-Dr Dan Plews
All endurance athletes eat, and all endurance athletes train. Whether consciously or not, all endurance athletes therefore have to make decisions about what they eat (or don’t eat) before training. Pre-exercise nutrition has the potential to impact the substrates we utilize to fuel training (i.e. fats and carbohydrates), our performance in training (i.e. the watts or pace we put out), and also our adaptive responses to the training stimulus (1, 2).
Pre-exercise nutrition is therefore a fascinating and highly relevant area of study in sports science. Recently, my PhD student Jeff Rothschild, AUT Professor Andrew Kilding and myself published a large review of the effects of pre-exercise nutrition on a range of metabolic and physiological responses in the open-access journal Nutrients (3). We pooled the results of 125 studies, which included data from 1245 athletes (~13% females) to assess the effects of pre-exercise carbohydrate (CHO) ingestion and pre-exercise muscle glycogen availability on substrate metabolism during exercise, and activation of the key molecular energy sensor AMPK. AMPK is a protein housed in muscle cells that has strong links to endurance training adaptations. This term will be no stranger to those of you have completed our online course LDT102: Training Program Fundamentals for Long Distance Triathlon. We paid particular attention to RER - which is a metric derived from respiratory gas analysis during exercise that provides indication of what substrates are being oxidized to fuel metabolism; specifically, a lower RER indicates greater fat and lower CHO oxidation.
Here is a summary of our main findings:
We ended the review with a flow-chart that indicates how this information can be used to make day-to-day training decisions, with specific approaches recommended dependent on the specific goal of the training session. This last point, that pre-exercise nutrition should vary according to the goals of the session, is really important, and often overlooked.
We can use the findings of this review to make decisions regarding the optimal pre-exercise nutrition strategy for training sessions focused on maximizing fat oxidation, cell signaling responses, or aerobic capacity and performance during training, and alter these strategies in accordance with the duration and intensity of the session and starting muscle glycogen concentration.
To receive a copy of the flow-chart, fill in your details below. It’s the perfect print off for the fridge door!
Endure IQ's online courses guide athletes and coaches to understand and solve real performance questions in endurance sport.