Stretching is a form of physical exercise in which a specific muscle or tendon (or muscle group) is deliberately flexed or stretched in order to improve the muscle's felt elasticity and achieve comfortable muscle tone. The result is a feeling of increased muscle control, flexibility, and range of motion. Stretching is also used therapeutically to alleviate cramps.
In its most basic form, stretching is a natural and instinctive activity; it is performed by humans and many other animals. It can be accompanied by yawning. Stretching often occurs instinctively after waking from sleep, after long periods of inactivity, or after exiting confined spaces and areas.
Increasing flexibility through stretching is one of the basic tenets of physical fitness. It is common for athletes to stretch before and after exercise in an attempt to reduce risk of injury and increase performance, though these practices are not always based on scientific evidence of effectiveness.
Stretching can be dangerous when performed incorrectly. There are many techniques for stretching in general, but depending on which muscle group is being stretched, some techniques may be ineffective or detrimental, even to the point of causing tears, hypermobility, instability, or permanent damage to the tendons, ligaments, and muscle fiber. The physiological nature of stretching and theories about the effect of various techniques are therefore subject to heavy inquiry.
Although static stretching is part of some warm-up routines, a study in 2013 indicated that it weakens muscles. For this reason, dynamic stretching is recommended before exercise in place of static stretching, while the latter helps to reduce muscle soreness afterwards.
There are four different types of stretching: ballistic, dynamic, PNF stretching, and static stretching.
Ballistic stretching is a rapid bouncing stretch in which a body part is moving with momentum that stretches the muscles to a maximum. Muscles respond to this type of stretching by contracting to protect itself from over extending.
Dynamic stretching is a walking or movement stretch. By performing slow controlled movements through full range of motion, a person reduces risk of injury.
Proprioceptive neuromuscular facilitation (PNF) is a type of stretch for a particular muscle and its specific job, so resistance should be applied, and then the muscle should be relaxed.
Static stretching is a type of stretch whereby a person stretches the muscle until a gentle tension is felt and then holds the stretch for thirty seconds or until a muscle release is felt, without any movement or bouncing.
Most of the research on stretching has focused on static stretching; there is less evidence on the other forms.
Improves flexibility and reduces likelihood of muscle injury.
Stretching improves flexibility, which increases the ability of a joint to move through its full range of motion; in other words, how far it can bend, twist and reach. Some activities, such as gymnastics, require more flexibility than others, such as running.
While the exact mechanics of what happens are not fully understood, regular stretching is thought to increase flexibility, both by making muscles more-supple and by retraining the nervous system to tolerate stretching further. Flexibility from regular stretching gradually disappears once you stop stretching – typically after four weeks.
There is some evidence that regular static stretching outside periods of exercise may increase power and speed, and reduce injury. The best time to stretch is when the muscles are warm and pliable. This could be during a yoga or Pilate’s class, or just after exercising.
A post-exercise stretch will also slow down your breathing and heart rate, and bring the mind and body back to a resting state.
Muscle injuries happen when the muscle is put under too much stress, typically when it is stretched under pressure – for instance, when lowering a heavy weight.
The injury occurs not because the muscle isn’t flexible enough, but because the muscle isn’t producing enough force to support itself. A muscle might not produce enough force, either because it is not strong enough or it didn’t contract at the right time for a particular movement.
Research suggests that stretching before exercise makes your muscles weaker and slower, even though you might feel looser. Warm ups are recommended before exercise.
The purpose of warming up is to prepare mentally and physically for your chosen activity. A typical warm up will take at least 10 minutes and involve light aerobic movements and some dynamic stretching that mimics the movements of the activity you’re about to perform.
Warm muscles are less stiff and work more efficiently. Increased blood flow enables more oxygen to reach the muscles and produce energy. The warm up also activates the nerve signals to your muscles, which results in faster reaction times.