Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Short on substance

The author's background is a gym rat, and it shows. The most important things in surfing are endurance and flexibility. This book spends most of the time (50 pages)talking about strength training. Surf two or three times a week and you'll have all the arm strength you need.Out of over 140 pages, endurance training only covers 5 pages. The flexibility and nutrition chapters are also weak. I sent the book back.My advice for those wanting to get fit for surfing - find a good book on stretching (Bob Anderson) and stretch everyday. Surf as much as you can, or go for a swim, run or bike ride when the waves are flat.