Purpose: To provide insights into a dose–response relationship between training and time-trial performance, as assessed in both a “fresh” and a “fatigued” state (durability), including proposed underlying factors for durability: gross efficiency and substrate oxidation (FatOx and CarbOx). Methods: Ten male semiprofessional cyclists underwent a performance test in both “fresh” and “fatigued” state (after 38.6 [4.6] kJ·kg−1) before and after an 8-week training period, containing the measurement of gross efficiency, FatOx, and CarbOx at submaximal intensity and maximal time trials of 1 (PO1) and 10 minutes (PO10). Relationships were assessed with the session rating of perceived exertion, kilojoules spent, Lucia training impulse, Training Stress Score, polarization index, and time spent in 3 zones in the intervening period. Results: No significant relationship was found between higher training load and performance on PO1 and PO10, with a large variation between assessed training-load measures and individual participants. However, CarbOx showed a strong correlation with training volume in the “fresh” state and with time spent below first-lactate-threshold intensity in the “fatigued” state. Also, the relationship between training load and change in performance between tests showed different trends for “fresh” compared with “fatigued” state, especially for FatOx and CarbOx. Conclusions: The fact that no clear relationships between dose (training) and response (time-trial performance) were shown in this study indicates that a single load measure is not able to predict performance improvements after an 8-week training period. However, the current study shows that the same training can have a different effect on “fresh” versus “fatigued” performance, having implications for the design of training plans.