This study evaluates muscle thickness of trunk and lower limb and balance in young and older healthy adults. The participants will be evaluated muscle thickness for 14 different muscle and balance which evaluated by computerized force plate system.

Aging had an adverse affect on musculoskeletal system and balance parameters. Decreased muscle strength or thickness negatively affect person's balance control. But there are no information in the literature about the relationships between muscle thickness and balance in healthy subjects. In addition to, it is not known which muscle responsible for balance. Therefore, this study will evaluate muscle thickness via ultrasonography and balance in young and older adults. Balance will be evaluated computerized Balance system. Muscle thickness for different 14 muscle ( diaphragm, transversus abdominis,multifidus, longissimus, quadratus lumborum, rectus abdominis, external and internal obliques, rectus femoris, vastus intermedius, vastus lateralis, tibialis anterior, gastrocnemius, soleus) will be evaluated by ultrasonography at the right side. Only diaphram muscle will be evaluated both right and left side.

Inclusion Criteria For Young Adults:

• To be a volunteer to participate
• to be an aged 18-40 years old.

Inclusion Criteria For Older Adults:

• To be a volunteer to participate
• to be an aged 65-90 years old.

Exclusion Criteria:

• Walking with assist device
• Having a visual deficits
• Having an orthopedic problems that affect balance
• Having a neurological disorders
• Having a musculoskeletal disorders that affect balance
• Having an undergone orthopedic surgery