The purpose of this study is to determine whether an aerobic training intervention will alter markers of immune cell aging, improve exercise capacity and blood pressure and decrease psychological distress over 24 weeks in 32 caregivers compared to 32 age-matched wait list control caregivers.

The investigators will prospectively examine whether an aerobic training intervention will alter markers of immune cell aging (i.e. increase telomerase activity in peripheral blood mononuclear cells, telomere length in peripheral blood mononuclear cells and leukocytes, mitochondrial function, epigenetic profiles, and mRNA expression), improve exercise capacity and blood pressure, and decrease psychological distress over 24 weeks in 32 caregivers compared to 32 age-matched wait list control caregivers. Our sample will be comprised of caregivers who provide unpaid care for a family member diagnosed with Alzheimer's disease or other dementia. Participants in the study will be highly stressed and inactive male and female caregivers of family members with Alzheimer's disease or other dementia. All eligible participants will complete one week of ecological momentary assessments (EMA) to examine whether (1) previously unfit, high-stressed caregivers benefit psychologically from becoming active, (2) this benefit is derived through changes in how caregivers react to and recover from stressful events, and (3) whether these salubrious psychological effects mediate changes in biological outcomes (e.g., cellular aging). Next, participants will participate in a one-week run-in period of stretching 30 minutes on 4 separate days prior to randomization to guarantee that the investigators are randomizing well-informed participants that are willing and able to complete the expected exercise. Next, participants are randomized into the aerobic exercise or wait list control arm. In the 24th week of the study, participants complete a second week of the EMAs sub-study, and return after week 24 for a final blood draw.

Research study assessments consist of self-report questionnaires, body composition, physical performance and fitness tests, and a fasting blood draw. The follow-up visit, 24 weeks later, consists of a repeat of the same morning health visit.

Inclusion Criteria:

• Age: 50-75
• Men and Women (women must be post-menopausal)
• Body Mass Index must be below 40 (to exclude for extreme obesity, which can confound outcomes)
• Must be a first or second degree family member providing unpaid caregiving for an adult relative with Alzheimer's disease or other dementias of longer than 6 months since diagnosis.
• Must report providing care for 10 or more hours per week.
• Perceived stress ≥ 15 for adults 65 and older; Perceived stress ≥ 18 for adults aged 50-64. (0.5 standard deviation above national average for adults)
• Do not meet Center for Disease Control recommendations for exercise (150 minutes per week of moderate activity levels or 75 minutes of vigorous)

Exclusion Criteria:

• Major Chronic Disease that interferes with activity levels as advised by a medical practitioner (Autoimmune disorders; severe asthma; lung disease - emphysema or chronic bronchitis; history of stroke, heart attack, cardiovascular disease, epilepsy, or brain injury)
• Heart attack in the past 6 months or repeated experience of chest pain or pressure, and/or arrhythmia.
• Cancer that is not in remission. Those who underwent chemotherapy or radiation within the past 5 years will be excluded.
• Eating Disorders
• Current substance dependence that can interfere with activity engagement.
• Current Post Traumatic Stress Disorder
• Current or recent smoking status. We will exclude current smokers and past smokers (who quit within the past 5 years).
• Confounding medications- Oral Steroids containing prescription drugs use and any other drugs that might interfere with the outcome measures.
• Current major injuries
• Any physical impairment that prevent participation in moderate levels of physical activity (e.g. musculoskeletal problems, prosthesis)
• Inability to walk a block or climb stairs without chest pain, losing breath, or dizziness