With some back conditions, specific positions are known to help manage symptoms. These positions are known as biases. There are three types of biases: extension, flexion and non-weight bearing.
If your back feels better and your symptoms abate when you arch your back, your injury or condition has an extension bias.
Extension bias is the term indicating that the preferred position for your spine is one that increases the lordosis in your low back and neck. In order to increase your lumbar and cervical lordoses, you need to extend your spine.
Herniated disc and injury to the posterior longitudinal ligament in the spine are two conditions with extension biases.
For injuries and conditions with an extension bias, symptoms tend to increase when your back is flexed (bent).