THE RELATIONS BETWEEN BONE MINERAL DENSITY (BMD) AND MECHANICAL LOADS ACTING ON THE LOWER LIMBS: USING THE GAIT ANALYSIS IN MIDDLE-AGED AND ELDERLY JAPANESE

Abstract

INTRODUCTION The mechanical loads are an important factor to evoke bone formation, absorption of restraint, and structural strength. But, the bone remodeling is closely associated with bone absorption when mechanical loads are removed. Vogel, et al and Krolner, et al 1,2 suggest that bone loss occurs in individuals exposed to a reduced gravitational environment, as occurs in prolonged space flight and bedrest. Several recent reviews suggest that physical activity is beneficial to bone mass. Most studies, however, have not cleared on the quantification of mechanical loads acting on the lower limb during exercise trials. Above all, little is known about the effectiveness of the Ground Reaction Force (GRF) acting on the lower limb during gait in the middleaged and elderly. The purpose of the present study is to examine how mechanical loads acting on the lower limbs during gait affect Bone Mineral Density (BMD). METHODS The subjects in the study were the participants in the National Institute for Longevity Science-Longitudinal Study of Aging (NILS-LSA). The subjects were 1885 males and females who had measured BMD and GRF on gait protocol, aged 40-82 years in the second phase examination of the NILS-LSA. GRF signals were collected using two force plates with a sampling frequency of 240Hz (Kister, type9286, Swizerland). Then, peak GRF data were created from vertical component of GRF for the foot flat to heel off phase during stance phase of gait with custom-made program (Fig1). In this study, peak GRF accepted as an index of mechanical loads acting on the skeletal.