D-Ribose is a five-carbon sugar that forms the structural backbone of ATP (adenosine triphosphate), the molecule that powers every muscle contraction and cellular process in the body. Unlike glucose, ribose does not raise blood sugar and is directed almost entirely toward ATP synthesis rather than energy storage. It is particularly useful for replenishing ATP depleted during intense or prolonged exercise, chronic fatigue syndrome, fibromyalgia, and cardiac conditions where energy production is compromised. Supplementation supports faster recovery between bouts of exertion and may reduce post-exercise muscle soreness and stiffness.