So the struggle is real people. Day 3 of trying to do 21DF and I ended up grabbing Tracie Long instead. While I think 21DF is solid and challenging, I'm not able to get into the 1 minute rounds. Not sure why.
I haven't had to do much subbing in with other exercises and following the modifier is fine.
It must be a preference thing. I think these sets offer quite a bit and was hoping to do a full 4 weeks of the 2 sets. Hmmm.... maybe I'll try again tomorrow.