A: If muscle tone is a major goal right now, you're on the right track with yoga. Of particular benefit are the poses that involve balance and extension. Achieving proper form in these positions takes a great deal of body awareness and muscle control, and holding these positions takes power. While specific poses, or asanas, should be integrated together into a cohesive yoga session, some of the poses that may best address your specific goals include:
Warrior I, II, or III
Downward facing Dog
In terms of other non-gym exercises that lead to muscle tone, consider some form of rock climbing or bouldering.
Other activities you may want to consider include squash and racquetball. These high-speed racket sports involve a great deal of powerful side-to-side, front-to-back running (typically its more lunging than running though) and theres a lot of twisting through the torso and use of the upper body for swinging the racket and maintaining balance. The best part about squash and racquetball is that the court is enclosed; you dont have to spend a lot of time retrieving poorly hit balls because they generally come back to within a few steps of you.