I can speak of a 500% improvement in performance  - which surprised me, and pleased me enormously.
Today's workout is called "Stack": 5-15 minutes of "Afterburner 2 " sequence, followed (after a rest of 5 minutes) by 10 - 30 minutes of cardio flow.

Remember the "Afterburner"? Take a quick look on the video (week 1 Day 2) how I coped with my first introduction to this high-intensity workout. I was sagging and exhausted after the first three rounds. Well today I did 15 rounds in the allotted time and still could have done more. Suddenly this "killer" of a workout is easy peasy... I feel so strong - imagine what this is doing for my motivation!

The cardioflow I'd already got well to grips with (Week 3 Day 6, Under-The-Knee) so this whole session was a, for me, phenominal success. Funny thing with that "getting-fitter" process... you don't see it coming. Just that one day you realize that you can do some things a lot easier than before.
Today was also a fast-day. So I was doing my workout on an empty stomach. Can't say I noticed any negative effect of not eating, and the results speak to the contrary.
Broke the fast in the evening with pork and salad. This was nice and light, and the salad was refreshing -  but I have to admit, later in the evening I really could have eaten a sweet snack to go with my coffee... some cake, or biscuits, or chocolate. Had to be strong and resist the temptation (there was nothing in the house to snack on anyway!).