I am a 9 minute miler, always wondering why my training didnt produce the result I thought I was capable of. After buying a heart monitor, I just couldnt figure out why my heart was going fast, and why I wasnt able to keep going at a high rate. This book told me exactly what I was doing wrong, and offered lots of advice and instruction on how to USE a heart monitor as opposed to WEARING one. It is brilliant!!!.. Since reading this book, I am now training properly, feeling less tired, doing MORE miles, and loving my running. It was hard at first, following the advice of the book, and often I had to walk to keep my heart down. But now I have cracked it, and I feel great. My advice BUY THE BOOK!!!