The purpose of this study is to test the hypothesis that physiological adaptations to regular exercise training (i.e. physical fitness) attenuates age-related decline in stress resilience to both oxidative stress and the neuroendocrine responses to psychosocial stress.

Aging is associated with diminished stress resilience, as in reduced ability to manage or recover from acute changes in homeostasis. Increased oxidative damage to cells and tissues and dysregulation of stress hormones have been linked to age-associated chronic diseases including atherosclerosis, cancer, cardiovascular disease and Alzheimer's disease. Interventions to improve the body's resistance to stress, resulting in lower oxidative stress and better regulation of the stress hormones, may prevent or delay the onset of age-related diseases and improve quality of life.

Oxidative stress is believed to be a key mechanism in the aging process, with free radicals also implicated in many pathological processes. Similarly, dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is thought to play a role in aging and is linked to the increased risk for age-related chronic disease.

The hormesis theory suggests that a certain amount of stress can lead to better survival and reduced tissue damage following a subsequent, more severe stress. One way to stress the system is through acute exercise. Regular exercise training, however, results in adaptive responses that increase the tolerance for successive (exercise) stress.

A relevant question is whether adaptations to regular exercise training translate to greater resilience to psychosocial stress and an increased capacity to resist acute oxidative stress, thereby providing increased protection from diseases associated with dysregulation of these systems.

This study will investigate stress resilience in two areas related to aging: oxidative stress and the neuroendocrine response to psychosocial stress. The effects of physical fitness on oxidative stress compensation and neuroendocrine stress reactivity will be determined by comparing fit and unfit older men and women. The overall aim of this study is to provide enhanced understanding of the mechanisms by which physical fitness modifies stress resilience in older men and women.

Inclusion Criteria:

• Men and post-menopausal women, ages 60-80 years
• Generally good health by self-report

Exclusion Criteria:

• Estrogen or testosterone supplementation within the previous 6 months
• Current smoker
• Body Mass Index (BMI) > 32 kg/m2
• Any chronic illness that could affect cortisol levels, including diabetes mellitus, liver or renal disease
• Evidence of a previous myocardial infarction within the last 6 months by EKG or history of angina or shortness of breath
• Clinically significant arrhythmia on a resting EKG or significant EKG changes during the baseline VO2max test
• Any other condition that would contraindicate maximal exercise testing, including elevated blood pressure at rest (systolic BP >140 or diastolic BP >90 mm Hg on at least 2 measurements, at least 10 minutes apart) or musculoskeletal problems
• Depression as measured by the Beck Depression Inventory (BDI score >17)
• Use of anti-oxidant supplements, in excess of standard multi-vitamins (1 tablet/day)

Community sample