How much physical activity is too much during a long fast?

Hey yall just a question since I’m new to fasting. I’m a blue collar worker (scaffolding) and an athlete. I work and train every day. I usually start work at 6:30 AM and end at 3:30. And then go home and get ready to train some Muay Thai for about 2 hours (45 minutes drilling and a hour and a half sparring) I’m currently trying to fast for 5 days but I gotta tell yall I am FEELING it 49 hours in. Not in a horrible way no dizzyness or anything like that. I just feel very weak and starving.

My question is if I am going to attempt a 5 day fast should I train or even work my heavy duty job during this time?