What causes brain freeze in the surf? Breaking down why your head feels as though it is about to explode after a wintery head dip.
Ice cream headache is a common and well discussed condition. It occurs when cold food or drink comes into contact with your palate on the roof of your mouth and makes the blood vessels in your palate contract. These vessels contract so vigorously that they can spasm. This spasm means that you experience pain. The same nerve that senses this painful spasm also receives sensation from the skin over your head. Your brain can’t distinguish between the different territories of its sensory inputs and therefore tells you that you have a headache. This is called referred pain.
Interestingly a similar situation of referred pain occurs when people with heart attacks (heart pain) have a sensation of discomfort in their left arm. Sensory nerves from the heart and part of the arm share the same nerve distribution (territory).
An ice cream headache therefore isn't what we experience whilst surfing, but the principle is the same. Brain freeze is probably a better name for describing the violent disorientating aching pain that we feel. I've often found myself questioning my pain tolerance after a few winter duck dives... Having said that, the patients I meet that tell me they have a high pain threshold, ironically, usually have the lowest.
To understand brain freeze is to help overcome it.
So what is the cause of that nauseating and crippling pain that I feel? A bit of reading and recent experiences from open water swimming have given me my theory.
All the skin over your face and head contain an enormous number of blood vessels. They all have the ability to expand and contract to control blood flow. One of the reasons why they relax is to increase blood flow to allow heat to escape. This is a normal response to help you thermoregulate. The heat is transmitted from your blood to your environment. If you are cold then they contract to reduce blood flow and therefore reduce the amount of heat you lose to your environment.
Water as we know conducts heat away from your body better than air. Wind causes water to evaporate, and by doing so removes heat energy from you to do so (latent heat of vaporisation). Wind chill is the cooling effect of an increased flow of air. More air is in contact with your body per second (with increasing wind speed) and so its able to remove more heat through conduction. The colder the air the more dramatic this wind chill is.
Little wonder then, when your head emerges from the water in winter wind, that it hurts. The cold water causes your previously expanded blood vessels to contract and potentially spasm. Just like in ice cream headaches it causes pain all over your face and head.
My cold water concussion theory
Concussion occurs as a result of traumatic brain injury. It from from mild swelling or contusions of the brain. The symptoms of concussion however (pain, nausea and disorientation) can all be momentarily experienced from a winter duck dive. 'Cold water concussion' therefore is arguably a better phrase, and the physiology behind why we feel concussed is quite interesting.
The pain isn't just because its cold. It’s because it’s suddenly cold when previously we were surprisingly hot. The speed of change is the key.
Think about cold water swimming. After the initial shock your body gets used to it. Its alright once you are acclimatised. Your body (and blood vessels) get used to being in an environment at a constantly cold temperature and act accordingly (by staying contracted to reduce heat loss).
Whilst we're surfing we are never really in the same environment. Our head spends most of its time above water, with periodic plunges into cold water. No wonder we struggle.
There we are in our super stretchy 5/4 windproof insulated state of the art wetsuit. We perform a huge feat of athleticism and endurance paddling out through winter surf and, surprise surprise, we get hot. Our body does what it does best and starts channeling our hot blood to exposed areas that have expanded blood vessels to help us cool off to reduce our body temperature. We then duck dive. Horrendous head pain caused by the rapid contraction and spasm of these blood vessels.
The same spasm in vessels experienced in ice cream headache is experienced all over our heads. Ever felt like you are going to puke sometimes after a few freezing duck dives? I do.
Turns out there’s a nerve that supplies the ear canal that also supplies the gut. Its called the ‘Alderman’s nerve’ (I’ve got no idea who Alderman was, or if he surfed). Cold water in the ear, according to text books, is supposed to stimulate appetite. Irritation (by cold water) of the eardrum can actually cause vomiting due to a reflex from the nerve that supplies this Alderman’s nerve and your gut (Vagus). Divers can experience this too. The 'diving reflex' is the slowing of your heart rate in response to cold water in your ear. It's the vagus nerve that slows the heart and essentially puts the body into a more relaxed state which uses less oxygen (for the same reason you should try and stay calm during a long hold down). An obvious advantage when your breath holding under water. Fortunately for some reason the diving reflex diminishes with age. Unfortunately pain from duck diving doesn't.