Originally posted on:
http://www.brothersiniron.com/phpBB2/viewtopic.php?t=12
VO2 max: What is it, Why is it so important, and how do you improve it?
by David Hampson
Exercise physiologists define VO2 max as your maximal rate of oxygen consumption. It is a measure of your capacity to generate the energy required for endurance activities and is one of the most important factors determining your ability to exercise for longer than four to five minutes. Improving your VO2 max by 10 percent without changing any other performance factors can take more than a minute off your 5k time, and is an essential factor in races from 800 meters to the marathon. Your sedentary VO2 max values are genetically determined. However, all individuals can make drastic improvements in VO2 max with the right training stimulus. Thus, to attain your best possible performances, VO2 max improvement is one aspect of your training that should not be ignored.
There are two ways to take VO2 max to its highest possible levels; increased volume and increased intensity. Studies show that sedentary people can improve VO2 max by over twenty percent when they begin a running program of 25 miles per week. By increasing mileage to 50 miles per week, VO2 max is improved a further ten percent. Unfortunately there are diminishing returns of VO2 max increases with increased mileage, so drastic improvements will not occur indefinitely. Based on the available research, it seems that maximal VO2 max gains are achieved with a weekly running volume of 60 to 90 miles. Although increases in weekly mileage have shown to be particularly effective at increasing VO2 max, it is important to remember that mileage should be increased gradually, with careful attention towards preventing over-training and injury. Also, VO2 max improvements only occur if you are keeping running intensity the same as you increase your mileage. If you increase your mileage, but slow down your daily running pace, little improvement will occur in VO2 max.
This brings us to the topic of intensity, the second method of enhancing VO2 max. Intensity has actually been proven to be more potent enhancer of VO2 max than volume. For VO2 max improvement to occur, training runs should be conducted at an intensity of at least 70 percent of VO2 max. Seventy percent of VO2 max corresponds to a pace that will bring your heart rate to 75-80 percent of maximum. Running at intensities close to 100 percent VO2 max is the best thing you can do to elevate your VO2 max. This corresponds to about two mile race pace, so unfortunately this intensity cannot be maintained for very long, and training this hard every day would quickly lead to over-training and/or injury. The best way to complete a significant volume of running at 100 percent of VO2 max is to use intervals of three to five minutes at 3k to 5k race pace with about equal recovery between each interval. By dividing your workload into intervals, you can run for more total minutes at 100 percent of VO2 max than if you attempted a continuous run. One interesting note is that running faster than 100 percent of VO2 max will not improve it more than running at 100 percent of VO2 max, and is likely to leave you more fatigued and unable to complete a high volume of work. Faster running is necessary to enhance other performance factors which I won't go into here, but when your focus in on enhancing VO2 max, a higher then 100 percent intensity should not be used.
Q & A on V02 Max
1. What are some different levels of VO2 max, and what do these numbers mean?
VO2 max values, typically expressed in ml/kg/min., can vary between 20 and 90 ml/kg/min. The average value for a sedentary American is about 35 ml/kg/min, while elite endurance athletes average about 70 ml/kg/min. Your sedentary VO2 max value is primarily determined by genetics (a sedentary person may have a VO2 max value as high as 50 ml/kg/min. or as low as 20 ml/kg/min). Although anyone can improve their sedentary VO2 max value through training, this genetic variation helps explain why everyone can't train themselves to be elite.
2. What are some of the highest levels of VO2 max ever recorded?
The highest VO2 max value ever recorded, 93 ml/kg/min, was from a Scandinavian cross country skier. Steve Prefontaine, at 84.4 ml/kg/min, had one of the highest VO2 max values recorded in elite runners. Grete Waitz had a VO2 max of 73 ml/kg/min. when she was running at her best, one of the highest recorded values for women and on par with the values for some elite men.
3. How do some elite runners make up for lower levels of VO2 max?
Although all elite runners have VO2 max values well above the population mean, the correlation between VO2 max and performance is not absolute. Derek Clayton only had a VO2 max of 69 ml/kg/min. and Frank Shorter only recorded a value of 71 ml/kg/min., yet both of these runners ran marathon times of under 2:11 and surely outperformed runners with higher values. This variation in VO2 max values among the elite is possible because VO2 max is only one of several factors that determine running performance. These other factors include mental attitude (ability to tolerate pain), running economy (how efficiently one runs), and lactate threshold (fastest pace you can maintain without accumulating large amounts of lactic acid in your blood). A runner with a relatively low VO2 max, but high in these other performance factors, could outperform a runner with a significantly higher VO2 max but with poor running economy and a low lactate threshold. For example, Derek Clayton and Frank Shorter compensated for their lower VO2 max values with their high efficiency and ability to run their marathons at a high percentage of their VO2 max without accumulating too much lactic acid (high lactate threshold).
4. Why do some people assimilate more oxygen than others?
Although there is still some debate among physiologists as to what limits VO2 max, the variation in maximal oxygen consumption in our population is likely determined by several factors. In order to produce the energy necessary for our muscles to contract at high rates, there must be a delivery system to bring oxygen to the working muscle cells as well as a means of utilizing this oxygen for aerobic respiration. The delivery of oxygen to muscle cells is limited by hemoglobin, the oxygen-binding protein in red blood cells (this is one of the reasons women tend to have lower VO2 max values than men), the number of capillaries surrounding each muscle cell, and the maximum volume of blood that the heart can pump each minute (cardiac output). The utilization of this oxygen is primarily limited by the amount of mitochondria available in the muscle cells to produce aerobic energy. It has also been theorized that utilization may be affected by the contractility of the muscle fibers. Muscle fibers with greater contractility can achieve higher work loads and thus utilize more oxygen.
5. How does oxygen play a role in the production of energy for aerobic exercise?
Oxygen is used by the mitochondria in the muscle cells as a reactant to produce ATP, the fuel for all cellular processes in our body. Although ATP can also be produced in the absence of oxygen (anaerobic respiration), it is a less efficient process yielding much fewer ATP and producing lactic acid as a byproduct. In addition, aerobic respiration allows our body to obtain energy by breaking down fats, which we have a much more abundant supply of than the 400-500g of carbohydrate stored as muscle glycogen.
6. Do other non-running factors that improve fitness (fat loss, increased muscle, etc. from cross-training) also increase VO2 max?
Other non-running factors that enhance fitness will not necessarily result in an increase in VO2 max. Since VO2 max is expressed in terms of body weight, a decrease in weight that is the result of fat loss can result in a significant increase in VO2 max. However, an accompanying loss of any of the muscles used in running can counteract this increase. Increasing muscle mass through weight training or some other non-running activity is unlikely to enhance VO2 max. This is because resistance training causes the muscle cells to grow larger without an increase in the number of mitochondria. This decrease in the density of mitochondria per muscle cell explains why an excessive body-building program can be counterproductive for runners who bulk up easily. However, this doesn't necessarily imply that increased muscle mass will never improve performance. Having a body that is balanced in terms of muscle strength may mean that you are injured less frequently, and thus able to train and race more consistently. It may also increase your running efficiency, so you use less energy to run at any given pace.
David Hampson is currently a student at Wake Forest University in North Carolina pursuing a degree in exercise science. His permanent residence is in Exeter, New Hampshire. He aspires to obtaining a doctorate in exercise physiology and possibly pursuing research in that field. He is an accomplished distance runner, competing in cross country and track for Wake Forest. His
PR's include 15:35 for 5 km, 32:35 for 10 km, and 54:57 for 10 miles.
from
http://www.coolrunning.com/major/97/...g/hampson.html
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