I just finished a 6.031km running that lasted about 0hh:28mm:43ss !
I find that when you don't have so much time for a proper workout, running on stairs are the best alternative in order to improvise a good cardio & strength exercise.
That's why, today, without any plan and not so much time available before the lunch, I said to my wife I would spend just 30', I went to a place where is easy to find steep stairs around.
Actually, there is one set of stairs followed by a flat surface of 400m in length that connects another higher set of stairs that, in total made a 700m long and around 90m high.
I tried this path for the first time and I think it could be a really good "workbench" for doing tough intervals of the same in the future but I have to think about the number of repetitions and the coming-back path to the start of the first set.
Keep on running!
Check out some detailed info at my EXHAUST page
Join me in testing out EXHAUST!
@toofasteddie