D-ribose, a natural occurring pentose carbohydrate, has repeatedly shown to enhance high-energy phosphates and improve function following ischemia, states of congestive heart failure, and recently in subjects with lung disease. An initial preliminary, open label pilot study demonstrated a positive benefit of D-ribose in "Baby-Boomer" subjects aged 50 to 65 years old complaining of persistent fatigue. The objective of this study will build on the previously collected data to evaluate oral D-ribose vs. dextrose (administered as a supplement) in relatively healthy, yet fatigued subjects with a goal of improving their state of fatigue.

Inclusion Criteria:

• Presents with complaint of fatigue with duration longer than one month
• Males/Females between the ages of 50 and 65 years of age
• No previous clinical diagnosis of pulmonary, cardiac or metabolic disorders based on history
• Capable of performing a sub-maximal incremental treadmill exercise using cardiopulmonary analysis methods
• Normal blood pressure or those with mild, untreated pre-hypertension (>120/70 or < 140/90 mmHg)
• Able to be compliant with the supplement regimen, repeat clinical visits and completion of the study questionnaires
• Must be able to understand the consent form, agree to participate, and to execute their signature

Exclusion Criteria:

• Not presently taking any adenine nucleotide enhancing supplements
• History of non-compliance in previous studies
• Known to be pregnant
• Uncontrolled cardiac arrhythmias causing symptoms or unstable hemodynamics
• Moderate to severe gout
• A diagnosis of arthritis of the lower extremities
• Mental impairment, inability to cooperate
• History of acute non-cardiopulmonary disorder that may affect exercise performance, (e.g. infection, renal failure, thyrotoxicosis, etc.)
• Any disorder or condition that in the opinion of the study physician would render exercise unsafe or would impact exercise performance
• Any person who is incarcerated, or on a work release program

Additional Exclusions observed and sequelae during initial baseline evaluation:

• Drop in systolic blood pressure of >10 mm Hg from baseline despite an increase in workload, when accompanied by other evidence of ischemia
• Moderately severe angina
• Increasing nervous system symptoms (e.g. ataxia, dizziness, or near syncope)
• Signs of poor perfusion (cyanosis or pallor)
• Technical difficulties monitoring the ECG or systolic blood pressure
• Subject's desire to stop
• Sustained ventricular tachycardia
• Electrocardiographic ST elevation (+1.0 mm) in leads without diagnostic Q-waves (other than V1 or aVR)