Regular physical exercise is essential to meet the demands of diving. However, there is a rumor that doing sports is not compatible with a diving vacation. A reader of the Dekoblog asked this exact question: Is it permitted to do sports during a diving vacation, and if so, what should you be aware of? This article has the answers.
Fitness as the key to safe scuba diving
Diving requires more than just technical skills and theoretical knowledge - it also requires a good physical and mental fitness. Sufficient fitness is crucial to safely cope with the usual demands of diving as well as unexpected challenges (currents, emergencies, stress situations). If you exercise regularly and keep your heart rate above 70% of your maximum heart rate - for at least 90 minutes per week - you can assume that you have sufficient physical stamina for recreational diving under various conditions.
But what is the effect of exercise immediately before or after a dive? It all depends on the right dosage and timing.
Effects of physical exertion immediately after diving
Intense physical exertion immediately after diving can significantly increase the risk of decompression sickness (DCS), especially in the first hour after surfacing. This is primarily due to the fact that supersaturation with inert gases is highest during this phase and therefore the probability of gas bubble formation is greatest. Various mechanisms further increase the risk of DCS during this phase:
Increased shunting at the lung level is one of the main reasons for an increased risk of DCS after intense physical exertion. Normally, microbubbles produced during ascent are filtered out in the lungs before they enter the arterial circulation. However, physical exertion can change the blood flow in such a way that more bubbles bypass this filter and enter the systemic circulation (shunting).
Remarkably, pulmonary right-to-left shunts have been observed more frequently not only during intense exercise, but also under all other types of stress. The release of stress hormones in itself can increase the likelihood of shunting. This could explain why not only physical exertion but also stress in general can increase the risk of decompression sickness after a dive.
A further risk is posed by a patent foramen ovale (PFO), a small connection between the atria of the heart, which is found in a proportion of the population. When breathing under pressure, the pressure in the right atrium can increase, which leads to microbubbles being forced into the left atrium, entering the arterial circulation directly and triggering symptoms. This is the case with exertion. Therefore, if a PFO is present, heavy lifting after a dive should be avoided. However, most people do not know whether they have a PFO or not. This is why you should wait several hours after a dive until the next weight training session. This is not possible during a vacation where you dive several times a day. In addition, residual saturation is always to be expected during non-limit diving, which is why weight training is not compatible with such a vacation.
No weight training after dives!
There are also hints that mechanical movement can contribute to the formation of bubbles. It is speculated that, similar to shaking a bottle of mineral water, strong movements cause existing microbubbles to grow, multiply, detach from the vessel walls and enter the circulation.
For these reasons, it is strongly recommended to refrain from intensive physical activity after a dive. Especially in the first hour after surfacing, physical exertion should be avoided and the body should be given time to desaturate from inert gases. Ideally, an even longer period of rest should be taken before any major physical exertion is performed. However, light activity can support desaturation by stimulating circulation. Just sleeping after a dive is probably not a good idea either.
Benefits of training before a dive
While physical exertion after diving can be a problem, there is a positive effect of endurance exercise in the days and hours before a dive. The exact mechanisms are not yet fully understood, but it is thought that regular physical activity has a stabilizing effect on the vascular walls and influences the metabolism in such a way that bubbles either develop less or their effect on the body is reduced. Another possible beneficial effect is a reduced inflammatory response that can be triggered by blisters in the bloodstream.
A moderate endurance workout before diving may be beneficial.
There is evidence that regular endurance training can generally reduce the risk of decompression sickness. In addition, smaller studies suggest that even moderate endurance training up to one hour before the dive can have positive effects. However, this immediate protection does not last for an unlimited period of time - studies suggest that the protective effect of endurance exercise lasts for a maximum of 48 hours.
First and foremost, it makes sense to exercise regularly in order to benefit from the general positive effects of endurance sports in the long term.
Dehydration and diving: An underestimated risk factor
In addition to a carefully considered training strategy, adequate hydration is also crucial. Dehydration can increase the risk of decompression sickness as it changes the flow properties of the blood (rheology). Increased blood viscosity can slow down the desaturation of inert gases and promote the formation of gas bubbles, particularly in the inner layer of blood vessels.
Many divers underestimate the fluid loss caused not only by diving itself, but also by physical activity on land. Those who also do sport in hot regions can become severely dehydrated without realizing it.
Another factor is the consumption of alcohol, which can further increase dehydration. If you do a lot of diving, you should moderate your alcohol consumption.
Beware of dehydration!
To counteract these risks, divers should drink enough water before and after each dive. Especially those who are active in hot regions should adjust their fluid intake accordingly. A good rule of thumb is to drink water regularly throughout the day and look out for clear signs of dehydration - such as headaches, dark urine or dizziness. During intense physical activity in warm climates, it can also be useful to consume electrolyte-containing drinks to balance your mineral intake.
Optimal training strategies for divers
In order to minimize the risk of decompression sickness and at the same time benefit from the advantages of physical fitness, divers should adapt their training routine accordingly. Endurance sports such as running, swimming, cycling or rowing are particularly recommended as they promote cardiovascular fitness and improve the body's ability to handle gas exchange processes efficiently.
Light strength training can increase general physical performance, but should not be done immediately after a dive. Particularly intense efforts such as interval training can lead to temporary exhaustion before a dive and impair physiological adaptation to the dive. It is therefore advisable to refrain from very strenuous physical activity at least one day before diving.
Moderate endurance training in the 24 hours before a dive, on the other hand, is not a problem and can even have a positive effect on the risk of decompression sickness. It is crucial that the body has sufficient time to recover and that it enters the water well hydrated. It is therefore advisable to plan sporting activities at least 4 to 6 hours before the dive.
Conclusion
Fitness is a crucial factor for safe diving, but the timing of physical activity plays an important role. While endurance training in the days before a dive can reduce the risk of decompression sickness, intense physical exertion immediately after diving increases the risk of DCS.
Another often underestimated risk is dehydration, which is aggravated by exercise, hot climates or inadequate hydration and can further increase the risk of DCS. Divers should therefore not only have a well thought-out training strategy, but also ensure that they are adequately hydrated in order to guarantee their safety. In particular, strength training immediately after a dive should be avoided strictly.
Literatur
1) Eldridge MW et al. Exercise-induced intrapulmonary arteriovenous shunting in healthy humans. J Appl Physiol 97: 797-805. 2004
2) Powell MR et al. Decompression gas phase formation in simulated null gravity. SAE Transactions, Vol. 104, Section 1: Journal of Aerospase (1995), pp. 834-84.
3) Imbert JP et al. Static Metabolic Bubbles as Precursors of Vascular Gas Emboli During Divers’ Decompression: A Hypothesis Explaining Bubbling Variability. Front. Physiol., 11 July 2019.
4) Diving and subaquatic medicine. Edmonds et al. 5th edition. 2016.CRC press
5) Lovering et al. Intrapulmonary arteriovenous anastomoses in humans –response to exercise and the environment. J Physiol 593.3 (2015) pp 507–520.
6) Wisloff et al. Exercise and nitric oxide prevent bubble formation: a novel approach to the prevention of decompression sickness? J Physiol.; Mar 16 2004; 555 (Pt 3): p825-829.
7) Blatteau J.E. et al. Aerobic exercise 2 hours before a dive to 30 msw decreases bubble formation after decompression. Aviat Space Environ Med.; Jul 2005; 76(7): p666-669.
8) Castagna O. et al. Endurance exercise immediately before sea diving reduces bubble formation in scuba divers. Eur J Appl Physiol.; Jun 2011; 111(6): p1 047-1 054.
9) Carturan D et al. Circulating venous bubbles in recreational diving: relationships with age, weight, maximal oxygen uptake and body fat percentage. Int J Sports Med. 1999; 20(6): 410-414.
7. Pollock NW. Aerobic fitness and underwater diving. Diving Hyperb Med. 2007; 37(3): 118-124.
Comments