Validity and Feasibility of the Constant‐Load Cycle Endurance Test in Lung Cancer Patients Undergoing Radiation Therapy

PURPOSE: This study evaluated the validity of the constant-load cycle endurance test (CET), performed at 75% of maximal power output, in patients with lung cancer undergoing radiation therapy. Its feasibility, responsiveness to pulmonary rehabilitation (PR), and clinical applicability were also examined. METHODS: Thirty-three patients participated in a 4-week PR program during radiation therapy. CET time was compared with the 6-min walk test (6MWT) to assess concurrent validity. Patients were stratified by 6MWT distance (≥ 450 m = active; < 450 m = inactive). CET, 6MWT, knee extensor strength, and handgrip strength were measured at baseline and post-PR. Adverse events were monitored. RESULTS: CET time showed a moderate correlation with 6MWT distance (r = 0.57, p < 0.001). The correlation was stronger in the active subgroup (r = 0.61, p < 0.001) but not significant in the inactive subgroup (r = 0.09, p = 0.63). After PR, significant improvements were observed in CET, knee extensor (left) strength (p < 0.05). Subgroup analysis indicated that inactive patients primarily improved in 6MWT, whereas active patients showed greater gains in CET. No adverse events occurred during testing or PR. CONCLUSIONS: CET demonstrated moderate validity with the 6MWT and was responsive to PR, particularly in patients with higher functional capacity. CET appears feasible, safe, and complementary to walk tests, potentially capturing improvements masked by ceiling effects. Larger studies are needed to confirm its role as a standard outcome measure in PR for lung cancer.