Energy to Burn on Your Next Dive

How to keep your energy level as high as it was on the first day of your dive trip.

- by John Francis

Silent Stickup: How You Lose Energy Without Knowing It | Stay Warm | How to Stay Warm in the Water | How to Stay Warm Between Dives | Swim Smart | Breathe Better | Travel Relaxed

Eat, Dive and Lose Five Pounds! | Take a Mid-Week Break | The Feel-Good Gas | Silent Hypothermia | More Energy Thieves

It's not uncommon to feel so wiped out by the third day of a dive vacation that you miss dives to take naps and don't really feel like pulling on that wetsuit again. You'll kick yourself after you get home. But right now, you'd rather flop into a hammock.

Where did all your energy go? How can you keep your energy stores high so you don't miss those dives you paid so much for?

Silent Stickup: How You Lose Energy Without Knowing It

Where did all your energy go? You burned it, but not in ways you'd notice--ways that work up a sweat.

• Heat loss is probably the biggest energy thief. Its effect is pretty obvious in cold water, where two dives a day is enough for many. What's surprising is that warm tropical water can actually take more heat out of you in a day than colder water can. Fooled by its apparent warmth, you don't protect yourself as much and you stay in longer.
• Swimming in scuba gear seems almost effortless because of your apparent weightlessness. But water is 800 times denser than air, creating 800 times more resistance to every movement you make. Finning along the reef, you're focused on the bright colors and interesting life, not on the work you're doing. Sweat doesn't run into your eyes to remind you of it. But four hours a day of this is strenuous compared to the sedentary lives most of us lead.
• Breathing is a muscular activity that requires energy just like any other. Breathing dense compressed air, through the resistance of a regulator, increases the workload of every breath. You're not aware of it, you don't feel tired from breathing, but it's a stress you're not used to, and it burns extra energy.
• Travel itself is fatiguing. It's no surprise that humping your dive gear through airports drains energy. But discomfort, dehydration and anxiety also take a toll. Even after you arrive, adjusting to different time zones and different eating and sleeping patterns also cost energy.

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Stay Warm

Water at 80F feels warm, but it's not. When water is in contact with your skin, especially when its flow can disrupt the boundary layer next to your skin, it is very effective at sucking away heat. Immersion in 80F water causes the same rate of heat loss as exposure to 42F air.

The loss of even two degrees of temperature in your body core brings on mild hypothermia. The chief symptoms of mild to moderate hypothermia are fatigue, mild confusion, impaired coordination and a reluctance to dive.

Heat lost is energy lost. Your body tries to cope by urging you to rest (you feel tired), by urging you to take on more fuel (your appetite increases) and by burning its fat stores. But your body's ability to generate more heat is limited. Basically, you have a fixed "bank account" of heat, which declines gradually through a week of diving. You have to spend it slowly both in the water and out of it.

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How to Stay Warm in the Water

You can conserve body heat in tropical water without having to bulk up on neoprene:

• Stop the flow. Keep water from flowing over your bare skin. A thin, full-length wetsuit will allow a boundary layer of water to form against your skin. This layer warms up, decreasing the temperature gradient at your body surface and therefore decreasing your rate of heat loss. Lycra and fleece skins are less effective than neoprene, however, because they usually leak badly. Often they pump water over your skin because they are not as flexible as neoprene. Pay special attention to sealing the neck opening of your suit.
• Wear a hood. Your body reduces its blood flow near your skin in order to reduce its heat loss. This happens everywhere except in your head, where blood flow--and heat loss--continue at full speed. That's why a naked human, submerged in water, will suffer 20 to 35 percent of his or her total heat loss through the head. And that's why wearing a hood is critical. If you object to the restriction of a hood, wear a tropic-weight beanie--it's shaped like a bathing cap and intended for warm-water diving.
• Insulate your torso. If you need more warmth, put most of the neoprene on your torso, where you need protection most and flexibility least. Still, don't forget to at least cover your arms and legs. A thin full-length wetsuit with a neoprene vest worn over it may be a good combination.

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How to Stay Warm Between Dives

It's easy to lose more heat between dives than in the water. If you've ever rushed to get back in the water so you can "warm up," you've been there.

• Stop wind chill. During a breezy surface interval, your wet exposure suit becomes a radiator, chilling you as it dries. Take your wet suit off or towel it off, and put on a windbreaker.
• Wear a hat. You lose a disproportionate amount of your body heat through your head, especially if your hair is wet. Even a baseball cap will stop the flow of air over your head and keep you warmer.
• Dress warmly. Yes, you came to the tropics so you could escape clothing. But if the air temperature is below 90F, you will lose body heat unless you cover up. If you dress a little on the warm side of the comfort zone, you'll conserve heat (and energy) for what you came for--the diving. Light, long-sleeved shirts and pants will keep heat in and also protect you from the sun and the bugs.

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Swim Smart

Finning in scuba gear consumes more energy than you realize. In fact, you are a very poor shape for hydrodynamic efficiency. Compare yourself to a dolphin: with arms, legs and head attached to the torso instead of incorporated into it, you have a much higher surface-area-to-volume ratio. Your mask, BC, tank, hoses and various attached gadgets all stick out at odd angles, creating turbulence.

You can't change nature and you can't discard all your equipment. But you can become a more efficient swimmer:

• Streamline your equipment. Take off your snorkel and put it in your BC pocket, or leave it on the boat. Figure out what else you can leave behind--you don't have to display your entire equipment inventory on every dive. Put what you can in pockets instead of leaving it to dangle. Reduce the lengths of your hoses where you can, and route them close to your body. Clip in your console and your octopus; when they hang loose they may harm the reef, and they certainly cause more drag. A BC sized properly for the amount of weight you're carrying, and for your body size, will have less drag than a bigger one.
• Drop weight. The less weight you carry, the less air you have to put into your BC to maintain buoyancy, and the less bulk you have to drag through the water. Most divers can drop two pounds or so.
• Get neutral. And get trimmed properly, so that when you're neutral you're horizontal. Being horizontal minimizes the size of the "hole" you have to make in the water when you swim. If you have to kick yourself up to maintain your depth, you are wasting energy by carrying weight with your fins and by presenting a larger frontal area to the water.
• Move slowly. Water resistance increases exponentially with speed. Swimming twice as fast requires four times as much energy. So all your movements, not just swimming, should be in slow motion.
• Kick within your slipstream. Keep your fins within that "hole" in the water made by your body. Wider kicks increase drag. It used to be said that large, slow kicks were more efficient than short, fast ones, but this is not necessarily true. Keep your fins within your slipstream and, if you have to go faster, increase the frequency of your kicks, not their size.
• Use efficient fins. Some fins deliver more thrust for a given effort than others. See past ScubaLab tests.
• Swim mid-water. Both the bottom and the surface cause turbulence that robs energy if you swim too near them. If you need to make a long surface swim, do it on your back so your fins will stay submerged for their full strokes.
• Manage currents wisely. Learn how to detect, avoid and cope efficiently with adverse currents. Read an article on diving in currents for more details.

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Breathe Better

Breathing at depth requires much more energy than at the surface. However efficient, every regulator presents some resistance to breathing. Denser air causes more friction. At two atmospheres, for example, there are twice as many molecules in a given volume of air, and twice as much friction. With every breath, your lungs have to drag this dense air through the regulator's demand valve, through the mouthpiece, and down your trachea to thousands of lung alveoli, then force it all the way back out again past another valve. But you can minimize the extra energy cost:

• Breathe slowly. Remember, friction increases exponentially with speed. Move the air slowly.
• Breathe deeply. The more complete each breath is, the fewer of them you have to take. Breathe "from the diaphragm," trying to completely fill and completely empty your lungs. Yoga breathing exercises are good training for breathing on scuba. For tips on breathing more efficiently, see the July 1996 issue or the web at www.scubadiving.com/ training/instruction/saveair.shtml.
• Use a high-performance regulator. Better regulators minimize the work of breathing. To read our reviews of regulators, click here.
• Maintain your regulator. They lose performance and increase work of breathing with use and age, and require regular maintenance. (The higher-performing units degrade the least between servicing.)
• Readjust your regulator. The purpose of the adjustment knob is not merely to prevent free-flowing on the surface. It's also to minimize work of breathing at depth. Periodically during your dive, open the valve until the regulator just begins to bubble, then back off on the adjustment a bit. You cannot save air by using the adjustment to increase breathing resistance. Just the opposite happens.

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Travel Relaxed

You already know how heavy your dive bag is, but that's only the beginning. Most of the stress of travel is hidden. Dry air and cramped seats on airplanes cause physical stress. So do unhealthy meals at irregular times, interrupted sleep patterns and changing time zones. Mental stress, over whether the wings will stay on the plane or the connection will be on time, may be even more significant.

Most of the stress-reducers are common knowledge for travelers: drink fluids, get up and stretch, minimize the alcohol, avoid tight connections. Some are especially important for divers:

• Pack dive gear early. There's always too much to do on the last day before a trip, increasing your fatigue and stress. Overhaul and pack your dive gear days beforehand.
• Put essentials in a carry-on. Dive resorts are often at the end of a third-world shuttle flight where same-plane arrival of luggage is not always possible. What is essential besides your C-card? Find out what's for sale or rent at your destination before you pack.
• Bring water. On airplanes, dry air, alcohol and coffee are dehydrating, and dehydration is a risk factor for decompression sickness. Bring a one-liter bottle of water in your carry-on luggage--and drink it.
• Lift as little as possible. Spring for a skycap (if you can find one). If resort personnel offer to carry your bags when you arrive, don't be macho--let them. Use gear bags or carts that have wheels.
• Don't dive immediately. It's tempting to squeeze in a dive as soon as you arrive, but your eagerness may cost you several dives at the end of the week. Instead, relax for the first few hours. Eat something, drink some water. Take a walk to get oriented. Let your body recover from the flight and get accustomed to a new climate and time zone. Take the time to unpack and assemble your dive gear carefully.

Of course nobody is going to do a perfect job of energy conservation all week. You're supposed to be on vacation, after all. But if you work it right you can enjoy almost every opportunity to dive.

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Eat, Dive and Lose Five Pounds!

The idea that you can lose weight by going on a tropical dive vacation is not entirely frivolous. Those who dive in paradise for a living frequently exhibit what's called "Dive Guide Syndrome": they're chronically tired, cold and hungry despite eating huge amounts of food.

That's because their constant exposure to diving robs them of energy faster than they can replace it. You don't see many overweight dive guides at busy resorts, do you?

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Take a Mid-Week Break

If you feel your energy and enthusiasm waning after the first few days of your dive trip, take an afternoon off. Play tourist and see the topside sights, read a book or take a nap.

A mid-week break accomplishes two things: It gives your body temperature a chance to recover. It lets you rest and replenish your energy stores. It also works to prevent decompression sickness by allowing your body to offgas bubbles. You may miss a dive or two now, but the remaining dives will be safer and a lot more fun.

 

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The Feel-Good Gas

Another cause of fatigue and energy loss is the work your body has to do to off-gas nitrogen. Authorities agree that decompression stress is real, but aren't sure how significant it is.

However, many nitrox divers believe that the gas leaves them less tired because its lower nitrogen content causes less decompression stress. No scientific studies have been done yet, but field experience has earned nitrox the nickname "the feel-good gas."

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Silent Hypothermia

Losing body heat not only makes you tired, it can lead to hypothermia. More than comfort is at stake here--hypothermia is a safety issue.

Much research has demonstrated that even mild hypothermia causes a significant decline in your ability to think through problems. Your manual dexterity can be impaired. And your ability to form short-term memory--such as what your SPG reading was a minute ago--is degraded. None of that is good in a life-threatening situation.

Hypothermia can occur even in 80F water, water that feels warm. Here, heat loss is so gradual that your body's defenses may not be triggered. You don't feel cold, you don't shiver, you don't gasp. Constriction of near-surface blood vessels, your body's main heat conservation mechanism, may not occur.

So-called "silent hypothermia" creeps up on you undetected. In fact, your feeling of fatigue and reluctance to dive may be your only warning of hypothermia. The cost can be a lot more than discomfort if you are faced with an under water emergency requiring quick, precise action.

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More Energy Thieves

Nothing will sap your energy like stress, and nothing creates stress on a dive like having to deal with problems such as seasickness, leg cramps and ear pain. Here are six thieves waiting to abscond with diving energy, and the best ways to stop them.

Energy thief: Ear pain
Citizen's arrest: Relax, ascend until you no longer feel any pain and then equalize. Resume your descent, slowly, making sure that you equalize continuously.

Energy thief: Leg cramp
Citizen's arrest: Stay calm and breathe deeply. If the cramps are in your calves, grab your fin tip on the affected side, straightening your leg and pulling on your fin to stretch the cramping muscles. To prevent leg cramps, try to switch kicking styles when swimming a long distance or against a current.

Energy thief: Seasickness
Citizen's arrest: Be one of the first divers in the water--most people feel better below the surface. If you're being buffeted by waves or surge once you're in the water, try to drop down to calmer, deeper water.

Energy thief: Nitrogen narcosis
Citizen's arrest: Stay calm and concentrate on ascending slowly and cautiously. The effects of narcosis dissipate rapidly at shallower depths and you can resume diving once your head clears.

Energy thief: Jellyfish sting
Citizen's arrest: Try to prevent stings by practicing good buoyancy skills and covering yourself with exposure protection. If you do get stung, try pouring vinegar on the affected area.

Energy thief: Jaw pain
Citizen's arrest: If you suffer from jaw pain when you dive, try a different mouthpiece on your regulator. One of the most popular is SeaCure's moldable mouthpiece, which allows you to customize it exactly to your bite.

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