Fig 1.
The construction of the new chair (a) was based on a conventional dynamic office chair (b) with the inverted dynamic principle of an instable chair (c). In contrast to instable chairs, the seat has a stable central position that rests at the lowest point of the arc corresponding to the centre of the seat.
Fig 2.
Lateral and posterior views of a subject during active sitting, including electrode and marker placement. The three pictures on the right show examples of the central and the maximum left and right positions. Note that subjects placed their palms on the wrist rest of the keyboard.
Table 1.
Marker placement.
Fig 3.
Temporal activity and motion pattern.
Time normalized muscular activity and kinematic motion pattern during spontaneous (ACTSIT) and maximum active sitting (ACTSITmax) over all subjects. The seat is at 0%, 100% and 200% in the central position and at approximately 50% (left) and 150% (right) in the extremal positions. The muscle activity is given as a percentage of the peak activity in walking, kinematics in millimetres (mm).
Table 2.
Average muscular activity.
Table 3.
Temporal muscular activity pattern.
Table 4.
Range of motion and movement speed.