I’m 61 and very fit, but I still can’t walk up a flight of stairs without get­ting out of breath and my legs feel­ing weak. Why is this?

The answer to this puzz­ling ques­tion may lie in the dif­fer­ent ways there are of being “very fit”. If you’ve been play­ing golf, press­ing weights in the gym or swim­ming back­stroke lengths three times a week for the past 30 years, for instance, each of these activ­it­ies will have kept you fit, but in rather dif­fer­ent kinds of ways, none of which may be very help­ful when it comes to climb­ing stairs.

One of the basic prin­ciples of exer­cise is that if you choose to keep fit by doing a lot of one par­tic­u­lar thing (play­ing foot­ball, spin­ning, aer­obics, yoga, jog­ging or whatever else), your body will improve its fit­ness levels in very spe­cific ways: those that help you to do your chosen activ­ity or sport. So over the weeks and months you get rather good at what you’re doing, which is very sat­is­fy­ing and helps you feel fit.

But if you spend six months going to spin­ning or yoga classes and then take up a friend’s chal­lenge for a game of squash, don’t expect to win! The com­bin­a­tion of fit­ness and skills required is very dif­fer­ent from those you’ve been hard at work per­fect­ing, and although you will have a gen­eral level of fit­ness, it isn’t going to improve your squash per­form­ance overnight.

So to ensure you are main­tain­ing all-​round fit­ness, the best approach is to mix it up and keep on gradu­ally increas­ing the chal­lenge. If you jog for six months, try cyc­ling or a row­ing machine for the next six. If you’ve always been a swim­mer, dis­cover the joys of cir­cuit train­ing. If yoga’s your big thing, how about some low-​impact aer­obics along­side it?

Here’s another thought: it’s a rather embar­rass­ing fact that most of us believe we are much fit­ter than we really are. In one major fit­ness sur­vey mar­ket research­ers found a third of us to be “fit” but clas­si­fied nearly half of us as “Healthy in mind” or “Healthy in the­ory” – which sug­gests more think­ing than doing! And as for climb­ing the stairs, an even more fam­ous fit­ness sur­vey found that one in eight men and a half of all women over 55 don’t have enough leg strength to climb stairs without using the hand rail.

So what kind of exer­cise is best for climb­ing stairs? Stair-​climbing – which in its own right is an excel­lent every-​day exer­cise. Set a goal, for instance, of climb­ing the stairs 3 times in one go every day next week. The fol­low­ing week make it four times each day. Then five and so on. After six weeks, you’ll be able to climb them while singing the Sound of Music at the top of your voice with no trouble!