We can’t tell you exactly how many pounds to lift or how steep a hill you should climb to reach a moderate or vigorous level of exercise. What is easy for one person often strenuous for another.
We can, however, give you some advice that is based on scientific research: Listen to your body. The level of effort you feel you are putting into an activity is likely to agree with what actual physical measurements would show. In other words, if your body tells you that the exercise you are doing is moderate, measurements of things like how hard your heart is working would probably show that you are working moderately.
One way you can estimate how hard to work is by using the Borg scale. You can use the numbers on the left of the scale to describe how hard you feel you are working. For endurance activities, you need to gradually work your way up to level 13 - the feeling that you are working at a somewhat hard level. Some people might feel that they are at level 13 when they are walking on flat ground; others might feel that way when they are jogging up a hill. Both are right for themselves. Only you know how hard your exercise feels to you.
Strength exercises are higher on the Borg scale. Gradually work your way up to level 15 to 17 - hard to very hard - to build muscle effectively. You can tell how hard an effort you make by comparing it to your maximum effort. How hard does your current effort feel compared to when you are lifting the heaviest weight you can lift? Once you start exerting more than a moderate amount of effort in you muscle-building exercises, your strength is likely to increase quickly.
As your body adapts and you become more fit, you can gradually make your activities more challenging. You might find, for example, that walking on a flat surface used to make you feel like you were working at level 13 on the Borg scale, but that now you have to walk up a mild hill to feel like you are working at level 13. Later, you might find that you need to walk up an even steeper slope.
The Borg scale is simple to use. But if you feel that your level of effort doesn’t match the numbers you see on the scale -- for example, if you feel you are doing exercises correctly, but you aren’t progressing or you feel exhausted by your effort -- review your exercise plan with your health care provider.
The Borg Rating Scale
7 very, very light
9 very light
11 fairly light
13 some what hard
17 very hard
19 very, very hard