Many people incorporate stretching into their exercise routine. They may perform stretching as a warm-up activity or as a way to improve flexibility. In both these instances, stretching may be a big mistake. In fact, stretching can actually predispose you to, or cause, an injury.
Stretching prior to activity: Stretching prior to activity is a recipe for disaster. There are two reasons for this. For one, most people have heard of the old adage "never stretch a cold muscle". Despite most people being familiar with this statement, people regularly stretch muscles prior to activity-when the muscle is cold. Stretching a cold muscle is akin to pulling on a piece of cold silly putty. When the silly party is cold it will only tolerate a small amount of stretch before it rips. Warm silly putty, on the other hand, can be stretched to extreme lengths without any trouble. The soft tissues in your body respond in a similar manner. Cold tissues tend to rupture more easily, whereas warmth tissues will be more extensible.
In addition to possibly causing an injury, stretching prior to an activity is also a bad idea because it stimulates your parasympathetic nervous system. The parasympathetic nervous system is the part of your nervous system that causes blood to be diverted to the internal organs and away from the muscles. Obviously the diversion of blood away from the muscles is counterproductive to exercise. For exercise, we need the blood to be going to the muscles in order to provide nutrition and oxygen for performance. The parasympathetic nervous system also causes the entire body to relax. This is the same system that is stimulated when you consume a heavy meal. After a heavy meal, it is common to feel sluggish and lethargic. Being sluggish and lethargic will decrease your athletic abilities and will also increase your likelihood of sustaining an injury.
So what should I do instead of stretching? You need to get the muscles warm so that they are more extensible and less prone to injury. You can do this with simple calisthenic exercises aimed directly at the muscles you tend to utilize. You can also perform your specific activity at a 50% intensity for approximately 5 minutes. This will allow the tissues to warm up and better prepare your body for exercise.
Stretching can predispose you to an injury. Many people equate flexibility with good health. This is true – but only to a point. Excessive muscle flexibility can place you at increased risk for an injury. This is because the muscles add support to the joints. In addition to providing your body with the ability to move, muscles also help provide a protective response at the joints. As a joint is moved, Slack is taken out of some of the muscles. As the slack is removed, the muscles become more taunt, providing additional support to the joint. If the muscle, however, is exceptionally loose or flexible, it will then be incapable of providing additional support to the joint. Too much flexibility can be a bad thing. The ideal amount of flexibility is that which allows you to perform the activities you normally engage in without any restrictions. Remember, mobility and stability are at the opposite ends of the spectrum. You cannot have it all.
Additional note: if you do not have enough flexibility in your body, you will place undue stress on the body, likely leading to an injury. Restrictions in the body will result in the body compensating in some manner to allow for the completion of the movement. When this occurs, stresses placed on the body oftentimes lead to repetitive strain type injuries. So how can I tell if I need to improve my flexibility? Unfortunately, the only way to truly ascertain whether you're in need of increased flexibility is to have a movement specialists such as a kinesiologist, or physical therapist perform a comprehensive examination and analyze your movement patterns.