Damping control of balance in the medial/lateral direction and the risk of falling in the elderly.

AIMS: A proportional-integral-derivative (PID) control has recently been used as a control algorithm of body balance. The purpose of this study was to elucidate an association of the proportional and derivative gain based on the PID control gain for balance for quiet standing with the risk factor for falls in the elderly. METHODS: The movement of a marker on the back of 23 elderly participants (age 75.6±6.6 years) was measured by our developed device with a complementary metal oxide semiconductor video camera and the trunk sway speed in the medial/lateral (M/L) direction (TSSX) was calculated as absolute values of the whole time series. The PID control gain (proportional gain: K(P), integral gain: K(I), derivative gain: K(D)) was identified using the trunk sway data, and normalized by individual height and weight (K(P)n, K(D)n and K(I)n). Individual risk factor for falls was additionally assessed with the Tinetti Performance Oriented Mobility Assessment (POMA) and the fall risk questionnaire. RESULTS: The score in the POMA and the K(D)n significantly decreased with age (P<0.01). The score in the POMA showed a positive correlation with the K(D)n, and negative correlations with the TSSX and K(P)/K(D) ratios (P<0.01). The average K(D)n and the score in the POMA of fallers were significantly lower than those of non-fallers (P<0.05). CONCLUSION: These results suggest that the decreased damping control by derivative gain for balance in the M/L direction is one of the risk factors for falls in the elderly.

[Study of the TCM acceleration sphygmograph based on high-precision calculation].

In order to get more pulse diagram valuable information, we summarized the traditional acceleration in the pulse chart based on the calculation of a new high-precision calculation of the acceleration pulse graph algorithms, being suitable for a large amount of data to adapt to requirements of high-resolution digital pulse diagram analysis, optimizing the acceleration pulse mapping process, reducing the impact of noise on data analysis, and improving the ability to distinguish details of the image. In addition, we used the spectrum analysis diagram for high-precision acceleration pulse. By doing so, we overcomed the traditional acceleration noise in the pulse data as the large loss, we found flat pulse, slippery pulse, taut pulse acceleration spectrum of feature points in the new Chinese medical traditional pulses. We then were able to recognize the pulse diagram calculated at the acceleration level to identify the frequency domain.

Effects of aging on lateral stability in quiet stance.

BACKGROUND AND AIMS: Recent studies have demonstrated that assuming the postural corrective torque is regulated by a proportional-integralderivative (PID) controller in the anterior/posterior direction, although few studies have discussed the medial/ lateral (M/L) direction through PID control. Instability in the M/L direction has been reported to be closely related with the risk of falling in the elderly. The purpose of this study is to evaluate the mechanism of postural control in the M/L direction in the elderly. METHODS: The movement of a marker on the subject's back was measured by a CMOS video camera and trunk sway speeds in the M/L direction (TSSX) were calculated as absolute values in whole time series. Using trunk sway data, we identified the gain of PID parameters (proportional gain: KP, integral gain: KI derivative gain: KD). In addition, we calculated the frequency spectrum of trunk sway using the marker locus from 0.016 to 5 Hz by fast Fourier transform. A total of 40 healthy subjects aged from 20 to 85 years old was evaluated with the PID control algorithm in a model of postural control in the M/L direction and their parameter values were estimated. RESULTS: KP significantly increased with age, whereas KD tended to decrease. The TSSX and power ratio of medium frequency (0.2-2.0 Hz) significantly increased with age, but the power ratio of low frequency (0.02-0.2 Hz) tended to decrease. KP and KI were significantly correlated with the power ratio of medium frequency. There was a significant negative correlation between KD and TSSX. CONCLUSIONS: Our results indicate that dependence on hip and ankle stiffness, which may be controlled by proportional gain, increases with age for postural control in the M/L direction. A disability in the feedback mechanism based on velocity information for postural control, which may be associated with derivative gain, tends to increase with age but shows considerable individual variation.