Development of a new instrument for evaluating leg motions using acceleration sensors (II).

OBJECTIVE: The purpose of this study was to investigate the characteristics of the average acceleration of elderly people during walking. METHOD: The subject cohort comprised nine men and 21 women aged ≥63 years. Subjects walked a 10-m straight course (walk test) which required stepping over six obstacles (hurdle walk test). The average acceleration was calculated from the accelerograms. Functional reach test scores and the Tokyo Metropolitan Institute of Gerontology (TMIG) index of competence, fall risk assessment, fall experience within the last year, and carelessness were used as standard indices to estimate the dynamic postural movement and fall risk. RESULTS: The average acceleration during the walk test was not significantly correlated with the standard indices. The average accelerations at the lumbar and knee positions clustered with fall experience and carelessness, while those at the ankle and toe positions clustered with the hurdle walk test, TMIG index of competence, and fall risk assessment. Between the high- and low-risk groups classified by the conventional indices, there was a significant difference in the average acceleration at some measurement positions. The receiver operating characteristic analysis showed the possibility to discriminate the high-risk group according to the standard indices with average acceleration. CONCLUSIONS: The average acceleration during walking may be a composite index that encompasses standard indices and discriminate the high-risk group. As such, it may be a useful tool to estimate the dynamic postural movement and fall risk at all measurement positions.

Development of new instrument for evaluating leg motions using acceleration sensors.

The purpose of this study is to develop a new system for measuring leg motions using a portable three-dimensional accelerometer. The measuring system is composed of acceleration sensors (Micro Stone, MA3-10Ac), a data logger, a data reader, and a personal computer. The personal computer draws a graph of the acceleration of movements (i.e., accelerogram) from the output signals of the acceleration sensors. We then calculated the average acceleration to evaluate leg motions. We drew the accelerograms from 19 young subjects and 36 elderly subjects during the performance of physical fitness activities and walking. Different accelerograms were obtained from two subjects for different walking styles. The average accelerations at the lumbar, ankle and toe points were higher at all axes during movements from the physical fitness activities in the elderly subjects. The accelerations of leg motion at the knee point were, however, lower in the up and down axis in the elderly subjects than in the young subjects, although they were higher in the back and forth and the right and left axes. The new instrument has enabled us to evaluate leg motions by measuring three-dimensional acceleration during the performance of physical fitness activities and walking. The average accelerations of leg motions showed age-related changes. Thus, the average acceleration of leg motions may be used as a new index for evaluating leg motions at the dynamic state.