Try it two or even three times for a great core workout!
10 normal crunches
10 single leg crunches (right leg in air)
10 single leg crunches (left leg in air)
10 no leg crunches (both legs in air)
10 right side oblique crunches (twist both legs to the right, keep upper body straight)
10 left side oblique crunches
Challenge: 2 times per day for 30 days