Standing Train Commute
"There is nothing better than riding the train with everyone else in the morning" - no one ever. That being said, riding the train and doing it in standing helps with any number of things including blood pressure regulation, balance and endurance.
A simple exercise but something that can be pretty challenging: Ride the train and do it while standing. To make it harder, try to only hold on with one hand or no hands at all. Just make sure you have space so you aren't running into anyone else while you work on your train riding abilities!