Patients with non-specific low back pain (LBP) may use postural control strategies that differ from healthy subjects. To study these possible differences, we measured the amount and structure of postural sway, and the response to muscle vibration in a working cohort of 215 subjects. Subjects were standing on a force plate in bipedal stance. In the first trial the eyes were open, no perturbation applied. In the following 6 trials, vision was occluded and subjects stood under various conditions of vibration/no vibration of the lumbar spine or m. Triceps Surae (TSM) on firm surface and on foam surface. We performed a factor analysis to reduce the large amount of variables that are available to quantify all effects. Subjects with LBP showed the same amount of sway as subjects without LBP, but the structure of their sway pattern was less regular with higher frequency content. Subjects with LBP also showed a smaller response to TSM vibration, and a slower balance recovery after cessation of vibration when standing on a solid surface. There was a weak but significant association between smaller responses to TSM vibration and an irregular, high frequency sway pattern, independent from LBP. A model for control of postural sway is proposed. This model suggests that subjects with LBP use more co-contraction and less cognitive control, to maintain a standing balance when compared to subjects without LBP. In addition, a reduced weighting of proprioceptive signals in subjects with LBP is suggested as an explanation for the findings in this study.
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A commentary on: Older adults can improve compensatory stepping with repeated postural perturbations by Dijkstra,B.W., Horak,F.B., Kamsma,Y.P.T., and Peterson,D.S.(2015).Front.AgingNeurosci. 7:201. doi:10.3389/fnagi.2015.00201. In sum, the results of Dijkstra etal. (2015) are of importance and significance for the field of falls prevention and stability control in aging. In particular, the work highlights the importance of multidirectional step or perturbation training, due to a lack of transfer across tasks. Whether this would hold for multidirectional gait perturbations is unclear, due to the influence of forward velocity during walking. Future work should explore different types, intensities and frequencies of perturbations in order to determine the most effective strategy for improving dynamic stability control in healthy older adults and inpatients with declined locomotor performance and increased falls risk. Finally, as Dijkstra etal. (2015) and previous studies found floor effects in the adaptation of young participants, further attempts should be made to appropriately scale perturbations to participant or groupability, in order to reliably compare adaptation across different groups.
Objectives: The strategy for dynamic postural stability might be different for male and female players. Additionally, dynamic and challenging tasks are recommended to measure differences in postural stability between injured and non-injured players. Therefore, the dynamic stability index (DSI) was developed which measures the ability of a player to maintain static balance after a dynamic task. The first aim of this study was to evaluate DSI differences between males and females for different jump directions. The second aim was to examine both preseason DSI differences between players with and without a history of ankle sprain, and between players with and without an ankle sprain during the subsequent season.Design: Prospective cohort design. Setting: Laboratory. Participants: 47 male (22.9 ± 3.9 y, 193.5 ± 7.9 cm, 87.1 ± 10.6) and 19 female (21.5 ± 2.9 y, 175.9 ± 7.3 cm, 69.0 ± 11.7 kg) sub-elite and elite basketball, volleyball and korfball players. Main outcome measures: Ankle sprain history was collected using a general injury history questionnaire. DSI on a single-leg hop-stabilization task measured preseason were calculated by using force plates and a Matlab program. Ankle sprains were reported during subsequent season. Results: Male players demonstrated larger DSI than female players on forward medial/lateral stability index (MLSI) (0.037± 0.007 vs 0.029 ± 0.005) and vertical stability index (VSI) (0.369 ± 0.056 vs 0.319 ± 0.034) (p < 0.001), diagonal VSI (0.363 ± 0.046 vs 0.311 ± 0.033) (p < 0.001), and lateral anterior/posterior stability index (APSI) (0.062 ± 0.015 vs 0.047 ± 0.011) and VSI (0.350 ± 0.054 vs 0.294 ± 0.037) (p < 0.001). Forward (0.384 ± 0.055 vs 0.335 ± 0.033), diagonal (0.379 ± 0.046 vs 0.328 ± 0.032) and lateral (0.368 ± 0.053 vs 0.313 ± 0.035) dynamic postural stability indices (DPSI) were larger for males (p < 0.001). No significant differences were found between players with and without a previous ankle sprain nor between players with and without an ankle sprain during subsequent season.
