During cold water swimming, limits are constantly being challenged, but it is always important to put safety first. Being aware of the symptoms of hypothermia in cold water will help you recognise when your deep body temperature is dropping and when it is time to abort the swim.

What is hypothermia?

The human body attempts to maintain a deep body temperature (DBT) of 37°C ± 0.5°C. Hypothermia occurs when this DBT drops below 35.0°C.

During cold water immersion, it is normal to experience cooling of peripheral tissues, especially in the extremities, for the first 30 minutes. This cooling may have an adverse effect on neuromuscular activity which leads to loss of motor control and makes it difficult to maintain a an effective swimming stroke.

When exposed to cold water for an extensive period (at least 30 minutes of cold water immersion), the body may start to lose its ability to generate enough heat, and the DBT starts to drop.

Stages of Hypothermia:

Hypothermia is further classified into stages of severity based on DBT.

• Mild Hypothermia (32-35°C)
• Moderate Hypothermia (28-32°C)
• Severe Hypothermia (below 28°C)

Symptoms of mild hypothermia are not always obvious and are often initially picked up by observers. Shivering is most likely the first thing you will notice as this is your body’s automatic attempt to warm itself. Other symptoms of mild hypothermia include shallow breathing, exhaustion, lack of muscle coordination and slight confusion or foggy thoughts.

As your deep body temperature drops even further, you may start to feel drowsy, clumsy and confused. When DBT drops below 32°C, shivering stops, at which point medical help is required.

How to reduce the risk hypothermia in cold water swimming

When you feel that you’re getting cold in the water, it is important to perform regular “self checks” to ensure you remain within the safe zone. Most importantly, always have somebody observing you, or buddy up with another swimmer or small group of swimmers.

Self Checks:

• Can I open and close my hands?
• Am I swimming in a straight line and maintaining my usual pace?
• Am I thinking and talking clearly? (observers to check)
• Is my breathing normal?
• I’m not shivering

If the answer is yes to all of these, you should be fine to carry on, unless instructed otherwise by your observer. Remember – safety first!