Our fuelling strategy has changed since using a continuous glucose monitor (CGM) but more importantly it continues to evolve the more we observe Joe’s data during training and racing.
When you start using a CGM you see a continuous stream of rises and falls, peaks and troughs and you can’t help but wonder what it all really means. As an athlete we are used to linear progression and the narrative of effort applied in a certain direction will have a particular result in a particular time frame.
There is nothing linear about watching blood glucose. It’s a constant stream of response and adjustment based on life circumstance but that stream has a relationship to energy management and when performing over time and distance you need a fair handle on energy management.
One figure we have become very interested in is glucose stability, a measure of how variable Joe’s blood glucose is over a particular training session, over the day as a whole and during sleep.
Granted our bodies maintain a tight grip of blood glucose levels amongst many other things through the process of homeostasis but what impact would maintaining an even tighter grip make on performance?
I can only speak from experience and our experience is that it makes a big difference, especially as you go further or if you aim to surf on that performance edge for longer.
During training, when we get Joe’s blood glucose up to his ‘performance zone’ and when we hold it there with minimal variation (think 15-22mg/dl) he experiences an ease and confidence around sustainable output.
We took that fuelling strategy to the Natchez 444 and it worked well for most of those 22 hours and 48 mins. However, we did notice that under extreme race load and as fatigue crept in during the night time hours the tendency was to reach for more fuel. It makes sense, “I’m fatigued, I must need more fuel.”
But when Joe’s blood glucose rose outside his ‘performance zone’ for too long we began to see glucose stability reach towards 30mg/dl and become erratic with significant peaks and troughs within very short periods of time.
He could still perform but then the first sign of ‘taste fatigue’ appeared - a turning away of usual food choice. My immediate thought was that we were starting to tip over that performance edge, the one we’d been so beautifully surfing on for about 18 hours. I quickly decreased the concentration of carbohydrate in his bottle to 4% and the volume of food (this isn’t my first rodeo) and watched his blood glucose levels like a hawk. They dropped back within his usual performance zone but his glucose stability never returned to where it had been.
The result is history. He delivered a stellar performance, 3rd overall and was able to push to the end with no gut issues.
This race experience posed some new questions though.
Would there have been a downstream impact on gut function eventually?
What is the downstream performance impact of maintaining high glucose levels when glucose stability has been uncoupled?
What is the impact of fatigue on glucose stability? Does the body lose some homeostatic control over the kinds of distances we cover? If so, what can I do about that?
Isn’t it great to be constantly asking these kinds of performance questions and to have the tool in Supersapiens to explore our enquiry.
When it comes to endurance, there are always more questions than answers, which is why it’s so important to observe, hold an open, enquiring mind, challenge what you think you know and be willing to test it over various terrains and environments.
We are constantly moving forward, aiming to be the best fuelled Supersapien we can be!