Effects of dynamic workstation Oxidesk on acceptance, physical activity, mental fitness and work performance.

BACKGROUND: Working in an office environment is characterised by physical inactivity and sedentary behaviour. This behaviour contributes to several health risks in the long run. Dynamic workstations which allow people to combine desk activities with physical activity, may contribute to prevention of these health risks. OBJECTIVE: A dynamic workstation, called Oxidesk, was evaluated to determine the possible contribution to healthy behaviour and the impact on perceived work performance. METHODS: A field test was conducted with 22 office workers, employed at a health insurance company in the Netherlands. RESULTS: The Oxidesk was well accepted, positively perceived for fitness and the participants maintained their work performance. Physical activity was lower than the activity level required in the Dutch guidelines for sufficient physical activity. CONCLUSIONS: Although there was a slight increase in physical activity, the Oxidesk may be helpful in the reducing health risks involved and seems applicable for introduction to office environments.

Dynamic posturography using a new movable multidirectional platform driven by gravity.

Human upright balance control can be quantified using movable platforms driven by servo-controlled torque motors (dynamic posturography). We introduce a new movable platform driven by the force of gravity acting upon the platform and the subject standing on it. The platform consists of a 1 m2 metal plate, supported at each of its four corners by a cable and two magnets. Sudden release of the magnets on three sides of the platform (leaving one side attached) induces rotational perturbations in either the pitch or roll plane. Release of all magnets causes a purely vertical displacement. By varying the slack in the supporting cables, the platform can generate small (0.5 degrees ) to very destabilising (19 degrees ) rotations. Experiments in healthy subjects showed that the platform generated standardised and reproducible perturbations. The peak rotation velocity well exceeded the threshold required to elicit postural responses in the leg muscles. Onset latencies were comparable to those evoked by torque motor-driven platforms. Randomly mixed multidirectional perturbations of large amplitude forced the subject to use compensatory steps (easily possible on the large support surface), with little confounding influence of habituation. We conclude that this gravity-driven multidirectional platform provides a useful and versatile tool for dynamic posturography.

Controlling the Ground Reaction Force During Lifting.

The control of the ground reaction force vector relative to the center of gravity (CoG) was examined while subjects performed a back-lifting task. Six male subjects (aged 24.0 +/- 2.5 years) repeatedly lifted a barbell. A biomechanical analysis that used a linked segment model revealed that the summed rotations of body segments during lifting yielded a specific rate of change of the angular momentum of the entire body. This equaled the external moment provided by Fsubg; relative to CoG. This implies that multisegment movements involve control of the angular momentum of the entire body through an appropriately directed Fsubg;. Thus, in dynamic tasks Fsubg; is pointed away from rather than lined up with the CoG, as is the case in static tasks.