Walking is an awesome workout and does all of the things running does, it just takes longer. Walking is a complete workout and something your body can tolerate as you get older. It is also nice because you will find you can be more mindful while walking due to the fact that you are not thinking about your body as much. There are ways to up the calorie burn through speed, incline, time or varied terrain. As you age, strength training should be a priority along with walking so all of the stabilizing muscles can help the major muscles do their work. With walking you spend more time moving through your entire foot so stretching of the calf muscles, hips and hamstrings are good to stay on top of. Take your water, listen to a podcast or audio book and know that along with getting fresh air and vitamin D you are doing something great for your body and mind!