What is the optimal balance between strength training and active recovery during the off-season for cyclists, and how can riders determine the ideal amount of strength training to complement their cardiovascular fitness without compromising their ability to maintain or build endurance? Should cyclists prioritize compound exercises that work multiple muscle groups, or focus on isolation exercises that target specific muscles used in cycling, such as the legs and core? How can riders incorporate strength training into their off-season routine without increasing the risk of overtraining or burnout, and what metrics or benchmarks can be used to measure the effectiveness of strength training in improving cycling performance?