The purpose of the zipper test is to measure the flexibility of the back and hamstrings, also known as the trunk lift test. This test involves lying face down on the ground and raising the upper body as high as possible while keeping the legs flat on the ground. Then measure the distance between your hands and feet. The test is often used to assess firefighters' dexterity because it simulates the movements needed to lift a heavy object off the ground.

The zipper test is useful for assessing flexibility in the back and hamstrings, which is important for preventing injury and maintaining mobility. It is also a useful test for people who perform manual labor or engage in activities that require lifting or stooping, such as firefighters, construction workers, and athletes.

By measuring the flexibility of the back and hamstrings, the zipper test can identify areas of the body that may be at risk of injury, or that may need additional stretching or strengthening exercises. It could also be used to track changes in flexibility over time, which could help individuals and healthcare professionals monitor progress and adjust exercise programs as needed.