Although our results did point toward amount being more important, it is very likely fitness levels can be improved by increasing either amount or intensity.
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.
People need to know: even without losing weight, you are getting significant benefits by exercising -- you're improving your fitness level, decreasing fat and increasing muscle and improving your lipid panel -- so don't stop exercising.
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.
Exercise amount appears to be more important than exercise intensity for eliciting gains in cardiovascular fitness.
The other thing to realize is that people gain 3 to 4 pounds a year, so exercise is really important for weight maintenance.
People find exercise 'hard' and few people want to exercise at an intensity higher than they have to. Walking briskly for 12 miles a week per week is realistic and does not require anyone to incorporate a hardcore training regimen. Increasing your mileage or intensity will give you even greater health benefits.
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.
A second very important message is that subjects enjoyed fitness benefits in the absence of weight loss. Many people exercise with the purpose of losing weight. When they do not lose weight, they do not think the exercise is benefiting them and they stop exercising.