How do I know if I have a weak muscle?

How do I know if I have a weak muscle?

The first and major indication is that something may not feel right. This can be seen as joint pain, muscle tension or instability of a joint, or in other words tight hamstrings, tight lower back, shin splints, aching knees, or a hyper-extended joint. Any feelings of pain or tightness can be signs of possible muscle weakness.