You've heard (over and over) how important it is to walk every day. But if you're getting older and contending with increasing weakness and tiredness and moving more slowly than before, the recommended target of 7,000 to 10,000 steps may be too much for you (at least to start).

Two new studies have great information on the amount of time spent walking and the pace you want to aim for in order to slow down your aging clock and speed up your chances of living longer and healthier.

The first study, published in the American Journal of Preventive Medicine, found that walking quickly (or climbing stairs or doing aerobics) for as little as 15 minutes a day (day after day, year after year) can cut your risk of death from all causes by 20%.

People who walked slowly for three or more hours a day only saw a 4% reduction in their risk of death.

But what is walking quickly?

The second study, in PLOSOne, says that over a three-month period, if pre-frail and frail seniors pick up their pace by 14 steps a minute (aiming for 100 steps a minute) they gain measurable improvement in strength, endurance, and stability.

And that increases their happiness quotient too.

For help walking more — and more quickly — check out smartphone apps that work to give you a pace for your steps.