This study will be conducted to investigate the effect of scapular stabilization exercises on scapular muscles strength (serratus anterior, lower fibers of trapezius, rhomboid major and minor), pain intensity level and kyphosis index in different duration of time using daily of smartphone in smartphone users.

Modern people use a smartphone along the day, including occupational and leisure activities. Repeated and prolonged use of smartphones affecting muscular activity and strength around the shoulders and upper back especially serratus anterior during maintaining an un ideal posture which may result in the development of postural changes as excessive thoracic kyphosis which in turn will result in inadequate muscles contractions, weakening of postural muscles and fatigue. Scapular muscles strength should be balanced or integrated (muscle balance) and worked in synchronized motion, so, alteration in scapulothoracic motion in resting position or dynamic motion of scapula described as scapulothoracic dysfunction. Muscle imbalances occurs and lower trapezius, serratus anterior and rhomboids muscles are the most common muscles prone to weakness due to exposure to sustained awkward posture or adaptive postures and restriction to specific activity. Continuous use of smartphone for more than 4 hours daily increases shoulder and parascapular pain, fatigue, decrease strength of scapular muscles (lower fibers of trapezius for scapular adduction and depression and rhomboids for scapular adduction and downward rotation) in right dominant side due to prolonged hyperactivity, then weakness.The excessive use of smartphones correlates with increases incidence of vertebral static disorders, especially kyphosis.

Scapular stabilization exercises were effective in the early rehabilitation and the balance of both sides of the trapezius with the movement and couple motion of the scapula. It is also effective in increasing muscle activation in the serratus anterior and lower trapezius.

Inclusion Critria

• Normal subjects from both genders.
• Subjects had to be right hand dominant.
• Age ranged from 17 to 45 years old.
• All subjects had at least 6 months experience in using touch-screen smartphones.
• The mean of smartphone size included in the study will be 5 inches (Mohamed et al., 2020).

Exclusion Criteria:

• Any pain or limitation (dysfunction) at neck and shoulder.
• Any congenital abnormalities in either the cervical or the lumbar spine.
• Previous history of severe surgical procedures.
• Any history of upper extremity injury within the past year.
• Visual problems, dizziness and vertigo.
• Any deformity in the upper extremities or spine.
• Neurological or systemic disorders.
• If they had taken any sedative drug or alcohol within the past 48 hours.