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The small muscles at the base of your skull right above where your neck meets your head are your occipital muscles. Tightness here is responsible for a lot of pain and tension, and sometimes headaches and dizziness. The best way to relieve these muscles is with ball massage. Use a tennis ball, racquetball, small foam roller, or anything with a similar shape. Lie flat on your back face up and place the ball under your neck right at the base of your skull on either side of your spine. Turn your head side to side to roll over different areas. Do this for about 5 minutes, and be sure to massage both sides. Stand up straight. Tilt your chin to your chest. Interlace your fingers and place them behind your head. Do NOT pull downward on your head, but allow the weight of your arms to apply gentle downward pressure on your head and stretch the back of your neck. Hold for 30 seconds. Repeat 3 times or more. Stand or sit up straight. Keeping your nose facing straight ahead, bring your right ear to your right shoulder.  Rest your right hand on the side of your head and allow the weight of your arm to gently pull, stretching the left side of your neck. Again, do not actively pull on your head – just let the weight of your arm apply gentle traction.  If your shoulders slump forward, bend your left elbow and place your left arm behind your back with your palm facing outward (when your head is tilting to the right). Do this for 30 seconds on each side, repeating 3 times. Your sternocleidomastoid (SCM) muscle is that strong, thin muscle that stretches from right behind your ear down to about the middle of your throat (it connects to the end of your collarbone close to your midline), creating the little V-shaped divot at the front of your throat.  You should be able to feel this strong band of muscle. Find it and gently massage it by pinching and rolling it lightly between your fingers. Go up and down the length of the muscle.  Don’t push too deep into your neck where you might hit other tender places. The massaging motion is like gently pulling or lifting the SCM away from other structures in your neck. It might help you find and relax the muscle by turning your head in the opposite direction, i.e. turn your head to the left with your nose staying straight ahead to feel your right SCM. Walk into an open doorway. Place your right arm against the right side of the door with your palm facing the door. Bend your elbow so that it is in a 90° angle, with your forearm flush with the side of the door. Take a small step forward with your right foot. Keep your forearm touching the door. You should feel a stretch in your pectoral muscles at the front of your chest near your armpit. Hold the stretch for 30 seconds and repeat on the opposite side. Chiropractors and massage therapists are experts at understanding how posture problems cause pain, and how to fix them. See a massage therapist or have a chiropractic session and ask about stretches and exercises you can do at home.
Relieve your occipital muscles with a massage ball. Regularly stretch the back of your neck. Stretch the sides of your neck. Release the SCM muscle at the front of your neck. Stretch your chest muscles. Speak to a professional body-worker for advice.