The training mode of the bike trainer is following the target power, which is calculated by the percentage of FTP. As the target power equals cadence multiples resistance, the decrease of cadence will cause the increase of resistance to maintain a constant power output, vice versa.
During the training courses, the resistance of the bike trainer will keep increasing if the user continues to decrease the cadence when it is close to or exceeds the FTP value, finally resulting a large resistance.
Suggestion: To solve this problem, user can increase the cadence in advance or choose a less difficult training course to start.