Your author, Dr. Jon Schiller, decided to write this book about walking defects and how to walk normally again after noticing that his daily 3 mile fast walk was not so fast anymore.
The 3 mile walk, which normally took ¾ hour, began to take 1+1/2 hour. In other words he was walking 2 miles/hour instead of 4 miles /hour.
He was normally a faster walker than his wife. She became a faster walker after he noted the walking defect.
After following the concepts in this book the author and his wife were able to walk 4 miles daily in 1 hour and 30 minutes