Hi everyone, I found this thread almost two years ago when I was started losing coordination of my legs when cycling or running. I used to be a triathlerte and did an Ironman race. About a week or two after I finished my first Ironman I started losing coordination of my legs while cycling. It would usually happen after around 1-1.5 hours of cycling that I would just totally lose coordination of either one or both of my legs. I would feel a slight tingling sensation in my feet and then eventually my leg would just start flailing outwards and my foot would want to point downwards. I couldn't control it and would have to stop cycling and it would stop. Then it also started happening while running. At anywhere between ~5-10 miles of running I would start to feel tingling in my leg which would lead to it just flailing outwards and me being unable to control it. I would have to start walking and it would go away, but then I would start running and it would come back making me unable to continue running. I was convinced I had whatever was being discussed in this forum.
Anyways, I went to see a neurologist and he basically said that it didn't seem like it was anything neurological but more likely a muscle issue. Long story short, I'm in medical school and started learning about electrolyte imbalances. I was looking at the symptoms of hypocalcemia and was like sh*t, that sounds an awful like what it is that I'm experiencing with my leg when I cycle/run. When I would do my long rides and I would usually only drink water unless I was doing > 2 hours. I also sweat like a pig so it made sense that I might have been deficient in electrolytes. So I started supplementing rides or runs longer than 70 minutes with electrolytes and lo and behold my weird leg thing went away. As an experiment I did a long bike ride where I only supplemented with maple syrup (no electrolytes) and the leg thing came back after around 2 hours. Next week I did a long 3 hr ride and supplemented with electrolytes and never had the weird leg thing. I was never able to go longer than 2 hours since this started happening.
So I'm convinced that what I was experiencing in my legs was paresthesia and tetany as a result of being deficient in electrolytes. I've been supplementing with gatorade endurance and all my runs and rides longer than 70 minutes and it has gone away. Just thought I would add it here in case it might help anyone in the future.