Hitoshi Makabe

Two-dimensional (2D) clinical gait analysis systems are more affordable and portable than contemporary three-dimensional (3D) clinical models. Using the Vicon 3D motion capture system as the standard, we evaluated the internal statistics of the Imasen and open-source OpenPose gait measurement systems, both designed for 2D input, to validate their output based on the similarity of results and the legitimacy of their inner statistical processes. We measured time factors, distance factors, and joint angles of the hip and knee joints in the sagittal plane while varying speeds and gaits during level walking in three in-person walking experiments under normal, maximum-speed, and tandem scenarios. The intraclass correlation coefficients of the 2D models were greater than 0.769 for all gait parameters compared with those of Vicon, except for some knee joint angles. The relative agreement was excellent for the time–distance gait parameter and moderate-to-excellent for each gait motion contraction range, except for hip joint angles. The time–distance gait parameter was high for Cronbach’s alpha coefficients of 0.899–0.993 but low for 0.298–0.971. Correlation coefficients were greater than 0.571 for time–distance gait parameters but lower for joint angle parameters, particularly hip joint angles. Our study elucidates areas in which to improve 2D models for their widespread clinical application.

Skin autofluorescence is a useful index to estimate the accumulation of advanced glycation end-products in human tissues. Elderly persons with higher skin autofluorescence have lower muscle mass, muscle strength and muscle power, however, little is known about the relationship between the skin autofluorescence level and each muscle activity. We measured the values of skin autofluorescence from five places on a lower limb, and the signals of surface electromyogram during isometric contractions from five muscles on that, simultaneously. The waveforms of surface electromyogram were analyzed by Daubechies-4 wavelet transformation. The value of skin autofluorescence was increased in the proximal part of the lower limb compared with the value of the distal part. The principal component of surface electromyogram activity in a time-frequency domain was lower in the proximal part compared with that of the distal part. There was a weak negative correlation between the value of skin autofluorescence on the gluteal region and the value of the mean wavelet coefficient of the surface electromyogram signals within the gluteus maximus muscle. The higher accumulation of advanced glycation end-products on the gluteal region might suggest the lower muscle activity in aging without disease and disability.

This study examined the characteristics of lower limb muscle activity in elderly persons after ergometric pedaling exercise for 1 month. To determine the effect of the exercise, surface electromyography (SEMG) of lower limb muscles was subjected to Daubechies-4 wavelet transformation, and mean wavelet coefficients were compared with the pre-exercise coefficients and the post-exercise coefficients in each wavelet level. The characteristics of muscle activity after pedaling exercise were also compared between the elderly subjects and young subjects. For the elderly subjects, the mean wavelet coefficients were significantly decreased in the tibialis anterior and the gastrocnemius medialis at wavelet levels of 3, 4, and 5 (125–62.5, 62.5–31.25, and 31.25–15.625 Hz, respectively), by pedaling exercise. However, the mean power of wavelet levels of 2 and 3 (250–125 and 125–62.5 Hz) within the rectus femoris and the biceps femoris were significantly increased in the young subjects. The effect of pedaling exercise is different from the effects of heavy-resistance training. It was suggested that the muscle coordination, motor unit (MU) firing frequency, and firing fiber type of lower limb muscles are changed with the different characteristics between elderly and young persons by pedaling exercise for 1 month.