Muscle Length Tests
If muscles do not have sufficient length to allow optimal ROM, they will often pull the body into mis-alignment and hold it there. This will stress the supportive soft tissues, increase inter-joint pressure and lead to discomfort or pain. Good flexibility will help prevent pain.
Many of the Muscle Length Tests (MLTs) are actually synonymous with ROM tests. As in most ROM tests soft tissue structures, in particular shortened muscles, affect the ability to freely move a body part through its natural range of motion.
Muscles Spanning Multiple Joints
In ROM tests it is sometimes difficult to isolate actions around single joints and quite a few MLTs and/or ROM tests involve movement in multiple joints. It takes lots of practice to develop sufficient skill to isolate single structures.
In flexion of the spine for example there are a lot of joints involved and sometimes it is difficult to isolate where the movement occurs. Although the overall result of a movement might be satisfactory (e.g. the client can touch their toes with their fingers), the movement may not always occur where it is supposed to and restriction in some structures will often be compensated by excessive movement in other areas.
Here are a couple of examples.
When testing the length of multiple joint muscles ensure the muscle is challenged at both joints (e.g. stretch the hamstrings by conducting both hip flexion and knee extension simultaneously).
Or, as in the case of spinal flexion, excessive hip movement might be compensating for lack of flexion of the spine or some segments of the spinal column might allow more flexion than they should.