The most common causes of "whiplash" are injuries that arise from automobile accidents or motor vehicle collisions (MVCs). So, let’s chat about why and how this happens in a "typical" MVC. You are stopped at a red light, patiently waiting for the light to turn green and suddenly, you hear the screech of tires followed by a sudden jolt as a car collides into the back of your vehicle. During this process, you may turn your head to the right to look in the rearview mirror to see what is happening. Even if you see the inevitable collision prior to the impact, the sudden jolt occurs so fast that you really don’t have a chance to adequately brace and you feel yourself being forced back into the seat and headrest followed by a rebound forwards. Since you always wear your seatbelt, you feel the restraint across your chest and lap belts tighten as you’re propelled towards the front of the car. The seat belt stops you from hitting the steering wheel or worse, propelling you forward through the windshield. Unfortunately, by now, the damage has been done! This ALL occurs in less than 500 milliseconds— you cannot voluntarily contract your muscles this fast, which means even if you had time to prepare yourself for the impact by bracing, you can’t stop the whiplash effect!
A 2010 study found the muscles in the front of the neck contract first at about 100 ms—which is 25 ms too late to prevent ligament or muscle damage—and they reach their peak stretch at 150ms. The muscles in the back of the neck start contracting soon thereafter but are injured more than the muscles in the front of the neck around the 300ms point. The reason for this is because as the head rebounds forwards, the muscles in the back of the neck are in the process of tightening up or shortening at the same time they are being stretched— NOT a good combination! This is one reason why many people injured in MVCs complain their neck pain is greater in the back of the neck. This also helps explain why headaches are common symptoms associated with whiplash as the upper three nerves that exit the top of the spine in the neck go into the head/scalp and are compressed or squeezed by the tight muscles in the back of the neck when they are injured, which can result in headaches.
