Your first judo class involves none of that whatsoever. Instead, you spend the overwhelming majority of your time falling down. You fall on your back and your side. You roll into a fall. You get reprimanded for sticking your arm out or not keeping your chin tucked. You are learning ukemi, the art of breakfalling. It is the foundational skillset that has allowed me, as a 41-year-old, to show up to the dojo multiple times a week and get thrown onto my back with full force by friends and strangers, and head home after to toss my kids around, carry the groceries, and do plenty of other things I'd struggle to do if I'd hurt myself.