Feasibility and Reliability of the YMCA 3-Minute Step Test in Adults With Cystic Fibrosis

Purpose: Given the paucity of studies examining the use of submaximal exercise field tests in adults with cystic fibrosis, especially those on elexacaftor/tezacaftor/ivacaftor (ETI) therapy, the purpose of this study was to examine the feasibility, test–retest reliability, and minimum detectable change (MDC) of the YMCA 3MST in adults with cystic fibrosis (CF). Methods: Thirty-one subjects completed two attempts of the YMCA 3MST. Test–retest reliability for physiologic parameters and the MDC for peak heart rate (HR), peak HR as a percent of predicted maximum (peak %MaxHR), and HR recovery were calculated. Results: Five patients (17.8%) were unable to complete the first test. The mean (standard deviation) time to complete the test was 9.7 (2.5) minutes. For test–retest reliability, intraclass correlation coefficient (ICC) (95% confidence interval) values were: peak HR = 0.95 (0.87, 0.97), peak %MaxHR = 0.94 (0.88, 0.97), and HR recovery = 0.65 (0.80, 0.95). The minimum detectable change values were calculated and presented. Conclusions: The YMCA 3MST is feasible to administer. Lower extremity musculoskeletal pain and test pace may be a barrier for some patients. Peak HR, peak %MaxHR, and HR recovery could be used clinically to longitudinally detect changes.