KR - I was so tempted to type something ridiculous. However, the answer is 'running'. Since increasing my mileage I'm not as flexible as I was even a year ago so I've started stretching after my runs, which I find utterly tedious!
I've realised I haven't answered your question from a couple of days ago, why sub3:10? There are 2 reasons really. The first is that I want to get GFA for London, as I'd quite like to have the experience of running it and secondly, because I think 3:15 or very near could have been possible at Loch Ness, if I'd got more miles and structured training in, so after 18 solid weeks of P&D I want to see considerable improvement.