Relationship between Muscular Strength of the Lower Extremities and Trunk Acceleration during Backward Stepping by the Elderly

[Purpose] The purpose of this study was to investigate the relationship between the muscular strength of the lower extremity and the trunk acceleration during a backward stepping reaction performed by the elderly. [Subjects] The study population comprised 11 elderly subjects (average age, 75.5 +/- 6.9 years). [Methods] Using a separation-type force plate and a small tri-axial accelerometer, we measured the vertical reaction force and the acceleration at the seventh cervical (C7) and the second sacral (S2) vertebrae in backward stepping reaction. Furthermore, we measured the muscular strength of the lower extremity using a hand-held dynamometer, and examined the relationship between the acceleration value of C7 and S2 and the muscular strength. [Results] Correlation analysis revealed that the acceleration values of C7 and S2 showed significant positive correlations with the muscular strengths of the hamstrings, tibialis anterior, and triceps surae. [Conclusion] These results suggest that the muscles controlling the dorsi/plantar flexion of the ankle and pelvic stability contribute to acceleration of the trunk in the backward stepping reaction.