The goal of this clinical trial study is to investigate the effect of performing lower limb kinetic chain exercise on muscle activation of scapular muscle strength ratio in patients with shoulder impingement. the main question it aims to answer is:

Does the addition of lower limb kinetic chain exercise to a shoulder exercise program improve scapular muscles strength ratio in patients with shoulder impingement? participants will be devided into two groups to be compared: The first group will be given a rehabilitation program consisting of strengthening exercises (for scapular stabilizers and rotator cuff) and stretching exercises (for pectoralis major, pectoralis minor, latissimus dorsi, levator scapula) The second group will be given the same exercises in addition to lower limb kinetic chain exercise

The term "kinetic chain" (KC) describes the sequential activation of body segments during functional movement patterns (Wilk et al., 2016). An effective KC will produce, summate, and enable effective mechanical energy transmission along the entire chain, which will support function. Any link in the KC that is inefficient has the potential to adversely affect force transfer to nearby segments (Ben kibler et al., 2000 & Martic et al., 2014). Consequently, therapists usually recommend incorporating trunk and lower extremity movements into shoulder rehabilitation programs in order to maximize efficient energy transfer throughout the entire KC (Sciascia et al., 2012 & Magarey et al., 2003). Thus, the investigators hypothesize that adding a lower limb (LL) kinetic chain exercise to a shoulder exercise program will improve scapular muscles strength ratio.

Inclusion Criteria:

• Age ranges between 20 and 45 years old

• Unilateral shoulder pain lasting more than 6 weeks

• At least one positive finding in each of these categories:

  1. Painful arc of movement during flexion or abduction
  2. Positive Neer or Hawkins-Kennedy impingement signs
  3. Pain on resisted lateral rotation, abduction or Jobe test

Exclusion Criteria:

• History of surgery
• History of fracture or dislocation
• Type III acromion
• Rotator cuff tear
• Long head of biceps tendon tear
• Cervical radiculopathy