Muscle Biopsies in Healthy Volunteers: a Pilot Study

Background: \- In individuals as they age, changes in muscle tissue can significantly affect their muscle strength and exercise endurance. This process, known as sarcopenia, may lead to decreased mobility and physical weakness, which is what we in general refer to as frailty. The causes of sarcopenia and why it affects some individuals more than others are not known, but many factors influence muscle physiology and function, including metabolic, hormonal, environmental, and lifestyle factors. Researchers interested in identifying factors involved in the start and progression of sarcopenia need of samples of human muscle tissue and cells for laboratory investigations. Objectives: * To train researchers in the appropriate procedures for performing muscle biopsies and collecting, labeling, and storing the samples. * Develop a data base of specific scientific studies evaluating the physiological and metabolic function of muscle that can be used in future studies. Eligibility: \- Healthy volunteers at least 18 years of age. Design: * Participants will be screened with a full medical history and physical examination, as well as blood and urine tests, and will schedule a date for the muscle biopsy. * Participants will have a muscle biopsy, with tissue and cells taken from the upper part of the thigh. A local anesthetic will be given for the procedure. Participants will also provide a blood sample and have an electrocardiogram to evaluate heart function. * Participants will have a followup visit 1 week after the biopsy visit to evaluate the healing process and provide any further treatment for the affected area, after which they may fully resume normal activities.