This is what’s weird to me. I’m on keto and have been for many months and my workouts are better than ever and I walk 10-15 miles a day. I don’t understand it and I don’t take any stimulants at all and I don’t drink coffee.
A lot depends on your rep range. When you are on keto your muscles don't store anywhere near as much glycogen- that is why you drop 10+ pounds the first week on keto because as the glycogen goes, so does stored water. When glycogen is low you don't have the sugars available for recharging the muscles very fast.
That being said, if your rep range is ~10 or less it is predominately creatine phosphate that is driving the exercise, not glycogen. So you really wouldn't see much of a drop in energy on keto unless you are doing sets with very little rest between. If you did higher reps you would because that is driven glycolytically.
As for walking- the intensity is so low that it is primarily driven by fat oxidation. Again - you wouldn't see much of a difference. As soon as you start running you will find you are limited.
I did a bicycle race series while in keto and had no problem hanging in when the pack was riding steady. As soon as they accelerated I was dying and could no longer keep up. This series was a week long and on the third day I said "screw keto" and went out and bought every sugary thing I could find. Within 2 days I was finishing in the top 10 and actually was contending for victory several times.