A key foundation of martial arts (and in fact many sports) is flexibility. Without flexibility, it takes more energy to perform as you must overcome not only gravity but the tension in tendons and ligaments. A martial artist needs to be flexible and have strength at all ranges of motion to become more effective. Thomas Kurz has done his homework (and shown his work) on flexibility and how to achieve it.
Kurz has a reputation in the martial arts community as being the foremost expert on the subject of flexibility. Stretching Scientifically describes in good detail the recommended methods of stretching (yes, there
are more than one method, and some can be harmful). It then gives recipes for a workout and examples for several different sports, including not only
martial arts but weightlifting, gymnastics, swimming and more. The speed at which your results will be realized depends on how aggressively you pursue Kurzís recommendations.
At this point you can stop reading, but Kurz taunts you into going further into the whys of flexibility, stating that low intelligence and low physical flexibility often go hand-in-hand (Iíd like to see the research on this). The book makes sense throughout. Iíve tried some of his methods and have seen some good results, as long as I kept up with the routines. Had I attacked it more aggressively (if only I had time for it!), Iím sure Iíd be doing the splits between two folding chairs as Kurz does on the cover.
Many of Kurzís readers send in photos of themselves doing just this as proof of concept. As with anything physical, what you get out of it depends on what you put into it. The few problems I find with the book are the way Kurz cites his sources as he uses their information. Not that this is a bad thing, but it does get a bit distracting. Maybe for the 5th edition, he could use symbols with a key or footnotes.