My doctor recommends 160 minutes of aerobic excercise per week. Similar numbers appear in the litterature:
Going the Distance: Right Amount of Exercise
Twenty minutes of aerobic exercise, three or four times a week, at moderate
exertion will get you significant benefits [source: MedicineNet].
Moderate exertion is when your pulse and breathing rate increase, but you can
still talk comfortably -- you're not out of breath. Jogging and jumping rope are
good examples. On the higher end, the Center for Disease Control (CDC)
recommends 30 minutes a day with only a couple of days off each week, or about
150 minutes per week.And how much is too much? Pain is a good indicator to stop...
Source: 90-minutes-of-exercise1