Relationship between muscular strength and deflection characteristics of the center of foot pressure during landing after crossover stepping in the elderly.

This study aimed to investigate the relationship between the muscular strength of the lower extremity in a load side and the characteristics of center of foot pressure (COP) during landing after crossover stepping in the elderly. The study population comprised 8 elderly subjects (average age, 75.8+/-8.0 years) and 9 young individuals (average age, 21.6+/-2.5 years). Using a separation-type force plate, we measured the deflection characteristics of the COP; these were defined by the root mean square of positional change (COP-RMS) and the deflection velocity of the COP (COP-Vel) during landing after crossover stepping. Furthermore, we measured the muscular strength of the lower extremity by using a hand-held dynamometer. By using multiple regression analysis, we detected the calculated muscular strength as the independent variable of the deflection characteristics of the COP. Compared to the young group the elderly group showed significantly higher anterior-posterior COP-RMS values (p<0.05) and lower lateral COP-Vel values (p<0.001). In the elderly, the muscular strengths of the tibialis anterior and adductor magnus were detected as a significant independent variable of the anterior-posterior COP-RMS (R(2)=0.85, R(2)=0.76, p<0.01) and lateral COP-Vel (R(2)=0.75, R(2)=0.65, p<0.05), respectively. With regard to the COP deflection characteristics during landing after crossover stepping in the elderly, we recognized the diagnostic character of the anterior-posterior COP-RMS and lateral COP-Vel. Furthermore, it was suggested that the muscular strengths of the tibialis anterior and adductor magnus played a role in regulating the COP deflection characteristics.