What are some strategies for improving pedal efficiency on electric mountain bikes, particularly in regards to optimizing the interaction between the riders pedaling input and the bikes electric assist system, and how can riders effectively utilize techniques such as cadence management, gear shifting, and body positioning to maximize efficiency and minimize energy expenditure, and what role do factors like tire pressure, suspension setup, and drivetrain maintenance play in achieving optimal pedal efficiency, and are there any specific training methods or exercises that can help riders develop the skills and physical conditioning needed to pedal efficiently on an e-MTB, and how can riders balance the need for efficiency with the demands of navigating challenging terrain and technical trails.