When you do a dynamic stretch — like that time in the gym when you hold your hands up above your head and yawn at the same time (it’s actually called pandiculation) — you elongate your muscles and increase blood flow, which can help boost the function of all your body’s tissues. It can also activate the parasympathetic part of your nervous system, causing the muscles in your entire body to relax. That’s why stretching is so important for feeling energized, and why it often feels good when you do it.
Stretching can feel great when you’re performing it correctly, but you’ll likely hurt yourself if you’re stretching cold muscles. That’s why it’s important to warm up before you begin your workout with light exercise like walking, jogging or biking at low intensity for 5 to 10 minutes before stretching.
Muscles are composed of bunched-up strands of fibers that are sometimes aligned and other times disorganized, all glued together by connective tissue. When you stretch, the muscle cells at the primary level — called sarcomeres — elongate little by little. This process also helps heal injuries and decreases the chance of injury in the future.
As a bonus, stretching can activate neurotransmitters called endorphins, which are similar to morphine and have pain-relieving effects. This helps reduce the aches and pains associated with tight muscles and can make you feel great after your workout. If your muscles start to feel uncomfortable and sharp during a stretch, however, it’s probably too much and you should stop the movement immediately.