Ever get a dry mouth before a big event? Maybe it’s a job interview. Maybe it’s the CrossFit Open. Maybe you’re about to ask someone out on a date.

Why do we get a dry mouth? And what can we learn from this experience to improve our performance?

Well, maybe it’s just because you’re dehydrated, and if that IS the cause, your performance will definitely drop. In fact, by the time you start to feel thirsty, you’ve usually lost between one and two percent body fluid, and by this time, your performance has already dropped. a 0.5% drop increases strain on the heart, our aerobic performance decreases with a 1% drop, at 3% we experience reduced muscular endurance, and by the time we’ve dropped by 4%, we not only experience reduced muscle strength, but also damage to coordination and skill levels, and we begin to suffer health (not just performance) effects.

So dehydration is definitely one cause of a dry mouth, but in the context of what we’re talking about, it’s probably not THE cause.

You see, there’s a branch of our nervous system called the ‘autonomic nervous system’, and it’s made up of the sympathetic nervous system and the parasympathetic nervous system. You’ve probably heard of the sympathetic nervous system by its more common name, ‘fight or flight’. It goes in to overdrive when we’re threatened or in a stressful situation (just like when you’re waiting for that job interview, preparing for an important workout, or about to ask that cute guy or girl out on a date). It causes a cascade of ‘performance chemicals’ to be released in to your body. Your pupils dilate, your start sweating, and your heart rate and blood pressure go up. You’ve entered a state of high physical performance. Your pupils dilate to take in all available light, you sweat to control your body temperature during intense activity, and your heart rate and blood pressure go up to take all available blood from around your body and send it to your muscles. And there’s our first clue for the dry mouth.

The second clue comes from the more common name for the parasympathetic nervous system – ‘rest and digest’. Basically, the exact opposite of ‘fight or flight’. In this state, we slow down and the blood is sent to the gut to digest food.

So ‘fight or flight’ fires up the ‘perform’ parts of the body, and ‘rest or digest’ fires up the ‘recover centres of the body. ‘Fight or flight’ sends blood to the muscles (and away from the digestive system), while ‘rest and digest’ sends blood to the digestive system (and away from the muscles). And what’s an important part of the digestive system, and the first place our body uses acid to break down food? The salivary glands.

As we go into our high physical performance state, our salivary glands are shut down, as all available resources are mobilised to create action. Hence, dry mouth. This also explains why you’re rarely hungry on competition day, and why having strategies to get food in are so important.

So this dry mouth is a sign we’ve gone into a high performance state, but sometimes it can be a case of ‘too much of a good thing’.

And it can be too much of a good thing, because while a dry mouth can be a sign of ‘fight or flight’, it can also be a sign of too much ‘flight or flight’… hyper arousal. There’s an inverted U model shows the relationship between performance and arousal. This model is specific to the individual, and specific to the task, so the inverted U is not always symmetrical. Being in the optimal level of arousal is know as an ‘ideal performance state’ or ‘being in the zone’. If we’re hyper-aroused (overly anxious or nervous to the point of reducing performance), we can experience muscle tension and coordination difficulties, and impairments in attention and concentration. Excessive sympathetic nervous system activity can also keep us out of a ‘flow state‘, an optimal state of consciousness where we feel our best and perform at our best.

In Arousal Regulation – Psychological Skills Training we discuss strategies to reduce arousal levels, including progressive relaxation, breath control, meditation, acting relaxed, being focused on the present, setting up stressful situations in training, and having a good game plan.

A dry mouth can be a window in to our nervous system. By understanding why it happens, we can learn to use techniques to reduce our arousal levels to our zone of optimal performance, enter a flow state state, and ultimately, improve our performance.