Author(s): TAKUYA, O., Institution: JAPAN WOMEN'S COLLEGE OF PHYSICAL EDUCATION, Country: JAPAN, Abstract-ID: 1881

INTRODUCTION:
The side raise exercise (SR) is one of the shoulder-strengthening exercises, primarily targeting the lateral deltoid muscles. The front and rear raise exercises (FR and RR, respectively) are also commonly employed to strengthen the shoulder girdle muscles. Despite the similarities in movement, the specific effects of these exercises on the shoulder girdle muscles remain unclear. Furthermore, given the presumed differences in maximal load capacity for each exercise, it is conceivable that muscle activities may be influenced by both the type of exercise and joint angles. This study aimed to elucidate the effects of exercise types (i.e., SR, FR, and RR), lifting loads, and joint angles on electromyographic (EMG) activities of the shoulder girdle muscles
METHODS:
Seven physically active, non-athletic females participated in this study. Following a warm-up exercise, participants performed maximal isometric shoulder lateral raise exercises, with the shoulder abduction angle set at 60 degrees, while seated, bilaterally, for 3 s. Subsequently, participants undertook six types of incremental isometric exercise tests: three exercise types (SR, FR, and RR) at two shoulder angles (60 and 90 degrees). The load for each test began at 1 kg, increased by 1 kg following a one-minute interval, and continued until reaching the load that could be sustained steadily for 5 s. EMG activity was recorded from four muscles on the right side (anterior and posterior deltoid, trapezius, and infraspinatus). These data were filtered, and root mean square values were calculated, then standardized as percentages relative to the values during maximal isometric side lateral raise exercise.
RESULTS:
The maximal load significantly varied depending on the interaction between exercise types and shoulder angles, with higher loads observed during the 60-degree exercises compared to the same exercise types. EMG activity in the anterior deltoid muscle during maximal load exercises differed between exercise types but remained consistent across shoulder angles. When comparing shoulder angles, maximal load differed among the three types of exercises, but EMG activity did not show significant differences. During incremental exercise, EMG activity in both the anterior and posterior deltoid muscles was similar across the three types of exercises, with higher maximal EMG values observed during RR exercises compared to the other exercises. Furthermore, EMG activity in the infraspinatus muscle remained unchanged across the three types of exercises, in contrast to the other three EMG activities.
CONCLUSION:
While the SR, FR, and RR exercises share similar movements and are intended to strengthen the shoulder girdle muscles, their effects on the EMG activity differ. This studys findings indicate that the effects of these exercises on the shoulder girdle muscles are influenced by exercise type, shoulder angle, and load. Additionally, the relationship between maximal load and EMG activity varies across different muscles.