The study objectives are the following: 1) To examine the acute vascular responses to continuous low- and moderate-intensity exercise and interval training; and 2) To examine the influence of age and gender on these responses.

The type, intensity and duration of exercise, fitness state, and timing of measurements have been reported to influence the acute vascular responses to exercise. However, little is known regarding the influence of interval training, aging and gender on these responses. The objectives of this study are: 1) to examine the acute vascular responses to continuous low- and moderate-intensity exercise and interval training; and 2) to examine the influence of age and gender on these responses. Subjects will perform the following 3 types of treadmill exercise in a random order: 1) slow-pace walking; 2) moderate-pace walking; and 3) interval training. Flow mediated dilation using high resolution ultrasonography and arterial stiffness using applanation tonometry will be measured before, immediately after and 1-hour after each acute bout of exercise.

Inclusion Criteria:

• Men and women 18 to 79 years of age
• Women will be premenopausal or postmenopausal (either natural or surgical) defined as a cessation of menses for at least 2 years.
• Premenopausal women will be eumenorrheic.
• Able to give consent.

Exclusion Criteria:

• History of hepatic disease or infection with hepatitis B, C or HIV
• History of other relevant on-going or recurrent illness
• Recent (within 3 months) or recurrent hospitalizations
• Current intake of medications that may affect study results
• Use of tobacco products
• Premenopausal women taking oral contraceptives and postmenopausal women taking hormone replacement therapy.
• Pregnancy (positive urine pregnancy test) or lactation
• Perimenopausal women

General population including men and women 18 to 79 years of age