The study proposes a rigid-body biomechanical model of the trunk and whole upper limb including scapula and the test of this model with a kinematic method using a six-dimensional (6-D) electromagnetic motion capture (mocap) device. Large unconstrained natural trunk-assisted reaching movements were recorded in 7 healthy subjects. The 3-D positions of anatomical landmarks were measured and then compared to their estimation given by the biomechanical chain fed with joint angles (the direct kinematics). Thus, the prediction errors was attributed to the different joints and to the different simplifications introduced in the model. Large (approx. 4 cm) end-point prediction errors at the level of the hand were reduced (to approx. 2 cm) if translations of the scapula were taken into account. As a whole, the 6-D mocap seems to give accurate results, except for pronosupination. The direct kinematic model could be used as a virtual mannequin for other applications, such as computer animation or clinical and ergonomical evaluations.
Sylvain Hanneton, Svetlana Dedobbeler, Thomas Hoellinger and Agnès Roby-Brami
Marie-Jasmine Lalonde-Parsi and Anouk Lamontagne
Whether a reduced perception of self-motion contributes to poor walking speed adaptations in older adults is unknown. In this study, speed discrimination thresholds (perceptual task) and walking speed adaptations (walking task) were compared between young (19–27 years) and young-old individuals (63–74 years), and the relationship between the performance on the two tasks was examined. Participants were evaluated while viewing a virtual corridor in a helmet-mounted display. Speed discrimination thresholds were determined using a staircase procedure. Walking speed modulation was assessed on a self-paced treadmill while exposed to different self-motion speeds ranging from 0.25 to 2 times the participants’ comfortable speed. For each speed, participants were instructed to match the self-motion speed described by the moving corridor. On the walking task, participants displayed smaller walking speed errors at comfortable walking speeds compared with slower of faster speeds. The young-old adults presented larger speed discrimination thresholds (perceptual experiment) and larger walking speed errors (walking experiment) compared with young adults. Larger walking speed errors were associated with higher discrimination thresholds. The enhanced performance on the walking task at comfortable speed suggests that intersensory calibration processes are influenced by experience, hence optimized for frequently encountered conditions. The altered performance of the young-old adults on the perceptual and walking tasks, as well as the relationship observed between the two tasks, suggest that a poor perception of visual motion information may contribute to the poor walking speed adaptations that arise with aging.
Deborah L. Feltz, Norbert L. Kerr and Brandon C. Irwin
The present investigation examined the Köhler motivation gain effect in a health game using an absent partner, presented virtually. The Köhler effect occurs when an inferior team member performs a difficult task better in a team or coaction situation than one would expect from knowledge of his or her individual performance. The effect has been strongest in conjunctive task conditions in which the group’s potential productivity is equal to the productivity of its least capable member. Participants were randomly assigned to one of four conditions (individual control, coaction, additive, and conjunctive) in a 4 (conditions) × 2 (gender) factorial design and performed a series of isometric plank exercises within an exercise game. They performed the first series of five exercises alone holding each position for as long as they could, and, after a rest period, those in the partner conditions were told they would do remaining trials with a same-sex virtual partner whom they could observe during their performance. The partner’s performance was manipulated to be always superior to the participant’s. Results showed that task persistence was significantly greater in all experimental conditions than in the individual control condition. The conjunctive condition was no more motivating than either the additive or coactive conditions. Results suggest that working out with virtually present, superior partners can improve persistence motivation on exercise game tasks.
Sukhvinder S. Obhi, Patrick Haggard, John Taylor and Alvaro Pascual-Leone
Bimanual coordination tasks form an essential part of our behaviour. One brain region thought to be involved in bimanual coordination is the supplementary motor area (SMA). We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz for 5 min to create a temporary virtual lesion of the rostral portion of the human SMA immediately prior to performance of a goal-directed bimanual coordination task. In two control conditions, participants underwent sham stimulation or stimulation over the primary motor cortex (MI). The experimental task was to open a drawer with the left hand, catch a ball with the right hand, and reinsert the ball into the drawer through an aperture just big enough for the ball to pass through, again with the right hand. Hence, the actions of one hand depend upon the actions of the other. We calculated time intervals between the successive component actions of one hand (unimanual intervals) and actions of both hands (bimanual intervals) and analyzed these intervals separately. Interestingly, none of the unimanual intervals were affected by the rTMS, but the variability of a critical bimanual interval—the time between the left hand opening the drawer and the right hand starting to move to catch the ball—was increased by rTMS over the rostral parts of the SMA. No such effect was seen following rTMS over MI or after sham rTMS. Our results suggest that the rostral parts of the SMA play an important role in aspects of functional bimanual tasks, which involve tight temporal coordination between different motor actions of the two hands.
Noah X. Tocci, David R. Howell, Dai Sugimoto, Corey Dawkins, Amy Whited and Donald Bae
Coordinate System Definitions The pelvis local coordinate system was defined as follows: origin, Pelvis_Origin virtual marker; longitudinal axis, a vector extending from the Pelvis_Origin to the mid_Hip virtual marker; mediolateral axis, a vector extending from the Pelvis_Origin to the sacrum marker; and
Bart Roelands and Kevin De Pauw
. Artificial intelligence experts have been working on the implementation of virtual-, augmented-, and mixed-reality sessions into the microcycle planning of athletes. These strategies seemed science fiction only a few years ago but are now being used in tactical training sessions. The integration of
Carlo Massaroni, Eugenio Cassetta and Sergio Silvestri
, to the best of our knowledge, the unique validated model for respiratory computation, it appears to be affected by some weaknesses: (i) it cannot be used in other motion capture systems; (ii) extra virtual markers are required to close the chest wall surface and calculate respiratory volumes (leading
Yi-Ching Chen, I-Chen Lin, Yen-Ting Lin, Wei-Min Huang, Chien-Chun Huang and Ing-Shiou Hwang
% MVC on the monitor during CT by resisting virtual perturbation of a 0.2-Hz sinusoidal signal (Figure 1 , the lower plot). Being blinded to the virtual perturbation that deviated force output, the participants had to carefully monitor the tracking mismatch at every moment. Actually, the participants
Denny Meyer, Madawa W. Jayawar, Samuel Muir, David Ho and Olivia Sackett
outcome measures. Methods Virgin Pulse is a global software as a service vendor addressing the need for workplace programs that encourage increased physical activity and improved nutrition. One of the Virgin Pulse programs called the Global Challenge (VPGC) consists of a 100-day virtual journey during
Lauren C. Benson, Stephen C. Cobb, Allison S. Hyngstrom, Kevin G. Keenan, Jake Luo and Kristian M. O’Connor
cluster was used to determine the locations of the second metatarsal head and the distal end of the shoe during the movement trials, using a modification of the virtual marker representation outlined by Nagano et al. 11 Based on the assumption that the shoe is rigid during the swing phase, particularly