ABSTRACT
There have been an apparent trend in the decline of back-lift strength of young people during recent years. The purpose of this study was to investigate the cause-effect relationship of such a trend using young peoples and university students. In order to examine the characteristics of activities in the lumber back muscles during various physical activities, the surface electromyography (EMG) was obtained from the trapezius, latissimus dorsi, and elector spinae muscles for individuals with poor back-lift strength (5 male children and 4 university male students) and individuals with relatively strong back-lift strength (5 male children and 2 male university students) . The children with poor back-lift strength had significantly less EMG activities in both the trapezius and elector spinae muscles during the measurement of back-lift strength using a dynamometer than the strong back-lift strength children. The former children also had a less EMG activities in elector spinae muscle and a greater EMG activities in trapezius muscle during cycling the bicycle elgometer. Such a trend became more distinct when the load was increased. The university students with poor back-lift strength had a less EMG activity in the elector spinae muscle during the measurement of back-lift strength than those with strong back-lift strength. During running, there was not a distinct difference in the EMG activities of the muscles in the back between the poor and strong strength students. However, as the running speed increased, a greater EMG activity in the trapezius muscle or the latissimus dorsi muscle were observed for the poor back-lift strength students than the stronger back-lift strength students.<BR>These results indicated that the individuals with poor back-lift strength relied more on the upper portion of the back muscle group than the lower portion of the back muscle group during both static and dynamic activities, suggesting that the trend in the decline of back-lift strength of children and students was due to a lack of opportunity to use the lower back muscles in the daily physical activities.