A phonophoresis-based drug delivery system is a synchronous approach to improve local drug penetration in neuromuscular diseases associated with neuronal damage, excruciating pain, and local inflammation. Chitosan, a semi-synthetic material, is obtained by partial deacetylation of chitin amines, resulting in copolymers of N-acetylglucosamine and N-glucosamine. Its use has been explored in various biomaterial and medical applications. Chitosan has emerged as a cost-effective, biocompatible, and biodegradable material with many desirable biological properties, improvement of homeostasis and antiviral potential. Chitosan was found to suppress pro-inflammatory cytokines and decreased peripheral nerve edema, the polycationic nature of chitosan allows it to absorb protons, which reduces inflammation and provides an analgesic effect.

The patients will randomly be divided into two equal groups; the control group which will receive the selected exercise program and the study group will receive the same exercise training program in addition to Chitosan Phonophresis, three times per week for four weeks.

Inclusion Criteria:

• Their age will be ranged from 16-18 years
• body mass index will be 26.58 kg/m2.
• used a smart phone for more than 1 year for at least 2 hours per day
• complaining of neck pain after using a smart phone, addiction to smart phone in accordance with the smart phone addiction scale (SAS)

Exclusion Criteria:

• any previous head and neck injuries or surgeries
• any congenital abnormalities or symptomatic deformity in either the cervical or the lumbar spine
• any uncorrected visual or auditory problems, dizziness, vertigo and headache
• any systematic diseases, any addiction to alcohol, any additive drugs and sedatives within 48 hours previous to tests
• body mass index of subjects over25 kg/m2.