OBJECTIVE: To analyze the balance function of injured lower limb by dynamic posturography. METHODS: Using the dynamic posturography instrument, the postural evoked responses of sixty-two normal people and two hundred and fifty-eight people with injured lower limb bones and joints were detected. The test was included sensory organization test (SOT) and adaption test (ADT). The results of two groups were compared by t test. RESULTS: Compared with the normal people, the impaired people had significant statistical differences in balance scores of SOT3-SOT6 and proportion score of dynamic proprioception (P < 0.05). There was no obvious decrease in ADT. CONCLUSION The balance function of injured lower limb significantly decreases.
Case-Control Studies ; Humans ; Lower Extremity/physiopathology* ; Postural Balance/physiology* ; Posture/physiology* ; Proprioception/physiology*

The present study was aimed at the optimal solution of the main muscular force distribution in the lower extremity during standing balance of human. The movement musculoskeletal system of lower extremity was simplified to a physical model with 3 joints and 9 muscles. Then on the basis of this model, an optimum mathematical model was built up to solve the problem of redundant muscle forces. Particle swarm optimization (PSO) algorithm is used to calculate the single objective and multi-objective problem respectively. The numerical results indicated that the multi-objective optimization could be more reasonable to obtain the distribution and variation of the 9 muscular forces. Finally, the coordination of each muscle group during maintaining standing balance under the passive movement was qualitatively analyzed using the simulation results obtained.
Algorithms ; Gait ; Humans ; Joints ; Models, Biological ; Models, Theoretical ; Movement ; Muscles ; physiology ; Postural Balance

BACKGROUNDAttention deficit hyperactivity disorder (ADHD) is one of the most commonly diagnosed psychiatric disorder in childhood. ADHD children with overlapping symptoms and signs of motor problems have more serious prognosis than that of children with ADHD only. However, the motor and sensory processing problems in children with ADHD have not been studied well. Few people adopt the technique of computerized dynamic posturography (CDP) in the study of ADHD, which is applied widely in clinical and laboratory research to objectively evaluate human's balance performance. This study aimed to assess the characteristics of postural control and sensory information processing of boys with two subtypes of ADHD by using CDP, so as to provide the proof for non-drug therapy of ADHD.

METHODFrom June 2003 to September 2004, a total of 73 boys (7-15 years of age) with ADHD and 73 normal developing boys matched by age and intelligence quotient from Peking University Institute of Mental Health were recruited in the study. The Sensory Organization Test was adopted to test the static balance performance under six sensory input conditions by SMART EquiTest 8.0 (NeuroCom) instrument. The sensory information from three sensory systems were available under condition 1, the visual inputs were removed or distorted under condition 2 or 3, the somatosensory inputs were in conflict with or without the visual inputs removed under condition 4 or 5, and both the visual and somatosensory inputs were in conflict under condition 6. The indexes of equilibrium score, somatosensory, vestibular, and visual ratios, and strategy scores were analyzed to indicate the subjects' postural control ability.

RESULTSADHD boys had significantly lower composite equilibrium score (CES) than the normal group (P < 0.05). Under condition 1 and conditions 3-6, the equilibrium scores (ES) of the ADHD group were significantly lower (all P < 0.05) than those of the control. Significantly lower visual and vestibular ratios and strategy scores under conditions 4-6 were found in boys with ADHD compared with the control group (P < 0.05). Boys of ADHD-predominantly inattentive (ADHD-I) type had a significantly lower CES and ES under conditions 4-6 than the controls (all P < 0.05) while the ESs of ADHD-combined type (ADHD-C) boys under each condition were similar with that of boys with ADHD-I and no significant difference was found between boys with ADHD-C and the control group (all P > 0.05). Compared with the control group, the ADHD-I boys showed significantly lower visual and vestibular ratios and strategy scores under conditions 4-6 whereas the ADHD-C boys showed a trend of lower visual ratio (all P < 0.05).

CONCLUSIONSADHD boys had a poorer static postural control ability and impaired function of processing visual and vestibular information compared with the normal control. Boys with ADHD-I showed particularly severe defect of static postural control and vestibular function integrating conflict information than normal boys. These deficits may be an important contributor to the clinical presentation of ADHD children and their cognitive deficits. Assessment and training of postural control function would be suggested during the diagnosis and treatment of ADHD children.

Adolescent ; Attention Deficit Disorder with Hyperactivity ; physiopathology ; Case-Control Studies ; Child ; Humans ; Male ; Postural Balance ; physiology

In order to find the linear region of adjustment process about human body balance under the passive movement, and provide the basis for the unified evaluation criteria of passive balance test, an equipment was built with pulsed excitation source and wave detector of gravity's center. The pulsed excitation source was a multi-dimensional motion platform with high accuracy. The wave detector was a force platform. Human body and force platform were treated as a whole object, and the dynamic model of the object was built using the method of system identification. The balance ability was evaluated by setting time. In the pulse excitement range from 2mm to 20 mm with 2mm increments, balance ability of 5 students was evaluated and analyzed respectively. Results showed that response curve of human balance regulation was a typical second order linear system characteristic, and in a large enough linear region, the evaluating result had good consistency.
Algorithms ; Equipment Design ; Female ; Humans ; Linear Models ; Male ; Movement ; Postural Balance ; physiology ; Young Adult

OBJECTIVE: To investigate the postural stability after head-shaking in the normal young individuals. METHOD: Twenty-eight normal young individuals were taken the static posturography under 4 standing conditions including (T1) head center and eye open (EO), (T2) head center and eye closed, (T3) after head-shaking and EO, (T4) after head-shaking and EC. The sway velocity (SV) of center of pressure under feet in each testing condition was recorded as parameter and each test protocol was 30 s. RESULT: All examinee did not fall in each testing condition. (1) The SV increased (4.60 +/- 6.36) % after head-shaking in the EO condition, while the (8.86 +/- 8.27) % was demonstrated in the EC condition. There was significant difference between these two degrees of increase (t = 2.759, P < 0.01). (2) In static head orientation, the SV of EC (T2) increased (9.83 +/- 5.10)% compared with the SV of EO condition (T1). However, the SV of EC (T4) increased (14.05 +/- 6.89) % compared with the SV of EO condition (T3) after head-shaking. And there was significant difference between these two degrees of increase (t = 2.772, P < 0.01). CONCLUSION The stimuli of head-shaking that interrupted input from vestibular end organ can affect the function of vestibulospinal reflex in healthy young individual, especially when the visual input was interrupted simultaneously. In order to keeping balance after head-shaking, there was a complex mechanism sensory reorganization even in the normal young subject.
Female ; Head ; Humans ; Male ; Postural Balance ; Reflex, Vestibulo-Ocular ; physiology ; Young Adult

Nowadays, for gait instability phenomenon, many researches have been carried out at home and abroad. However, the relationship between plantar pressure and gait parameters in the process of balance adjustment is still unclear. This study describes the human body adaptive balance reaction during slip events on slippery level walk by plantar pressure and gait analysis. Ten healthy male subjects walked on a level path wearing shoes with two contrastive contaminants (dry, oil). The study collected and analyzed the change rule of spatiotemporal parameters, plantar pressure parameters, vertical ground reaction force (VGRF), etc. The results showed that the human body adaptive balance reaction during slip events on slippery level walk mainly included lighter touch at the heel strikes, tighter grip at the toe offs, a lower velocity, a shorter stride length and longer support time. These changes are used to maintain or recover body balance. These results would be able to explore new ideas and provide reference value for slip injury prevention, walking rehabilitation training design, research and development of walking assistive equipments, etc.
Adaptation, Physiological ; Foot ; Gait ; Humans ; Male ; Postural Balance ; physiology ; Pressure ; Reference Values ; Walking

In order to evaluate the ability of human standing balance scientifically, we in this study proposed a new evaluation method based on the chaos nonlinear analysis theory. In this method, a sinusoidal acceleration stimulus in forward/backward direction was forced under the subjects' feet, which was supplied by a motion platform. In addition, three acceleration sensors, which were fixed to the shoulder, hip and knee of each subject, were applied to capture the balance adjustment dynamic data. Through reconstructing the system phase space, we calculated the largest Lyapunov exponent (LLE) of the dynamic data of subjects' different segments, then used the sum of the squares of the difference between each LLE (SSDLLE) as the balance capabilities evaluation index. Finally, 20 subjects' indexes were calculated, and compared with evaluation results of existing methods. The results showed that the SSDLLE were more in line with the subjects' performance during the experiment, and it could measure the body's balance ability to some extent. Moreover, the results also illustrated that balance level was determined by the coordinate ability of various joints, and there might be more balance control strategy in the process of maintaining balance.
Acceleration ; Biomechanical Phenomena ; Humans ; Models, Biological ; Motion ; Nonlinear Dynamics ; Postural Balance ; physiology

Aiming at slips and falls occurred during adults' walking, a method was proposed that could predict slips and falls based on center of mass (COM) recovery response. This method, based on the Kane's equation dynamic walking model of the lower extremities, can be used to rapidly detect dynamic parameters in each gait cycle, and analyze any instantaneous balance status of slips and falls, and the characteristic COM curves may be accomplished on the basis of the measurement data. Moreover, causations, phases and processes about gaits of adults' slips and falls could be judged and analyzed by the characteristic curves. When the distance between the projection point of COM to base of support (BOS) domain is more than 0.012-0. 015m, human gaits have a tendency to slip and fall. When COM velocity response curve value is between 0.9-2. 1m/s, human gaits are normal and stable. The experimental results of slips and falls about the two different age groups showed that the method is able to predict and revise slips and falls by the COM recovery response characteristic curves.
Accidental Falls ; prevention & control ; Biomechanical Phenomena ; Computer Simulation ; Gait ; physiology ; Humans ; Models, Biological ; Postural Balance ; physiology ; Walking ; physiology

BACKGROUNDLow back pain (LBP) is a common clinical problem. Many researchers have demonstrated that LBP disorders have difference in sensory strategies for postural control. Optokinetic stimulation (OKS) of optic flow has been widely applied to study its effect on vision, but has not been applied to LBP. Here we used OKS on different surfaces to investigate the characteristics of chronic nonspecific LBP (CNLBP) posture control, so as to provide new theoretical and experimental data for further recognizing CNLBP and enriching its treatment.

METHODSFifteen individuals with CNLBP (age range 25-40 years) and 15 age and gender-matched control subjects were recruited. Each subject, while standing on a stable or soft surface, was exposed to random-dot patterns projected on a large screen, with the dots displaying expansion (+) and contraction (-) and velocities including 80°, 40°, and 20° per second. The visual stimulus used a "stimuli-interval" pattern. The peak velocity, different phases' standard deviation (SD) of the anterior-posterior centre of pressure (COP) displacements and the total length of the medial-lateral COP sway (LML) for stable surface and soft surface were recorded by force platform.

RESULTSThe main effect of surface on all parameters was significant, while the main effect of group and OKS showed no significance with the exception of peak velocity (F(3, 95) = 3.6, P = 0.01) and A2 (F(5, 140) = 9.34, P < 0.01) for which the effect of OKS was significant. The interactions of group by OKS of A2 (F(5, 140) = 3.65, P < 0.01) and group by surface by OKS (F(5,140) = 2.83, P = 0.02), and surface by OKS of A1 and A3 (P < 0.05) were significant. It was reported that significantly more SD in amplitude in the T2 phase was seen in persons with CNLBP when confronting the + 40 stimuli on the soft surface (P < 0.05) compared to healthy individuals.

CONCLUSIONSThere was no significance between persons with CNLBP and healthy people when using the stable surface. Subjects with LBP showed decreased efficiency of postural adjustment when exposed to more complicated tasks and environments, especially OKS in the expansion direction, and displayed a visual-dependent phenomenon. This result suggested that the treatment of abnormal motor patterns in people with LBP should take the properties of task and environment into account.

Adult ; Case-Control Studies ; Female ; Healthy Volunteers ; Humans ; Low Back Pain ; physiopathology ; Male ; Postural Balance ; physiology ; Posture ; physiology

OBJECTIVETo compare balance ability between elderly individuals who practiced Tai-Chi-Chuan (TCC) for average 9.64 years and elderly individuals who did not practice TCC and its relationship with lower extremity muscle strength and ankle proprioception.

METHODSTwenty-five elderly volunteers were divided into two groups according to their TCC practcing experience. Sixteen were TCC group and the other nine were control population. Subjects completed a static balance test and ankle proprioception test using a custom-designed evaluation system, and concentric and eccentric knee extensor and flexor muscle strength tests. Subjects stood on the plate form to measure the proprioception in functional standing position which was differed from the previous studies. Multiple linear regressions were also used to predict the important factor affecting balance.

RESULTSTCC group performed better than the control group in balance, proprioception, and muscle strength of lower extremity. The proprioception was the most important factor related to balance ability and it can be accounted for explaining 44% of variance in medial-lateral sway direction, and 53% of variance in antero-posterior sway direction. The proprioception may be a more important factor which affecting the balance ability.

CONCLUSIONTCC training is recommended to the elders; as it can improve balance ability through better proprioception.

Aged ; Ankle Joint ; physiology ; Female ; Humans ; Kinesthesis ; Linear Models ; Male ; Middle Aged ; Muscle Strength ; physiology ; Postural Balance ; physiology ; Posture ; physiology ; Proprioception ; physiology ; Tai Ji