What are the most effective ways to structure an e-bike ride to maximize cardiovascular benefits, considering factors such as intensity, duration, and frequency, while also taking into account the assistive nature of e-bikes and the potential for over-reliance on motorized power? How can riders balance the benefits of e-bike riding with the need to challenge themselves physically and avoid complacency, and what role can heart rate monitoring and other performance tracking tools play in optimizing cardiovascular gains?