Identifying Markers of Exercise Training in Heart Failure

Inclusion Criteria: Be 18-89 years of age Not be pregnant or lactating in the last 12 months, or planning to become pregnant for the next 4 months. A pregnancy test will be performed on the day of DXA scan in women of child-bearing potential. Not be post-partum during the last 12 months. patients must carry a diagnosis of heart failure with ejection fraction < 40% Be willing to provide informed consent for all study procedures be willing to participate in cardiac rehabilitation Exclusion Criteria: Diabetes (self-report and screening tests), which includes: i) treatment with any hypoglycemic agents (self-report, even for non-diabetic reasons) or ii) fasting glucose >125 or A1c >6.4 (screening test). Chronic renal insufficiency (screening test): estimated glomerular filtration rate <60 mL/min/1.73 m2 from serum creatinine (mg/dL) by the Chronic Kidney Disease Epidemiology Collaboration equation Individuals receiving any active treatment for autoimmune disorders (including monoclonal antibodies) within the last 6 months. Alcohol consumption (self-report): i) more than 7 drinks per week for women and more than 14 drinks per week for men; ii) history of binge drinking. Hospitalization for any psychiatric condition within one year (self-report). Any musculoskeletal or ligamentous injury, amputation or congenital neurological defect that, in the opinion of the team clinician, would negatively impact or mitigate participation in and completion of the protocol. Mental incapacity and/or cognitive impairment on the part of the participant that would inhibit adequate understanding of or cooperation with the study protocol. Taking Androgenic anabolic steroids, anti-estrogens, anti-androgens Taking Growth hormone, insulin like growth factor-I, growth hormone releasing hormone Taking Any drugs used to treat diabetes mellitus or to lower blood glucose Taking Any drugs used specifically to induce weight loss Taking Any drugs used specifically to induce muscle growth/hypertrophy or augment exercise-induced muscle hypertrophy Taking Narcotics and narcotic receptor agonists Taking Monoclonal antibodies Taking Any other medications that, in the opinion of local clinicians, would negatively impact or mitigate full participation and completion.