Effects of an automated stride assistance system on walking parameters and muscular glucose metabolism in elderly adults

Hiroyuki Shimada ^1*, Takao Suzuki ¹, Yuichi Kimura ², Takashi Hirata ³, Miho Sugiura ¹, Yosuke Endo ³, Ken Yasuhara ³, Kei Shimada ³, Keishiro Kikuchi ³, Keiichi Oda ⁴, Kenji Ishii ⁴ and Kiichi Ishiwata ⁴

¹ Tokyo Metroplitan Institute of Gerontology, Japan
² Image Analysis Team, Biophysics Group, Molecular Imaging Center National Institute of Radiological S, Japan
³ Fundamental Technology Research Center, Honda R�@&�@D Co., Ltd.,, Japan
⁴ Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Japan

^* To whom correspondence should be addressed. E-mail: shimada{at}tmig.or.jp.

Accepted 22 January 2008

Abstract

Objective: To identify the effects of an automated stride assistance system (SAS) on walking scores and muscle activities in the lower extremities of elderly people.<br> Methods: Seven healthy elderly men (73-81 years) participated in this study. Subjects walked continuously at a constant speed for 50 min on a treadmill with and without the SAS, which is a device to control the walk ratio (step length/cadence) and to add support power to the thigh during walking. A step counter equipped with an infrared device was used to record walking data. The average speeds during treadmill walking were 2.89-3.82 km/h without the SAS and 3.03-4.03 km/h with the SAS. Positron emission tomography (PET) and [¹⁸F]fluorodeoxyglucose (FDG) evaluation of glucose metabolism were conducted on each subject twice after walking with and without the SAS.<br> Results: Walk ratio, walking speed and step length were significantly improved in all subjects by the SAS, while cadence was significantly decreased by the SAS in all subjects except one. The SAS did not have a significant effect on glucose metabolism of the muscles of the lower extremities. There were no significant correlations between change in walking speed and change in SUV values in each muscle without the SAS and with the SAS. In contrast, significant correlations between walking speed and SUV uptake were shown in gluteus minimus (r = -0.929), hip related muscles (r = -0.862), soleus (r = -0.907), and medial gastrocnemius (r = -0.952) without the SAS. In with the SAS condition, there were significant correlations in gluteus medius (r = -0.899), hip related muscles (r = -0.819), and medial gastrocnemius (r = -0.817) in the elderly subjects.<br> Conclusions: The SAS increases walking scores in elderly people without increasing energy consumption of lower-extremity muscles. The elderly subjects with low walking speed showed higher glucose metabolism in hip related muscles and triceps surae. Thus, this association suggested that decreased walking speed in elderly adults have higher metabolic cost in these muscle regions.<br>