The aim of this study is to determine whether supplementation of glutamine and fish oil can improve peripheral skeletal muscle function and metabolism in patients with heart failure. The investigators propose a randomized, double-blind, placebo controlled study comparing the combined supplementation of fish oil and glutamine with placebo in patients with stable heart failure. 30 patients with heart failure will be randomized to either receiving 6.5 g fish oil/d and 8 g glutamine/d (n=15) or placebo (n=15) for 90 days. The primary outcome in this study is the change in muscle functional capacity measured as changes in maximum muscle strength and fatigability, peak VO2 and exercise time after supplementation. A secondary outcome is the measurement of systemic and local markers of inflammation.