The purpose of this study is to investigate the impact of creatine supplementation alone or in combination with a moderate session of physical activity on vascular reactivity and heart hemodynamics in elderly men.

Before beginning baseline testing, subjects' vitals will be measured (heart rate, blood pressure) in order to ensure that they are safe to participate in the submaximal exercise test. Subjects will also complete the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+) to screen for cardiovascular risk factors. Information about physical activity level, medical history, and creatine supplementation use history will also be acquired. After anthropometric measurements, subjects will be asked to lay down in a hospital-type bed for measuring heart function and vascular responses at rest.

For measures of heart function, a non-invasive bioimpedance device will be used. Five ECG electrodes will be placed on chest and neck areas that will continuously collect information about heart rate, stroke volume, contractility index, ejection fraction and systemic vascular resistance. Vascular responses will be assessed using a non-invasive arterial pulse wave velocity equipment. This test uses four blood pressure cuffs placed on the wrists and calves, which, after 10 seconds inflation, are able to calculate an index of stiffness.

After resting values are collected, the cuffs will be removed, and subjects will be asked to walk on a treadmill at 6 km/h (3.1mph) and 5% grade for 10 minutes. During the treadmill walking, subjects will have their heart monitored using the non-invasive bioimpedance device with the ECG attached to their chest and neck. After 10 minutes have passed, subjects will be asked to step down from the treadmill and lay down on in the same hospital type bed.

At this time, the four blood pressure cuffs will be placed again on the wrists and calves to measure the vascular responses. We plan on performing two arterial stiffness measurements, after 10 and 20 minutes of the treadmill walking. After 20 minutes of monitoring while lying in bed, subjects will be disconnected from all ECGs and blood pressure cuffs.

Randomization in one of the three groups will occur using a computer generated sequence. The groups will have 15 subjects each and will consist of creatine supplementation, placebo supplementation (maltodextrin) and control (no supplementation). After randomization, subjects will receive their assigned packages containing the supplementation supplies corresponding to their group allocation (creatine or placebo). After 7 days of 20g/day supplementation, subjects will be asked to come back to the testing center for a repeat of the exercise test and corresponding heart monitoring and vascular responses before and after the treadmill walk.

To ensure good compliance with supplementation, subjects will receive daily text messages with reminders about their dose ingestion. The 20g/day will be divided in 4 dosages of 5g each that should be taken with water or other liquids throughout the day (breakfast, lunch, afternoon and evening).

Inclusion Criteria:

• Males
• 55-80 years old
• No restrictions based on race, ethnicity, or socioeconomic status

Exclusion Criteria:

• Females
• <55 or >80 years old
• Individuals with known serious cardiac pathology
• Individuals with known serious kidney pathology
• Appropriate for moderate intensity exercise (screening using PAR-Q+)
• Individuals currently consuming or had consumed creatine supplement within 3 months prior to screening