To date, the effects of pain on motor learning have not been thoroughly investigated, particularly in older adults. Broadly, the purpose of this research is to investigate the impact of acute pain on locomotor learning and its retention in older adults. The investigators hypothesize that acute pain impairs retention of locomotor learning in young and older adults and that in older adults, these deficits are worsened and are related to the degree of normal age-related cognitive decline.

Abbreviations: YA= young adult; OA= older adult; HR= heart rate, bpm= beats per minute; BP= blood pressure; ADD= attention deficit disorder; ADHD= attention deficit hyperactivity disorder; MoCA= Montreal Cognitive Assessment; GAD-7= Generalized Anxiety Disorder 7 Scale; PHQ-2, PHQ-9= Patient Health Questionnaire-2 and -9.

Inclusion Criteria:

1. 18-35 (YA group only) or 55-85 (OA group only) years old
2. Sex-matched to a participant in the OA group (YA group only)
3. Self-identifying as generally medically healthy
4. Able to read, write and speak English
5. Able to provide informed consent and attend all testing sessions
6. Willing to undergo the experimental pain or non-painful electrical stimulation, if selected

Exclusion Criteria:

1. Resting HR < 50 or > 100 bpm
2. Resting BP < 90/60 or > 140/95 mmHg (YA group only) or > 165/95 (OA group only)
3. Any history or current mental health condition, learning/developmental disability or cognitive impairment, including severe untreated ADD/ADHD, severe untreated anxiety, severe untreated depression, autism spectrum disorder, insomnia, mild cognitive impairment, etc.
4. Score on the MoCA <23
5. Score on the GAD-7 ≥ 10
6. Score on the PHQ-2 ≥ 2 and score on the PHQ-9 ≥ 10
7. Any current (within last 3 month) or chronic medical conditions, including any musculoskeletal, cardiovascular, endocrine, pulmonary, metabolic, psychiatric or neurological diagnosis that (for OA group only) affects activities of daily living or would confound testing or place the subject at risk by participating, such as a significant cardiovascular condition or event (e.g., heart attack < 3 months ago, uncontrolled atrial fibrillation, uncontrolled angina, or congestive heart failure, chronic obstructive pulmonary disorder, peripheral vascular disease)
8. Any impaired sensation or weakness in either lower extremity or in the area targeted for the stimulus
9. History of serious concussion or head injury, defined as a loss of consciousness for > 5 minutes and/or requiring medical treatment, or > 2 concussions over the lifespan
10. Any history of acute or chronic problems with balance, any dizziness, or > 1 fall in the last 12 months
11. Taking 4 or more medications (YA group only)
12. Currently or regularly using any analgesic medications, over-the-counter remedies, or any other treatment for the purposes of pain relief (i.e., baby aspirin for heart health permitted, etc.)
13. Any current or chronic pain condition during the last year, located anywhere in the body with a (OA group only) pain intensity of > 2/10
14. Allergy to capsaicin or hot peppers
15. Any skin lesion, breakage or irritation in the area targeted for the painful stimulus
16. Skin sensitivity to soaps/creams/perfumes or to heat
17. Poor circulation in the area targeted for the painful stimulus
18. Prior participation in a locomotor learning study in this lab within the last 2 years or prior participation in a study in this lab that included the cognitive testing battery within the last 2 years.

Application of pain or no stimulus cannot be masked from participants, nor from outcomes assessors.