Exercise after Scuba Diving

After Saturday’s long day of shallow diving, I rightfully felt pretty tired. Getting home later than usual, I wasn’t all that keen on doing my usual Saturday run, and as my wife believes that it is my duty after going diving to do some chores around the house (more about wives and diving in a later post), I reluctantly chose to forego the exercise for the day.

My Sunday run is the longest of the week, but within a minute of starting I knew it was going to be tough. Even though the run is also the slowest of the week, my heart rate climbed rapidly right out of the gate. So I had planned to run for 85 minutes but only managed 70. For the last 6 or 7 minutes my heart rate was 95% plus of maximum. Mind you, my maximum heart rate is only 171 (167 by the 220-age formula), down considerably due to age. For the last 15 minutes I kept my heart rate at about 80% by adjusting the elevation on the treadmill and walking, so I’d at least exercise for the planned amount of time.

This extra fatigue could have been due to the nature of Saturday’s diving, tiredness from the exertion (i.e. not due to compressed air), fairly recent changes in diet, or maybe even the fact that I missed Saturdays’s run. I have completed the long run without difficult on other occasions even after diving the same day, so it may take some time to figure out what’s going on.

Guidelines for exercise and Scuba are usually in regard to the risk of Decompression Sickness (DCS), and usually go something like this:

1. Exercise before diving is OK, but heavy exertion immediately before diving is probably inadvisable.
2. Excess exertion at depth is to be avoided, as increased circulation will increase the perfusion of compressed inert gases, like Nitrogen or for deep diving, Helium, into the tissues of the body. It can also increase Carbon Dioxide levels in the bloodstream, which cause or aggravate Narcosis and CNS Oxygen Toxicity.
3. Light exertion on decompression stops is probably a good thing, as increased circulation will help flush those same compressed inert gases out of the body.
4. Heavy exertion on decompression stops or immediately after diving is potentially a bad thing as inert gas bubbles can pass from the venous to the arterial side of the lungs’ alveoli leading to Neurological DCS.

One 2006 study suggests that heavy post-dive exercise might be beneficial, although it was done on fit military divers and cautions that more study is required for average sport divers. Other articles more or less support what I’ve outlined above.

General fitness, which is why I’m running in the first place, is universally agreed to be a good thing. Aside from specific benefits in the prevention of DCS that are often mentioned, being fit means I’m less likely to be out of breath either underwater or on the surface, and able to respond to the demands that may be placed on me to handle difficult situations or emergencies.