Scuba diving, the sport of couch potatoes

April 19, 2017

Scuba diving, the sport of couch potatoes

When learning to scuba dive, many of the lessons we learn intuitively suggest that regular exercise isn’t an essential part of being a good diver; don’t fight against the current, relax (as much as possible), keep your arms in check and don’t try to mix exercise with diving.

In fact, there’s a general consensus that most of the skills in diving, come from having the right attitude, planning well, having self-confidence and being self-reliant, not having muscles!

So why can’t scuba divers just be couch potatoes when we’re out of the water?

Let's have a look at what happens to our body when we scuba dive...

First of all, our body has to deal with the effects of immersion.
In water temperature near our own body temperature, our body is exposed to a pressure gradient, which shifts blood from the vessels in our legs to those in our chest cavity. Our heart takes in more blood and its four chambers become larger. There’s an increase in pressure in our right atrium, over 30% increase in cardiac output and a slight increase in our overall blood pressure.
Our baroreceptors, the sensors that perceive a change in blood pressure within our body's major vessels, react to all these changes by decreasing the activity of our sympathetic nervous system. Then our heart rate declines while the level of another hormones drops too, forcing  our kidneys to excrete more sodium and to produce more urine.
That is also one of the reasons we almost always feel the need to pee when we dive.

Then the body might have to deal with the effects of cold, another reason to keep warm when diving.
When our body starts losing heat our blood vessels constrict, our heart will need more blood and will have to work harder. But the constriction of the small arteries will make it harder for blood to reach the periphery of our body, resulting in increased blood pressure.

For this reason it’s really important to keep warm when diving in cooler climes, especially once you’re back out of the water. Having something to quickly throw on once out of the water can drastically reduce the impact of wind chill, if you like you can check out our poncho/robe selection here.

Then, of course, there’s pressure.
Breathing compressed air at depth affects our ears & sinus, tissues, our respiratory system and cardiovascular system in many ways.

Our body has to deal with an increased carbon dioxide level in both our respiratory system and blood stream, which triggers our reflex respiratory centre to stimulate us to breathe more frequently and/or more deeply to eliminate it.
This excess carbon dioxide is the result of breathing in that air left in the so called “dead air spaces”, present in diving (and snorkelling) equipment. Water pressure on our thorax also reduces the volume of air our lungs need when we breath normally at rest (the so called “tidal volume”) and when we breath in from our regulators fresh air mixes up with the carbon dioxide richer air present in the “dead air spaces”. Although our body can compensate for this, we instinctively need to breathe deeper, to maximise the tidal volume of our lungs.
The compressed air we breath in is also more turbulent and denser, resulting in our bodies needing more energy to breathe and overcome resistance.
This is why we need to relax, breath deeply and conserve energy.

Pressure also creates a much bigger problem that regards nitrogen absorption, which involves not only the heart, blood and plasma but tissues in our whole body.
Nitrogen makes up 78% of what we call air but it’s not used by our body, we don’t metabolise it.
On the surface our body contains as much nitrogen as it can hold - we are saturated.
When we scuba dive depth affects the partial pressure of nitrogen and we’re no longer saturated because the nitrogen dissolves into our tissues (Henry’s Law). At this point nitrogen can form the bubbles that cause decompression sickness so we need to manage it by diving according to well-known and well-studied decompression models for nitrogen elimination…which pretty much means following what our computer says. What is important to know is that different tissues eliminate nitrogen at different rates and that body fat is a slow releasing tissue.
This is somehow a slightly controversial issue as it is still at a theoretical stage but it can’t nonetheless be ignored. The more body fat we have the more susceptible we could be to getting bent - it’s as simple as that.

Our body is also affected by exertion when diving.
A short swim against the current at depth or a long swim in full scuba gear on the surface can have a huge impact on our body. Not to mention getting in and out of a skiff in choppy water with your gear on, it’s fairly obvious that, for this, at least some upper and lower body strength is necessary. It’s impractical to expect the help of a nice crew member in these situations all the time, it’s important to plan for the worst. If something goes wrong you need to be able to be self-reliant.

Then there’s stress.
Stress has varying impacts on our body at depth, but it certainly shouldn’t be overlooked. Our sympathetic system could for example prevail and produce a "fight-or-flight" response, increase our heart rate and in general make us very uncomfortable. Stress can play tricks on us in the most unexpected ways and our body has to cope with it.

Not for couch potatoes after all?

If we sum all of this up and add the fact that the sea might be rough, that we might feel excessively cold or hot, maybe we partied too much the night before, our equipment is heavy and that maybe we’re even jet lagged, and we can understand how much we are asking from our body when we scuba dive.

That’s why it’s important to look after your body if you want to keep scuba diving safely and enjoyably - which, (perhaps unfortunately), means getting, and staying, fit.

It's easy to trick yourself into thinking that being fit is not a necessity for divers, that somehow we’re going to be okay because "we always have been" or that "accidents will always happen, but to someone else - not me" but this attitude can be a slippery slope. Sometimes a little bit of motivation is all you need to get started, treat yourself to some new workout gear, it might just be the push you need to change your routine.

Our Calypso T-shirts can very well double up as sports T-shirts. They are super comfortable, stretchy, lightweight and quick dry. The same applies to our Calypso tops for girls. Our Water shorts, in the Men's and Women's version, can also be great for exercising. You can also take your poncho to the gym, it's perfect for getting dry and changing in privacy.

Walk, run, cycle, lift weights at the gym, play tennis, squash, golf, do yoga, swim, do martial arts, throw a ball around, go hiking - do whatever it takes to look after your body and heart. Even simple things like watching food portions, enjoying alcohol responsibly or quitting smoking all can have huge impacts on our ability to safely enjoy scuba diving.

I'll be the first one to start, as I'm not exactly the best example myself!
I'm in my mid-forties, I don't smoke but I love beer and food. I'm also time poor and I travel a lot on planes. My preferred form of exercise is an unusual one; Hot Yoga.

Hot Yoga provides everything I need from exercise - intensity, stretching, breathing, cardio exercise, balance, discipline, and importantly, it gives me a "mind over body" experience, something incredible valuable for any diver.

No more excuses...let’s get moving!

Tom


Sources: DAN, PADI Encyclopaedia of Recreational Diving