An individuals joint flexibility is determined by numerous factors, including the following:
1) Activity level: People who are active tend to be more flexible than sedentary individuals.
2) Training in a limited range of motion, especially resistance training (weight training) in a limited range of motion can reduce flexibility over time, thus it is important to work muscles in a full range of motion.
3) Bulk: An increase in muscle bulk or percent fat can limit joint range of motion and limit flexibility. The additional tissue mass acts as an obstruction to joint motion limiting bone segment movement.
4) Muscular imbalance: Muscle strength and length imbalances reduce flexibility.
5) Age: flexibility decreases with age. Older adults lose muscle fibers.
6) Gender: women tend to be more flexible than men in certain areas, especially in the hips.