Sarcopenia is an age-related loss of muscle mass that may affect over 25% of individuals over the age of 60 and results in a 3 to 4 times increased likelihood of developing a disability. Despite these observations, sarcopenia is rarely subject to a systematic screening process as a part of customary geriatric care. Furthermore, when lean body mass (LBM) is measured via dual energy X-ray absorptiometry (DXA) in older adults, it is typically within a reactive, hospital-based, model of healthcare where muscle wasting is only assessed after a loss of functional independence. The investigators propose an affordable, portable screening method with ultrasound imaging to be performed in primary care settings.

The investigators long term goal is to identify individuals at risk, and intervene with treatments that may prevent the onset of debilitating loss of muscle function in the elderly.

Purpose: The overall goal of this pilot project is to validate a rapid, portable, cost-effective, sarcopenia identification method using diagnostic sonography. This method would be used for screening to aid early detection, diagnosis in clinical settings, and monitoring the effects of formal intervention. The investigators central hypothesis is that the sonographic muscle characteristics will be significantly associated with estimates of lean body mass (LBM) and functional status.

Research Setting: George Washington University, Exercise Science Laboratory.

Participants: Subjects will include a healthy young reference group (18 - 29 years of age) and an older comparison group (55 - 75 years of age; n = 15 per group; approximately 50% female), consecutively recruited from George Washington University and the surrounding community.

Implications/Significance: Diagnostic musculoskeletal ultrasound is a portable, inexpensive modality suitable for bedside use or community health initiatives, and features no exposure to low-dose radiation. It is important to note that DXA is considered a relatively low cost procedure, and DXA-based measures may continue to be used as the standard for the sarcopenia syndrome LBM criterion. Consequently, this study will examine if LBM values obtained with ultrasound may serve as a viable proxy of LBM measures obtained with DXA.

The innovation in the investigators study is reflected by a proactive approach to sarcopenia screening that is responsive to the growing shift of healthcare from hospitals to alternative, community-based settings.

Inclusion Criteria: You are eligible to participate if:

1. You are between the ages of 18 - 29 years, or 55 - 75 years.
2. You must be able to stand comfortably for 10 minutes and walk a short distance (use of assistive devices are acceptable).

Exclusion Criteria: You are not eligible to participate if:

1. You have a medical condition that results in edema.
2. You have had an upper or a lower extremity amputation.
3. You are, or may be, pregnant.
4. You have a body mass index (BMI) > 30.0.

Enrolled subjects in this pilot study will include a healthy young reference group (18 - 29 years of age) and an older comparison group (55 - 75 years of age; n = 15 per group; approximately 50% female), consecutively recruited from George Washington University and the surrounding community.