The American College of Sports Medicine recommends fitness enthusiasts and recreational athletes stretch the major muscles groups a minimum of two to three days per week. Generally, hold each stretch for 10 to 30 seconds until mild discomfort -- three to four repetitions per stretch.
Proper stretching should not result in stretching-related soreness afterwards. If soreness occurs, it is a sign of overstretching. Overstretching damages muscles. One of the easiest ways to overstretch is to stretch a cold muscle, (i.e., stretching without a warm-up). Prevent this by beginning workouts with five to 10 minutes of light cardiovascular activity, (e.g., walking, cycling, etc.). This will raise the core body temperature, thereby warming up the muscles for physical activity, including stretching.
If a proper warm-up is included in a workout and stretching related pain still occurs, it is an indication of overstretching and the need to ease the intensity of the stretching. Overstretching will actually increase the amount of time it takes to gain flexibility because it damages muscles and the muscles need time for repairing. If you skip the warm up or try to stretch too aggressively, a nerve reflex (or stretch reflex) occurs. The stretch reflex is an automatic response to the stretching of nerve fibers. It contracts muscles against the direction of muscle stretch. This often leads to mild pulled muscle that reduces athletic/fitness performance.
The effects of the stretch reflex is preventable by only stretching to a mild discomfort, breathing during the stretch, and remaining relaxed while stretching. If overstretching occurs and results in muscular pain, soreness, and/or stiffness, it may the effect of torn tissues or muscle spasms.
Torn Tissue
Overstretching and poor warm-ups often lead to microscopic tearing of muscle fibers or connective tissues. The pain from a minor tear is usually felt the next day and heals within a couple of days of injury. If the pain occurs during or immediately after the activity, it may be a more serious tear requiring medical attention. Studies suggest torn muscles heal at a shortened length. This decreases the flexibility of the injured muscle. If a minor tear occurs, very light stretching may reduce loss of flexibility; however, intense stretching can worsen the injury.
Muscle Spasms
Exercising above an individual’s fitness level can cause a decreased flow of blood to the active muscles, possibly causing pain that activates the protective stretch reflex. The reflex contraction causes further decreases in blood flow, which causes more reflex contractions. This cycle can lead to a muscle spasm. Individuals experiencing a muscle spasm often feel it as a muscle cramp. Immediate stretching of the muscle can alleviate the pain; however, it also can exacerbate the pain by continuing to activate the stretch reflex and contracting the muscle. Relaxing and massaging may help more than stretching.
It is important for individuals to remember that inactivity will cause some soreness. If an individual has not stretched or exercised in a long while, begin a fitness program slowly to help prevent muscle soreness, torn tissues, and muscle spasms. If an individual feels or hears a muscle tear or “pop”, stop exercising immediately. Seek medical advice and rely on resting, icing, compressing, and elevating the injury (RICE).
For more information on proper stretching, please consult a fitness professional or Mayocliniccom's Stretching.
