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