Sex-specific Adaptation to Resistance Training in Older Adults

Inclusion Criteria: * Older adult (65-75 years old) volunteers will be healthy, by self-report, and sedentary, defined as no formal exercise program for the year prior to evaluation and \< 2 sessions (30 min or more) of volitional exercise per week. Volunteers will be ambulatory without the use of walking aids and living independently in the community. All participants will be required to obtain a physician's consent to participate in the study, due to the exercise component, as is common practice in the Department of Kinesiology. Exclusion Criteria: * History of major neurological or neuromuscular condition that may impact physical function, including cerebrovascular disease, peripheral neuropathy, neurodegenerative disease, demyelinating disease, cerebellar or extrapyramidal disease, etc. * History of myocardial infarction, angina, peripheral vascular disease, surgical or percutaneous coronary artery revascularization * History of severe pulmonary disease (i.e., dyspnea that limits activities of daily living such as household ambulation and self-care) * History of rheumatoid arthritis * History of diabetes or other metabolic disease that may impact neuromuscular function * Uncontrolled hypertension (blood pressure \> 140/90) * History of smoking in the past 1 year * Moderate to severe lower extremity arthritis or pain (i.e., pain on level walking or that limits activities of daily living such as household ambulation and self-care) * Pain, muscle cramps, joint stiffness, dyspnea, angina, light-headedness or other symptoms upon exertion * The use of beta-blockers, sedatives, tranquilizers, or other medication that may impair physical function * Individuals taking statin medications who report symptoms of muscle pain or myopathy * Body-mass index \>30 kg·m-2, as increased fat mass may alter single muscle fiber performance (Choi et al. J Gerontol A Biol Sci Med Sci 71:557-564, 2016) * Body-mass index \<18 kg·m-2, as this may be an early sign of frailty * Must pass the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+, in Appendix) * Any persons taking anti-coagulant medication or with known coagulapathies will be excluded, due to increased bleeding risk from biopsy procedure * Participants with a contraindication for magnetic resonance testing, including a pace-maker or other implant * Women will be postmenopausal, as defined as cessation of menses for at least 12 months prior to study * Men and women undergoing hormone replacement therapy, because this treatment may circumvent normal age-related declines in sex hormone levels (if taken hormone therapy must have been \> 5 years ago) * Unintentional weight loss of greater than 2.5 kg during the last 3 months * Currently participating in or have participated in a weight loss or exercise training program in the last year * An inability to understand written and spoken English * An inability to follow instructions, as determined by the investigators during the consenting process