Fitness, Diving and Dehydration

As times goes by, some of us are guilty of doing less exercise than we should. Others work hard at it. However, maybe those who exercise frequently should take a break from a physical fitness regime when on a scuba diving trip.

In his article about physical fitness for diving, Neal Pollock, research director at Divers Alert Network, writes that conducting intense physical exercise too close to diving activity can be problematic. "Bubble formation, while not equivalent to or a guarantee of decompression sickness, can indicate an increased risk for it. Intense physical activity -- generally with substantial muscular forces and joint loading, or the application of forces on joints -- is believed to transiently increase micronuclei activity, the presumed agent of bubble formation. Physical activity after diving may also stimulate additional bubble formation, possibly through a combination of increased micronuclei activity and increased joint forces.

Pollock recommends that intense physical training should be avoided 24 hours on either side of diving activity. "Any exercise within 24 hours of diving should involve the lowest possible joint forces." (You can read Pollock's entire article at www.diversalertnetwork.org/medical/articles/Juggling_Physical_Exercise_and_Diving).

Nobody would argue against keeping fit, but when a British coroner suggested this year that a police officer might have died while diving in Spain's Canary Islands last September because she was too fit, eyebrows were raised.

The coroner contended that, because Justine Barringer did a 40-minute run the night before her dive off Gran Canaria, possible dehydration might have caused a condition that triggers muscle damage, affecting organs such as the heart and kidneys.

The Telegraph reports that Barringer, a 44-yearold from Sittingbourne, England, lost consciousness 33 feet below the surface during an ascent on an Advanced Open Water course. She was completing her first "deep" dive to 88 feet. Attempts to revive her on the dive boat proved futile.

A subsequent post-mortem in the U.K. gave decompression sickness as the cause of death; however, it added that Barringer's recent exercise could have caused rhabdomyolysis, the breakdown of damaged skeletal muscle, which causes the release of myoglobin into the bloodstream. Myoglobin stores oxygen in your muscles. If you have too much myoglobin in your blood, it can cause kidney damage.

Simon Mitchell, head of the Department of Anesthesiology at the University of Auckland and now editor of the journal Diving and Hyperbaric Medicine, told Undercurrent, "For a fit and well person to become unconscious at 33 feet during ascent from an uneventful dive is extremely unusual. . . . It is not clear whether the ascent was normal, and the pathological basis for the speculation about rhabdomyolysis is not clear either."

Some argue that a 40-minute run would amount to little more than a warm-up for such an athlete. As usual, there are many conflicting theories offered and little actual evidence.

Was Barringer severely dehydrated when she went diving? Good hydration is especially important to scuba divers to reduce the risks associated with diving. Some diving doctors believe most people are dehydrated most of the time.

Although we are submerged in water when we dive, breathing dried and filtered air from a scuba tank can drain water from your body with each exhalation. Added to that is the effect of sweating in tropical weather. Mild dehydration can make you feel tired. Muscle cramps and headaches follow. So, it's important to drink plenty of fresh water and add re-hydrating powder during a dive trip.

And let's not forget the deterring effect of alcohol. It inhibits the pituitary secretion of the anti-diuretic hormone (ADH), which acts on the kidneys to reabsorb water. When ADH levels drop, the kidneys do not reabsorb as much water, and instead produce more urine.

So take it easy between dives, and drink plenty of water. And when it comes to alcohol, A couple drinks before dinner on a dive trip, followed by a good meal and water, will not cause dehydration. But add a bottle of wine to those two pre-dinner drinks and you may start causing problems for your next-day dives.

-- John Bantin