LIMITATIONS OF VO2MAX

Topics: Exercise physiology, VO2 max, Muscle Pages: 16 (4361 words) Published: December 5, 2013
LIMITATIONS OF VO2MAX

INTRODUCTION
The maximum volume of oxygen that the body can consume, transfer, or employ during a given exercise is called VO2max. This indicates the physical well-being of an individual. However, a multitude of physiological functions limit a person’s endurance for exercise by limiting maximum oxygen consumption by the body (Katch et al., 2011). VO2max is used to determine the fitness levels, not only in athletes, but also in patients with heart failure, and is therefore both a prognostic and diagnostic tool. It is measured as ‘millilitres of oxygen used/Kg of body weight/per minute’ (Baechle and Earle, 2008). An average weighed healthy male usually has a VO2max of 35–40 ml/Kg/min approximately. Similarly, an average weighed female usually scores a max oxygen consumption of 27–31 ml/Kg/min approximately (Heyward, 2006).

The table below displays standard VO2max classification ranges for both men and women. VO2max (mL•kg-1•min-1) Classifications for Women (Skinner, 2005)

Age (years)
Poor
Fair
Good
Excellent
Superior
20 – 29
≤ 35
36 – 39
40 – 43
44 – 49
50+
30 – 39
≤ 33
34 – 36
37 – 40
41 – 45
46+
40 – 49
≤ 31
32 – 34
35 – 38
39 – 44
45+
50 – 59
≤ 24
25 – 28
29 – 30
31 – 34
35+
60 – 69
≤ 25
26 – 28
29 – 31
32 – 35
36+
70 – 79
≤ 23
24 – 26
27 – 29
30 – 35
36+

VO2max (mL•kg-1•min-1) Classifications for Men
Age (years)
Poor
Fair
Good
Excellent
Superior
20 – 29
≤ 41
42 – 45
46 – 50
51 – 55
56+
30 – 39
≤ 40
41 – 43
44 – 47
48 – 53
54+
40 – 49
≤ 37
38 – 41
42 – 45
46 – 52
53+
50 – 59
≤ 34
35 – 37
38 – 42
43 – 49
50+
60 – 69
≤ 30
31 – 34
35 – 38
39 – 45
46+
70 – 79
≤ 27
28 – 30
31 – 35
36 – 41
42+

The Fick principle (West, Schoene, and Milledge, 2007) states that oxygen uptake is dependent upon central oxygen delivery and peripheral tissue extraction. The oxygen uptake of the subject must equal the product of pulmonary blood flow and arteriovenous oxygen content difference.

VO2 = Q (Cao2 - Cvo2)
Q: Cardiac output
Ca: arterial oxygen content
Cvo2: venous oxygen content

This essay will describe and discuss the mechanisms involved in the limitation of VO2max, the concept of a central governor, classical view and new concepts of VO2max limitation, factors affecting athletic performance and whether VO2max is a true indicator in predicting an athlete’s performance. CENTRAL LIMITATIONS OF VO2MAX

The argument regarding the central limiting factor of maximum oxygen consumption states that it is the cardio-respiratory mechanisms of the body that are responsible for producing fatigue through limiting the delivery of oxygen to the exercising muscle. However, oxygen utilisation can also be limited by the Kreb’s cycle because of its rate limiting enzymes, or the mitochondrial inability in utilising oxygen also poses to be a limiting factor for VO2max (Kolkhorst and Buono, 2004). Stroke volume, heart rate, cardiac output, and pulmonary limiting factors in the muscles are all considered central features in limiting the maximum oxygen consumption (Raff, 2003). In addition, some pulmonary factors like red blood cells’ capability of carrying oxygen is also considered central.

PULMONARY AND CARDIOVASCULAR SYSTEM AND VO2MAX
It has been proposed initially by Bassett and Howley (2000) that the individuals with more training experience have additional cardiac output, and such individuals are able to operate with even less oxygen saturation. It is also argued that, in elite athletes, decreased transportation time of the RBCs in the pulmonary vessels causes oxygen desaturation in the arteries due to increased cardiac output. Moreover, increase in flow rate occurs due to increase in volume of blood flow in the vessels or capillaries having constant diameter (Pelliccia et al., 2002). If flow rate is so fast, then red blood cells will surpass oxygen hurriedly to the haemoglobin, which will result in less saturation of...

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