ヒトの二つの投動作様式における負荷量と performance との関係

The purpose of this study was to relat the muscle strength and the differenciation of two basic throwing patterns. As we know both in our daily life and sports activities there are commonly seen that putting heavy things and over hand throwing light things for the purpose of getting distance. These phenomenon also found in children\u27s motor development of throwing movement. At the early stage of children\u27s throwing movement putting or putting like movement appeared early than that of throwing, particularly to the over hand throwing. There are qeustions what coused this differenciation, and what were the factors or imformation for us to select throwing patterns while facing a load? May be nuromascular function from physical aspect, and motor learning in daily activities are factors which coused this differenciation that mentioned above. In this study we thought that the muscle strength could be one of the most powerful limiting factor. For the purpose of this hypothesia we used a loads alternative ball asked subjects to push and over hand throw it in sitting position, stablized by a belt tightly around the subjects\u27 hip. The load increased gradually by 500g from 1.0kg to 6.0kg. Performances were measured, including fine trials for each load. EMGs were recorded by surface electrodes from muscles of shoulder gardle and arm, seven muscles included. A high speed cinecamera used to analyze the change of throwing patterns. Subjects were seven groups of male and female volounteers that were distance runner, shotputtor, javelin thrower, and weight liftor, totally up to 26 subjects included. Some evidences obtained in this study summalized as follow : 1) Throwing patterns ; As load increased there were no significant change of the patterns of push from series of tracings made from motion picture films, but the over hand throw were quite disguised when the load increased which were lower the elbow joint, and exerted the movement with a mixed pattern of push and throw, especialy at the heavier load. (fig. 1. 2. 3.) The quality change following the increasing of loads were ; Lengthening the movement time and movement distance, and lowering the angle of incident and initial velocity. (table 1). 2) EMGs of two throwing patterns ; Electromyographical study of the muscle function reveals what muscle actually does at any moment of these movements. In this study results of EMGs were ; At light load the Triceps (caput longum), Deltoideus (medius), and Trapezius (superior) worked quite difference in character for two throwing movements which indicated these muscles had their own functions differ in exerting push and over hand throw, but no these differences found when the load was increased to the maximum or nearly the maximum (the maximum load in this study is 6.0kg), muscles worked almost the same manner from the beginig to the ending of two of these movements. The amplitude of EMGs increased linearly on line with the increasing of load also found. 3) The perfomances decreased with the increasing of loads could be found in two movements, particularly the over hand throw decreased more sharply than the push in the first half during the load increasing processes. (fig. 7) 4) There were an intersection point of the performances of two throwing movements at certain load during the increasing of loads, here we called the point of intersection in term of cross point, and the loads at the cross point was called critical loads. This cross point appeared in all subjects in this study. 5) The percent of the loads at cross point to the maximum back strength were differ in groups as follow ; 1.80% (0.28) for shotputter, 2.04% (0.60) for distance runner, 2.12% (0.19) for javelin thrower, 1.53% (0.30) for weight liftor, and 2.29% (0.37) for hand ball player of male subjects. The percent of two groups of female subjects were 2.12% (0.18) for hand ball player, and 1.73% (0.11) for discus thrower and javelin thrower. The range of these persent were centered around 1.53% to 2.29% with a small stander diviation as descriped above. (table 2) 6) There were differences largely in back strength which messured as an index of maximum muscle strength, the range of back strength were 156kg. for male hand ball player, 125kg. for famel hand ball player, 181.7kg. for male shoputter, 160kg. for male javelin thrower, 112.5kg. for male distance runner, 166.7kg. for male weight liftor, and 148.3 kg. for female discus and javelin thrower respectly. 7) The percent of the cross point were differ in groups which were higher in male and female hand ball player as well as male javelin thrower, lower in weight liftor male shoputter and female discus and javelin thrower, and the long distance runner located in the middle. (table 3, 7 and fig. 8