Stretching requires temporary lengthening of your muscle fibers. It is best to partake in flexibility training after a light warmup; this allows increased blood flow to the muscles which in turn increases mobility. Take a minute to imagine your muscles as a rubber band – a cold and brittle rubber band will snap, whereas a rubber band that is warm and flexible will stretch and return to its original shape. You should always warm up before you stretch in order to avoid injury.
Muscles have a unique characteristic known as elasticity that allows for the ability to lengthen and contract. The physical makeup of your muscles is what allows for length changes without injury. The largest unit of your muscle is known as a fascicle. Fascicles are made up of a large number of smaller components known as myofibrils, according to "Skeletal Muscle Circulation." Each myofibril is composed of bands called sarcomeres. Sarcomeres are further made up of overlapping thick and thin fibers known as myofilaments. During the stretching phase of your muscle there is a decrease in the amount of overlap experienced at the myofilament level – this allows your muscle fibers to lengthen. Conversely, increased overlap of the myofilaments creates a muscular contraction.
Referring back the rubber band analogy, warming up your muscles is of utmost importance in regards to avoiding injury. You should engage in a light cardiovascular warm-up of approximately five to 10 minutes of moderate walking, light jogging or cycling prior to stretching. This allows for increased blood flow to the active area. Heat is a byproduct of the work generated by your muscles. When your muscles are warm they are more elastic.
Dynamic stretching is an active stretch involving a series of controlled swings, kicks and rolls. These motions occur around the joint and work to increase range of motion. Dynamic stretching mimics more functional motions and can improve a joint’s flexibility in multiple directions. Because dynamic stretching requires movement of your muscles, blood flow to the active area is increased keeping that muscle group warm and elastic. You should stretch only to the point of gentle discomfort, stretching to the point of pain could cause injury. Examples of dynamic stretching include arm circles, arm swings, leg kicks and hip rolls.
Flexibility tends to decrease with age. A significant decrease in flexibility could diminish your ability to bend over to tie your shoes, stand upright or maintain your balance. To maintain or improve your flexibility you should engage in flexibility training a minimum of two to three days per week, always after a brief warm up or at the conclusion of your fitness routine. Each stretch should be performed two to four times for a period up to 60 seconds per stretch.