During work my physical activity was fairly limited to my desk as I worked and munched away on my crisps and chocolates.
Recently my manager decided to axe our bins for one rubbish depository and I've found it has proved beneficial to walk to put my waste away as previously I had experienced tiredness in my calf muscles. I try to stand up more as well (just need to find a laptop that allows me to work whilst standing!)
I always try to go out for lunch to eat or just a walk round the block.
As I'm primarily office based it's probably expected to feel lethargic at the end of a day but not being active at work and too stationery hasn't helped matters.