Metabolic Assessment: The Coach’s Perspective

Created On: 06 February 2011

As a coach I am always looking for ways to gauge my athletes' current level of fitness, identifying their potential areas for improvement and providing them with meaningful methods of monitoring or guiding their training intensity.

Metabolic assessment is a great way of achieving all of the above and more besides.

A metabolic assessment provides me with a profile of the athlete's aerobic conditioning and their fat vs. carbohydrate fuel utilisation which is excellent for determining whether their training needs to be adjusted to achieve optimum performance over short, medium or long course racing.

In order to help an athlete monitor and control training intensity, most athletes and coaches are familiar with the idea of using heart rate (HR) training zones. The difficulty with setting HR zones, is knowing what terms of reference to use. Here are some considerations to bear in mind;

You can start with gross assumptions based upon percentages of HR Max, and we can factor in their resting HR, but why do we use 80% or 90% for instance? And what if the athlete's aerobic profile changes as an adaptation to the training, surely that would mean the zones could or should change too (hint - the answer is yes).

What is HR Max? Is it a meaningful number? Does it vary depending on current level of fitness and/or how well rested the athlete is? In my opinion it certainly isn't good enough to use a calculated value i.e. 220 minus your age, or any other more convoluted calculation based upon the athlete's age for that matter because the margin of error is significant and zones derived in this way could lead to over or under training.

A more sophisticated method based upon the athlete's current performance profile would be to use HR at Lactate Threshold or Anaerobic Threshold and define training zones as derivations of that number. In its most basic guise we take the Lactate Threshold to be the HR the athlete can sustain for a best effort time trial of an hour's duration. You can take the same approach using HR at Functional Threshold Power - which leads off into a separate article on bicycle training with a power meter.

The optimum method for determining the HR zones would be to actually measure blood lactate accumulation and/or analyse the exhaled air composition to determine exactly what HR corresponds to Lactate Threshold and Anaerobic Threshold respectively. A metabolic assessment provides the latter of these two measurements as well as other useful information.

The metabolic assessment profile also provides me with an understanding of the athlete's calorific burn rates and fuel utilisation (fats vs carbohydrates) at different training intensities, which is useful when determining whether adjustments to the training composition might yield a better performance over the target race distance or indeed a recommendation that the athlete is better suited to short, medium or long course racing. This information is also extremely useful for planning race and training nutrition strategies, as well as planning the diet in order to achieve a weight management goal.

Our understanding of how to use the results of metabolic testing is growing as more data is gathered and more research is undertaken. Sports scientists might not like me using the cliché "its as much of an art as it is a science", but ultimately as a coach you've just got to make a judgement call based upon the information at your disposal. If it works you are more likely to make the same decisions again, if it doesn't, you strive to learn from the results and try something different.

How the metabolic assessment results are interpreted and used will vary considerably from person to person, depending on lots of other factors, such as anecdotal evidence about training performances, empirical data from actual training and race performances, race and training objectives and weight management goals. So be very wary of trying to follow the same advice given to someone else based upon his or her metabolic assessments and training prescription!

As you have been reading you may have wondered why I haven't mentioned VO2 Max yet, because that's often the first thing people think of when you describe a metabolic assessment.

That has been quite deliberate on my part because I feel that referring to a metabolic assessment as a VO2 Max test places too much emphasis on the one parameter that we cannot do much about (unless the person under assessment is overweight or currently leads a sedentary lifestyle and therefore is not at their full genetic potential for Oxygen Uptake).

To be clear, VO2 Max is a characteristic that we can establish during metabolic assessment but it is widely acknowledged in the literature that it is not the best indicator of performance potential and in a trained individual it is unlikely to change very much at all.

As coaches we are far more interested in the Aerobic and Anaerobic Thresholds (or Lactate Threshold) and we can achieve significant improvements to these metabolic characteristics through appropriate training and it is indeed our understanding of these parameters that we use to set the training zones.

But I think we all know that most 'A Type' personalities want to know their VO2 Max number (relative to body mass) - so they can compare themselves with Lance Armstrong or the Nordic Skiers.

I shall finish this article with an example of why VO2 Max is not something to get hung up on or too excited about - at 38 years of age I recorded a VO2 Max of 72 ml/kg/min. I was performing at a moderate level in triathlon at the time, but not my best by any means (I have performed at a much higher level before and since).

Arguably a VO2 Max of that order is what you would expect to see amongst elite athletes, BUT - clearly it isn't the only indicator of elite performance or elite performance potential otherwise you'd have read about my sporting exploits or seen me on the TV! At the same time I was excited by what that could mean and disappointed that I had never reached notable elite potential. But what I did do was take on board the other information I learned through the process and adapted my training, which led to improved performances and better utilisation of time available to train.

All sorts of other factors come into play to determine performance potential, such as; biomechanical efficiency, speed skill, strength, muscular endurance, lactate tolerance, mental strength, pace judgement and avoiding over training syndrome.

Remember with out good coaching guidance its all just numbers ;-)

About the Author:

Steve Casson is a British Triathlon Federation Level 3 Coach and a GB Age Group Triathlete. At the beginning of 2009 Steve set up a triathlon performance coaching studio in Northampton to fulfil a vision of providing a range of 1-2-1 technical coaching sessions and performance testing services to complement his interactive coaching support package.

During 2010 Cassonz Performance Coaching helped a wide range of triathletes from Novices to Age Group World Championship medallists achieve their goals.

Find out more at www.cassonz.com/

Tags: run,training

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