Thursday, 24 September 2015

LCHF and endurance riding - Part 2

Hitting the wall (a term used in running parlance) or bonking (cycling terminology) describes a condition where the body runs short of stored glycogen resulting in extreme physical fatigue often accompanied by reduced mental facility. The mental impairment ranges from wanting to give up to symptoms consistent with hypoglycaemia (low blood glucose) such as confusion and hallucinations.
I have experienced this condition on three occasions. Once while running and twice on my bike. The bike incident in 2010 was the interesting one because it came an hour into my second day of an event. I wasn't riding particularly hard but I was tired. I wasn't in race condition and as it was a social ride I planned to take each day slowly. At the end of day one (a 12 hour effort) I was shattered and my exhaustion made eating a schlep. I only managed a small helping of dinner and had an equally small portion for breakfast. The result was that I didn't build up my glycogen reserves and an hour into the second day I bonked. I sat next to the trail staring at my bike convinced there was something wrong with it. I didn't want to talk to anyone else. I was simply miserable. Having experienced the condition previously I knew what needed doing and started stuffing food down my throat. Particularly food high in sugar. I continued dribbling down the trail and after 2 hours the lights came back on and I was able to continue normally.

So what does this incident have to do with LCHF? A lot actually. Pin this incident to your mind as we are going to use it a bit later in this discussion. We will label it 'The incident of 2010'.

A few words about muscle fuelling. Again, I am no expert. We store glycogen in our muscles and liver. If we engage in high energy activities with a heart rate in excess of 65% of our heart rate reserve (HRR, the usable heart rate between resting and max) we drawn heavily on these reserves and they begin to deplete. Glucose is then drawn from the blood to replenish these reserves, which, it not supplemented by refuelling with carbs, will lead to low blood sugar and bonking as your brain and your muscles start wrestling for the dwindling reserves.

As I understand it, our muscles are capable of being fuelled by glucose, fatty acids and ketones. Ketones, as stated earlier are produced when we metabolise fat. The brain can use either glucose or ketones as a fuel. It is suggested that ketones are the brain's fuel of choice.
Excessive use of carbohydrates leads to massive doses of insulin being released into our system. Is is claimed that insulin has the effect of reducing our cells ability to fuel off fatty acids or ketones making them dependant on glucose.
Endurance endeavours generally take place at lower levels of exertion and are better suited to fat metabolisation. Thats fine if your body hasn't been hammered by carbs which results in a reduced ability to process fat instead of glucose.
This explanation is simplistic but Is the gist of it.
Next up, LCHF adaption....

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