The purpose of this observational study is to examine whether differences in muscle strength between the dominant and non-dominant sides of the body are associated with sarcopenia in older adults. The study will include adults aged 65 years and older with and without sarcopenia. Muscle strength will be measured on both sides of the body using handgrip strength as well as strength measurements of the biceps (upper arm muscle) and quadriceps (thigh muscle). The difference in strength between the dominant and non-dominant sides will be calculated and compared between participants with sarcopenia and those without sarcopenia.

The main question it aims to answers are:

• Do older adults with sarcopenia have larger differences in muscle strength between the two sides of the body compared with those without sarcopenia?
• Can differences in arm and leg muscle strength help identify older adults who may be at higher risk of sarcopenia?

Sarcopenia is a clinical condition in elderly individuals where muscle strength, muscle mass, and physical performance decrease, negatively impacting their quality of life. The European Working Group on Sarcopenia in Older People (EWGSOP) has developed a simple clinical definition and diagnostic criteria for age-related sarcopenia. Measurements of walking speed, grip strength, and muscle mass are taken to detect sarcopenia. The severity of the disease is It is measured by physical performance. Unilateral measurements in hand grip strength measurement used in diagnosis may lead to the neglect of muscle symmetry. Hand grip strength asymmetry (difference between dominant and non-dominant hands) has recently been evaluated as a sarcopenia risk indicator.A significant association has been demonstrated between handgrip strength asymmetry (>10% difference between limbs) and sarcopenia. Individuals with asymmetry were found to have a 2.67-fold higher risk of sarcopenia, indicating that this approach also has diagnostic utility. In addition, it has been shown that the dominant side has greater strength and muscle mass in the upper extremities; however, this difference decreases with age. A significant relationship has been identified between handgrip strength asymmetry and muscle mass, with asymmetric individuals being more likely to have low muscle mass.. In the lower extremities, quadriceps strength was found to have a clearer relationship with health outcomes. In the ISCOPE study, although the relationship between quadriceps strength and handgrip strength was limited, the combination of the two was found to be appropriate in defining the fragile group. In light of these studies, it can be suggested that dominant-non-dominant muscle strength asymmetry (upper and lower extremities) is greater in sarcopenic individuals and that this asymmetry parameter may have a guiding value in diagnosis. In the current literature, there is no study that evaluates asymmetries between biceps, quadriceps, and handgrip strength together and compares their predictive power specific to sarcopenia. This study aims to compare the differences in dominant-non-dominant biceps, quadriceps, and handgrip strength in sarcopenic and non-sarcopenic elderly individuals, and to examine its potential value as a novel biomarker in the diagnosis of sarcopenia.

Inclusion Criteria:

• Age 65 years or older
• Ability to walk independently or with minimal assistance
• Ability to understand and follow simple instructions
• Willingness and ability to provide written informed consent
• Availability of muscle strength measurements (handgrip, biceps, and quadriceps)

Exclusion Criteria:

• Lack of cooperation, moderate to severe dementia (e.g., MMSE <24) or conditions impeding cooperation.
• Those with severe cardiovascular disease
• Those with pacemakers
• Surgical/fracture/acute pain in the measured extremities within the last 6 months.
• Neurological and muscular disease affecting the upper or lower extremity (acute stroke, severe peripheral neuropathy, etc.)
• Active systemic disease attack significantly affecting the measurement.

The study population will include older adults aged 65 years and older who are evaluated in a hospital or outpatient clinic setting. Participants will be grouped as sarcopenic and non-sarcopenic according to established diagnostic criteria and will undergo standardized assessments of muscle strength, body composition, and physical performance.

Individual participant data will not be publicly shared due to ethical and privacy considerations. Aggregate results will be reported.