著者

近藤 正行 染岡 慎一 大渡 伸 山口 和正 藤本 博一 小坂 光男

出版者

長崎大学熱帯医学研究所

雑誌

熱帯医学 (ISSN:03855643)

巻号頁・発行日

vol.23, no.2, pp.p111-118, 1981-06

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常温環境下にて6名の健常被験者の上腕二頭筋(M. Biceps brachii)に随意・等尺性筋収縮を誘起し,その経過中に出現する筋疲労のEMG波形をデータ処理システム(ATAC450及びPC-8001)を用いて解析し以下の結果を得た.(1)等尺性筋収縮による筋疲労時のEMG波形には寒冷ふるえ時のEMGと同様に群化放電(grouping discharge: G.D.)が観察された.(2)G.D.の形成機序を解明するために,G.D.の構成成分である連続する2個の筋放電パルスのインターバルについて相関行列を求め,更にP-mode Cluster分析を行った.その結果得られたdendrogramは,2個のパルスのインターバルが1~19 msecと20~50msecの2群に分かれ,かつ,両群のヒストグラムは筋疲労の進行過程において相反的な動態を呈した.(3)(2)で示したCluster分析のdendrogramで,インターバルが2群に区分できなかった例に関して,相関行列を求めた後にDirect Varimax法による因子分析を行い因子行列を作成した.因子分析の結果から,G.D.形成のインターバルは19msec~21msecが適当値と判明し,この事は従来の研究結果が妥当である事を立証した事になる.(4)即ち,従来の研究ではG.D.の条件設定に主観的要素が混入する可能性を残していたが,本研究(上述(2)(3))の結果は,多変量解析の駆使によってG.D.の条件設定がより客観的となった点が進歩である.(5)体熱産生の寒冷ふるえと随意・等尺性筋収縮の誘発法や,そのEMG波形分析,特に,Cluster分析や因子分析の統計学上の意義について二・三の検討が加えられた.In a neutral temperature environment, six healthy human volunteers aged 22-33 years were examined by computer analysis of EMG patterns of dominant biceps brachii muscle throughout its isometric contraction against a constant load. The isometric contraction was performed from a seated position with the elbow resting on a flat surface and 45°angle to the table (90°flexion). Fatigue EMG of unilateral biceps brachii was recorded during 40% maximum contraction value (MCV) isometric contraction, using both surface and fine needle electrodes. Properties of grouping discharge in EMG patterns of cold shivering and muscular fatigue were investigated. The interval of consecutive two pulses, mean frequency and mean duration of grouping discharge were analyzed by Cluster analysis as well as by Factor analysis using an analogue computer ATAC 450 and a personal computer PC-8001. Two different modes of interval of grouping discharge were found from a dendrogram of P-mode Cluster analysis. One had an interval time of 1-19 msec and the other had 20-50 msec of consecutive two pulses of grouping discharge. The data of Factor analysis using a Direct Varimax method also revealed a significant difference between the two modes interval, namely in the one, less than 19 msec and in the other, more than 21 msec, respectively. These results indicate that the range of interval of consecutive two pulses of grouping discharge in EMG of cold shivering and isometric muscular contraction is conclusively 20 msec and that the range is identical with the result of previous studies. The difference between Cluster analysis and Factor analysis was further discussed to evaluate the purposes and nature of the statistical analysis.