And this is just the beginning of the stress you are going to put your body through. You still have to swim to go down, swim on the bottom, swim to go up, on-gas, off-gas, fight against the current and drag off your deco tanks, your bailout tank(s), your huge twinset (the one you nicknamed Potemkin!) or your favourite rebreather, swim at the surface, climb the ladder or the shore and carry everything again! And some people think we do that just for fun! Needless to say, preparing for these kinds of dives goes beyond just resting the evening before the dive and drinking a so-called energy drink a few minutes before kitting up. It takes year-round preparation. Moreover, it’s a lifestyle!

The benefits of fitness training
A better cardiovascular system means a lot for your body. It doesn’t only improve your dives but also your general health. Some studies show that there is a relationship between VO2max (your maximal O2 consumption, i.e. the ability of your body to efficiently transport and use the O2 in your lungs) and risks of Decompression Sickness. And a better use of the oxygen means a better/slower ventilation. You are less exerted if you have to swim for a long time, or harder than usual, and it becomes easier for your body to get rid of the CO2 you produce.

The Body Mass Index (BMI) is a way to determine the ratio between fat tissues and muscles in your body, based on your age. A lower BMI has the following significance for a rebreather diver:

• Less fat and more muscles is a good way to decrease your susceptibility to DCS. Because of a higher vascularisation, muscles tend to be less prone to DCS than poorly perfused fat tissues.

• Muscles are heavier and less buoyant than fat tissues (1.10gr/cm3 for muscles and only 0.90 gr/cm3 for fat tissues). So, a lower BMI means a less buoyant body, which in turn means a lesser need for weights, something that all divers should appreciate. And with less weight, rebreather divers have usually a better trim.

• More muscles also mean more strength, something that can prove to be useful in case of an unexpected situation (fighting against a strong current, holding on a shotline, etc.) or an emergency (helping another diver to surface, rescuing a diver and removing him/her from the water, etc).