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.
Ronald G. Marteniuk, Chris J. Ivens, and Christopher P. Bertram
Marcos Rodrigo Trindade Pinheiro Menuchi and Lilian Teresa Bucken Gobbi
Locomotion generates a visual movement pattern characterized as optic flow. To explore how the locomotor adjustments are affected by this pattern, an experimental paradigm was developed to eliminate optic flow during obstacle avoidance. The aim was to investigate the contribution of optic flow in obstacle avoidance by using a stroboscopic lamp. Ten young adults walked on an 8m pathway and stepped over obstacles at two heights. Visual sampling was determined by a stroboscopic lamp (static and dynamic visual sampling). Three-dimensional kinematics data showed that the visual information about self-motion provided by the optic flow was crucial for estimating the distance from and the height of the obstacle. Participants presented conservative behavior for obstacle avoidance under experimental visual sampling conditions, which suggests that optic flow favors the coupling of vision to adaptive behavior for obstacle avoidance.
Alexandra S. Voloshina and Daniel P. Ferris
Understanding human and animal locomotion on different surfaces could improve clinical rehabilitation and the design of prosthetic devices. Currently, studies focusing on locomotion on uneven terrain are conducted either on short, uneven walkways 1 – 8 or in natural environments, such as grass
E. Yu Shapkova, A.V. Terekhov, and M.L. Latash
We studied the coordination of arm movements in standing persons who performed an out-of-phase arm-swinging task while stepping in place or while standing. The subjects were instructed to stop one of the arms in response to an auditory signal while trying to keep the rest of the movement pattern unchanged. A significant increase was observed in the amplitude of the arm that continued swinging under both the stepping and standing conditions. This increase was similar between the right and left arms. A dynamic model was developed including two coupled nonlinear van der Pol oscillators. We assumed that stopping an arm did not eliminate the coupling but introduced a new constraint. Within the model, superposition of two factors, a command to stop the ongoing movement of one arm and the coupling between the two oscillators, has been able to account for the observed effects. The model makes predictions for future experiments.
Scott W. Ducharme and Richard E.A. van Emmerik
Biological systems are inherently variable, and this variability has been the focus of much research in the movement sciences. In human locomotion research, a commonly accepted convention has been that variability is a one-size-fits-all parameter; more is bad. This “negative” perspective towards
Hendrik Reimann, Tyler Fettrow, and John J. Jeka
Being able to move from one place to another is an essential part of being an animal. Moving in a goal-directed way is a complex problem, and locomotion is no exception. It is especially hard for two-legged walkers such as us humans, because our center of mass (CoM) is relatively high above our
Lana M. Pfaff and Michael E. Cinelli
. Therefore, the objective of the current study was to examine the effects of a human obstacle’s location and the form of locomotion (i.e., running or walking) on path selection of female rugby backfield players during a collision avoidance task. It was hypothesized that when the rugby players performed the
Adam M. Fullenkamp, Danilo V. Tolusso, C. Matthew Laurent, Brian M. Campbell, and Andrea E. Cripps
The use of traditional motorized treadmills (MTs) is an established approach for physiological conditioning, sport-specific training, gait retraining, and the study of human locomotion. In particular, MTs offer the convenience of spatial control, enabling locomotion in an environment that is
Mhairi K. MacLean and Daniel P. Ferris
walking and/or running is usually one component of the user’s likely tasks. 1 – 4 If a robotic exoskeleton can reduce the metabolic energy expenditure during locomotion at a constant speed, the device could make it easier for users to accomplish their goals with less physical exertion. So far, few