Kaz posts about being unfit - it must be our age, because I too have been worrying recently about my increasing weight and expanding waistline. Been getting more sedentary, at work and at home, and I have a sweet tooth (several, in fact, with a lot of fillings).
Attempts at getting back into jogging over the last couple of years have got nowhere, partly because of the weakness of the knee I broke, and partly because I was used to running several miles easily, and it's very hard to start from almost scratch again. Then there is a lack of motivation - since I gave up competitive orienteering in 1992 there hasn't been a strong motive for fitness, and as I have been unable to get DH interested, and have been trying to do it on my own, it's been hard. Jogging with other people is good, as you help each other with commitment and progress, but it's absolutely no good trying to join a club when you can't run at least 3 miles at 10 minute mile pace (and better at 8 minute pace) - you would be on your own again as all the others disappear into the distance, leaving you to feel really bad; or some kind soul sacrifices their own run to keep you company, and you feel really bad about that.
Cycling has never been a favourite activity - pointless riding up and down the railway paths, and the traffic is too dangerous on roads; and I can run out of energy quite suddenly and spectacularly cycling. Last time I got on my bike, my knee was too weak to turn the pedals. And then the saddle slipped.
Swimming? Public baths are a nasty mixture of liquids, most of which are not good to swallow, and I find sweating underwater an unpleasant experience. Then there's the lack of any view, and do you wear your glasses and risk them falling off in the water, or do without them, and be half-blind?
Dancing is excellent - vigorous activity and fun. Ceilidhs are great, and I would think that lots of other types of dancing would be good too, but again there's the problem of a partner, finding a group or class nearby, and is a couple of hours once a week enough?
So it comes back to walking - easy, cheap, no special kit, do it anywhere and any time. If you keep going at a speed to raise your breathing rate and make you sweat, it has to be good. No pounding on the joints, either. And if you have your binoculars or camera in your pocket and there's something interesting, you can stop for a moment and look. Getting out of doors is good for skin and hair, and for the mental health. No need for the iPod, either, there's always plenty of things to see, and you can hear the cattle lorry approaching along the lane. If you keep you eyes open, there's often a free snack available - yesterday I found a few sloes and loads of beech nuts. Probably ate as many calories as I used up, but when I got home, the lungs and muscles felt as if they'd been working.