Unlike running, where the mid-foot lands first, walkers start by planting the heel then gently rolling onto the toe. If you are looking to add some variety or intensity to your walks, there a few tricks of the trade that will improve your fitness level. First, walk faster. A quicker-paced walk calls for faster not longer strides. As your speed increases, so do the number of steps per mile.
Hills are also an easy way to add intensity.
Modifying your route to include a few climbs will encourage your heart and muscles to work harder. If hill workouts don't interest you, add a couple of speed intervals to your walk. Pick up the pace to a higher intensity for one minute, then reduce your speed back down to a more comfortable level. Start by adding a couple of speed intervals to the middle of your walk. Challenging yourself during your workout is both physically and mentally stimulating and will provide additional fitness benefits.