A kinematic and kinetic analysis of spinal region in subjects with and without recurrent low back pain during one leg standing

Postural control and trunk stability on sway parameters in adults with and without chronic low back pain

BACKGROUND

Postural sway changes often reflect functional impairments in adults with chronic low back pain (LBP). However, there is a gap in understanding how these individuals adapt their postural strategies to maintain stability.

PURPOSE

This study investigated postural sway distance and velocity, utilizing the center of pressure (COP) and center of gravity (COG), between adults with and without LBP during repeated unilateral standing trials.

METHODS

Twenty-six subjects with LBP and 39 control subjects participated in the study. Postural sway ranges, COP/COG sways, and sway velocities (computed by dividing path length by time in anteroposterior (AP) and mediolateral (ML) directions over 10 s) were analyzed across three unilateral standing trials.

RESULTS

A significant group interaction in sway range difference was observed following repeated trials (F = 5.90, p = 0.02). For COG sway range, significant group interactions were demonstrated in both directions (F = 4.28, p = 0.04) and repeated trials (F = 5.79, p = 0.02). The LBP group demonstrated reduced ML sway velocities in the first (5.21 ± 2.43 for the control group, 4.16 ± 2.33 for the LBP group; t = 1.72, p = 0.04) and second (4.87 ± 2.62 for the control group, 3.79 ± 2.22 for the LBP group; t = 1.73, p = 0.04) trials.

CONCLUSION

The LBP group demonstrated decreased ML sway velocities to enhance trunk stability in the initial two trials. The COG results emphasized the potential use of trunk strategies in augmenting postural stability and optimizing neuromuscular control during unilateral standing.

Compensatory latency time delays during consecutive perturbations in older adults with and without kinesiophobia

BACKGROUND

Fear of movement has been related to lower limb activation patterns in older adults. However, insight into consecutive perturbations on stepping strategy while considering fall-related confidence is unknown.

RESEARCH QUESTION

Are there latency time delays following three consecutive slip perturbations between subjects with and without kinesiophobia when considering limb dominance and fall efficacy differences?

METHODS

There were 15 older adults with kinesiophobia and 15 age- and body mass index (BMI)-matched control subjects. The subjects stood on the platform during three consecutive perturbations (250, 300, and 400 msec excursions), which were produced by a Bertec device. The subjects completed questionnaires to evaluate the psychological features of their fall-related fear (Tampa Scale for Kinesiophobia: TSK) as well as the modified fall efficacy scale (FES). The latency times (msec) measured the time it took for a subject to respond to a translation.

RESULTS

Overall, the results of the FES demonstrated a moderate negative association with the TSK (r = -0.52, p = 0.004). There was a significant group difference for the FES (t = 2.78, p = 0.01). The FES demonstrated significant positive correlation coefficients (ranging from 0.40 to 0.51) and significant negative correlation coefficients (ranging from -0.41 to -0.61), except for the slow perturbations. The groups demonstrated a significant interaction on consecutive latency times and limb side (F = 5.84, p = 0.02). The latency time during the fast perturbations on the dominant limb (F = 5.53, p = 0.02) was significantly shorter in the kinesiophobia group.

SIGNIFICANCE

The control group demonstrated confidence during fall-related activities, but the latency times were significantly different between groups when considering the dominant limb following repeated slip perturbations. The kinesiophobia group demonstrated shorter latency times on the dominant limb to protect against potential fall-risks from perturbations. The group interactions on limb side and consecutive perturbations need to be considered with fall-related confidence and improved standing balance in older adults with kinesiophobia.

Normalized stability time analysis within the boundaries between adults with and without fear of falling

BACKGROUND

The unilateral stance test, measured by the center of pressure (COP), has been widely used to identify balance deficits. However, there is a critical gap in understanding the specific COP thresholds on postural stability in adults with a fear of falling (FOF).

AIMS

To investigate the normalized stability time, which was defined as the ratio of time spent within stability boundaries to the total test duration, under different visual conditions and specific thresholds between adults with and without FOF.

METHODS

Twenty-one older adults with FOF and 22 control subjects completed the unilateral limb standing test in eyes-open and eyes-closed conditions. Normalized stability times were computed based on five pre-determined COP sway range thresholds: 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm.

RESULTS

Receiver operating characteristic analysis determined the diagnostic accuracy of FOF. There were significant differences in the effects of both visual conditions (F = 46.88, p = 0.001) and threshold settings (F = 119.38, p = 0.001) on stability time between groups. The FOF group significantly reduced normalized stability time at the 10 mm COP threshold under eyes-closed conditions (t = - 1.95, p = 0.03).

DISCUSSION

The findings highlight the heightened sensitivity of the 10 mm COP threshold in identifying group variances in postural stability when eyes are closed. Moreover, the FOF group displayed a marked reduction in stability duration based on visual scenarios and normalized thresholds.

CONCLUSION

The study highlights the need to account for both COP boundaries and visual conditions in adults with FOF. When assessing postural control during unilateral stances, clinicians must also give attention to non-visual cues.

Postural adaptations within normalized stability between older adults with and without chronic low back pain

BACKGROUND

Adaptations of dynamic balance performance are related to sway excursions in older adults with chronic low back pain (LBP). However, there is a lack of understanding on postural control within different thresholds of radius from the center of pressure (COP).

PURPOSE

This study was conducted to compare the normalized stability based on the time-in-boundary (TIB) during repeated unilateral limb standing trials between subjects with and without chronic LBP.

METHODS

There were 26 older adults with LBP and 39 control subjects who completed three trials of repeated unilateral limb standing on a force plat.

RESULTS

The TIB based on the seven thresholds was analyzed, and the groups demonstrated a significant interaction on thresholds for TIB (F = 8.76, p = 0.01). The TIB was significantly different in the 10 mm (F = 4.01, p = 0.04), 15 mm (F = 5.21, p = 0.03), and 20 mm (F = 4.48, p = 0.04) radius of thresholds only in the second trial. However, there was no group difference on TIB at the first and third trials due to potential compensatory and/or adaptive reactions to avoid fall risks.

CONCLUSION

The LBP group lacked postural stability within the thresholds less than a 20 mm radius at the second trial of unilateral standing. The significant group interaction with the thresholds indicates an adaptation strategy on sway thresholds. This postural reaction from repeated trials should be considered with sway excursion adjustments and fall prevention in older adults with LB.

The dynamic postural steadiness and stabilization time between older adults with and without recurrent low back pain

BACKGROUND

Although postural control measures were reported to identify neuromuscular impairments, postural steadiness and stabilization time were not carefully investigated between subjects with and without recurrent low back pain (LBP). Research QuestionAre there group differences in the stabilization time, direction of sway, and dynamic postural steadiness index (DPSI) during one-leg standing?

METHODS

Thirty-four control subjects and 29 subjects with recurrent LBP participated in the study. Each subject stood upright on a single leg with and without visual input. The outcomes were measured for standing duration (sec), direction of sway, and the DPSI, which included the vertical steadiness index (VSI). The VSI assesses fluctuations to standardize the vertical ground reaction forces on the force plate.

RESULTS

The control group demonstrated significantly longer standing duration compared to the LBP group during the eyes-open condition (t = 3.55, p = 0.001). The LBP group demonstrated significantly faster stabilization time (t = 2.53, p = 0.01) in the sagittal plane. The DPSI demonstrated an excellent relationship with the VSI without visual input in the control group (r = 0.98, p = 0.001). The directions of sway demonstrated a significant interaction between groups (F = 9.29, p = 0.004).

SIGNIFICANCE

Although standing duration in the eyes-open condition decreased in the LBP group, a faster stabilization time in the sagittal plane was evident compared to the control group to adapt postural stability. These results indicated that vertical dynamic steadiness with visual input might be important to enhance compensatory postural control.

The Effect of Toe-grasping Exercises on Balance Ability in Home-based Rehabilitation: A Randomized Controlled Trial by Block Randomization

OBJECTIVE

The purpose of the study was to clarify the causal effect of toe-grasping exercises on the improvement of static or dynamic balance ability in home-based rehabilitation users.

METHOD

Our study included 34 subjects who met the criteria and were evaluable out of 98 rehabilitation service users at home nursing stations. This study was a randomized controlled trial. The intervention group performed towel gathering exercises in addition to the regular home-based rehabilitation program. The primary outcome was one-leg standing time, and the secondary outcomes were two-step test and toe grip strength.

RESULTS

Seventeen subjects were assigned to the intervention group and seventeen to the control group by block randomization. Data from 15 and 12 subjects in the intervention group and control group, respectively, who were able to complete the initial evaluation and the evaluation after 3 months, were analyzed. We compared the amount of change after 3 months of evaluation in the intervention group with the change in the control group. The results showed that the left/right mean value of oneleg standing time in the intervention group was significantly greater than that in the control group. In terms of the amount of change in the intervention period (T2-T1) within each assessment, there were significant improvements in both the toe-grip strength and the two-step values in the intervention group.

CONCLUSION

We found that toe-grasping exercises could improve the balance ability of home-based rehabilitation users. This suggests the clinical significance of toe function in rehabilitation programs.

Gait Asymmetry Comparison between Subjects with and without Nonspecific Chronic Low Back Pain

Individuals with chronic low back pain (LBP) report impaired somatosensory function and balance. However, there is a lack of investigation on limb motion similarities between subjects with and without LBP during gait. The aim of this study was to compare gait parameters as well as combined limb motions using the kinematic similarity index (KSI) between subjects with and without LBP. Twenty-two subjects with LBP and 19 age- and body mass index-matched control subjects participated in this study. The combined limb motions in the gait cycle of subjects with LBP were compared with those of a prototype derived from healthy subjects. The calculations resulted in response vectors that were analyzed in comparison to control-derived prototype response vectors for the normalized index at 5% increments in the gait cycle. The results of our study indicated that the KSI of the control group demonstrated higher similarities in the swing (t = 4.23, p = 0.001) and stance (t = 6.26, p = 0.001) phases compared to the LBP group. The index for the whole gait cycle was significantly different between the groups (t = 6.52, p = 0.001), especially in the midstance and swing phases. The LBP group could have adjusted the gait patterns during these specific phases. The KSI is useful for clinical outcome measures to differentiate kinematic changes and to demonstrate quantified similarities in the gait cycle between subjects with and without LBP. It is warranted to validate the KSI for the analysis of physiological gait asymmetry using a larger sample in future studies.

Preferred Limb Reaction, Swing and Recovery Step Times between Subjects with and without Chronic Low Back Pain

A compensatory stepping strategy following repeated perturbations may compromise dynamic balance and postural stability. However, there is a lack of study on preferred limb reaction, swing, and step time adjustments. The purpose of this study was to investigate limb reaction, swing, and recovery step times following repeated trip perturbations in individuals with and without non-specific chronic low back pain (LBP). There were 30 subjects with LBP and 50 control subjects who participated in the study. The limb reaction, swing, and recovery step times (s) were measured following treadmill-induced random repeated perturbations (0.12 m/s velocity for 62.5 cm displacement), which caused subjects to move forward for 4.90 s. Both groups demonstrated a significant interaction of repetitions and times (F = 4.39, p = 0.03). Specifically, the recovery step time was significantly shorter in the LBP group during the first trip (t = 2.23, p = 0.03). There was a significant interaction on repetitions and times (F = 6.03, p = 0.02) in the LBP group, and the times were significantly different (F = 45.04, p = 0.001). The initial limb reaction time of the LBP group was significantly correlated with three repeated swing times to avoid falls. The novelty of the first trip tends to enhance a protective strategy implemented by the LBP group. Although limb preference did not demonstrate a significant difference between groups, the LBP group demonstrated shorter recovery step times on their preferred limb initially in order to implement an adaptive strategy to avoid fall injuries following repeated perturbations.

Physical Abilities in Low Back Pain Patients: A Cross-Sectional Study with Exploratory Comparison of Patient Subgroups

An abundance of literature has investigated the association between low back pain (LBP) and physical ability or function. It has been shown that LBP patients display reduced range of motion, decreased balance ability, impaired proprioception, and lower strength compared to asymptomatic persons. The aim of this study was to investigate the differences between LBP patients and healthy controls in terms of several physical abilities. Based on the premised that different biomechanical and physiological causes and consequences could be related to different types of LBP, a secondary exploratory attempt of the study was to examine the differences between LBP subgroups based on the pain location (local or referred) or type of pathology (discogenic or degenerative) on the level of impairment of function and ability. Participants performed range of motion tests, trunk maximal voluntary contraction force tests, a sitting balance assessment, the timed up-and-go test, the chair rise test, and the trunk reposition error test. Compared to the control group, symptomatic patients on average showed 45.7% lower trunk extension (p < 0.001, η² = 0.33) and 27.7 % lower trunk flexion force (p < 0.001, η² = 0.37) during maximal voluntary contraction. LBP patients exhibited decreased sitting balance ability and lower scores in mobility tests (all p < 0.001). There were no differences between groups in Schober’s test and trunk repositioning error (p > 0.05). No differences were observed among the LBP subgroups. The exploratory analyses are limited by the sample size and uncertain validity of the diagnostic procedures within this study. Further studies with appropriate diagnostic procedures and perhaps a different subgrouping of the LBP patients are needed to elucidate if different types of LBP are related to altered biomechanics, physiology, and function.

Gender difference of hip-ankle compensations following a novel trip perturbation in young adults

BACKGROUND

Women have an increased likelihood of sustaining a fall-related injury compared to men; however, little is known about fall prevention strategies between genders. The purpose of this study was to compare the gender differences in lower limb reactions and three-dimensional recovery patterns following a treadmill-induced trip perturbation.

METHODS

Seventy-six participants who are right limb dominant enrolled in the study, which included 41 females (26.15 [9.92] years old) and 35 males (27.11 [9.15] years old). The outcome measures included a three-dimensional (3D) range of motion (ROM) analysis on the bilateral hip, knee, and ankle joints following the trip perturbation at a 0.89 m/s velocity for 0.12 m. This induced trip caused subjects to walk forward for a 0.26 s duration.

FINDINGS

The female group demonstrated significantly increased frontal plane ROM in the right hip (t = 2.71, p = 0.01) and left ankle (t = 2.16, p = 0.03) as well as increased sagittal plane ROM in the right (t = 2.07, p = 0.04) and left (t = 2.36, p = 0.02) ankles. There was a significant gender interaction on 3D body region (F = 6.84, p = 0.01) following the perturbation.

INTERPRETATION

There was a 3D gender difference on the lower limbs for balance control. The female group demonstrated increased sagittal motion in both ankles following a trip perturbation. In addition, their ROM increased on the dominant hip and non-dominant ankle in the frontal plane, which was compensated by step width for standing stability. Clinicians might want to consider the implications of gender differences on lower limb reaction patterns to help patients avoid potential injuries/falls.

Adaptive trunk sway velocities following repeated perturbations in subjects with and without low back pain

Faster trunk motions could be a strategy to prevent loss of balance and fall injuries due to unexpected perturbations. However, it is unclear how trunk sway velocities can be compensated during stepping in subjects with low back pain (LBP). The purpose of this study was to investigate lower limb reaction, swing, and step times, as well as trunk sway velocities at heel strike and toe-off, following repeated step perturbations between subjects with and without LBP. There were 30 subjects with LBP and 42 control subjects who were exposed to treadmill-induced perturbations at a velocity of 0.12 m/sec for 0.62 m. The treadmill-induced steps caused subjects to walk forward for 4.90 sec after the perturbation. The groups demonstrated significant interactions on the lower limb reaction times and on the number of repeated perturbations (F = 4.83, p = 0.03) due to a decreased step time at the first perturbation (t = 2.52, p = 0.01) in the LBP group. For the trunk sway velocities, the repeated perturbations demonstrated a significant interaction between groups (F = 4.65, p = 0.03). This adaptive trunk strategy for gait stability increased step times with repeated perturbations in the LBP group. The group interactions on the trunk sway velocities also indicated a possible somatosensory integration for step time adjustments to avoid potential fall hazards. This adaptive response with repeated step perturbations could result in compensatory trunk sway for gait stability.

Compensatory spinopelvic motions with and without a handheld task following a perturbation in standing between subjects with and without chronic low back pain

BACKGROUND

A handheld task-related compensation strategy could be used to avoid injuries in subjects with chronic low back pain (LBP). Those who suffer with LBP demonstrate reduced spinopelvic motion; however, there is a lack of understanding on dynamic mobility with a handheld task.

RESEARCH QUESTION

Are there differences in three-dimensional spinopelvic motions following a treadmill-induced perturbation in subjects with LBP while considering a handheld task?

METHODS

Twenty-five subjects (11 female and 14 male) with LBP and 38 control subjects (15 female and 23 male) participated in the study. Each group was introduced to walking perturbations (0.86 m/sec, velocity in 0.1 sec) with and without a handheld tray in a standing position. The induced trip allowed subjects to recover by walking forward for a 5 second duration while the spinopelvic angles were measured during the trip and the subsequent recovery period.

RESULTS

There was no significant group difference in the three-dimensional (3D) spinopelvic motions while holding or not holding a tray. However, the groups demonstrated a significant interaction on tray usage with 3D motions in the spinopelvic regions (F = 13.46, p = 0.001). The sagittal plane motion was significantly minimized with a handheld task for both the lumbar spine and pelvis in the LBP group.

SIGNIFICANCE

The LBP group demonstrated minimized lumbar and pelvic motions in the sagittal plane, which underpins their concern to reduce motion while holding a tray. The significant interaction between groups on tray usage for spinopelvic compensation represents a strategy for avoiding injuries. Further studies are required to determine strategies to enhance lumbopelvic integration with handheld tasks in individuals with LBP.

Stepping over an obstacle in patients with lumbar spinal stenosis: Trunk and lower extremities of kinematic and muscle activation normalized by double limb support. A preliminary study

BACKGROUND

Patients with LSS tend to adopt a flexed lumbar posture and trunk position, particularly when stepping over an obstacle, as this activity alters the biomechanical demands placed on the trunk and lower extremities.

OBJECTIVE

To investigate the effects of lumbar spinal stenosis (LSS) on patients' trunk and lower-extremity kinematics, and on activities involving the gluteus medius (GMed) and vastus lateralis (VL).

METHODS

All participants (9 older adult patients with LSS and 11 control subjects) were required to negotiate an obstacle while walking. Trunk and lower-extremity kinematic data and GMed and VL activities were recorded using a synchronized 3D motion capture system and surface electromyography.

RESULTS

The thoracic (12.01∘± 8.82∘ and 16.45∘± 10.80∘) and spinal (9.92∘± 14.03∘ and 5.99∘± 15.94∘) flexion angles of the leading and trailing swing limbs were higher, and the pelvic anterior tilting angle (2.37∘± 7.76∘ and 10.38∘± 8.07∘) was lower in the LSS group than in the control group (p< 0.05). With the exception of toe-off and normalized GMed activities in the contralateral leading limb (p> 0.05), all GMed (256.73 ± 112.22%, 174.00 ± 75.79%, and 270.57 ± 114.45%, respectively) and VL (208.98 ± 124.81%, 182.97 ± 93.23%, 283.91 ± 154.71%, and 394.42 ± 108.94%, respectively) activities of the contralateral leading and trailing swing limb (heel-strike and toe-off normalized activities) were significantly higher in the LSS group than in the control group (p< 0.05).

CONCLUSIONS

Patients with LSS exhibited trunk-flexed postures when stepping over an obstacle, and these trunk alignments placed higher demands on the GMed and VL activities normalized by double-limb support during joint loading in the single-leg stance. These findings support clinical recommendations for regulating the physical activity of obstacle negotiation that may be beneficial in the management of patients with LSS.

Trunk Reaction Time and Kinematic Changes Following Slip Perturbations in Subjects with Recurrent Low Back Pain

Postural responses following slip perturbations are critical to fall prevention strategies. It is unclear how postural reactions with a handheld task can validly be transferred to treadmill-induced slip perturbations in subjects with recurrent low back pain (LBP). The purpose of this study was to investigate trunk reaction times and trunk flexion angle as well as velocity following the slips between subjects with and without LBP. There were 29 subjects with LBP and 40 control subjects who participated in the study. Three levels of consecutive treadmill-induced slip perturbations were introduced at level 1 (duration: 0.10 s, velocity: 0.24 m/s, displacement: 1.20 cm), level 2 (0.12 s, 0.72 m/s, 4.32 cm), and level 3 (0.12 s, 1.37 m/s, 8.22 cm). The trunk reaction time, swing/step times, and trunk flexion angle as well as velocity at heel strike/toe-off were compared between the groups. There were significantly longer trunk reaction times (t = - 2.03, p = 0.04), swing times (t = - 2.63, p = 0.01), and step times (t = - 2.53, p = 0.01) in the LBP group at the level 1 slip perturbation. The groups demonstrated a significant interaction between the levels and trunk flexion angles (F = 4.72, p = 0.03), but there was no interaction between the levels and trunk flexion velocities (F = 0.07, p = 0.79). The LBP group demonstrated longer reaction times at the level 1 perturbation due to a possible pain recurrence. However, this compensatory tolerance was limited at the level 3 perturbation due to increased trunk flexion angle at heel strike and toe-off in the LBP group. Clinicians may consider a compensatory strategy to improve reaction time and minimize trunk flexion following slip perturbations in patients with LBP.

Effects of vision and cognitive load on static postural control in subjects with and without patellofemoral pain syndrome

OBJECTIVE

To compare the effects of vision and cognitive load on static postural control in subjects with and without patellofemoral pain syndrome (PFPS).

METHODS

Twenty-eight PFPS patients and 28 controls participated in the study. Postural control was assessed in isolation as well as with visual manipulation and cognitive loading on symptomatic limb. The outcome measures of postural control were quantified in terms of area, anterior-posterior (AP), medial-lateral (ML), and mean velocity (MV) of the displacements of center of pressure (COP). In addition, cognitive performance (auditory Stroop task) was measured in the forms of average reaction time and error ratio in baseline (sitting) and different postural conditions.

RESULTS

PFPS subjects showed greater increases in area (p = 0.01), AP (p = 0.01), and ML (p = 0.05) displacements of COP in the blindfolded tasks as compared to control group. However, cognitive load did not differently affect postural control in the two groups. Although PFPS and control group had similar reaction times in the sitting position (p = 0.29), PFPS subjects had longer reaction times than healthy subjects in dual task conditions (p = 0.04).

CONCLUSION

Visual inputs seem to be essential for discriminating postural control between PFPS and healthy individuals. PFPS patients biased toward decreasing cognitive performance more than healthy subjects when they perform the single leg stance and cognitive task concurrently.

Reliability of the Kinematic Steadiness Index during one-leg standing in subjects with recurrent low back pain

PURPOSE

To assess the reliability of standing time and the Kinematic Steadiness Index (KSI) in one-leg standing compared with the Timed Up and Go (TUG) test while considering anthropometric factors in subjects with recurrent low back pain (LBP).

METHODS

Sixty-six individuals participated in the study. The data were collected on two different days, 1 week apart. The KSI of the core spine, using video motion-capture techniques, was based on the relative standing time and relative standstill time. The intraclass correlation coefficient (ICC_2,1) was compared for the reliability between measures. The covariates, such as age, Body Mass Index, and the Oswestry Disability Index (ODI), were analyzed for any interactions based on these measures.

RESULTS

The standing time (t = - 1.01, p = 0.32) and the KSI (t = - 1.70, p = 0.09) were not significantly different between measures. The TUG results were not different between measures (t = 1.01, p = 0.32). The Cronbach's alpha for the standing time was 0.84, for KSI was 0.89, and for TUG was 0.76. The standing time and KSI demonstrated an interaction with age, while the TUG demonstrated an interaction with the ODI score.

CONCLUSIONS

The KSI during one-leg standing could help to develop a practical tool to justify quantity and quality of balance outcome measures, which identify balance deficits and core spine rehabilitation strategies in subjects with recurrent LBP.

Kinematic chain reactions on trunk and dynamic postural steadiness in subjects with recurrent low back pain

Although subjects with recurrent low back pain (LBP) demonstrate altered trunk control, the kinematic and kinetic responses of the trunk have not been carefully investigated. This study was conducted to compare the standing time, spine range of motion (ROM), and dynamic postural steadiness index (DPSI) based on visual condition between subjects with and without recurrent LBP during upright one leg standing. Sixty-three individuals participated in the study, including 34 control subjects and 29 subjects with recurrent LBP. The DPSI was a composite of the medio-lateral (MLSI), anterior-posterior (APSI), and vertical steadiness indices (VSI) on a force platform. The control group demonstrated longer standing time (s) during the eyes-open condition than the LBP group (26.82±6.03 vs. 19.87±9.36; t=2.96, p=0.01). Regarding spine ROM, visual condition was significantly different between groups (F=7.09, p=0.01) and demonstrated interactions with spine region and group (F=5.53, p=0.02). For the kinetic measures, there was a significant interaction between visual conditions and indices (F=25.30, p=0.001). In the LBP group, the DPSI was significantly correlated with the MLSI (r=0.59, p=0.002), APSI (r=0.44, p=0.03), and VSI (r=0.98, p=0.01) in the eyes-closed condition. Overall, the results of this study indicated that the LBP group decreased thorax and lumbar spine rotations during the eyes-closed condition. The LBP group also demonstrated positive correlations with the kinetic indices, enhancing dynamic postural steadiness in the eyes-closed condition in order to possibly avoid pain or further injury. This dynamic postural steadiness strategy is necessary to improve kinetic and kinematic chain reactions in the LBP group. This compensatory pattern supports the development of optimal postural correction strategies to prevent LBP recurrence and might represent a chain reaction to protect trunk control without visual input.

The kinetic and kinematic stability measures in healthy adult subjects with and without flat foot

BACKGROUND

Flat foot problems are associated with impaired mobility and postural stability. The purpose of this study was to compare the kinematic and kinetic indices during one leg standing between subjects with and without flat foot.

METHODS

Forty-four participants enrolled in the study, including 22 subjects with flat foot and 22 control subjects. The measurements included kinematic stability on the trunk as well as kinetic stability from a force plate. All participants were asked to maintain one leg standing with the contralateral hip and knee flexed to approximately 90° for 25seconds.

RESULTS

The kinetic index decreased in the flat foot group (t=-5.08, p=0.001) during one leg standing without visual input. There were strong correlations between kinetic and kinematic stabilities (0.75-0.86) with visual input and moderate correlations (0.49-0.67) without visual input in the control group.

DISCUSSION

The flat foot group exhibited a significantly decreased kinetic index without visual input. The more effective postural stability in the control group might be due to efficient compensatory strategies utilized without visual input to maintain one leg standing. These outcome measures could help to develop a practical test leading to kinematic postural changes.

The ground reaction force thresholds for detecting postural stability in participants with and without flat foot

Foot mobility commonly contributes to injury via altered motion of the lower extremities. However, there is a lack of understanding of sensitive kinetic changes with flat foot. The purpose of this study was to investigate the threshold that best distinguishes between participants with and without flat foot. The kinetic stability index was developed based on the three-dimensional data from the ground reaction force (GRF) during one leg standing. In total, 34 control participants and 30 participants with flat foot were asked to maintain one leg standing for 25s with the contra lateral hip and knee flexed approximately 90°. The various thresholds (3, 7, 15, 30, 50, and 200N) were analyzed by the kinetic stability index. The standing time was not significantly different between groups (t=1.07, p=0.28); however, there were significant differences on threshold level (F=369.23, p=0.001) as well as group interactions with threshold (F=6.72, p=0.01). The post hoc test indicated that less than 15N was the best to detect the kinetic stability index between the groups. Clinicians need to understand sensitive threshold settings to differentiate the participants with and without flat foot. The threshold changes might be altered to detect postural deficits by the kinetic stability index.