Why interval training is the way to go for walkers

It’s cheap, good for your health and easy to do, but just how fit do you get from your weekly walks around the neighbourhood?
Generally, improving your fitness level requires a workout intense enough to make your heart and lungs work harder. So if your walk is more of a stroll, chances are your cardiovascular system isn’t being challenged enough to become stronger and more efficient.
This doesn’t mean your walk is for naught. Walkers tend to go for distance rather than speed, w