Then , add a few minutes on to your exercise session each week for four weeks .
If possible , start with an exercise session of 15 to 20 minutes , but if this is too long , start where your fitness level allows .
Add a few minutes on to your exercise session each week for four weeks .
If possible , start with an exercise session of 15 to 20 minutes , but if this is too long , start where your fitness level allows .