Alan Couzens, MS (Sports Science)
In my last post, I outlined the importance of establishing a
firm base of ‘metabolic fitness’ to both performance and general health.
When it comes to exercise for health, having a very good
metabolic profile will take you a long way towards your goals of health &
longevity. Considering that the most pervasive debilitating disorders of modern
society are strongly linked to metabolic dysfunction (or the excessive
inflammation that is related to this faulty metabolism), keeping your metabolic
and stress hormones in an optimal balance will take you a long way towards
optimal health. However, for the athlete intent on maximal performance, having
a strong basal metabolism is only a part of the picture.
Once a strong basal metabolism is established, the serious
athlete must address the limits of exercise metabolism, i.e. sugar burning. To
put the relative importance of these 2 systems into perspective, check out the
figure below which shows relative fat and carbohydrate contribution for a top
age group Ironman athlete for each of his training zones.
While the breadth of the fat burning system is virtually
limitless, its height, or power is not. Generating energy from fat is a rate
limited process. Meaning there are inherent limits to exercise intensity if the
athlete is intending to ‘run on fat’. Indeed, in this athlete’s Ironman power
zone of 220-240W, for a 75kg, you can see that aerobic glycolysis (sugar
burning) makes up more than 2/3 of the performance picture.
This fact has important implications with regard to the
current push for “low carb, high fat” diets. When dealing with athletes, it’s
important to recognize the difference between eating and training for optimal
health vs eating and training for maximal performance. Make no mistake, the
majority of athletes can greatly improve their ability to use energy for fat by
making better choices in their daily nutrition. After such interventions, I’ve
seen athletes double their fat oxidation rates in tests like the one above,
i.e. go from the typical 3-5kcal/min up to an incredible 10kcal/min energy
generation from fat! This adaptation greatly improves the athlete’s long term
endurance. However, if we look at the 10kcal/min mark on the chart above you
can see that it equates with a power output of less than 200W, a level that’s simply
not going to cut it for an average sized athlete with competitive aspirations
of a Kona slot or beyond.
The aim of the game, then, for the competitive athlete is to
maintain a developmental balance between the fat burning and
sugar burning systems over the long term.
In terms of nutritional and training periodization, this is
a yin-yang concept. During the bulk of the year, when you are working on
building your ‘health base’ and focusing your training on your ability to
generate energy from fat, if you’re a competitive athlete, you should still
include sufficient training (& sufficient carbohydrate in your diet) to
maintain your glycolytic (i.e. ‘sugar burning’) power & capacity. On the
flip side, when you are approaching your ‘A-Race’ & a good chunk of your
training is metabolically similar to your event, i.e. focused on ‘sugar burning’,
for the sake of your health and recovery, you should maintain your body’s
ability to use fat for fuel.
In practice, for a high level AG male athlete of average
size, this may look something like this….
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General Prep (Base)
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Specific Prep (Build)
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Training
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90% Fat Burning/10% Sugar Burning ---------------------->
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75% Fat Burning/25% Sugar Burning
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Nutrition
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40/30/30 diet
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50/20/30 diet
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Rather than give recommendation for all sizes and levels of
athlete, the litmus test of ‘taking it too far’ is very simple. When an athlete
is not including enough carbohydrate in the diet or enough ‘sugar burn’
training in the program, top end performance is noticeably compromised.
A great example of this comes from my experiences in the
lab. When we schedule blood lactate or metabolic testing for an athlete, one of
the pre-test instructions is to ‘come rested’, i.e. ideally tests take place
towards the end of a recovery week. Invariably, though, over the course of a
year an athlete will show up far from ‘rested’, sometimes without advising the
tester of this (!) This may happen immediately after a big training camp or
block of training, i.e. when the athlete’s glycogen stores are very low &
their ability to generate energy from sugar is, consequently, compromised. The
test unfolds as follows… The athlete looks spectacular in their ‘easy zone’
generating very high levels of energy from fat and showing a very slow rise in
lactate & then they just… stop. When the body goes looking for sugar to fuel
the increasing workloads, it comes up short. Therefore, the maximal lactate and
maximal power that the athlete reaches are very low (often less than 7mmol/L
LaMax)
This bring us to 2 practical recommendations for the athlete
looking to improve their metabolic fitness without sacrificing performance…1. Periodically ‘check in’ on your glycolytic power via short, maximal tests to ensure that you’re not overdoing the low carb thing.
2. As you get closer to your ‘A Race’ shift the emphasis to improving race pace endurance. Being able to roll 150W for 20hrs on water & chia seeds is a great test of your basic metabolic fitness but if your race requires 225W for 9hrs, you’re going to need to add a little something to your training (& your nutrition) to get ‘race ready’.
Train Smart,
AC
