Based on Cardio Training

Frequency
Exercise a minimum of 3 times per week. Little additional training benefits occur when the frequency is greater than 5 times per week when compared to the amount of effort involved.

Intensity
You must maintain your heart rate in the Target Heart Rate Zone for the required time to gain benefits. Your Target Heart Rate Zone is determined by your fitness level and your age. Low fitness individuals will attain results training at 50% to 70% of their maximum heart rate as their Target Heart Rate Zone. Higher fitness individuals will train at 70% to 85% of their maximum heart rate as their Target Heart Rate Zone.

Time
It is necessary to maintain your proper intensity (target heart rate zone) for a duration that will create a training benefit. Low Fitness individuals should maintain their heart rates in their target zone for a minimum of 12 to 15 minutes. This does not include warm-up or cool down periods. As your fitness level increases the exercise time in your target heart rate zone can be extended to 20 - 60 minutes of continuous aerobic activity. Unless you are a competitive athlete, training beyond 60 minutes in your target heart rate zone provides little additional training benefits for the amount of effort exerted. If you are overweight however, long training sessions at a low intensity (50% to 60% of maximum heart rate) utilize fat as an energy source and are helpful in a weight/fat reduction program.

Type
Choose an exercise that will involve as much muscle mass as possible. In other words, exercises that use the whole body or the larger muscle groups such as the legs and/or the back.