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Chapter 4- Diving Physiology Diving Physiology 143 See your physician before trying any new fitness program or exercises. Aerobic Fitness Aerobic fitness is the ability of your lungs, heart, and blood vessels to deliver O2 and the ability of your muscles and other cells to extract and use it. You need aerobic fitness for cycling, jogging, skating, dancing, hiking, rowing, swimming, fin-swimming, and walking along the beach to your dive site. Good aerobic fitness reduces your risk of heart disease, stroke, diabetes, high blood pressure, high cholesterol, cancers, and many other diseases in a variety of ways. Being in good aerobic shape is important, even if your diving is not routinely strenuous. Being in good aerobic shape increases your tolerance to cold. Your level of aerobic fitness is one of the most important determinants of your ability to tolerate activity in the heat. Aerobically fit people usually use less air than unfit people doing the same activity and are less likely to experience hyperventilation and panic stress reactions. For the times you need to get out of surf, or rescue yourself or a buddy, your fitness is critical, and the consequences of exhaustion are greater. Being fit increases your chance of survival after an accident. A good aerobic exercise program is one of the best things you can do to improve your personal health, diving health, and diving enjoyment. A highly effective way to get in shape for diving is regular fin swimming, combined with common scuba tasks such as entries, exits, and gear handling (figure 4-22). Other regular aerobic exercise, such as dancing, skating, cross-country skiing, jogging, biking, and swimming are important for general fitness. Exercise guidelines recommend exercise between 60% and 85% of your maximum heart rate, at least three times per week for at least 20-30 minutes a session. Maximum heart rate (in beats per minute) is often estimated by subtracting your age from 220, but is subject to individual variability, as is resting heart rate. There are other ways to estimate and directly measure your maximum heart rate. Another way to gauge your exercise intensity is how you feel. How you feel, called “perceived exertion” in exercise physiology, closely matches how hard you really are working. The effort does not have to be extremely hard or exhausting. Train in a range of exertion that you feel is moderately hard to hard. Your heart rate is often lower while swimming than doing comparable exercise on land. That does not necessarily mean you are getting less of a workout. You may be getting less of a workout if you only swish around in the water. But if you are doing good laps, your heart rate may still be lower than running laps on land, because of the effects of immersion. Heart rate is not the only indicator of work intensity. During immersion the amount of blood returning to your heart increases for several reasons, discussed at the beginning of this chapter in “Effects of Immersion.” Increased blood volume reflex- FIGURE 4-22. SWIMMING WITH FINS IS A GREAT WAY TO STAY IN SHAPE FOR DIVING.


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