Abstract
The purpose of this study was to identify the primary muscles during long-time walking in young and elderly adults by mean of positron emission tomography using [18F]fluorodeoxyglucose (FDG-PET) for quantitative evaluation of glucose metabolism in the skeletal muscle. Ten young males (mean 24.1 ± 2.1 years old) and six elderly males (mean 75.5 ± 2.1 years old) underwent a FDG-PET after 50 min treadmill walks. Regions of interest (ROIs) were located on the central or activated regions of skeletal muscles: the hip flexors, extensors, and abductors, knee flexors and extensors, and ankle dorsiflexors and plantar flexors. Glucose metabolism in ROIs was evaluated as the standardized uptake value (SUV). FDG uptakes were high values significantly in the hip abductors, ankle plantar flexors, and ankle dorsiflexors in the young adults. The elderly adults showed markedly high SUV value in the hip abductors. There was a significant difference in SUV values between the hip abductors and hip flexors, knee extensors, ankle plantar flexors in elderly adults. The gluteus minimum showed especially high SUV uptake nearly threefold SUV in the gluteus medius in the young adults (p < 0.01). On the other hand, the elderly adults showed high SUV uptake in the hip surrounding muscles including the gluteus medius or the gluteus maximus. The ankle plantar flexors showed high SUV values in the young adults, whereas the low SUV values were recognized in the elderly adults. These results suggest that the hip abductors had an important functional role during long-time walk, and that muscle activity of ankle plantar flexors deteriorated with age. We considered that physical therapy focused on these muscles might be beneficial intervention to improve long-time walking ability.
