Cardiovascular fitness, or aerobic fitness, involves how efficiently one’s system takes in, transports, and utilizes oxygen in the muscles and other tissues during exercise or physical exertion. The key component of cardiovascular fitness has to do with efficient oxygen utilization.
Once the intensity of exercise reaches a high enough point (this point differs for each person), the body cannot transport oxygen quickly enough for the demand of the effort. This exercise is said to be anaerobic, or absent of sufficient oxygen, whereas aerobic exercise involves utilizing oxygen efficiently.
When the system is able to transport sufficient oxygen to the muscles being used, the body is utilizing fat more than carbohydrate as a fuel source. Fat will only be used when exercise is at an intensity that allows the muscles to receive oxygen, when it is aerobic. When exercise intensity gets too high or into the anaerobic zone, the body starts using the limited supply of carbohydrate in the muscles and liver as its energy source. This type of exercise cannot be sustained for long durations and will usually cause exhaustion and carb cravings, and fat will stick around!
Increasing cardiovascular fitness significantly improves fat metabolism and fat mobilization. Cardiovascular fitness can be improved with regular physical activity. Depending on one’s beginning fitness level, exercise intensity should start low and increase gradually as fitness improves. The “fat burning zone” involves exercise done at a much lower intensity than many people assume. Therefore, if you are looking to lose fat and inches around the belly or thighs, you don’t actually need to push yourself quite as hard as you may think. The idea is to exercise for a longer duration at an intensity you can sustain for ideally 30 to 60 minutes and do this 3 to 5 times per week. This will yield the best results for improved fitness and metabolized fat. Walking or jogging for an hour where you can breathe very comfortably the entire time will be a much better fat burning effort than running as hard as you can for 20 minutes while huffing, puffing and feeling dizzy. The dizzy feeling and the need to stop and catch your breath indicate a lack of oxygen in the system, and the body is in the anaerobic zone, not the fat burning zone.
Cardiovascular Fitness Tests
Cardiovascular fitness tests can be done in a laboratory on a treadmill or a bicycle ergometer using the maximal oxygen intake (VO₂max) test. You can also estimate your aerobic fitness on your own with the Rockport Walking Test. The result of these cardiovascular fitness tests will be strikingly close to that you’d receive from a lab test. The value will be in milliliters per kilogram per minute and indicates your maximum effort. It is not ideal to continue to exercise at your highest effort level, but it is necessary to put in your maximum effort while doing the test.
Your VO₂max fitness measurement is largely determined by your genetics. Therefore, average increases from training are limited to around 20–25% for adults, but children and teenagers can have increases beyond 30%. Low cardiovascular fitness levels are represented by values under 35, medium fitness levels are 35 to 45, and high fitness levels are values over 45.
Fat Burning Zone
Your overall cardiovascular fitness level is also determined by your endurance, or how long you can sustain a certain exercise intensity. The training zone, or the zone where exercise is kept at an intensity where muscles are using oxygen and burning fat, is based on keeping your heart rate at a certain level. To be in the fat burning zone, you must keep your heart rate at a specific percentage of its maximum during exercise. You can estimate your maximum heart rate by using this equation:
Max Heart Rate = 220 – age.
For those at low fitness levels, or who have VO₂max scores under 35, the heart rate should remain at 60 to 75 percent of its maximum rate during exercise. As your cardiovascular fitness increases, you should also increase your percentage. For medium levels of fitness (scores 35 to 45), the percentage should remain at 70 to 85 percent. And for high fitness levels (VO₂max scores over 45), it should be 75 to 90 percent of your maximum heart rate.
Though monitoring your heart rate is a good way to estimate if you are exercising within your fat burning zone, a better and easier indicator is to use the Rating of Perceived Exertion (RPE) Scale. The RPE uses your perception of your breathing ease or difficulty to measure your exertion on a scale from 6 to 20 and estimates how long you’ll likely be able to sustain the exercise. To burn fat in an exercise session, it is important to sustain the elevated heart rate for 30 to 60 minutes, where you might rate your exercise intensity and breathing at a 12-14 on the RPE Scale (see below).
Improving Cardiovascular Fitness
Improving cardiovascular fitness involves exercising in your fat burning zone, or keeping your heart rate at the correct percentage of its maximum during exercise and checking in with your breathing to monitor your perceived exertion. This way, you can be certain that you are working at an intensity that you can sustain.
After you’ve worked at your exercise program consistently for a few weeks, check your heart rate directly after an exercise session and see if it is lower than when you began the program. Do this several more times and if each of these sessions turns out a lower heart rate than when you started the program, you can begin increasing exercise intensity. You can jog a little faster, a little harder, while maintaining the same duration as before. Do this at several stages in your exercise program and adjust for improved breathing and heart rate, and you will increase your aerobic fitness. You can even re-test for your VO₂max score a bit further into your program.
Remember to monitor your breathing ease or difficulty and try to stay at a comfortable intensity that allows oxygen to be used efficiently. Please note that before starting any exercise program--especially if you’ve been inactive for a long time--it is very important to have a doctor do a physical examination and give you the go ahead for an increase in your activity level.
A Little Means A Lot!
A little exertion can go a long way, provided that it is done regularly and at a sustained duration. You may also be able to get the same effect by increasing and decreasing intensity at intervals. More meticulous monitoring of perceived exertion or heart rate may be necessary for exercise involving intervals. Either way, slip on some jogging shoes and get out there for 30 to 60 minutes 3 to 5 times a week. Or go for a moderate hike or do some laps in the pool for half an hour. This minimum effort will put you on the fast track to a strong and efficient cardiovascular system, a lean body, and a happy attitude. The difference in the way you look and feel will be amazing; the fat will burn right off! Your energy, your body, your life--are worth it!
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