Obesity is a global health problem. It changes the measurement of the human body and makes a big change to move the body. The increased weight and mass change the way the limbs and whole body generate and react to force Excess fat also interferes with joint-muscle interactions that are important for functional capacity and postural balance The tendency to increase the thickness of the abdomen contributes to anterior movement of the COM of the body. The purpose of the study is to investigate the biomechanical effect of weight on foot stability in children.

Inclusion criteria:

• Their age will be ranging from 7 to 9 years.
• All children have normal stature for age percentile according to CDC chart.
• The sample will include both sex and will be divided in to 4 groups according to the CDC (Centers for Disease Control and Prevention) growth charts
• All children are normal &perform all activities of daily living
• They were able to understand and follow verbal commands and instructions included in the testing procedures.

Exclusion criteria:

• All of them could be part of recreational activities in their public schools but no competitive sports. Children who participated in any regular sport activities involving the lower extremities will be excluded.
• None of them had any surgical intervention in the lower extremities.
• None of them had any history of musculoskeletal deformities or neuromuscular disorders.
• They had neither visual, auditory defect.

Two hundred healthy non-athletic children from both sexes will participate in this study.

They will randomly be recruited from primary school stage.