Previous tools used to measure fitness levels used to consist of comparing your height and weight against numbers on a large chart. Today, thankfully there are more sophisticated field and laboratory tests that health and fitness experts have devised giving a much more accurate picture of physical fitness. One fitness component frequently measured is cardiovascular capacity. How efficiently your body uses oxygen during exercise is a measurement of your VO2 max. The higher the VO2 max, the better your endurance, which means the longer and faster you can do any sport or activity. The most valid and reliable measurements of cardiorespiratory fitness uses computers to read and record all the different metabolic changes that occur while exercising. But these are time consuming, expensive and require rather sophisticated equipment and personnel. Alternative field tests have been created using a stop watch, a good pair of running or walking shoes, a measured distance, usually a track or treadmill and some good, old-fashioned maths equations. While these are not as accurate as the lab tests, they do give you a very good idea of your current cardio fitness level. The Rockport Fitness Walking Test is one such field test and is recommended by the American College of Sports Medicine. It is designed to approximate your VO2 max; the amount of oxygen per minute your body is able to use while exercising. The higher the VO2 max, the better your endurance. For sedentary individuals who are otherwise healthy, this is the safest test to measure cardiorespiratory levels. Warm up for at least 10-15 minutes by walking slowly on a flat surface and doing some light stretching. Then walk one-mile as fast as you can (use common sense; stop if you feel dizzy or have chest pains). After the mile, keep walking but slow the pace down. Take your pulse for 10 seconds and multiple by six to get your heart rate (or use a heart rate monitor). Now you need to do some math: VO2 max (L/min) = 6.9652 + (0.0091 x body weight in pounds) - (0.0257 x age years) + (0.5955 x gender/0 for female and 1 for male) - (0.2240 x mile walk time in minutes) - (0.0115 x ending heart rate). This gives you a VO2 reading in litres per minute. In order to compare your results to others you need to convert the VO2 max from litres to milliliters and change body weight from pounds to kilograms. Do this by multiplying the VO2max by 1000 and divide the body weight by 2.2046. Next divide this new VO2 max figure by your body weight in kilograms. For a healthy 35-year-old male, if your VO2 max is equal to or less than 34, then your fitness level is considered low; between 35-51 - moderate and equal to or greater than 52 is high. For a healthy 35-year-old female, if VO2 max is equal to or less than 27 than the cardiovascular fitness component is considered low, a VO2 max of between 28-47, fitness is moderate and anything over 48 is considered high or superior. A similar test involves running instead of walking. This is only recommended for people who are used to exercising or who run for at least 15 minutes without stopping. It is also best done at a track or on a treadmill where the distance is accurate. Warm up for 10 minutes with very easy jogging and some light stretching. Then run six laps of a 400 metre track or 2.4km on the treadmill maintaining a steady pace you can just keep up over the entire distance. Take note of the time it took to complete, then cool down for at least 10 minutes. For a woman between the ages of 30-39, anything 18 minutes or slower equates to a VO2 max of approximately 27 ml/kg/min; in other words, a poor cardio fitness level. For men between the ages of 30-39, a running time of 15 minutes or slower equates to a VO2 max of about 35 ml/kg/min, again a poor cardio level. Running faster than 12 minutes puts the men into an excellent category and anything faster than seven minutes, 11 seconds means you are in the top 1 per cent and have a VO2 max of about 59 ml/kg/min. For women a time of 15 minutes or better is good enough to have bragging rights regarding cardio fitness and anything of 10 minutes and 5 seconds or faster means your VO2 max is in that top 1 per cent. If you're still not sure of how to run these tests, ask a qualified fitness expert at your local gym.