Did I just make a really big mistake?

In a moment of good-meaning I may possibly have registered for next year's BUPA 10K in London, to raise money for Alzheimer's UK...

This is questionable for a number of reasons:

1. I am asthmatic, and have never been very successful at running - especially on tarmac (it makes my knees hurt!).

2. Although usually quite a fit and healthy person I am currently incredibly unfit, as a result of undertaking office-based work. Because of said office work I have also put on quite a lot of weight, and am a wee bit chubby right now.

3. The run is in May which gives me 5 months to train, but most of those will be cold months, and cold air is the main trigger for my asthma.

4. I am not a very organised person, or dedicated when it comes to exercise. Training could prove problematic.

I signed up though because I knew if I hesitated these reasons would take over, and I wouldn't do it. But I need to get fit, and if there's anyone worth doing it for, it's my granny. If this was 10 years ago she'd be extremely proud - though would probably say I was a loony.

More than anything I want to raise awareness for Alzheimer's and other forms of dementia, which is a fact I strongly believe I will have to refer to when I have pulled muscles and cramps later down the line....