There’s a lot to be said for the role of flexibility when it comes to fitness. While it is one aspect of fitness and has seemingly nothing to do with the other aspects such as stamina, strength and size, which usually predominate in the focus of sports or regular gym goers, there are several very good reasons why flexibility can help all of these goals.
1) Range of Motion (ROM) = Efficiency. Increased flexibility enables the body to move through greater ranges of motion, which in turn, means more distance for each rep/step/pull/push, etc.
2) ROM = Less Resistance. With a greater ROM there is less resistance from the body’s own muscles and joint capsules. It’s literally like working against your own body’s resistance when a movement is tight and restricted. Not only do you have to move the weight of the bar/body/object but you also have to overcome the elastic restraint of the antagonist muscles and associated joint ligaments. Take a shoulder press for example. If you easily press your own arms effortlessly overhead to full extension then adding a small weight will make it only slightly more challenging, but if you struggle to lock out in full extension without any weight because of your own restrictions then even the smallest weight will make it extremely more difficult, ultimately limiting your strength output.
3) ROM = a stronger stretch reflex. When you stretch a muscle it turns on harder. In efforts to promote muscle growth it is very plausible to work a muscle through it’s full ROM so as to place it under stretch while it is also under tension. With increased flexibility you are able to achieve this in a more pronounced way and benefit from the muscle’s stretch reflex.
With more ROM and more efficiency you can literally work with less effort to produce the same result as the next person who is slightly more restricted. In the long run you will outlast them, which may look like a superior stamina or strength but could simply be because you don’t have to work as hard due to better ROM.
Start stretching!