6. The Stretch Reflex - Stretching can sometimes actually make you feel tighter than before, due to a protective reflex known as the Stretch Reflex.
7. Chronic Contraction - if a muscle is held contracted, for whatever reason, for an extended period of time if will become much harder to let go of. Instead of focusing on stretching that muscle, focus must be made on the true origin of the contraction.
8. Genetics - While we cannot choose our genetics, we can chose how we work with what we have. Try not to blame your Mum and Dad for your tight hamstrings, even if they have them to!
9. Lifestyle factors - Lifestyle factors, especially including the amount and type of physical training that someone is doing, will dramatically change not only their body shape, weight and physical make up, but will also help develop the motor patterns that will actually shape who they becomes physically as an adult.
10. Emotional and Psychological Factors - Emotions and psychological states have a massive effect on our posture and how much tension we hold in certain areas of our body. Resolving deeper issues that are influencing these states can have a profound impact on the tension in the body and therefore our flexibility.