How many sets of crunches should I do to achieve optimal results in my abdominal training regimen? Is there a specific number that experts recommend, or does it vary based on individual fitness levels and goals? Moreover, what factors should I consider when determining the appropriate number of sets for my routine? For instance, should I focus on the quality of each crunch over quantity, or is there a threshold that must be met in terms of volume to induce noticeable muscle hypertrophy? Additionally, how do variations in intensity, frequency, and rest periods between sets come into play when crafting my workout plan? Furthermore, are there other complementary exercises that should be integrated to enhance core strength? With such a plethora of considerations at hand, how can I ascertain a balanced approach that is both effective and sustainable? Are there any common pitfalls to avoid while structuring my crunch set regimen?