Exercise amount appears to be more important than exercise intensity for eliciting gains in cardiovascular fitness.

People only need to walk up to 12 miles per week or for about 125 to 200 minutes per week to improve their heart health. Our data suggest that if you walk briskly for 12 miles per week you will significantly increase your cardiovascular fitness levels compared to baseline. If you increase either your mileage or intensity, by going up an incline or jogging, you will achieve even greater gains.

The classic question always is: What's the minimum amount I need to do to enjoy the benefits of it. If you just walk 12 miles a week at a brisk pace, it's scientifically proven now that you will get some benefits.

The other thing to realize is that people gain 3 to 4 pounds a year, so exercise is really important for weight maintenance.

Anything beyond walking briskly for 12 miles per week, whether increasing your intensity or the amount of miles, has additional benefits. So there is a separate and combined effect.

The participants in our study received the fitness benefits without losing any weight. Many people exercise to lose weight, and when that doesn't occur, they stop exercising. However, the truth is that you can improve cardiovascular fitness and reduce the risk of heart disease by exercising without losing weight.