I had a moment of thought the other day during my morning kickbike scoot. After pushing outward bound, coming back was hard. But not hard as in strenuous. It was hard as in weak.
You think, "maybe I should get off and walk?"
There's no pain or seeming strain just the absence of strength.
Am I talking about a phenomenon unique to myself or is this a norm?
It wasn't until I had raised this question that the obvious hit me.
The depletion of glycogen stores in the liver and muscles, manifests itself by sudden fatigue and loss of energy -- hitting "The Wall".
In my case I suspect that because I have reduced -- further -- my carbohydrate intake recently, I'm promoting this response. On the morning in question I had scooted off without having breakfast. (So I was asking for it, right?)
That's why the symptom stands out for me as being novel. I don't make it a habit of running out of fuel.
The advantage is that supplying the body with fewer carbohydrates during exercise teaches it to burn fat instead. This is the first principle of ketogenic diets. So while I may be entering a ketosis I am suggesting to my body that it should look elsewhere for fuel.
There is going to be a period of transition, maybe a rough ride for a while.
To make sure I'm not losing muscle for fuel I need to eat plenty of protein.
So either I'm doing myself damage by being ketotic on exertion (and this is a symptom) or I'm remaking my metabolism to better effect...
For this reason it is usually recommended to long distance runners and cyclists that they up their carb intake in order to generate easily accessible fuel in the form of glycogen.
But in one study aerobic endurance exercise by well-trained cyclists was not compromised by four weeks of ketosis. This was accomplished by a dramatic physiologic adaptation that conserved limited carbohydrate stores (both glucose and muscle glycogen) and made fat the predominant muscle substrate at this submaximal power level.
But the research work is ongoing.... I just didn't expect that my own body would be so much a lab rat. So what I have to watch is how much further (and with whatever intensity) I can go before hitting the wall.
If I faint during a scoot -- and make it back -- I'll let you know. If I faint and don't return, my absence from this forum should be word enough.