I recently wrote a critique of a well known study about decompression methods, which gave rise to some interesting discussion with some old friends, and with a specialist in decompression science whom I had not interacted with before. I definitely learned some things during these discussions.
I do of course think it is very important what kind of decompression model one uses for deep dives. But the discussion also made me take a step back and look at the big picture. There are other factors involved in staying healthy during a dive. Fitness is one.
I have recently upped my strength training program again, and this had further contributed to me re-assessing the role of fitness in diving. In my experience as a diving instructor I found that people who engage in no sport whatsoever have real problems when they want to dive. A few percent of prospective students seem to be in that kind of physically passive state (I’ve also had super fit diving students!). It can happen to folks at any age. Overweight is an indicator of trouble, but not necessarily the only one – and some moderately fat people are in surprisingly good shape. Skinny people can be in horrible shape if they spend all their lifes in an office chair. It seems that the problem is the fact that some folks are not used to doing anything serious with their bodies, and they are often a bit frightened once they are supposed to use their muscles – this is really surprising to me. What do these folks do on weekends? No hikes, or bike tours, ever? It seems that these sedentary people, be they skinny or fat, are suffering from a synergistic lack of strength, cardio fitness, coordination, balance and flexibility. A diver needs all of the above.
Walking a few steps on a shaky boat with heavy gear is easy if you have leg muscles and a sense of balance, but can get you hurt if you don’t. Any type of serious exercise works to get you in diving shape, in my opinion. Fitness training, tennis, soccer or running all can provide the fitness you need. Swimming takes a special place in diving fitness – if you can swim very poorly you are in trouble. You will simply be uncomfortable to float in mid-water of you are not confident that you can move yourself around in the ocean. Then your mind will be preoccupied with your (perceived) safety or lack thereof, and you will not be able to learn to dive as easily as it’s possible.
Diving fitness is also related to a decreased likelihood of getting decompression sickness. This study (Carturan et al., 1999. Circulating Venous Bubbles in Recreational Diving: Relationships with Age, Weight, Maximal Oxygen Uptake and Body Fat Percentage. International Journal of Sports Medicine 20, 410–414.) measured the amount of bubbles (which cause dcs) in male recreational divers, post-dive. They found that “the effects off age, weight and maximal oxygen uptake are more significant than the effect of percentage body-fat.”. You can’t change your age, but all the other factors are changeable in response to training and nutrition.
What I have been seeing during the last month, after spending more time in the gym again, are lots of leg-day skippers, and cell-phone-aficionados (in my new gym there is one ladyboy who always spends hours texting while perched on a yoga mat – yes, I’m in the Philippines). Just showing up to the gym does not provide any benefits. You actually have to make a real effort to train. No pain, no gain – I believe in that piece of bodybuilding wisdom.
One advantage of being fit while diving is that it leaves your mind capable of dealing with new information. Back in my American Football days I saw surprisingly smart people forget surprisingly simple plays when they were out of breath and beaten up in the 4th quarter. You don’t get hit during a normal dive, but you can get exhausted if you have to swim hard. And the more exhausted you are, the less capable of dealing with an unforeseen situation during a fun dive, or with new skills during a course. If you are in good shape, the same swim will only slightly tax you, and you can cope with the aforementioned situations much more easily. The effect is easy to understand: Try multiplying double-digit numbers. And now try doing similar multiplications after a 200 meter sprint. It will be so much harder to perform the same mental task. If swimming 20 meters in full scuba gear feels like a 200 meter sprint to you, then your mental capacities will be reduced when you need to keep a clear head during a dive.
There is of course the issue of exercising on the day of a dive. There is a big difference between post- and pre- dive exercise. Post-dive exercise is generally not recommended, since it can lead to bubble formation from the excess nitrogen still in a diver’s tissues. Pre-dive exercise is a different story, and has been deemed beneficial for avoiding decompression sickness in a scientific studies. This one (Blatteau et al., 2005. Aerobic Exercise 2 Hours Before a Dive to 30 msw Decreases Bubble Formation After Decompression. Aviation, Space, and Environmental Medicine 76, 666–669.) tested the effect of a strenuous 45 minute run, 2 hours before a dive. Again, the scientists measured the bubbles in the venous blood stream of the divers (who did not actually dive, but sat in a hyperbaric chamber for a simulated dive to 30 meters). The bubbles, as scored by a universally agreed upon system, were about a third of the bubbles in the divers who did not run.
There is a balance to be found: A bit of exercise in the morning before a dive should be beneficial, but you don’t want to exhaust yourself! I would certainly be tired after a 45 minute run at a high pace.
Furthermore, I think that dehydration is something all divers have to take very seriously. The importance of proper hydration is of course well known to the diving physiologist – but not to all divers! Hangovers and the type of explosive diarrhea often encountered in tropical diving destinations can lead to serious dehydration.
There is a dichotomy in diving – it’s a vacation past-time, but also a sport. On the one hand it’s something people do, and sometimes only do, when they are on a holiday. They might be jet-lagged and hungover, and that’s when they expose their body to a pressure of 2 or more atmospheres, and to a type of physical activity they are not used to. On the other hand, diving is of course a sport, and should be treated as one. Proper preparation, and listening to your body are vital in every sport.
Finally, I have been thinking about developing a sport supplement tailored for scuba diving. Check back here to see how that comes along!