VO2max

The monthly newsletter of RunCoachJason.com

Jason Karp, professional coach, consultant, freelance writer

February, 2006

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In this issue:

Integrating Science with Application—Running On an Empty Stomach

Periodization

Sex Differences in VO2max

Customized Training Programs

Elite Running Team

In Press

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Integrating Science with Application—Running On an Empty Stomach

Have you ever heard that you’ll burn more fat if you run first thing in the morning before breakfast?  The argument typically is that if you exercise when your muscle glycogen stores and blood glucose are low (as they would be first thing in the morning), your body will be forced to rely on fat.  However, it has been known for 40 years that carbohydrates, not fat, are our bodies’ preferred fuel during exercise.  Of the small amount of fat used during exercise, much of it comes from intramuscular triglyceride (small drops of fat inside muscles), rather than from the fat around your waist.

 

A study published in International Journal of Sports Medicine in 1988 found that more fat calories were used when subjects exercised on an empty stomach following an overnight fast compared to when they exercised either 60 or 90 minutes after breakfast.  However, the total amount of calories burned during the 30-minute run was the same for all experimental conditions.  Another study published in Medicine and Science in Sports and Exercise in 1999 found no difference in carbohydrate and fat oxidation between exercising after an overnight fast and exercising 3 hours after eating breakfast, although subjects eating breakfast first were able to exercise longer at 70% VO2max than those who did not eat breakfast.  Another study published in American Journal of Physiology in 1997 found that oxidation of palmitate (a long-chain fatty acid) was greater during exercise when fasted compared to during exercise after eating carbohydrates, but there was no difference in the oxidation of octanoate (a medium-chain fatty acid) between fasting and pre-fed exercise conditions.  Yet another study published in Journal of Applied Physiology in 1999 found that fasting decreased the respiratory exchange ratio (an indirect indicator of fuel use) during exercise, indicating a greater use of fat when fasted, but only at very low exercise intensities (22-40% VO2max). 

 

Taken together, these studies suggest that exercising after an overnight fast increases the amount of fat used during exercise, especially when the exercise intensity is low, however it does not burn more calories, which is what’s most important for fat and weight loss.  Furthermore, fasting decreases the ability to sustain a given intensity, which may cause you to burn fewer calories.  The important question is, “Does it matter if more fat is burned during your run?”  The answer is, “No.” That's why sprinters still have very low percentages of body fat despite the fact that they do very little aerobic running during which fat is used.  You don't have to burn fat while running to lose fat from your body.  People who run before breakfast are not any thinner than people who run after breakfast.  So, if you want to get the most out of your running, make sure you’re glycogen-full, not glycogen-depleted. 

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Periodization

(excerpted from Karp, J.R. Periodization Training. Track Coach. 154:4905-4908, Winter 2001.)

The idea to divide a training program into periods, or cycles, began in Europe in the 1910s.  During the early part of the 20th century, athletes stopped training only occasionally and began to train year long.  Since coaches thought that athletes shouldn’t train hard for long periods of time, a need arose to structure the overall training program.  The first attempts at this focused on different stages of training, such as general, preparatory, and specific.  General training was a starting base for developing the cardiorespiratory system.  Preparatory training, which lasted 6 to 8 weeks, aimed at developing strength using more sport-specific exercises.  Finally, specific training intended to prepare the athlete for the specific sport event.  This final phase was further divided into 2 stages—initial training and main training, with each stage lasting about 4 weeks.   

 

In the 1920s and ’30s, the structuring of clearly-defined cycles of training began to emerge.  Recommendations during that time included that the training process should present a clear alternating of work and rest, that the work should gradually progress from high volume/low intensity to low volume/high intensity, and that each specific training period should lie on a generalized base.  During the 1950s and ’60s, prominent New Zealand running coach Arthur Lydiard refined this concept by using phases of base training, hill training, and sharpening in his training program to bring his athletes to a physical peak.  It was not until the latter half of the 20th century that the idea of periodizing an athlete’s training program was accepted in the United States.

 

Much of the information regarding periodization is anecdotal or conjectural in nature and not yet supported by scientific research.  There have been only a handful of studies that have examined the effectiveness of a periodized training program, with most focusing on strength/power gains following strength training.  Most of the studies have shown a greater increase in strength in the periodized training groups compared to the non-periodized training groups.

 

The positive physiological adaptation to training is the result of a correctly timed alternation between stress and regeneration.  If there is too great a stimulus and/or too little regeneration, negative adaptation results.  Following the introduction of a controlled training overload, there is a period during which the organism adapts to the overload and works to reestablish homeostasis.  Essentially, the organism physiologically overcompensates its adaptation so that the same stimulus, if reintroduced to the body, will not cause the same disruption of homeostasis.  It is much like getting a flu shot.  Following the adaptation to the overload, the organism is capable of doing more work for an equivalent homeostatic displacement.  This is called over- or supercompensation.  The basic aim of training, therefore, is to apply a series of stimuli that will displace the homeostasis of the organism’s functional systems and provide a stimulus for adaptation and supercompensation.

 

The periodization training method divides a year of training into major periods called macrocycles, which last about 3 to 4 months.  The macrocycles are subdivided into mesocycles, which typically last 3 to 4 weeks (but can last up to 6 weeks) and microcycles, which are typically 1 week long.  Thus, 3 to 4 microcycles comprise 1 mesocycle, and 3 to 4 mesocycles comprise 1 macrocycle.  As the smallest unit of training programming, the microcycle should be considered the most important period of training because its structure and content determine the quality of the training process.

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Sex Differences in VO2max

The main reason for the difference between men’s and women’s world distance running records is that men have a higher VO2max.  Even when the difference in muscle mass between men and women is accounted for and VO2max is expressed relative to lean body mass, men still have a higher VO2max than do women.  This difference is primarily attributable to biological differences in cardiovascular preload (resulting in a larger cardiac output) and blood oxygen-carrying capacity (due to greater blood hemoglobin concentration).  Given the (nearly) equal opportunities that now exist between the sexes to participate in sports, it is unlikely that any further narrowing of the difference in running performance between men and women will occur without a narrowing of the biological difference in VO2max.

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Customized Training Programs

Want to PR at a 5K, 10K, half-marathon, or marathon this year but can’t afford a coach?  RunCoachJason.com offers customized training programs for beginner, intermediate, and advanced levels.  To purchase your own program, e-mail jason@runcoachjason.com.

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Elite Running Team

In addition to coaching recreational and competitive runners, RunCoachJason.com is launching an Elite Running Team for U.S.-based athletes in 2006.  Selection will be based on past race results, national- caliber personal best times, and exhibited potential to place in major races throughout the U.S.  If you or someone you know wants to run for a post-collegiate team and is interested in using RunCoachJason for your scientific coaching needs, we encourage you to apply.  Please send your running résumé to jason@runcoachjason.com.  For more information, go to http://www.runcoachjason.com/eliterunningteam.

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In Press...

Both weight machines and free weights have their advantages and disadvantages.  So which type of equipment is better?  Weight Machines vs. Free Weights, my “boxing-match” comparison of the two types of weight training, appears in the February, 2006 issue of Fitness Management.

 

Optimal Recovery, my article that discusses strategies for recovery from hard workouts, including refueling, rehydrating, reducing inflammation, and tapering, appears in the February, 2006 issue of Atlanta Sports & Fitness.

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©2006 Jason Karp.  All rights reserved.