Six days to go until London Marathon day, and it's too late for any extra training to make a difference. Healthy eating, no alcohol and plenty of stretching is what the experts suggest.

I started doing some training last May, but it wasn't until October that I was finally able to get my running shoes on.

Whizz-Kidz, one of the charities I am running for, put me in touch with its coach, Nick Berners-Price. His advice was clear: the best way to prepare and avoid injury was to start with strength training, to re-energise stiff and inactive muscles. So for five months I did step and flexibar three times a week – bobbing up and down and wibbling away in the front room as I watched the news and cooking programmes on TV.

My plan only allowed me to start running the week after the Labour party conference – helpfully spurred on by the lingering memory of those rather "middle-aged" pictures of me playing football. Starting with four miles on a Saturday around Pontefract racetrack, I built up to double figures in early January, made it to a half marathon at half term, and finally hit 20 miles last weekend before my taper to race day began.

My reflections so far? Getting a pair of proper, computer-modelled insoles was transformational for me, stopping at once a building problem in my left ankle. And odd as it seems before you do it, a couple of sports massages work wonders to stop your legs stiffening after 13 miles.

But don't expect to lose weight. Muscle is heavier than fat – although a little bit of redistribution is no bad thing.

You can back Ed Balls' run for Whizz-Kidz and Action for Stammering Children at: justgiving.com/teams/edballs