Updated: Oct 9, 2019
The way you feel after a cold water swim is the reason you go back again and again. Shivery, jubilant, invigorated... what's normal and when should you take action?
Get to know your cold body
Taking the temperature before a swim and snuggling up afterwards, both important parts of the winter swim experience. And as you swim more often, you get used to how you feel after a swim. But, as spring is both a time for new dippers to take to the water and when seasoned swimmers are most likely to push it, what feelings are normal and what might be cause for concern?
In the water, blood vessels in our extremities and skin close sending warm blood to our core. Our heart rate and blood pressure increases, and our bodies respond by shedding liquid in the easiest way possible, which is why you always need to pee when you go swimming.
While there are very small risks associated with that increased heart rate and blood pressure, these are the same as with any exercise. It's when you get out of the water that you need to be observant about how you feel. This is because your cold blood and warm blood mixes as you warm up, causing your overall body temperature to drop.
So, what's normal? Everyone's a bit different, but among normal responses, you may feel:
Shivery - as your core temperature cools it triggers your shiver response. Even quite a violent shiver is perfectly normal.
Numbness - it may take a while for your fingers and toes to wake up again.
Tingly - it's normal to tingle all over your skin
Heavy - your muscles may well feel tired and sluggish
Expect those tingly, cold feelings to last a couple of hours.
From time to time our bodies can throw us a curve ball. Sometimes there will be a reason, such as staying in for too long, being under the weather, or being hungry or dehydrated. Sometimes there might not be an obvious reason.
Extreme reactions may give the following symptoms:
Dizzy and nauseous
Stopping shivering or not shivering when you do normally
Slurred speech or mumbling
What causes these symptoms? Two things can happen to cause worrying symptoms. One is when your body temperature cools too much or too fast. Our normal body temperature is 36-37 degrees centigrade and hypothermia is when that temperature drops below 35, so there's not much margin for error.
The other is where the blood that moves away from your extremities pools around your legs and your cold heart can't pump blood around your body very well, causing your blood pressure to drop. It's worth bearing in mind that while cold water exacerbates this reaction, it can also happen at warmer temperatures (UK waters a technically 'cold' most of the year round), especially if you've been swimming hard in a horizontal position and quickly go into a vertical position to get out of the water.
How to keep risks to a minimum
Living life is about managing risk, not avoiding it. Managed well, the risks associated with outdoor swimming are pretty small and they are far outweighed by the benefits. There are few simple things that you can do to keep yourself as safe as possible:
Make sure you're well hydrated and well before you swim.
Arrive warm and jump around before you get in to start raising your heart rate.
Swim together. Make sure you and your swim buddies know each other's names and health conditions.
Don't stay in too long (one minute per degree centigrade maximum to begin with).
Kick hard or tread water before you get out.
Warm up properly - get straight out of your cold, wet swimmers and into warm dry clothes as quickly as possible and have a warm drink.
Avoiding warming up too fast - no hot showers or boiling drinks.
Know the symptoms of hypothermia and post-swim collapse and brush up on what to do if it happens.
It's really hard to find information about this phenomenon, yet I have seen it happen twice this winter. Known as post-rescue collapse or curcum rescue collapse, it's something that rescuers come across, but it also applies to swimmers in cold water. The main cause is standing up quickly after being horizontal, causing orthostatic hypotension - a drop in blood pressure as the vascular system cannot constrict fast enough in the lower limbs and abdomen to squeeze oxygenated blood up to the brain. This feels like dizziness or a head rush and something I've felt after swimming hard in a wet suit in water that was 18 degrees.
When you're in the cold water, your blood pressure is elevated and your stress hormones are doing their thing. So when you get out and relax it can exacerbate this response. Added to that, as your cold blood and warm blood mix, your heart can get too cold to do its job well. It's important to get yourself into a horizontal position if you feel dizzy post-swim.
Swim safe and enjoy
Ultimately, swimming outdoors is a joyful, life-affirming activity. So many people do it with no ill-effects, and it's something that people of all ages can do. Armed with a little bit of knowledge and respect for the cold water, you can make sure that you keep it that way.