I got the first Moderna jab a couple of weeks ago. Felt fine for the first few hours, then suddenly felt achy and sleepy. That lasted about four hours while I napped. I woke feeling fine, but was a bit tired the next few days. Arm was a bit sore at the injection site, but less sore than my injections for prednisone the last couple of times I had bronchitis. Prednisone injections sting like a wasp for about 15-20 minutes.
I took the day off when I got the vaccine. I walked a leisurely 3 miles the next day, and jogged 4 miles the second day, no problems. Back to my usual jogging and other activities a couple of days post-jab. I haven't done much cycling this year but that's due to neck pain from old injuries, nothing to do with the coronavirus or vaccine. I've done more jogging since last November and I haven't noticed any significant changes since two or three days post-vaccine.
I check my heart rate and HRV daily, and BP fairly often. No changes there either.
This was the first vaccine I've had any reaction to in years. Usually I feel no reaction to flu and pneumonia vaccines.