Saturday, December 10, 2016

Basics of VO2 Consumption

The measurement of energy expenditure in an individual can be applied to learn the energy cost of different tasks at rest and at exercise. This information is useful to know how your body is responding to exercise and how efficient or inefficient an exercise program is. One of the ways to measure energy expenditure is measuring oxygen consumption, an indirect calorimetry method1.

Oxygen consumption (VO
2) can be measured in a variety of ways to express energy expenditure. The first (VO2 (L∙min-1)), is measuring liters of oxygen consumed per minute. The second (VO2 (ml∙kg-1∙min-1)), is measuring milliliters of oxygen consumed per kilogram of body weight per minute. This may also be referred to as relative VO2. The latter can be used to compare two values between people of different body size. When referring to activities such as walking and running, relative VO2 is commonly used because they are weight bearing activities1.

When individuals train to increase their endurance, they are training to increase their maximal oxygen uptake (VO2 max) 1. VO2 max is the limit for endurance performance and is an important measurement of peak performance in elite athletes2. A common measure of VO2 max is 44 ml∙kg-1∙min-1 in males, and 37 ml∙kg-1∙min-1 in females, aged 20-29.  Maximum oxygen uptake is produced by cardiac output and systemic oxygen extraction. Cardiac output is the product of heart rate times stroke volume. The systemic oxygen extraction (a-v O2 difference), is a measurement of how much oxygen is used by the tissues after it is removed from arterial blood1.

VO2 max = maximal cardiac output x (maximal a-v O2 difference)

Therefore, an increase in VO2 max is due to either an increase in cardiac output or an increase in the a-v O2 difference. These increases are not arbitrary, they are a result of progressive overload. The individual must train at a level they are not accustomed to in order to make changes to their VO2 max. A great way to increase VO2 max in an individual is to program endurance training that utilizes dynamic exercise with large muscle mass at an intensity of greater than 50% VO2 max1.

This information can be very useful in determining responses to exercise, limitations of workout programs, adaptations of workout programs, and the effects of regular exercise throughout life.
1.    Powers, S.K. and Howley, E. T. Exercise Physiology. Theory and Application to Fitness and Performance. 2015; (9): 22-23, 282-283.

2.    Bassett, D. R., Howley, E. T. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exercise. 2000; 32(1): 70-84.

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