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

During this pilot study, the investigators will examine the effects of whole-body electrical muscle stimulation exercise (WB-EMS Exercise) on motoneuronal activation in healthy adults, which typically decreases with age. The investigators will also test whether WB-EMS Exercise will improve measures of physical function. Participants will undergo clinical and electrophysiologic testing before and after the WB-EMS Exercise intervention. The WB-EMS Exercise intervention will be delivered two times per week for four weeks. The hypothesis is that whole-body electrical muscle stimulation combined with physical exercise (WB-EMS Exercise) could bypass the problem of insufficient motoneuronal activation to improve exercise effect in older adults.

During this pilot study, the investigators will examine the effects of whole-body electrical muscle stimulation exercise (WB-EMS Exercise) on motoneuronal activation in healthy adults, which typically decreases with age. The investigators will also test whether WB-EMS Exercise will improve measures of physical function. The intervention consists of WB-EMS Exercise twice a week for four weeks. The investigators will use decomposition electromyography, interpolated twitch technique, and clinical measures to assess pre- and post-treatment motoneuronal activation and physical functioning. Correlation matrices will be performed associating the measures of motoneuronal activation to the measures of physical function (pre-intervention values, post-intervention values, and change values). At the conclusion of the study, expected outcomes include that whole-body electrical muscle stimulation combined with physical exercise (WB-EMS Exercise) could bypass the problem of insufficient motoneuronal activation to improve exercise effect in older adults. This project represents early work to uncover motoneuronal mechanisms of WB-EMS Exercise in older adults. An intervention that combines voluntary and involuntary activation of motoneurons to enhance the effectiveness of exercise could have significant impact in maximizing the functional independence of an aging population.

Eligibility Criteria:
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