Elsevier

Gait & Posture

Volume 36, Issue 3, July 2012, Pages 580-585
Gait & Posture

Effect of visual input on normalized standing stability in subjects with recurrent low back pain

https://doi.org/10.1016/j.gaitpost.2012.05.020Get rights and content

Abstract

Although a number of studies have evaluated kinematic stability changes in subjects with low back pain (LBP), the combined sensitivity of normalized standing stability from the ground force and kinematic rotational angle of the body segment were not carefully examined for postural responses. The purpose of this study was to evaluate normalized standing stability in subjects with and without recurrent LBP while they stood quietly with the tested foot parallel to the other lower extremity at hip width. The subjects were then instructed to stand freely on one leg for 25 s with the contra lateral hip flexed 90° based on dominance side (dominant leg vs. non-dominant lower extremity) and visual condition (eyes open vs. eyes closed). A total of 42 subjects (27 subjects without LBP and 15 subjects with LBP) participated in the study. The dominant leg standing stability was significantly different during the eyes closed condition (0.68 ± 0.30 for control vs. 0.37 ± 0.32 for LBP, T = −3.23, p = 0.002) compared to the eyes open condition. The standing kinematic stability, especially of the dominant thigh, was greater in the control subjects than in the subjects with LBP (T = −2.43, p = 0.02). This sensitive detection of kinematic imbalance with postural stability is important for effective rehabilitation strategies and to understanding compensatory mechanisms in subjects with recurrent LBP.

Highlights

► The dominant leg standing stability was significantly different with visual input. ► The standing stability of the control group was significantly better than the subjects with low back pain (LBP). ► The index of normalized kinematic stability and rotational angle was sensitive to measure balance deficits. ► The sensitive detection of kinematic imbalance was important for effective rehabilitation strategies. ► The combined normalized standing stability and kinematic rotational angle should be utilized for compensatory mechanisms.

Introduction

Low back pain (LBP) is one of the most common types of musculoskeletal pain, and it still remains a challenging problem which accompanies diverse impairments in individuals who suffer from this condition [1], [2]. Clinical observations show that subjects with LBP often present impairments of postural control and dynamic stability [2], [3]. Though several studies on postural control have supported decreased balance performance in subjects with recurrent LBP, there is a lack of understanding regarding the mechanism of increased postural stability and kinematic changes [1], [2], [4].

It is generally accepted that subjects with recurrent LBP have an altered body inclination that might be caused by anticipation of postural stability problem [2], [4], [5]. As a result, we established an objective way to evaluate lower extremity stability during one leg standing in previous studies [6], [7]. The relative rotational angles of the body segments were calculated between two adjacent joints in three dimensions and then combined to quantify postural stability from the force plate to assess the stability index [8]. These studies reported valuable findings and began to establish movement patterns of the lower extremities; however, kinetic sensitivity on the ground is still lacking. It is necessary to assess valid results from a force plate considering the kinematic stability of the rotational angle for postural control.

Several reports indicated that the spine should not be considered in isolation from the lower extremities when trying to understand balance strategies in subjects with LBP [9]. Since altered lumbopelvic control and stability could affect the lower extremities, it is important to understand that a possible pelvic dysfunction might lead to different lower extremity movement patterns in subjects with recurrent LBP. Although these results demonstrated that subjects with recurrent LBP exhibit greater postural dysfunction than healthy controls [6], [7], [8], [10], the relationship of visual feedback based on dominance side was not carefully considered.

This postural stability may provide additional information about fundamental mechanisms of standing balance since asymmetric postural responses related to the imbalances around hip joint [11]. This research further supports the need for the assessment and treatment of hip muscle imbalance in individuals with LBP. Therefore, balance stability of the proximal hip musculature is important in the prevention of lower extremity injuries [10], [12]. In order to maintain postural stability within a certain range of motion (ROM), the body requires not only reliable sensory feedback from the ground reaction force (GRF) or muscle activation from all involved joints, but also the sensitive kinematic response of proprioceptive receptors to environmental changes.

The relative kinematic stability on the lower extremities has not been carefully considered in subjects with recurrent LBP. It has been frequently used for balance assessments based on the GRF. Since it is clear that subjects with recurrent LBP exhibit proprioceptive deficits, the kinematic changes for the stability of the pelvis could be affected in subjects with LBP as well [13], [14]. These results could be due to the methodological issue that, in the absence of a standard method to quantify postural stability, the force measures were compared with functional balance tests. However, one other report has shown no significant correlations in force plate measures to reflect the performance of postural stability [15]. Therefore, this study evaluated both kinematic stability for the body segments and normalized stability from the force plate in order to objectively measure dynamic postural responses. Moreover, comparison of postural control between the normalized stability from the force plate and kinematic angular displacement measures may contribute to a further understanding of postural adjustability without visual input in relation to lower extremity movement.

Therefore, the purpose of this study was to investigate normalized standing stability and kinematic changes while considering visual input and dominance side between subjects with and without recurrent LBP. It was hypothesized that kinematic stability and standing stability on the force plate would be different in subjects with recurrent LBP. We expected that the normalized stability and kinematic angular displacement would be different for each specific region of the lower extremities between subjects with and without recurrent LBP.

Section snippets

Target population

Subjects were recruited from the greater city of Seoul, Korea. Subjects who expressed interest in the study became eligible for the study. Those subjects who met study inclusion criteria received information regarding the purpose and methods of the study and signed a copy of the Institutional Review Board approved consent form.

Subjects were eligible to participate if they: (1) were 18 years of age or older, (2) had a current episode of recurrent LBP for more than two months without pain

Description of samples

In total, 42 subjects enrolled in the study, including 27 subjects without LBP and 15 subjects with LBP. The average age of the subjects was 37.8 ± 12.6 years and ranged from 19 to 63 years. The subjects without LBP were slightly younger (35.0 ± 10.0 years) than the subjects with LBP (46.7 ± 14.5 years), but there was no significant difference between groups (T = −1.67, p = 0.10). In addition, there was no gender difference between groups (χ2 = 0.21, p = 0.73).

The subjects without LBP were slightly taller

Discussion

The purpose of this study was to evaluate normalized standing stability of GRF data in combination with pelvis and lower extremity kinematics with and without visual input during one leg standing. A cross-sectional design was conducted to determine whether steadiness of the pelvis and each segment of both lower extremities as well as fluctuations of GRF are different between control and LBP groups.

The results of this study indicated that the subjects with recurrent LBP demonstrated less

Conclusion

The standing stability of the dominant leg in the control group was significantly better than for the subjects with recurrent LBP. The postural stability decreased significantly in the lower extremities, especially in the pelvis and thigh, during the one leg standing test in subjects with recurrent LBP. This sensitive detection of kinematic imbalance combined with force plate measures is important for developing effective rehabilitation strategies and to understanding compensatory mechanisms in

Conflict of interest statement

The authors have no conflict of interest to disclose.

Acknowledgements

This work was supported by Korea University and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (2010-0003015).

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