Scientists probe a muscle protein that may hold clues to Age-Related weakness

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Adults between the ages 18-35 or 65-80 years * Healthy by self-report * Willing to participate in all aspects of the study design including muscle biopsy, unilateral exercise, and physical activity monitoring * Fluent in English (due to lack of translation services, it is not practical to conduct the study using a language other than English). Exclusion Criteria: * Orthopaedic limitation (severe knee osteoarthritis, prior joint replacement, etc.). * Volunteer has dementia or related mental issues that potentially put the subject at risk as determined by prior diagnosis. * Volunteer has known untreated endocrine disease (hypo/hyper thyroidism, Addison's Disease or Cushing's syndrome, etc.) * Volunteer has untreated/poorly-controlled hypertension (stage 2, per American College of Cardiology \[\>140/90 mmHg\]). * Volunteer has significant heart, liver, kidney or respiratory disease. * Volunteer has diabetes (insulin dependent or non-insulin dependent). * Volunteer has known coagulopathies. * Volunteer has taken anabolic steroids in the prior six months. * Volunteer has received treatment for cancer (other than effective Mohs Surgery for successful removal of basal cell or squamous cell carcinomas) * Unexpected weight loss \>5kg is last 12 months * Volunteer is an active smoker or quit within the last year. * Volunteer has known current alcohol or drug use disorder (AUD; defined as binge drinking of \>4 days in the last month. Binge drinking is \>5 drinks for men and \>4 drinks for women, per occasion). Or, if a volunteer reports drinking in excess of "low risk" per NIAAA (\>7 drinks/week for men and \>3 drinks/day for women and \>14 drinks/week and \>4 drinks/day). * Volunteer has a diagnosed neuromuscular disorder. * Volunteer has allergy to lidocaine.