Annals of Rehabilitation Medicine

Assessment of Autonomic Function in Stroke Patients by Power Spectral Analysis of Heart Rate Variability.: Chon, Joong Son , Chun, Sae Il , Park, Seung Hyun , Ahn, Juhn , Baek, Soh Young , Kang, Youn Joo , Doh, Won Su , Jeong, Kee Sam , Shin, Kun Soo , Lee, Myoung Ho; J Korean Acad Rehabil Med 1998;22(4):778-783.

Abstract
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Objective: To evaluate the effects of orthostatic stress with a head-up tilt on the autonomic nervous system and to determine how a cerebral stroke influences the cardiac autonomic function, using the power spectral analysis(PSA) of heart rate variability(HRV).

Method: We studied 11 stroke patients with a left hemiplegia and 14 patients with a right hemiplegia. Their hemispheric brain lesions were confirmed by the MRI. The ECG and respiration signals were recorded at the tilt angle of 0^o and 70^o for 5 minutes under the condition of frequency controlled respirtaion(0.25 Hz). Data were compared with the age- and sex-matched 12 healthy controls.

Result: In a control group, the normalized high frequency power showed a significant decrease during the head-up tilt(p＜0.05), whereas the normalized low frequency power showed a significant increase(p＜0.05). But for the left and right hemiplegia groups, there were no significant changes of normalized high and low frequency power under the orthostatic stress(p＞0.05). Compared with the right hemiplegia and control groups, the left hemiplegia group was associated more with a reduced low and high frequency power and showed no significant changes under the orthostatic stress.

Conclusion: PSA of HRV can identify the reduced cardiac autonomic activity in stroke patients, with a greater reduction in the left hemiplegia group than in the right hemiplegia group, which may cause a high risk of cardiac arrhythmias and sudden death.

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EMG Power Spectrum of Lumbar Back Muscle in Chronic Low Back Pain Patients.: Sohn, Min Kyun , Yoon, Yeo Sam , Jun, Kae Ho; J Korean Acad Rehabil Med 1998;22(1):68-76.

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Surface electromyogram in the lumbar paraspinal muscles was studied to evaluate back muscle impairment in twenty chronic low back pain patients and twenty control subjects. Turns-amplitude and power spectrum analysis of electromyographic signals were performed at different force levels during fatigue from sustained isometric contraction and recovery from fatigue in trunk extensor muscles. Results indicated that with increasing force level mean amplitude and Root Mean Square (RMS) values were increased, but mean and median frequencies increased initially until 20% Maximal Voluntary Contraction (MVC) and decreased tendency after then. Turns, mean amplitude, RMS, mean and median frequencies were all higher in control subject than those of low back pain patients. During sustained isometric contraction at 70% MVC, mean and median frequencies were linearly decreased, and the slopes were steeper in the patients group. Mean amplitude and RMS value showed decreased tendency during fatigue. During recovery from fatigue turns, mean and median frequencies increased especially in the first 3 minutes and nearly completely recovered in the 7~8 minutes in both patients and control groups. Therefore the mean amplitude and RMS value could be used as indicators of the level of muscle contraction and the mean and median frequencies reflect well the muscle fatigue in paralumbar muscle. These results validate the use of surface EMG spectral parameters as an objective measure of back muscle impairment in chronic low back pain patients.

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Assessment of Autonomic Nervous Function in Young Adults by Power Spectral Analysis of Heart Rate Variability.: Chon, Joong Son , Chun, Sae Il , Cho, Kyung Ja , Jin, Mi Ryeong , Kim, Tae Sun , Kim, Deog Young , Ahn, Juhn , Jeong, Kee Sam , Shin, Kun Soo , Lee, Myoung Ho; J Korean Acad Rehabil Med 1997;21(5):928-935.

Abstract
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The powers of the low-frequency(LF) and high-frequency(HF) components characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympatho-vagal balance occurring during orthostatic stress with head-up tilt.

We studied 24 healthy volunteers (median age, 23.1 years) who were subjected after a rest period to a series of passive head-up tilt steps chosen from the following angles: 0⁰. 15⁰, 30⁰, 45⁰, 70⁰, and 90⁰under the condition of frequency controlled respiration(0.25Hz) in order to get data of the Korean young adults.

During head-up tilt, heart rate and normalized low frequency power(LF_N : 0.05∼0.15 Hz) of HRV showed significant increase(p=0.000), but normalized high frequency power(HF_N: 0.2∼0.3 Hz) and total power showed progressive decrease(p=0.000, p＜0.01 respectively). Male showed significantly higher LF_N and lower HF_N than female at tilt table angle 0⁰(p＜0.01).

Power spectral analysis of HRV appears to be capable of providing a noninvasive quantitatibve evaluation of graded changes in the state of the sympatho-vagal balance.