UKH

Does anyone know the scientific reasoning behind the dreaded Disco Leg? 

I have days where I can suffer from it real bad while climbing routes that aren’t necessarily outside my comfort zone. I can be enjoying or cruising a climb and boom disco leg almost throws me off. 

I’ve had double disco leg which threw me off a HVS which was well within my remit, and I really would like to know why it happens! 

Force your weight through your heels to relax.  It's just a calf spasm from time under tension. It's the foot equivalent of overgripping.

For me, not scientific, but being out of condition/ unfit is the cause

I very much doubt that has anything to do with a neural spasm of the leg muscles. 

Funny one isn't it.  Often seems attributed to physical stress in the calves (as suggested in above posts), but for me it seems more psychological.  Never get it on easy routes well within my comfort zone, which can still often be small footholds that I'd expect to generate the sort of stress that would induce a spot of Elvis leg, if physical reasons were the cause.  Never get it on my hardest red-points or on my hardest on-sight attempts.  Only get it on routes that I'm attempting to on-sight that are hardish (for me) but a bit below my limit.  When it happens no amount of heel lowering or calf relaxation helps.  That it doesn't happen when I'm really pushing myself suggests to me that in such situations I don't have the mental capacity left for my natural wussiness to take over.

Thare are a few old threads on it. To me it's when you are out of balance, in a stress position and aren't weighting or loading your feet properly. 

Its funny how disco leg stops witbout a change in foot position as soon as a solid runnwr goes in. I assumed it was because, under stress, i was inadvertently tensing both sets of opposing muscle groups at the same time.