What are the most effective plyometric exercises for cyclists looking to improve their explosive power, and how can they be safely incorporated into a training regimen without exacerbating existing injuries or muscle imbalances? Are there any specific considerations for cyclists who are new to plyometric training, such as starting with lower-intensity exercises or gradually increasing the volume and frequency of plyometric workouts? How can cyclists measure the effectiveness of plyometric training in improving their explosive power, and what are the key performance indicators to focus on when assessing the impact of plyometric training on cycling performance?