Flexibility is the range of motion (ROM) available in a joint or group of joints. It can be measured either in linear or angular units. There are two types of flexibility: Static flexibility is range of movement in a joint with no emphasis on speed of the movement. Dynamic flexibility is the ability to use a range of joint movement in the performance of physical activity.

Benefits of Stretching
The benefits of stretching are many. They include promotion of relaxation, diminishing of muscle contraction, lowering of blood pressure, improvement of symmetry and the correction of muscular imbalance which is caused by the lack of flexibility in certain muscle groups, and correction of postural misalignment also due to a disparity of flexibility of opposing muscle groups. Other benefits include better coordination, balance and joint stability. Stretching can also help or avert low back pain by increasing the mobility of the trunk and flexibility of the lumbar spine. Generally, by increasing the biomechanical parameters, stretching and increased flexibility can enhance velocities, energies and momentum involved in all physical activity.

Injury Prevention and Alleviating Muscular Soreness
Since muscle and connective tissue injuries are often caused by limited joint mobility, stretching can help to prevent such injuries by increasing ROM in the joints. In addition, static stretching can relieve muscular soreness due to weight training workouts or other athletic/physical activity. It is thought that this occurs because stretching helps to break down and disburse the build up of lactic acid and to decrease electrical activity in the muscle.