log 2 (2 A / W ), where A represents movement amplitude and W the width associated with a goal