There are lots of different types of exercise. Cardio, weight lifting, stretching/yoga, tai chi/chi kung.. I wonder if different people respond differently to different types of exercise? Did you try them all?

I can relate to that. When I exercise in the morning I cannot get anything done during the day.

On the other hand I find it relaxing to workout after work. My mind becomes more or less empty afterwards. When I then do things that require more complex thinking the effect wears off pretty quickly though.

Lifting after work gives me something to look forward to.

It also wears me the fuck out - so I go to bed early, sleep really well, and wake up the next day feeling recharged.

My initial days of running had a dramatic positive effect on my productivity. However once my body got used to running I see no difference. I must admit I have stuck to the same pace and distance more or less. 5k in about 35 mins.

I wonder if some of it has to do with perception. When you begin a new habit, or change up your routine, time seems to go a bit slower than usual, and thus maybe you feel that you are more productive?

Quite possible.

I'm the same. Exercise just makes me more tired.