An 8-minute Self-Paced Cycling Test designed for endurance fitness monitoring: Cross-sectional validity, test-retest reliability, and practical implementation.

Monitoring cycling fitness remains challenging. Most submaximal tests rely on physiological responses to imposed workloads and overlook perceptual responses. This study evaluated the cross-sectional convergent validity and test-retest reliability of the Self-Paced Cycling Test (SCT-RPE), an 8-minute rating of perceived effort (RPE)-regulated protocol. Twenty-one cyclists completed the SCT-RPE, comprising three 2-minute stages at RPE Moderate, Strong, and Very strong, followed by recovery and a 6-second sprint (Ppeak). Power output-to-heart rate ratios (PO/HR) and weighted indices (wPO/HR) were calculated at stage and overall levels. Validity was evaluated against graded exercise test outcomes and sprint performance, and reliability across repeated trials. wPO/HRoverall was retained as a candidate endurance-fitness index because it showed a strong association with peak work rate (Wpeak, R2 = 0.77, p < 0.001, slope = 13.4 W per unit), acceptable reliability, and power-dominant weighting aligned with the RPE-regulated design. Endurance-related variables showed moderate-to-very-high interday reliability (intraclass correlation coefficients, ICC3,1 = 0.72-0.94; coefficients of variation of the typical error, CVTE = 3.29%-7.97%). Ppeak showed high reliability (ICC3,1 = 0.86; CVTE = 8.96%) and an almost perfect correlation with sprint performance (r = 0.93). The SCT-RPE showed cross-sectional convergent validity and acceptable reliability; longitudinal responsiveness remains to be established.