As we grow into our bodies over time in life we realize that it is advantageous to keep our bodies flexible no matter what we do. Whether we are athletes, the regular working person, a world traveler, or just trying to live the best we can -- we owe it to ourselves to maintain a flexible body.
As the ancient Chinese Sage Lao Tzu said in the Tao Te Ching which translates roughly as the 'Ancient Way of Virtue' --
"The stiff and unbending is the disciple of death.
The gentle and yielding is the disciple of life.
Thus an army without flexibility never wins a battle.
A tree that is unbending is easily broken. "
It is key in any physical activity to be flexible. No matter what we want to call our 'science of stretching' -- figuring out how to stretch is a great thing -- and can lead to much freer range of movement and a more vital and energetic physical body.
I am an athlete and I study and practice Yoga. My Yoga is a bit different at times. It is an evolving process and at different times different things. I've read books here and there and have seen videos and have somehow evolved my own style of Yoga that keeps me flexible and content. Concerning 'Yoga' -- which is a word that means many different things to many different people -- I know enough to feel I have a decent grasp on it, but of course there will always be more to learn. I might not know an incredible amount about Yoga but I do understand that you don't have to be into the philosophical side of Yoga to benefit from it.
Although Yoga stems from certain spiritual traditions that emphasize a philosophy of purity which includes 'keeping one's temple clean' or a 'cleanliness is Godliness' belief, it can also be practiced regardless of religious or philosophical orientation or lack thereof.
Alone, without spiritual or philosophical connotations, Yoga serves to be a system of postures and exercises combined with deep breathing techniques that can greatly enhance the human experience by giving one mobility, flexibility, healthy bones and spine, release from tension or knots, and a greatly uplifted and tranquil spirit which often accompanies lack of pain and discomfort.
It is a systematic healing tool for our vehicle, being the body, that us humans have been given to live our lives. A type of user's manual created after hundreds or even thousands of years of observation of the human body and what makes it healthiest and most comfortable -- most agile, strong, and quick.
I have looked into multiple spiritual philosophies including some of the ones of Yoga -- which are mainly Hinduism, Buddhism, and Taoism. Hinduism is the religion that most people associate with Yoga, partly for the reason that Yoga became so widespread within the Hindu Religion and also because the practice of Yoga in India dates back to ancient times. Although the Indian styles of Yoga (Primarily Hatha, Ashtanga, Kundalini, and Iyengar) are some of the most popular, there are also Taoist and Buddhist styles and adaptations to the ancient art. The systems of Tai Chi and Qigong involve a large amount of Yogic technique and practice. Although being mostly Taoist in nature, there are also Buddhist systems of these moving and still meditational arts.
There are many styles and types of stretching techniques or Yoga techniques. I strongly believe that the best thing for anyone to do is find the ones that they are most drawn to. Find what works best for them and stick to a basic system of stretching that keeps their joints flexible and their spine supple. For many that system is Yoga. For many it is merely stretching.
I have found that some of the most basic and traditional forms of Yoga can be the best introduction and I personally recommend Hatha (Sun/Moon) Yoga. The reason I like it so much and feel it is good for everyone, regardless of age or ability, is that it is a fairly simple series of static postures which allow one to release tension in all the major muscle groups and spine, which is easy to practice anytime or anywhere.
The Sun Salutation is a perfect example of this. With regular practice of this basic series of stretches, one could become quite limber and stay flexible for life. It only takes a few minutes and is a perfect way to start or end the day -- or even just to refresh the 'spring' in our step.
If you get adventurous and decide to try more than the Sun Salutation, you could continue on to learn some more advanced Asana (posture) sequences as well as breathing techniques to allow the muscles and mind to relax. Some great books to read are The Sivananda Companion to Yoga: A Complete Guide to the Physical Postures, Breathing Exercises, Diet, Relaxation, and Meditation Techniques of Yoga or Light on Yoga: Yoga Dipika by BKS Iyengar. Also, 'The Power of Breath' by Swami Saradananda is an amazing discovery of the powerful effects of breathing exercises.
I highly recommend buying a DVD and practicing at home while one is alone. It is a great way to relax and worth more than any amount of time you could put into it. Many become hooked after they start to feel how great it feels to release tension and stress. Two of my favorite, most straightforward teachers are Rodnee Yee and Patricia Walden. Their beginning as well as advanced material is top notch and easy to follow. The music is calming and the scenery very nice. Rodney mostly does his filming on the beach in Maui so it a relaxing way to learn -- watching the tropical background while relaxing and clearing one's mind.
I am not a physician so I am not officially recommending anything here. just giving some advice on what has worked for me. If it benefits you that is wonderful. Keep searching and stay healthy. Namaste, and Aloha.