重量物持ち上げ動作における荷台の高さの差が四肢体幹筋の活動量に及ぼす影響

重量物の持ち上げ動作において,荷台の高さの違いが四肢体幹筋に及ぼす影響を調べるために,筋電計を用いて実験を行った.対象は,筋骨格系障害の既往がない健常男子大学生10名(平均年齢22.2±0.9才,平均身長169.9±4.3㎝,平均体重62.3±4.0㎏)であった.被験筋は,持ち上げ動作に重要な僧帽筋,上腕二頭筋,脊柱起立筋,大腿直筋とした.荷台の高さを身長の40%,50%,60%に設定し,重量物の質量は体重の30%とし床面から荷台へ合計10回荷揚げさせた.得られた筋電波形のIEMGを求め,しゃがみ込み開始から重量物の離床まで(以下Prepare-Periodと略)と,重量物の離床から重量物の着床まで(以下Carrying-Periodと略)に分けて分析した結果,各荷台高においてPrepare-Periodでは荷台の上昇に伴い僧帽筋と大腿直筋の働きが大きくなることが認められた.また,Carrying-Periodにおいても荷台の上昇に伴い僧帽筋と大腿直筋が他の筋より大きな値となり,重量物の高位への持ち上げに重要な働きをすることが示唆された.

The Influence on Limbs and Trunk muscles in Lifting a Weight at Different Platform LevelsMasahiko. Fujimura, Isao Nara, Mitsutoshi KawamuraInstitute of Health Sciences, Hiroshima University Faculty of MedicineThe purpose of this study is to examine the influence on limbs and trunk muscles in lifting a weight at different platform levels. This is to report a basic study on the muscle activity data with the use of surface EMG and the calculated integrated EMG (IEMG) value. Ten male university students (average age 22.2±0.9 years, average height 169.9±4.3cm, average weight 62.3±4.0kg) who were healthy and had no history of disorders participated in this study . The subject lifted up a weight 10 times. (The weight used in this study was adjusted to 300f subjects weight and the platforms levels were set at the height of 40%, 50-0x1.4aa00bfffa2ep-149nd 6026651131640f subjects height.) Surface EMG were collected from trapezius, biceps brachii, elector spinae, rectus femoris by electromyograph (Myosystem1200, Noraxon USA). Set the term "Prepare-Period" is the squatting motion to lift a weight, and "Carrying-Period" is the motion from lifting a weight to putting it on a platform The footswitch (Nor Switch, Noraxon USA) was attached to the bottom of a weight to observe the timing of these two motions. The motions of 10 times were identified by the foot switch signal and IEMG per motion was calculated with normalizing time. All IEMG values were normalized to theIEMG of lifting a weight to the level of 400f subject's height. In the Carrying-Period, the IEMG of rectusfemoris showed larger value than other muscles at the height of both 50-0x1.4aa00bfff764p-149nd 60%.0This suggests that therectus femoris plays an important role at these heights. In the Prepare-Period, the IEMG increased at eachheight. Especially, the IEMG of trapezius and rectus femoris at the height of 60howed larger valuecompared with biceps brachii and elector spinae. The reason is that subjects seem to have prepared at thePrepare-Period stage so as to make the trapezius and rectus femoris function effectively, muscles whichnaturally work well in the lifting motion at the "Carrying-Period". In short, Prepare-Period falls under theimportant introduction period for Carrying-Period and is regarded as an essential process of the lifting motion.