Yes crossfit is very effective! The program I am taking at home has many elements from crossfit. Plank or push-up for example, really does not require equipment and so effective for strengthening the core! All professional ballet dancers do that. I will soon be traveling for a week. My daily training program (TLB from https://trainlikeaballerina.com/ ) can be accessed online. I can do the exercise in any hotel. Elevé, relevé, tendu, frappé, slow motion fondue, and many streching exercises are even doable in a fully stuffed long-haul plane. Let's train into a healthy and prosperous 2024!