Background: Foam pads are increasingly used on force platforms during balance assessments in order to produce increased instability thereby permitting the measurement of enhanced posturographic parameters. A variety of foam pads providing different material properties have thus been used, although it is still unclear which characteristics produce the most effective and reliable tests. Furthermore, the effects of participant bodyweight on the performance
of the foam pads and outcome of the test are unknown. This project investigated how different foam samples affected postural sway velocity in participants of different weights.
Method: Four foam types were tested according to a modified American Society for Testing and Materials standard method for testing flexible cellular materials. Thirty-six healthy male factory workers divided into three groups according to body mass were tested three times for each of the 13 randomly-selected experimental situations for changes in postural sway velocity in this cross-over study. Descriptive and inferential statistics were used to compare the results and evaluate the difference in sway velocity between mass groups.
Results: For the materials considered here, the modulus of elasticity of the foam pads when compressed by 25% of their original heights was inversely proportional to their density. The largest changes in postural sway velocity were measured when the pads of highest stiffness were used, with memory foam pads being the least likely to produce significant changes.
Conclusions: The type of foam pads used in posturography is indeed important. Our study shows that the samples with a higher modulus of elasticity produced the largest change in postural sway velocity during quiet stance. The results suggest that foam pads used for static computerised posturography should 1) possess a higher modulus of elasticity and 2) show linear deformation properties matched to the participants’ weight.
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