Inclusion Criteria:  Confirmed diagnosis of CLL as per the International Workshop on CLL Guidelines. Male or female ≥ 18 years of age No history of prior treatment of CLL Able to walk on a treadmill or cycle on an ergometer Pass the CPET evaluation of aerobic fitness and cardiac health  Exclusion Criteria:  Clinical evidence of significant disease progression with first line therapy expected within 6 months Corticosteroid therapy initiated less than 7 days prior to study entry. Prednisone 10mg or less or equivalent is allowed as clinically warranted. Topical or inhaled corticosteroids are permitted. Malignancy within 3 years of study enrollment requiring intervention except for adequately treated basal, squamous cell carcinoma or non-melanomatous skin cancer, carcinoma in situ of the cervix, superficial bladder cancer not treated with intravesical chemotherapy or BCG within 6 months, localized prostate cancer and PSA stable Absolute contra-indications to exercise: Recent (<6 months) acute cardiac event unstable angina, uncontrolled dysrhythmias causing symptoms or hemodynamic compromise, symptomatic aortic stenosis, uncontrolled symptomatic heart failure, acute pulmonary embolus, acute myocarditis or pericarditis, suspected or known dissecting aneurism and acute systemic infection. Significant orthopedic limitations, musculoskeletal disease and/or injury. Due to the nature of the study, persons with known joint, muscle or other orthopedic limitations that restrict physical activity may be excluded. Type I diabetes mellitus or uncontrolled Type II diabetes mellitus (HbA1c >7%), or chronic obstructive pulmonary disease Uncontrolled blood pressure (≥180/90) at rest during screening and confirmed on repeat manual measurement Unable to travel to fitness center or comply with other study requirements Known concurrent HIV, Hepatitis B or Hepatitis C