trunk oriented exercises include: stretching exercises, stabilization exercises (active or active-assisted), arm exercises in fixed trunk position, trunk-oriented exercises (active or active-assisted), trunk mobilization (sitting and lying position), and functional reaching exercises with different ranges of motion in shoulder elevation

The thickness of four abdominal muscles will be measured with ultrasonography (device type GE Logiq P6) with a frequency of 7.5 MHz. The probe will be placed 2 or 3 cm from the midline, using the umbilicus as a landmark, then will be moved in a semi-circular motion until the deepest image on the screen, the TA, will be visible. To confirm this position and measure the thickness, a skin marker pen will be used. The probe will be then moved in an oblique manner to detect the thickness of the EO, IO, RA, and TA. A large amount of contact gel will be used, and the probe pressure will be adjusted to obtain optimal values of muscle thickness. After image capture, a vertical line will drawn between the superficial and deep aponeurosis to determine muscle thickness.

the Biodex Balance System (BBS) (Biodex medical system, Shirley, New York) will be used for balance assessment.

Before the evaluation procedures all children will be given an explanatory session to be aware about the different test steps, also the support rails and biofeedback display screen will be adjusted for each child to ensure comfort and safety during the test procedure, then each child will be trained 1 min for adaptation to the machine. During the test, children will be instructed to stand on the platform in the most comfortable posture, and maintain their visual level by focusing straight ahead on the monitor. The platform will be unlocked and children will be allowed to adjust their foot placement until a comfortable standing position will be achieved while they simultaneously maintained a moving pointer at the center point on the monitor and children will be encouraged to maintain the moving pointer at the center point throughout the test.