Friedreich's ataxia is a rare, chronic, progressive, neurodegenerative condition affecting multiple organ systems, including neurological, musculoskeletal, cardiac, and endocrine systems, and is marked by low cardiopulmonary fitness. We tested the effect of exercise and NAD+ precursor supplementation with nicotinamide riboside, which have each shown benefits in animal and early clinical studies, on cardiopulmonary fitness in individuals with Friedreich's ataxia.