An accelerometry system was developed based on the inverted pendulum model and its effectiveness to measure the body's sway path and sway angle was verified in healthy adult volunteers. Sway path represents the body's movement from its center of mass position projected to the ground surface while sway angle represents the body 's orientation from the vertical. M athematical models were developed to determine the sway displacement and sway angle from the accelerometry system. The resulting values were compared with the manual measurements obtained from a plumb bob based setup and found to correlate closely. Using the developed system, measures that analyzed the contribution of the visual, somatosensory and vestibular systems to balance were obtained. It was found that the accelerometry system followed the principle of motion of an inverted pendulum and provided information that can assist in better understanding of balance and thus it may assist clinicians in diagnosing balance dysfunctions.

Kohonen neural network (KNN) was used to investigate the effects of the visual, proprioceptive and vestibular systems using the sway information in the mediolateral (ML) and anterior-posterior (AP) directions, obtained from an inertial measurement unit, placed at the lower backs of 23 healthy adult subjects (10 males, 13 females, mean (standard deviation) age: 24.5 (4.0) years, height: 173.6 (6.8) centimeter, weight: 72.7 (9.9) kg). The measurements were based on the modified Clinical Test of Sensory Interaction and Balance (mCTSIB). KNN clustered the subjects’ time-domain sway measures by processing their sway’s root mean square position, velocity, and acceleration. Clustering effectiveness was established using external performance indicators such as purity, precision-recall, and F-measure. Differences in these measures, from the clustering of each mCTSIB condition with its condition, were used to extract information about the balance-related sensory systems, where smaller values indicated reduced sway differences. The results for the parameters of purity, precision, recall, and F-measure were higher in the AP direction as compared to the ML direction by 7.12%, 11.64%, 7.12%, and 9.50% respectively, with their differences statistically significant (p < 0.05) thus suggesting the related sensory systems affect majorly the AP direction sway as compared to the ML direction sway. Sway differences in the ML direction were lowest in the presence of the visual system. It was concluded that the effect of the visual system on the balance can be examined mostly by the ML sway while the proprioceptive and vestibular systems can be examined mostly by the AP direction sway.

A number of mechanisms and sensory systems in humans are associated with the maintenance of balance. Diagnosis and monitoring of balance dysfunctions could be assisted by exploring deviations of data recorded from patients with comparative or reference data from healthy individuals. To this effect, principal component analysis (PCA) was applied to accelerometry obtained time domain balance data. The data were recorded from 21 healthy adults (10 males and 11 females, mean age 24.5 years, standard deviation 4.0 years, mean height 173.6 cm, standard deviation 6.8 cm, and mean weight 72.7 kg, standard deviation 9.9 kg) in the medio-lateral (ML) and anterior- posterior (AP) directions. The subjects performed tasks specified in the modified clinical test of sensory interaction on balance (mCTSIB) while an accelerometry device was attached at their lower back, in the position of the iliac crest. Eighteen-time domain measures that quantified body's displacement, velocity and acceleration were obtained and processed using PCA. Based on the observations from PCA, further investigations were carried out on the root mean square (RMS) velocity using the Bland and Altman plots and other statistical related analysis. It was observed that the anterior and posterior directions were more sensitive to the absence or presence of balance sensory (visual, somatosensory and vestibular) inputs as compared to the mediolateral (ML) direction. A greater coherence in sway information was observed in the somatosensory system as compared to the visual and vestibular systems. There was more stability in the interaction between the somatosensory and the vestibular systems as compared to that of the visual and vestibular systems. The results obtained could be helpful to clinicians in balance related analysis and diagnosis.