Why to decrease insulin intake during exercise ?

I have been always told to decrease basal or even stop the pump during exercise to avoid hypoglycemia ... so I have been following this rule for while until I found that you basically do not have any energy when you do that...

Its different when you go cycling for 20-30km around your house, but try to do 150-200km daily in high tempo...

I first found out about this, when going on first long distance trip with my cycling friends. First days I was not unable to catch up with them ( I had pump basal almost completely turned off) and I was not feeling well at all. So next days I decided to return or even increase my basal and instead eat much more and check my bg more often (as I did not have cgm at that time) and it was something different, because I finally had enough energy and to catch up with my friend was not any pain...

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So the advice to decrease insulin during exercise is maybe correct if you do some recreational sports like running for 5km etc .. otherwise you will soon run out of glycogen from liver and you will feel very exhausted ...