Effects of Whole-body Electrical Muscle Stimulation Exercise on Spinal Motoneuronal Activation in Older Adults

Inclusion Criteria: * Age (65 years or older) for healthy older adults and between 18-39 for healthy younger adults * Ambulatory without an assistive device * More than anti-gravity strength in major muscle groups as assessed by manual muscle testing * Medical clearance to participate in an exercise program * Ability to conform to the requirements of the study (i.e. attendance at assessment and intervention visits, maintain current level of non-study physical activity for the duration of the study, no intention to relocate mid-study) Exclusion Criteria: * Regular use of an assistive device for mobility (i.e. cane, walker, wheelchair) * Presence of a pacemaker, metal implants, or other implanted medical devices that could impact participant safety during WB-EMS intervention * Known pregnancy at the time of screening * Presence of unstable acute or chronic disease (i.e. renal failure, rheumatologic disease cardia arrhythmia, neoplasm, uncontrolled hypertension) * Presence of terminal disease (i.e. receiving hospice services) * Current of previous use of any drugs known to influence muscle mass or performance within 6 months; these may include but are not limited to anabolic steroids, IGF01, growth hormone, replacement and androgen therapy, anti-androgen therapy. * Known neuromuscular or neurologic condition affecting somatosensory or motor function/control (i.e. motor neuron disease, muscle disease, severe peripheral neuropathy, NMJ disease, Parkinson's disease, Multiple Sclerosis, h/o stroke, TBI, SCI, ataxia, apraxia, hemiplegia, etc.) * Musculoskeletal condition or surgery in the past year that would confound results of exercise interventions (i.e. TKA, THA, RTC repair, spinal fusion) * Other medical conditions, signs, or symptoms that would interfere with study conduct or interpretation of results as determined by a PI