VO2max

The monthly newsletter of RunCoachJason.com

Jason Karp, professional coach, consultant, freelance writer

November, 2005

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In this issue:

Integrating Science with Application—Muscle Fibers

Pep Talks

Limits of VO2max

Public Speaking

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Integrating Science with Application—Muscle Fibers

Ever wonder why some athletes can sprint faster than others or why others can hold a hard pace for long periods of time?  The answer may reside in your muscles. 

 

Humans have 3 different types of muscle fibers (as well as gradations between the 3 types).  Slow-twitch (ST) fibers, with lots of mitochondria, capillaries, and aerobic enzymes, are used for endurance activities.  Fast-twitch (FT) fibers, which are divided into fast-twitch A (FT-A) and fast-twitch B (FT-B), are used for anaerobic activities.  FT-B fibers, with lots of glycolytic enzymes, creatine phosphate, and glycogen, are used for short, quick bursts of activity.  FT-A fibers, with both glycolytic and aerobic enzymes, represent a transition between the two extremes of ST and FT-B fibers.  Studies on identical twins have shown that muscle fiber composition is greatly determined by genetics.   

 

Everyone knows that distance runners have a greater proportion of ST muscle fibers, while sprinters have more FT fibers.  Even within a group of sprinters or distance runners, there is variability in the fiber types.  Not all sprinters have the same percentage of FT fibers, nor do all distance runners have the same percentage of ST fibers. 

 

Distance runners with lots of ST fibers (80-90%) are more suited for a large amount of aerobic work (high weekly mileage and lactate threshold training) and long races (marathon), while distance runners with less ST fibers (60-70%) would benefit more from moderate mileage and more intensity and are more suited for shorter distance races (1,500 meters, 3,000 meters).  For these latter runners, it would take years of a lot of aerobic work before they can become just as good at the longer distances. 

 

You may have seen tables in books that give “equivalent performances” for various races.  One of the best uses of these tables is to show you where your strengths are.  Acknowledging fiber type as a key component to racing success, it is unlikely that you will be able to run equivalent performances for every race from the mile to the marathon.  (If that were the case, the world record holder for the mile would also hold the world record for the marathon.)  While athletes should try to improve their weaknesses, they should train with greater emphasis on their strengths.      

 

Although you cannot convert one fiber type to another, the metabolic characteristics of muscle fibers can adapt specifically to different types of training.  For example, with endurance training, FT-B fibers can take on some of the endurance characteristics of FT-A fibers and, with sprint training, FT-A fibers can take on some of the speed and power qualities of FT-B fibers.  Training can also change the amount of area taken up by a fiber type in a muscle.  For example, an athlete may have a 50/50 mix of FT/ST fibers in a muscle, but since FT fibers are larger than ST fibers, 60% of a muscle’s area may be FT and 40% may be ST.  After months or years of endurance training, the area of the muscle may change to 40% FT/60% ST even though the number of FT and ST fibers remains the same (50/50).  Consequently, endurance of the muscle has improved. 

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Pep Talks

(excerpted from Karp, J.R. I’ve Written the Training Program, Now What Do I Do? Track & Field Coaches Review. 74(2):17-21, June 2001.)

 

As a coach, one of my favorite things to do is give pep talks.  The pep talk is a lost art.  But it is one of the most important things for a coach to do when getting his or her athletes ready for competition.  What the coach says and how he or she says it can have a dramatic effect on the athletes.  The pep talk represents the coach’s last chance before competition to motivate and inspire his or her athletes to do things that they never thought possible.  

 

We all want to win, but it is important that the coach emphasize during the pep talk the importance and significance of performing at your best, even if you don’t win.  In the U.S., we put a great emphasis on winning, but success should not always be measured by running fast; success should also be measured by your ability to stand up to yourself and your hopes and your fears and trying to improve your best performance.  The coach should always remind his or her athletes of that.  It is important that the coach help his or her athletes to stay positive at all times, even in the face of negative circumstances.

 

I usually give two pep talks—one the day before the race and another the day of the race, right before it is about to start.  The first pep talk is used to remind the athletes of the hard work they have put in, and how they

should use the race as an opportunity to learn about themselves.  The mood is calm and the intent to motivate is subtle.  The second pep talk is used to ignite the fire in the athletes and pump them up.  The mood is loud and the intent to motivate is direct.   

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Limits of VO2max

As discussed in an earlier newsletter, the most compelling research on what limits VO2max supports an oxygen supply limitation to the muscles.  However, this answers the question from a “limit of human performance” perspective.  Runners and coaches want to know what limits VO2max in each runner so we can understand how to improve it.  This is a different question with a different answer.  Runners with low or average VO2max values are not limited by oxygen supply but rather by a metabolic limitation to use the available oxygen.  Several studies have found that breathing a greater amount of oxygen increases VO2max in athletic subjects, but VO2max does not increase when unfit subjects breathe more oxygen.  Training appears to result in a shift of the limitation on the sliding scale—the more fit you become, the more you move away from a metabolic limitation to VO2max and the closer you move to an oxygen supply limitation.  The implication of this is that progressive increases in mileage from month to month and year to year will improve VO2max by increasing the muscles’ metabolic capacity.  When you have achieved a high level of mileage, the intensity of training becomes more important to increase the cardiac factors responsible for maximizing oxygen supply to the muscles.   

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Public Speaking

Are you or someone you know looking for a speaker at your running or coaching clinic?

Are you a high school, college, or club coach looking for a guest speaker for your team?

Are you a race organizer looking for a speaker for your pre-race clinic?

To find out more about how Coach Jason can customize a presentation for you or to book Coach Jason as a speaker for your event, e-mail jason@runcoachjason.com.  

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©2005 Jason Karp.  All rights reserved.