Walking not good exercise

I would worry more about a "friend" who tells you that your efforts are not sufficient than whether or not walking is good exercise.

The goal of walking is to elevate your heart rate to a specific range for an extended period of time, to breathe deeply and clear your lungs, and to get a good release of endorphins.Your ability to do that is determined by a number of things including your age, weight, level of fitness, A few years ago w walk around the block would have done nothing for me. It would not have raised my heart rate, or required any effort from me. Today, due to some unfortunate health issues, I am lucky to get a quarter of a mile before I have to stop and catch my breath. What works for you may not work for your friend. That doesn't mean it is bad exercise. What works for you now may not work for you in a year... you can always adjust by picking up the pace, choosing to walk up a big hill, or using wrist/ankle weights.

Don't let your friend intimidate you away from what works for you. Enjoy your exercise, and when it stops doing the job, then you can make your changes.