Effectiveness of just showing up works wonderfully for fitness as well. How much ever unfit one is, just showing up for a long period of time changes oneself. All one has to do drag oneself to the class, day in and day out, and then universe takes over..
I've been doing strength training once a week since the pandemic startet, and it has been great. Obviously I could have made much more progress with more frequent training, but I still look much better naked and more importantly, I feel much better. So many random aches and pains have just disappeared.