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VO2 Max - "The Endurance Factor"

How it works -

Peak Oxygen Uptake or VO2 max - Your body's maximum potential

Peak oxygen uptake or VO2 max (VO2 - Volume of O2 consumed per minute) represents the ability of your heart, lungs, and circulation to deliver oxygen to your exercising muscles. It is a gauge of the maximum amount of energy output or work your body can produce at peak performance. You only reach your VO2 max for a brief moment as you near exhaustion. Your O max is determined by factors that include your current level of fitness, age, sex, body size, and heredity.

Anaerobic Threshold or AT - Your body's level of fitness or condition

The AT represents how efficiently your muscles use oxygen to produce energy or work. As such, the AT represents the level of work your body can sustain over an extended period of tome and is sometimes referred to as your "operational threshold" When your body is called upon to perform above your AT, lactic acid builds in the muscles creating fatigue and your ability to continue to perform at this level will be very limited (a few seconds to a few minutes depending on how fit you are). You can improve your anaerobic threshold by training at the proper intensity of exercise and conditioning. The closer your AT is to your VO2 max, the better your level of fitness.

Caloric Burn Rate & Fuel Type - other elements of your metabolic profile

Your metabolic profile yields two important variables.

1. The first is your caloric burn rate or the number of calories your body burns during each minute of activity. To put your caloric burn rate into perspective 3500 calories equates to 1 lb of fat. So if you want to lose 10 lbs., you'll need to increase the amount of exercise and/or reduce your food intake by a total of 35,000 calories to achieve your goal.
2. The second is the Fuel Type your body uses at various exercise intensities. At lower intensities (aerobic), you primarily utilize fat for fuel. At higher intensities (anaerobic), your body shifts to a less efficient form of quick energy and uses carbohydrates (sugars) as its primary source of fuel. The metabolic profile enables you to determine your optimal fat and sustainable caloric burn zone (exercise heart rate) to effectively manage your energy expenditure.

Respiratory Quotient (RQ) aka Respiratory Exchange Ratio (RER)

Carbohydrate, fat and protein all play a part in energy metabolism and for a certain volume of oxygen the energy released will depend upon the energy source. It is possible to know which particular fuel (carb, fat or protein) is being oxidized by calculating the RQ. RQ is the rate of carbon dioxide (CO2) produced to oxygen (O2) consumed.

If carbohydrate is completely oxidized to CO2 and water (H2O) then the relationships is as follows:

• 6O2 + C6H12O6 >> 6CO2 + 6H2O + 38ATP (Adenosine Triphosphate)
• RQ = 6CO2 / 6O2 = 1.0

If fat is completely oxidized to CO2 and H2O then the relationships is as follows:

• C16H32 + 23O2 >> 16CO2 + 16H2O + 129ATP
• RQ = 16CO2 / 23O2 = 0.7

A value between 0.7 - 1.0 indicates a mixture of fat and carbohydrate as the energy source. A value greater than 1.0 indicates anaerobic respiration due to more CO2 being produced than O2 consumed. Energy is primarily supplied from two sources:

• Carbohydrates - in the form of glycogen stored in the muscles
• Fat - stored around the body

During exercise we use a combination of these energy sources. At a high intensity the main source of energy is carbohydrate and at a low intensity, fat is the predominate source. As there is a limit to the amount of carbs that can be stored in the muscles, high intensity work can only be sustained for short periods. We have large stores of fat so low intensity work can be maintained for long periods of time. Therefore the metabolism of fat consumes a great deal more oxygen relative to the production of carbon dioxide than the metabolism of carbs.

How do you compare?? Normative data for VO2 max

A Guide to VO2 Max - showing VO2 Max In Athletes and Non Athletes