Warming up before a dive could make a diver more susceptible to decompression sickness. However, warm ups should be done before the usual exercises that are necessary to keep a diver in excellent physical condition. In these cases, the warm up makes the person more resistant to injury.
Getting warmed up for exercise means one thing in particular and it’s not what most people think. Stretching is not a warm up. And, some very common activities done for warm ups in exercise classes are not warm ups either. Should divers warm up? The answer is yes for some things and probably no for others.
What Is A Warm Up?
Warming up means doing enough muscular work to raise your body temperature several degrees. You literally get warmer. People usually call just about any preparatory activity a warm up but if you want to be in the know, use the term to specifically mean getting hot under the collar.
About 75 percent of all the energy you expend by moving around, digestion and every other body process converts to heat. You wouldn’t want to own a car only 25 percent fuel efficient but human inefficiency works in your favor to heat you to 98.6oF (37oC) at rest. Continuous muscular work above resting levels, using large muscles, converts more mechanical energy into heat, which increases your temperature.
What Is Not A Warm Up?
You won’t raise your body temperature with deep breathing, arm waving or small muscle activity. And, warming up doesn’t mean just moving any muscle. For example, in many exercise classes you start out rising up and down on your toes, supposedly to warm up your calves. Or, maybe you’re instructed to bend and straighten your elbows. Worse yet, you may start with stretching. These are not warm up activities. Stretching doesn’t make you warm. (More on this a little later.) Your bicep and calf muscles are too small to contribute enough heat to warm your body. Starting out with small muscle activities will only poop you out before you can get some real exercise started.
Why Warm Up?
Warming up changes your body in several ways that make exercise orthopedically safer and lessen the chance of cardiac abnormalities. When above resting body temperature, your muscles become more pliable, more injury resistant and can work faster. Increased body temperature enhances diffusion of oxygen, carbon dioxide and metabolites to and from tissues. Blood viscosity lessens and blood vessels widen, slightly reducing resistance to blood flow in muscles, including the heart. Beginning intense activity abruptly, without adequate warm up, can leave your heart without enough blood and oxygen. In a study of men with chest pain accompanying exercise (because of narrowed heart blood vessels), warming up increased the length of time they could walk before the onset of chest pain.
How Does Warming Up Work?
Your body’s chemical processes are very sensitive to small temperature increases. The enzyme reactions in your cells that produce energy and control body functions speed up proportionally as your body temperature rises. A 10oC rise would double the rate of enzyme reactions. This is called the Q10 Effect. Of course, your internal temperature could never change ten degrees without severe health consequences. But, the two to four degrees that a warm up raises your temperature uses the Q10 Effect to boost athletic performance.
Who Doesn’t Need A Warm Up?
You won’t benefit by warm up exercises if you’re a lizard. Lizards are cold blooded, meaning they can’t change body temperature on their own. They have to lie in the sun before they’re hot to trot. Their internal temperature changes as their environment changes so they are called poikilotherms (poy’-kill-oh-thurms), which means variable temperature. Warm blooded beasties like us maintain remarkably constant internal temperature at rest so we are called homeotherms (home’-ee-oh-thurms), which means same temperature.
Like lizards, scuba divers may not benefit from warm up activities. Higher body temperatures increase gas perfusion both in and out of the body. Lower temperatures inhibit nitrogen uptake and elimination. A study of hot water suited versus wetsuited divers found the colder divers in wetsuits were less likely to develop decompression sickness. Another study, using Doppler bubble scores as an indication of decompression stress, found an increase in bubble scores following dives where the diver was warm throughout, compared to cold.
Being warm or cold at different stages of your dive also seems to matter. A diver starting a dive warm could absorb more nitrogen than in a cooler thermal state. If that diver then chills, which is common toward the end of a dive, eliminating that additional nitrogen gas burden slows, increasing the risk of decompression sickness.
Although at this point the argument against warm ups for diving is mostly theoretical, the thermal effect on gas dynamics may outweigh any benefit that warming up could have to reduce foot and leg cramps. To reduce possible cramping keep in good physical condition, maintain good foot, ankle and hip flexibility, wear properly fitting fins and regularly swim with fins.
How To Warm Up
It seems you don’t want to raise your body temperature through warm up exercises as preparation for diving. However, for the regular exercise you need to keep in shape for diving, warming up is the way to start.
You can warm up for exercise in three ways: active direct warm up, active indirect warm up and passive warm up. An active direct warm up is the same activity as the actual exercise but at a lower intensity. For example, fast walking warms you for jogging. Slow jogging warms you for running. Slow cycling warms you for faster cycling. Slow swimming is a good warm up for pool training.
An active indirect warm up uses any large muscle activity, such as pedaling a bicycle. In an exercise class look for rhythmic leg motions that use the hip and knee, without concentration on small muscle activity such as arm movements and calf raises.
A passive warm up is getting in a sauna, steam or conventional hot bath. This will raise your body temperature, although passive warm up lacks all the circulatory benefits of active exercise. That’s not to say passive warm ups aren’t useful. Hot steamy showers give people with arthritis or other injuries a head start on muscle heat they need to reduce pain and increase range of movement enough to start exercising.
How Do You Know When You’re Warmed Up?
You’re warm when you break into a sweat. It takes about ten minutes of exercise at any given intensity to reach a steady muscle temperature so give your warm up five to ten minutes.
Is Stretching A Warm Up?
Only by a stretch of the imagination is stretching a warm up. Stretching will not raise your body temperature so it’s useless as a warm up. Moreover, stretching while you are still cold can microtear and weaken your muscle fibers. People damage themselves over time with five main stretching mistakes. The first is not waiting until after you are warmed up to stretch. Next month will cover the five great stretching mistakes in detail so stay tuned.
Here’s What To Do
To get warmed up start with large muscle exercises that move upper legs and hips. Large muscle activity converts more mechanical energy into heat. A warm up is most efficient when you do the large muscle exercises yourself. Start off easy then gradually increase the work. If anything hurts or doesn’t want to move, slow down. Spend five to ten minutes warming up and continue until you break into a sweat. Don’t stretch until after you’re sweating. Most important, have fun so that you’ll look forward to the next time.