Comparative study of plantar pressure during step exercise in different floor conditions.

Mechanical load has been estimated during step exercise based on ground reaction force (GRF) obtained by force platforms. It is not yet accurately known whether these measures reflect foot contact forces once the latter depend on footwear and are potentially modified by the compliant properties of the step bench. The aim of the study was to compare maximal and mean plantar pressure (PP), and maximal GRF obtained by pressure insoles after performing seven movements both over two metal force platforms and over the step bench. Fifteen step-experienced females performed the movements at the cadences of 130 and 140 beats per minute. PP and GRF (estimated from PP) obtained for each floor condition were compared. Maximal PP ranged from 29.27 +/- 9.94 to 47.07 +/- 12.88 N/cm2 as for metal platforms, and from 28.20 +/- 9.32 to 43.00 +/- 13.80 N/cm2 as for the step bench. Mean PP ranged from 11.09 +/- 1.62 to 14.32 +/- 2.06 N/cm2 (platforms) and from 10.71 +/- 1.54 to 14.22 +/- 1.77 N/cm2 (step bench). GRF (normalized body weight) ranged from 1.43 +/- 0.14 to 2.41 +/- 0.24 BW (platforms) and from 1.38 +/- 0.14 to 2.36 +/- 0.19 BW (step bench). No significant statistical differences were obtained for most of the comparisons between the two conditions tested. The results suggest that metal force platform surfaces are suitable to assess mechanical load during this physical activity. The forces applied to the foot are similar to the softer step bench and the hard force platform surface. This may reflect the ability of the performers to adapt their movement patterns to normalize the impact forces in different floor conditions.