Yoga Journal: Yoga For Core Strength

Tone your belly and feel better every day. Activate your abdominal muscles and strengthen your core with sequences designed to improve stability and flexibility. Four sequences by yoga teacher Coral Brown will tone your arms, back, and abdominal muscles, helping you flow through powerful yoga practices with precision and ease.
You can use these practices to:

Tone your Abs: Learn fresh, creative exercises to strengthen and firm the muscles in your core, and to add power to your poses.
Build Stability: Improve your balance in standing poses and arm balances, and get the most out of your yoga practice.
Increase Flexibility: Activate your abs for effortless twists and backbends.