The Biering-Sørensen Test is a test of trunk-muscle endurance. It measures how many seconds the subject is able to hold the upper body in a horizontal position without support. The subject is usually strapped into a special chair or to a table with support from the pelvis down.

The person starts in a head-down position. The arms are crossed over the chest. The subject flexes at the waist to raise the trunk to a horizontal position. This position is held as long as possible. The test is stopped by fatigue or pain.

The advantages of this test are how easy it is to perform without expensive equipment or computers.