For those who want their left brain to get a workout along with their bodies, Tamilee Webb's <I>Science of Fitness</I> series, including <I>I Want That Body!</I>, is are just what the personal trainer and professor ordered. Webb, an appealing and inspiring fitness instructor, includes scientific demonstrations conducted in a lab, showing how her exercises target each muscle group. This disc contains workouts for abs, arms, and buns, and each of those areas is divided into two 15-minute segments. If you're just starting out, do just one segment each; if you really want to up your results, go for both. Webb is encouraging without being off-puttingly perky, and she has the presence of mind, while doing very challenging moves, to calmly remind us of the science behind working each particular muscle. A small complaint: For the arms routine, all she says is to use some free weights; we don't know what size she's using, and there aren't different sizes for the different types of exercises, which can be a good modifier. But if you build in the option of lighter or heavier weights yourself, you should be able to proceed nicely. Extras include a quiz about common exercise forms, nutritional tips and different-angle shots of the routines. If you <I>Want That Body</I>, you better be prepared to work it, but Webb is an accessible leader and trainer and manages to inspire without being a cheerleader. <I>--A.T. Hurley</I>