In Search of a Relationship Between Body Mass Index Classification and Balance Acquisition

Purpose

Although it has been suggested that body weight is a strong predictor of postural stability, the influence of body mass index (BMI) on learning a dynamic balance task has not been examined. Therefore, the purpose of this research was to investigate the relationship between BMI classifications and balance acquisition in a postural perturbation task.

Methods

Thirty college students (age: 20-35) were classified based on their BMI into a normal weight (M=21.43, SD=2.17), overweight (M=26.16, SD=.92), and obese (M=34.42, SD=3.08) group. Participants were asked to stand on a balance board and maintain it parallel with the floor for 12 consecutive trials lasting 30 s for each. To assess balance performance, a Biopac MP100 System was used to record board movements at 50 Hz, providing a novel way to collect real-time data of the angular displacement. Board movement was demarcated to 15 degrees on each side. Moreover, in an effort to minimize the interference of head movements on postural control, each participant was instructed to look at a computer monitor placed six feet (1.83 m) in front of the board which displayed Chinese characters paired with their English equivalents to keep each subject's attention focus on the same place.

Analysis/Results

The primary dependent variable was root mean-squared error (RMSE) of the board's angular displacement. A 3 (normal, overweight, obese) x 12 (trials) ANOVA with repeated measurement on trials was used to determine mean effects. The results demonstrated a main effect on classifications of BMI, F (2, 27) = 7.37, p<.01, and a practice effect on trials, F (11, 297) = 34.41, p<.01. Also, the interaction between classifications and trials was significant, F (22, 297) = 1.71, p<.05. Therefore, a simple main effect was used to further analyze the results. It revealed that the obese group had a significant learning deficit on balance performance from trial 3 to trial 12 compared to the other two study groups (p<.05). In contrast, there was no difference on balance performance of the first two trials among the three groups (p>.05). An additional correlation analysis showed both greater body weight (r = .63, p<.01) and height (r = .39, p<.05) contributed to poor balance.

Conclusions

The present findings indicate that a BMI classification of obese adversely affects the ability to acquire balance in a postural perturbation task.