25 2 pp52 62 213 INFLUENCE OF AFFERENT INFORMATION ORIGINATED FROM FINGER TACTILE SENSATION ON IMPROVED EQUILIBRIUM IN THE ELDERLY ADULTS Motoki Kouzaki and Kei Masani SUMMARY Declined equilibrium is main risk factor of falling in the elderly, and this will impair the quality of life The present study focused on the finger tactile information during quiet standing because this information will enhance the equilibrium irrespective of mechanical support The purpose of present study was to examine whether the enhanced tactile sensation caused by light touch effects in the elderly adults improves the equilibrium during quiet standing in elderly adults who have declined body balance During the quiet stance in young n 4 and elderly n 136 subjects for 6 s with and without fingertip light touch LT, center of pressure CoP, center of mass acceleration ACC, center of mass velocity CoMvel, horizontal finger touching force were measured The velocity information maintaining postural stability as neurophysiological property was determined by a positive peak of cross-correlation function CCF from CoMvel to CoP sway For LT trials, CCF from LT sharing force to CoP sway to compare the LT effects between young and elderly adults Mean velocity of CoP CoP path length divided by calculated time and standard deviation SD of ACC as an assessment of amplitude of postural sway in both young and elderly adults significantly decreased due to LT The LT effects were significantly larger in elderly adults than young adults The decreased postural sway was related to decreased low-frequency component 1Hz of postural sway Positive peak of CCF from CoMvel to CoP sway tended to increase by LT in both young and elderly adults The positive peak of CCF from LT sharing force to CoP as an index of LT effects was higher in elderly adults as compared to young adults There results lead us to conclude that the enhanced finger tactile sensation by LT is able to compensate the declined equilibrium in the elderly In addition, we measured the motor unit MU action potential of soleus muscle by using fine-wire electrodes during quiet standing with and without LT to investigate the MU activation strategy As a result, relatively large MU during quiet standing disappeared due to LT This result strongly supports our conclusion that LT has a beneficial effect on postural balance because derecruitment of large MU conduces to steady postural sway Key words: light touch, quiet standing, center of pressure, center of mass acceleration, aging Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
53 緒 言 3 19 Jeka 5 9 Kouzaki and Masani 9 方 法 A 被 験 者 4 136 1 2 6 65 65 6 12 2-H-21 B 立 位 平 衡 機 能 の 測 定 9281B Kistler 7 light touch; LT 2 1 LT 2 LT 3 LT 4 LT 4 1cm 5 cm 5 cm center of pressure; CoP center of mass acceleration; ACC LT 3 1 Table 1 Physical characteristics of the young and elderly subjects Number Age Height Body mass Male Female yrs cm kg Young 25 15 17 11 171 83 678 99 Elderly 41 95 655 63 1535 8 562 77
54 1 Fig1 Schematic illustration of quiet standing with fingertip light touch LT 9251A Kistler 1 LT LT 3 1 N 9 1 N 5 1 N CoP ACC 1Hz 6 1 CoP CoP 2 CoP CoP CoP 2 CoP CoP CoP ACC ACC standard deviation; SD ACC SD CoP 16 CoP ACC SD CoP ACC 15Hz 2 CoP CoP CoP FFT CoP 1 Hz 1 1 Hz 17 CoP Hz 1 Hz 1 Hz 1Hz 1 3 CoM CoP center of mass; CoM 15 CoM COM velocity CoMvel CoP 18 CoMvel CoP CoM
55 6 CoMvel CoP crosscorrelation function; CCF CCF CoMvel ACC 1 CCF CoMvel CoP 4 Hz 15 4 CoP LT 5 LT 7 CoP CoP CCF CCF 4 Hz C LT による 主 働 筋 の 運 動 単 位 動 員 パターン の 変 化 6 5 256 6 4 136 LT LT 1μm Spike2 ver64, Cambridge Electronic Design D 統 計 LT LT CoP LT LT LT CoP CCF 4 結 果 A 若 齢 者 および 高 齢 者 の 姿 勢 動 揺 の 結 果 2 LT LT CoP ACC LT CoP ACC CoP CoP F=513, P 5 F=583, P 5 ACC SD F=466, P 5 F=52, P 5 LT 3 9 CoP 1 1Hz LT F=268, P=11 F=341, P=7 1 Hz F=15, P 1 F=1472, P 1 LT 3 LT LT LT CoP ACC 4 LT CoP ACC CoP CoP F 3132, P 1 F 3653, P 1 ACC SD F 316, P 1 F 2342, P 1 LT 5 LT CoP 14% 16% ACC 17% 17%
56 w/o LT 2 2 CoP (cm) -2-2 8 8 ACC (cm/s 2 ) 4-4 4-4 -8-8 Time (s) LT force (N) - Time (s) 2 6 Fig2 Representative examples of center of pressure CoP, center of mass acceleration ACC, and light touch LT force for a single trial in one young subject during quiet standing with eye closed condition for 6 sec with right panels and without left panels LT Time series data were low-pass filtered using Butterworth filter cutoff frequency 15 Hz CoP velocity (cm/s) 15 SD of ACC (cm/s 2 ) 2 15 EO EC EO EC Power [<1Hz] (cm 2 ) (cm 2 ) w/o LT 2 15 1 5 Power [1-1Hz] 8 6 4 2 EO EC EO EC 3 1 Hz 1 1Hz 4 Fig3 Mean velocity of CoP sway, standard deviation SD of ACC, frequency component of CoP sway below 1 Hz, and frequency component of CoP sway ranging from 1 Hz to 1 Hz during quiet standing with and without LT in 4 young subjects Open and closed bars indicate the without LT and with LT, respectively EO and EC indicate the eyes open and the eyes closed trials, respectively indicates the significant difference between LT conditions P 5 Values are mean SD
57 w/o LT 2 2 CoP (cm) -2-2 8 8 ACC (cm/s 2 ) 4-4 4-4 -8-8 Time (s) LT force (N) - Time (s) 4 6 Fig4 Representative examples of CoP, ACC, and LT force for a single trial in one elderly subject during quiet standing with eye closed condition for 6 sec with right panels and without left panels LT Time series data were low-pass filtered using Butterworth filter cutoff frequency 15 Hz CoP velocity (cm/s) 2 15 SD of ACC (cm/s 2 ) 25 2 15 EO EC EO EC Power [<1Hz] (cm 2 ) (cm 2 ) w/o LT 2 15 1 5 Power [1-1Hz] EO EC EO EC 5 1 Hz 1 1Hz 136 Fig5 Mean velocity of CoP sway, SD of ACC, frequency component of CoP sway below 1 Hz, and frequency component of CoP sway ranging from 1 Hz to 1 Hz during quiet standing with and without LT in 136 elderly subjects Open and closed bars indicate the without LT and with LT, respectively EO and EC indicate the eyes open and the eyes closed trials, respectively indicates the significant difference between LT conditions P 5 Values are mean SD 2 15 1 5
58 Young Elderly 8 8 4 4 CCF CCF -4-8 -1-5 5 1 6 3 CCF CCF -4 CoMvel vs CoP -8-1 -5 5 1 6 3 w/o LT -3-6 -1-5 5 1-3 LT force vs CoP -6-1 -5 5 1 Time lag (s) Time lag (s) 6 18 Fig6 Typical examples of cross-correlation function CCF from center of mass velocity CoMvel to CoP displacement upper panels, and CCF from LT force to CoP displacement lower panels during quiet standing for 6 sec in the young left panels and elderly right panels subjects Vertical axes present normalized CCF Higher positive CCF indicates strong similarity between variables Higher negative CCF indicates strong similarity between variables in opposite phase Horizontal axes present time lag Positive lag indicates CoM velocity upper panels and LT force lower panels preceded CoP displacement Bold and gray lines indicate LT and without LT conditions, respectively Young Elderly CCF CCF w/o LT EO EC EO EC 7 Fig7 Positive peak value of CCF calculated from CoMvel to CoP with and without LT in the young left panels and elderly right panels subjects Open and closed bars indicate the without LT and with LT, respectively EO and EC indicate the eyes open and the eyes closed trials, respectively Values are mean SD
59 高齢者 CoP 動揺 開眼 22% F 465, P 5 閉眼 28% F 1396, P 1 ACC 開眼 39% F Ｂ CoMvel と CoP 動揺および指先接触力と 1384, P 1 閉眼 38% F 141, P 5 若齢者 図 6 左 および高齢者 図 6 右 の は有意に大きかった 若齢者と同様 1 1Hz の高周波成分 開眼 F 36, P 6 閉眼 F 226, P 13 は LT による変化はなかったが CoMvel と CoP 動 揺 と の CCF 図 6 上 段 お よ CoP 動揺との関連性の若齢者と高齢者の比較 び指先接触力と CoP 動揺との CCF 図 6 下段 の典型例を図示した いずれの群も LT により 1 Hz 未 満 の 低 周 波 成 分 開 眼 F 775, P 1 閉眼 F 5915, P 1 は LT により有 CoMvel と CoP 動揺との正のピーク値が増加し 意に低下した 図 5 下段 から CoMvel が CoP 動揺より時間的に先行して た また 正のピークが正の時間差であること いた 指先接触力と CoP 動揺との CCF の正の ピーク値は正の時間差であったことから LT が CCF 姿勢動揺より時間的に先行していたことが確認さ young elderly れた この先行時間はすべての被験者で 25 28ms であった CCF 波形に若齢者と高齢者の 差異を見いだすことはできなかった CoMvel と CoP 動揺との間 図 7 および指先 EO 接触力と CoP 動揺との間 図 8 における CCF の EC 図 8 若齢者および高齢者のライトタッチあり条件に おける指先接触力と足圧中心動揺の相互相関関数の ピーク値 Fig8 Positive peak value of CCF calculated from LT force to CoP with LT in the young hatched bars and elderly shaded bars subjects EO and EC indicate the eyes open and the eyes closed trials, respectively Values are mean±sd 正ピーク値の平均値を図示した 若齢者 開眼 F 245, P 12 閉眼 F 36, P 8 およ び高齢者 開眼 F 347, P 6 閉眼 F 297, P 9 とも LT により CCF のピーク値が高く なる傾向を示した しかしながら いずれの変数 間も LT ありと LT なし条件で統計的に有意では なかった w/o LT 1 mv 1s 1 ms 図 9 ライトタッチなしおよびライトタッチあり条件の静止立位時におけるヒラメ筋の運動単位活動 電位の典型例 Fig9 Typical examples of 1-s time series of motor unit action potential in soleus muscle during quiet standing for 6-s with right panel and without left panel LT Upper and lower panel indicate that time window is 1-s and 1-s, respectively Filled cycles indicate different motor units action potential
6 CoP CCF F 64, P 83 F 24, P 62 LT C LT による 運 動 単 位 の 動 員 パターンの 変 化 9 LT LT LT LT 考 察 A ライトタッチの 姿 勢 動 揺 に 及 ぼす 影 響 CoP CoM ACC 5 1 N 3ms 1 N CoP 25 28ms 6 ACC CoM CoP 16 ACC CoM CoP CoM CoP CoP 1 1Hz LT 1 Hz 3 19 CoP 1 Hz 1 Hz CoP 1 5 13 CoM CoP 18 CoM CoP CoMvel CoP CCF CoP 8 CoMvel CoP CoM
61 B ライトタッチによる 足 関 節 底 屈 筋 の 運 動 単 位 動 員 パターンの 変 化 1 8 14 CoM CoMvel 13 5 統 括
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