Fuel for the work required: periodisation of carbohydrate intake

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Fuel for the work required, Impey et al, Sports Med (2018) 48:1031–1048

Last week I attended an event announcing the forthcoming launch of a new fitness app called Pillar. It offers combined training and nutrition advice to help athletes achieve their goals. Pillar is backed by a strong scientific team including Professor James Morton, Team Sky Head of Performance Nutrition, and Professor Graeme Close, England Rugby Head of Performance Nutrition.

James Morton gave a fascinating presentation about the periodisation of carbohydrate (CHO) fuelling, including a detailed description of the nutrition strategy he created to support Chris Froome’s famous 80km attack on stage 19 of the 2018 Giro d’Italia. His recent paper explains the underlying science. These are some of the key points.

  • Always go into competition fully fuelled with carbohydrate
    • Well-fuelled athletes perform for longer at higher intensities than those with depleted reserves
    • Basic biochemistry: fat burning is too slow and supplies of the phosphocreatine are too small to sustain intensities over 85% of VO2max
    • Theory is backed up by experiment
  • There are pros and cons to training with low levels of carbohydrate
    • Positive effects: Improved fat burning, changes in cell signalling, gene expression and enzyme/protein activity, potential to save precious glycogen stores for crucial attacks later in a race
    • Negative effects: Inconsistent evidence of improved performance, ability to complete training session may be compromised, reduced immunity, risks to bone health, loss of top end for those on high fat/low carb (ketogenic) diet
  • Different ways to train with low carbohydrate
    • doing two sessions in one day with minimal refuelling
    • low carb evening meal and breakfast: sleep low, train low the next morning
    • fasted rides
    • high fat/low carb diet

Is there a structured method of training that provides the benefits without the negatives?

  • The authors propose a glycogen threshold hypothesis
    • Positive effects seem to be dependent on commencing with muscle glycogen levels within a specific range
    • Levels have to be low enough to promote positive effects
    • But when too low, protein synthesis may be impaired and the ability to complete sessions is compromised
  • This leads to the idea of periodising carbohydrate consumption, meal by meal, around planned training sessions
  • “Fuelling for the work required”
    • low carbs before and during lighter training sessions
    • high carbs in preparation for and during rides with greater intensities
    • always refuel after training
  • The diagram above provides an example for an elite endurance cyclist
    • The red, amber, green colour coding indicates low, medium or high carbohydrate consumption
    • On day 1, the athlete aims to “train high” for a hard session
    • A lighter evening meal on day 1 prepares to “sleep low, train low” ahead of a lower intensity session on day 2
    • Carbohydrate intake rises after exercise on day 2 in anticipation of a high intensity session on day 3
    • Fuelling is moderated on the evening of day 3 as day 4 is assigned as a recovery day
    • Carbohydrate rises later on day 4 to prepare for the next block of training
  • The Pillar app aims to provide these leading edge scientific principles to amateur cyclists and other athletes

In order to put this into action, you need to know how much carbohydrate you are consuming. My assumption has been that my diet is reasonably healthy, but I have never actually measured it. So I have been experimenting with free app MyFitnessPal that can be downloaded onto your phone. This provides a simple and convenient way to track the nutritional composition of your diet, including a barcode scanner that recognises most foods. You can link it to other apps such as Training Peaks to take account of energy expended. However, neither of these tools plans nutrition ahead of training sessions. Pillar aims to fill this gap. It will be interesting to see whether this turns out to be successful.

References

Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis, SG Impey, MA Hearris, KM Hammond, JD Bartlett, J Louis, G Close, JP Morton, Sports Med (2018) 48:1031–1048, https://doi.org/10.1007/s40279-018-0867-7

Fuel for the work required: a practical approach to amalgamating train-low paradigms for endurance athletes, Impey SG, Hammond KM, Shepherd SO, Sharples AP, Stewart C, Limb M, Smith K, Philp A, Jeromson S, Hamilton DL, Close GL, Morton JP, Physiol Rep. 2016 May;4(10). pii: e12803. doi: 10.14814/phy2.12803

Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, Burke LM, Ross ML, Garvican-Lewis LA, Welvaert M, Heikura IA, Forbes SG, Mirtschin JG, Cato LE, Strobel N, Sharma AP, Hawley JA.  J Physiol. 2017;595:2785–807

Low energy availability assessed by a sport-specific questionnaire and clinical interview indicative of bone health, endocrine profile and cycling performance in competitive male cyclists, BMJ Open Sport & Exercise Medicine,https://doi.org/10.1136/bmjsem-2018-000424

Author: science4performance

I am passionate about applying the scientific method to improve performance

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