Objectives: 

Constraints in a man's limits of stability (LOS) may correlate to risk for fall or instability during weight shifting activities. The aim of this study was to investigate the effect of changing slope angle of support surface on LOS.

Materials: 

In the study participated 8 young healthy volunteers (6 female, mean age 26.1 ± 0.9 yrs). Subjects stood on support surface with variable slope angle which was placed on force platform. Three dual-axis accelerometers (ADXL203) were placed on the fifth lumbar (L5), the fourth thoracic (Th4) vertebra and on the posterior aspect of the right thigh (RT). Participants were instructed to make a maximal voluntary forward inclination (using ankle strategy) after hearing sound signal and persist in this position till trial end. Each trial lasted 10s and was repeated 3 times, under 3 levels of slope angle (S0, S1, S2) and with open eyes (EO) and eyes closed (EC). We evaluated the maximal displacement of CoP and amplitude of body segment tilts. ANOVA with 2-way repeated measures was used as a statistic method.

Results: 

We observed that the lifting of surface slope angle up resulted in decrease of CoP displacement (p<0.001). Data from accelerometers placed at RT and L5 had a similar trends in decrease of amplitude (p<0.01) and data from Th4 accelerometer showed significant effect on amplitude reduction too (p<0.05). We also found out a significant influence of vision on amplitude in CoP and RT (p<0.001) and L5 (p<0.01). From Th4 data a significant effect of vision was not improved. Significant interaction was not also found between vision and support surface slope angle.

Conclusions: 

The present study showed that the functional limit of stability in forward direction is influenced by change of support surface slope angle. The decline of functional limit of stability could leads to higher risk of falls and injures. To determine limits of stability should be a suitable approach for analysing of balance control changes.

Supported by VEGA grant No. 2/0186/10