Here’s An Idea.
“While adapting to burning fat instead of glycogen it may take up to 30 minutes to get into your stride on longer runs”.
This is a thought that has been crossing my mind during the first 2 weeks of reverting to a LCHF diet after 2 weeks on carbs on holiday in France.
The French Experiment is starting to look like a success - by which I mean can I go on a carb-bender for 2 weeks and then easily switch back to LCHF? - after just 8 days back on LCHF I managed a gentle 13 mile run (longer than I have run in 5 months) with none of the classic fatigue symptoms that hit me when I first tried the diet in January. The intensity is less, and I am mixing the exercise with cycling, but it has been a problem-free return to LCHF so far.
One thing that I have noticed, and I recall this from January; my longer runs and rides have tended to feel harder at the beginning, much harder . In some ways this is not surprising – I'm not an early riser and the knowledge that I am nearing home often lifts my mood and my speed. This week though I have noticed my energy levels rise significantly after 20 minutes or so and then remain that high for the rest of each run/ride.
If true this could explain a lot about why some people reject the diet –“it made me feel worse than ever before when I was running”. But didn't we all feel this way for the first week or so when we first started running? The body has to adapt; only this time it is the energy supply that is adapting rather than the muscles. If false then no matter, it's just an idea.
I have precisely no data to back this idea up; but today's 17 miler was a good example; the first hill was lousy and I had to walk some of it, which is a rear event. Then after 40 minutes I had to slow down a lot as I was daydreaming and casually running much faster than I had planned (my coach/wife thinks this is why I get injured so much!). The second hill at 9 miles was a breeze, as was the third and it was only the fourth at 14 miles that actually had me properly knackered.
Perhaps it was the gentle breeze behind me!
I don't have a good explanation for this experience; apart from the idea that maybe when we first set off our muscles have some stored glycogen and they want to burn it; but there is not enough so they can't perform; once this runs out the fat-adapted state wakes up and gets to work.
I can find no articles on the internet that talk about this subject. So, head down and time to find out more.