Fig 1.
Flow chart presentation of the measurements.
Each of the two visits contained the same testing protocol with the sole difference being the flexion (i.e. intervention) condition. Measurements of body sway during sitting on unstable surface were done but are not included in the paper.
Fig 2.
Position of the participant during intermittent flexion.
Visual feedback was provided to the participant about the lumbar flexion (α) and trunk inclination (β) with marks for the required position. In the unsupported condition, a thin rope was placed horizontally in front of the participant at the appropriate height to serve as the orientation point during the flexion and in the supported position the rope was replaced by a padded bar on which the participant was leaning during the flexion.
Fig 3.
Measurements of the trunk stability in a kneeling-seated position and the perturbations were applied at the level of 10th thoracic vertebrae.
Table 1.
Reliability results within sessions (at each visit) between control and pre-exposure test, and between test sessions for the control and pre-exposure tests.
Table 2.
Main and interaction effects results of the RMANOVA for supported and unsupported flexion on the EMG amplitudes.
Fig 4.
Mean muscle activation expressed as a percentage of maximal voluntary contraction and median frequency measured while resisting the 60N pushing force applied at the level of T10 spinous process before (Pre) and after (Post) intermittent flexion for male and female participants in support and unsupported conditions.
*—Time effect (p < .05); † - Condition effect (p < .05); - Interaction effect (p < .05).
Fig 5.
Mean range of motion (with standard deviations) before (Pre) and after (Post) intermittent flexion for male and female participants in supported and unsupported condition.
*—Time effect (p < .05); † - Sex effect (p < .05); - Interaction effect (p < .05).
Fig 6.
Frequency response function pre (′) and post (☐) supported and unsupported intermittent flexion averaged across all subjects.
The shaded area represents the standard deviation. *—Exposure effect (p < .05); † - Condition effect (p < .05); - Interaction effect (p < .05).
Table 3.
Main and interaction effects of the RMANOVA for the gain of admittance and reflexes.