Postural control is the process of maintaining the Centre of gravity (COG) within the base of support through continuous activity of muscular activity and joint positioning [1]. Postural stability is important in maintaining body balance during activities of daily living, like quiet standing, walking and mostly important during high degree of balance control when participating in sports and dancing. Sway is the horizontal movement of COG present in the body even when a person is standing still. A certain amount of sway is unavoidable due to some perturbations within the body during breathing, shifting weight from one foot to other foot. During standing, there will be separate Centre of pressure under each foot. An appropriate motor response, sensory detection of body’s movement and integration of sensory motor information into the CNS are important to maintain body balance [2,3,4].The position of the body in relation to space is determined by visual, vestibular and somatosensory systems. Static and dynamic maintenance of body balance involve the activity of coordinated muscular kinetic chain. Individuals with poor postural balance are more prone to falls that causes injuries, fractures, etc..[5]

Increased adipose tissue and body mass leads to reduction in body balance and causes risk of falls mainly when combined with lower muscular mass, which leads to biomechanical failure of muscular response results in loss of stability. Increased abdominal fat in obese individuals leads to increased lumbar lordosis, so there will be more anterior dislocation of COG [6,7]. The prevalence of overweight and obese among college students was found to be 13.2% and 5.2% respectively.

In underweight individuals due to poor nutrition supply they loss their energy quickly. Due to poor nutrition their muscles may become weak and it get fatigue easily. Mainly the lower limb muscles will get easily fatigue. Due to muscle fatigue there is altered somatosensory input which results in deficits in neuromuscular and postural control [8,9].

In normal weight individuals they have normal appropriate motor response, visual, vestibular and somatosensory systems. The body mass is measured using BMI [10]. Body mass index is a measure of body fat based on height and weight of an individual.

According to body mass index (BMI) the value below 18.5 is considered as lean, 18.5 to 24.9 as normal, 25 to 29.9 as overweight and above 30 as obese. Forceplate and Posturography is a simple method that is commonly used in the contemporary laboratory and clinic to measure postural sway. However, it is an expensive procedure and may not be easily available in rural set-ups. Sway meter is an inexpensive method and sway measurement obtained from sway meter is strongly correlated with the measurements obtained from the force plate, in this sway can be measured during bipedal stance [11]. Hence, this study was intended to analyze the correlation between the body mass and postural control in bipedal stance among healthy individuals.

To analyze if there is any effect of body mass on postural sway in healthy individuals.

Seventy-five young individuals between 18 to 23 years of age were included in the study (both males and females). After initial general assessment each individuals were assigned into three groups based on their BMI by using BMI chart: group A (n=25) underweight subjects (BMI below 18.5), group B (n=25) normal weight subjects (BMI 18.5 to 24.9), group C(n=25) obese subjects (BMI>30). Then postural control was analyzed using the sway meter for all the individuals.

The sway meter was developed with a 40 cm pole attached to a belt and at the opposite end of the bar pen was appended to quantify the postural sway. The belt was fit at level of anterior superior iliac spine. The graph sheet was set behind the subject and relocation of graph sheet ought to be avoided amid the estimation. Sway meter was set behind the subject, where the impact of vision was likewise barred as illustrated in Fig.1 and Fig.2. Subject should remain on the sheet of paper with foot impressions; the separation between the feet was around 3 inches. The technique was explained to the subjects previously beginning every preliminary.

Fig 1.Sway measure posterior view

Fig 2.Sway measure lateral view

The subjects were told to keep their hands by their side and stand as still as possible on the foot imprints in bare foot. Duration of each trial was 30 seconds. A starting point was marked on the graph sheet, at the end of 30 second the rod of the sway meter was taken away from the graph sheet. Rest period of about 5 to 10 seconds was given to the subjects after each trial, but the subjects were not allowed to move the feet from the footprints. The procedure was repeated for each trial. Six trials were done, first three trials with eyes opened and next three trials with eyes closed. Total duration of all trials was 6 to 7 minutes, maximum deviation in three trials was taken for analysis.

The collected data were tabulated and analyzed using both descriptive and inferential statistics. All the parameters were assessed using statistical package for social science (SPSS) version 24. One Way ANOVA includes following tests (Test of Homogeneity of Variance, ANOVA, Post Hoc test Tukey HSD) (multiple comparison) was adopted to find statistical difference between three groups. Pearson’s Co- relation of Co-efficient analysis was done to find the association factors between three groups.

On comparing Mean values of Group A, Group B & Group C on Body Mass Index (BMI) & Postural Control in Eye Open from Graph I and Table-1. There significant difference in Anterior, Posterior & Postural Sway towards left between (Group A) ,(Group B)& (Group C) (*- P ≤ 0.001). Hence Null Hypothesis is Rejected. But there is no significant difference based on Body Mass Index (BMI) & Right Postural Sway with Eye open between (Group A) ,(Group B)& (Group C) in (*- P > 0.05).Hence Alternative Hypothesis is Rejected.

On comparing Mean values of Group A, Group B & Group C on Body Mass Index (BMI) & Postural Control in Eye Closed from Graph II and Table-2. There is significant difference in Anterior, Posterior & Postural Sway towards left between (Group A) ,(Group B)& (Group C) (*- P ≤ 0.001). Hence Null Hypothesis is Rejected. But there is no significant difference based on Body Mass Index (BMI) & Right Postural Sway with Eye Closed between (Group A), (Group B)& (Group C) in (*- P > 0.05).Hence Alternative Hypothesis is Rejected.

GRAPH – II Comparison of Body Mass Index (BMI) & Postural Control with Eye Closed using Test of Homogeneity of Variance &One Anova Test between Group A, Group B and Group C

On analyzing Table-3 and Table-4, it is inferred that there is a Positive association and strong correlation between Body Mass Index and Postural Control with eye open & eye closed in anterior, posterior &postural sway towards left between the Groups at (P ≤ 0.05). Likewise, there is a Negative association and Weak correlation between Body Mass Index and Postural Control with eye open & eye closed in postural sway towards right between the Groups at (P ≥ 0.05).

TABLE-1. Comparison of Body Mass Index (BMI) & Postural Control with Eye Open using Test of Homogeneity of Variance &One Anova Test between Group A, Group B and Group C

ANT- ANTERIOR, POST - POSTERIOR, GROUP A - UNDERWEIGHT, GROUP B - NORMAL, GROUP C- OVERWEIGHT(*- P > 0.05),(**- P ≤ 0.05),),(***- P ≤ 0.001)

TABLE- 2. Comparison of Body Mass Index (BMI) & Postural Control with Eye Closed using Test of Homogeneity of Variance&One Anova Test between Group A, Group B and Group C

GROUP A - UNDERWEIGHT, GROUP B- NORMAL , GROUP C- OVERWEIGHT(*- P > 0.05),(**- P ≤ 0.05),),(***- P ≤ 0.001)

TABLE -3. Pearson Correlation of Coefficient in Body Mass Index& Postural Control with Eye Open between Group A, Group B &Group C

TABLE-4. Pearson Correlation of Coefficient in Body Mass Index& Postural Control with Eye Closed between GroupA,Group B &Group C

This study aimed to find whether there is any correlation between Body Mass Index and balance control in healthy individuals .The postural sway was measured in two diverse conditions using sway meter, in eyes opened and eyes closed condition. In both eyes opened and closed conditions, there were subjects in normal group who did not show sway in any directions.

In some individuals, absence of sway was found in right lateral and left lateral direction. Maximum number of individuals did not show any sway in right lateral direction comparing to other directions as suggested by Sivakumar Ramachandra et al 2010¹². There is a negative and weak correlation between Body Mass Index and postural control with eyes opened and eyes closed in postural sway towards right between the groups, this is because the individuals participated in this study had right hand dominance. When the subjects were solicited to share their experience of their participation in the study, 30% of the subjects reported that there was less time interval between the six trials, 60% of the subjects also admitted that they attempted to control their sway and many of the subjects stated they felt no discomfort.

For underweight individuals in eyes opened condition, the sway increased to a maximum in posterior direction and minimum sway in right side direction. In the eyes closed condition they had more sway in anterior direction and minimum sway in right side direction. The sway found in lean individuals could be due to localized plantar flexor fatigue that cause impairment to postural control as suggested by Yoav Gimmon et al 2011.

For normal weight subjects in eyes opened condition the sway increased in anterior direction and minimal sway was noticed in left side direction. In eyes, closed condition the sway increased in anterior direction and decreased in posterior direction. The increase in anterior sway could be because of the Wand phenomenon explained by Dennet.¹³

For overweight subjects, in eyes opened condition the sway was maximum in left side and minimum at right side. In eyes, closed condition the maximum sway was in left side and minimum sway in right side. Bulsara Z et al 2015 suggested that change in BMI affects the balance of the individuals and found that in increased BMI there is difficulty in making adjustments in response to external disturbances in orthostatic position and cause increase postural instability. In our study we found that there was least amount of sway in normal individuals followed by underweight and overweight individuals.

The limitations of this study are less sample size and the anthropometric influence on postural sway was not considered. 60% of the subjects reported that they attempted to control the postural sway, few subjects reported that they were not able to give 6 trials continuously (3 trials with eyes open & 3 trials with eyes closed) and difference in the postural sway within both the sexes was not considered.

In conclusion, this study reveals that there is strong correlation between Body Mass Index and postural control. Subjects with eyes closed and eyes opened condition showed sway in anterior, posterior and left directions, but there is weak correlation between BMI and postural control towards right side direction.

We thank Dr.M.G.R Educational and Research institute for granting permission for doing this research work at ACS medical college and hospital. Our sincere thanks to Dr.S.Sudhakar, Associate professor, Faculty of physiotherapy for his support and guidance in completion of the statistical analysis of this work.