Electrical activity of shoulder muscles during abductionof Upper Extremity atScaption and Frontal Planes with Different Speeds and Loads

The objective of this study was to compare the shoulder muscle activation during upper arm elevation in scaption and frontal planes under different speed and loading conditions.
Sixteen females (20-28 years old) were studied. A surface EMG system (MA300-16) was used to record the activity of shoulder muscles including anterior, medial, and posterior deltoid, supraspinatus as well as the upper, middle, and lower trapezius muscles during upper arm elevation in scaption and frontal planes. Tasks were repeated in slow and fast speed with and without load (5% of body mass). Under SPSS-22 environment, repeated measure ANOVA was used for statistics analysis with the significance level of p
In condition intraction between muscle, speed, load, plane motion factors was not effect significant (P=0.06). The activation levels of anterior, medial, and posterior deltoid, supraspinatus, upper, middle, and lower trapezius muscles in frontal plane were %53, %68, %73 ,%55, %58, %33, and %51 respectively. These values for shoulder elevation in scaption plane were %43, %73, %96, %67, %69, %43 and %62 respectively. In total, the muscle activity in frontal plane was 0.16 times more than that in scaption plane (P=0.0001). The total mean of muscle activitiesin fast motionswas about 0.11% higher than that in slower speed motions (P=0.0001). Also, with load, the muscle activity was 1.52 times more than that in without load condition (P=0.0001).
The muscle activity pattern of the arm elevation in frontal plane is different from that in scaption plane by means of higher activation in the frontal plane. In upper limb elevation, posterior deltoid muscle displayed higher activity than the other deltoid portions. Middle trapezious and anterior deltoid muscles had the least activity in upper arm elevation. Increasing the speed and load affected the activity of the posterior deltoid more than the other muscles.