Most, if not all, scuba-diving manuals urge divers to stay physically fit as part of their readiness for diving. Being a fit diver helps reduce your gas consumption during a dive, helps you fight against a current, lets you dive longer with less physical strain, and reduces your risk of decompression illness (DCI).
With all the advantages of physical exercise, many divers do seek to boost their physical fitness levels through training. However, while it is important that you do exercise, when you exercise in relation to your diving may be equally important. If diving is your priority, you’ll want to schedule your fitness routine to accommodate your scuba diving, especially if you’re planning an active vacation, where you’ll be participating in other physical activities as well, such as hiking, biking or kayaking.
For the purpose of this article, “exercise” is defined as a physical activity that exceeds the exerciser’s current capacity, in order to trigger a response in the body that improves physical fitness. This is what is known as progressive overload. While scuba diving may require a diver to undertake some physical strain, such as carrying tanks to a boat, it’s typically not intense enough workout, nor a long enough workout to trigger progressive overload.
Performing strenuous exercise right before scuba diving, however, may result in dehydration and muscle fatigue, which can be problematic when you’re underwater. As for the increased risk of DCI posed by exercise before scuba diving, the picture is a bit muddled. Some studies have shown a potential increase in risk of DCI, especially if the exercise is quite challenging and includes a lot of muscular activity, as found in strength training, or impacts heavily on the joints, such as running and other cardio. Other studies seem to indicate that exercise right around 24 hours before scuba diving might have some preventative effect on the risk of DCI. However, this effect is largely unproven. In any case, it is wisest to avoid strenuous exercise 24 hours before diving, and this is also what the Divers Alert Network (DAN) recommends.
As for exercise after diving, the statistics are a little more clear-cut. Studies have shown an increase in the presence of microbubbles in test subjects’ bloodstreams after intense exercise, which are indicators, though no guarantee, for risk of DCI. We already know that a diver who is physically fatigued during a dive is at an increased risk of DCI; hence the dive-table recommendation for calculating the dive as being longer and more challenging than it actually is. It’s only natural to assume that this same calculation, to some extent, also comes into play after diving, and so follows the recommendation to avoid physical strain after a deep dive.
In short, while there haven’t been any reported cases of DCI that have, without a doubt, been caused by exercise after diving, the general recommendation is to avoid hard exercise for 24 hours before to 24 hours after scuba diving, especially when doing long, deep, or repetitive dives. For the vacation diver, this is usually possible, and is a perfect excuse for a siesta. For the occasional diver, this is hardly a huge issue, either, as a workout schedule can easily be made to accommodate weekend diving. Dive professionals, however, will want to be careful — physical fitness is important, but tailoring your workout around your diving is important, too.
