UKC

What is actually happening?

In reply to Lupine Lacuna: Your leg is shaking. hope that helped

In reply to Lupine Lacuna: It's my dad's teddy boy gene rearing it head

In reply to Lupine Lacuna:

Good question. It's odd how I seem to need one episode of this at the start of each season before my body gets "warmed up" and used to it.

This involuntary tremor never seems to affect other body parts, no matter how strenuous the position. Are there equivalents in other sports, gymnastics for example?

In reply to Lupine Lacuna: Muscle overcontraction, resulting in spasm. Though I suspect fear adds to it, though whether the fear makes your legs shake, or your legs shaking causes fear, I can't tell

In reply to JBlackout: It's caused by your thighs and buttocks tightening to stop your arse letting you shit yourself..

Well...That's my theory

In reply to Lupine Lacuna:

Try googling clonus. Might make a good route name maybe?

In reply to Dave Garnett: http://www.ukclimbing.com/logbook/c.php?i=84009

In reply to mrchewy:

I was thinking of the Crafnant one.

In reply to Dave Garnett: interesting, wonder if it is caused by a burst of serotonin. It definatly seems to occur when you are scared doing someing pysically challenging.

In reply to Dave Garnett:


For anyone who has "googled" clonus don't worry, this is not the cause of Disco Leg!

Although I don't know the exact physiology my guess would be that it is due to muscle fatigue, you can get a similar reaction in your arms and probably other muscles. (Try holding a packed rucksack on a fully out stretched arm at shoulder height for a minute...). Your calf muscles are most commonly used for walking which works through brief contraction/relaxation cycles. When you're perched on a small foothold or the front points of your crampons they are contracted constantly for a long period of time and as they start to fatigue they try and relax causing the rhythmical jerking (spasm) as the heel tries to drop to stretch the muscle. I personally find that by dropping my heel and shaking the leg out relieves the shaking and I assume this is because the muscle has been fully stretched and is ready to contract again.

Like I said I don't know the exact physiology but this is my educated guess, definitely certain it has nothing to do with clonus though!

Iain

In reply to tom r:


I'm curious. What would cause a burst of serotonin? I know that high levels of serotonin can cause funny effects on muscles including clonus and other jerking movements but as far as I remember the causes of high serotonin are mainly due to drugs (both prescribed and non-prescribed).

Iain

In reply to Lupine Lacuna:

I'm no expert but I'd say it is more to do with nerves/fear. I have suffered it once when driving. Not a problem under normal circumstances, but it was my clutch leg whilst doing a 3-point turn on my driving test! Still pulled it of without any troubles though, and passed

i often thought a contributing factor may be that its your body running low on adrenaline and pullin a U turn from "fight" to "flight" mode.. as in, enough of this get me off of this damn wall, which is the opposite of the kind of mental processes you want to be going through which then leads to panic. answer is to push down with your heel though, nearly always sorts it out

In reply to Lupine Lacuna: Heartbreak Hotel?....

In reply to IainMunro:

This sounds like a very plausible explanation. I'm most likely to get it when I've been perched on the same foothold for some time with most of my weight on just one foot. This probably occurs in two situations (either I'm struggling to place adequate gear or I'm baffled by the next sequence). In both of these situations I'm may be more fearful, but I don't think that the fear is the cause for my discoleg.

In reply to IainMunro:

I believe it is directly linked to adreneline. My experience is that I can do the above for a long period of time and never get disco leg, yet on another occasion make one move up to a certain small foothold, dangerously high above gear and get it instantly...!!?

In reply to Lupine Lacuna:

I never get it on sport climbs, only on trad climbs way above questionable gear thus for me it's fear.

In reply to samoflak:


Levels of adrenaline have little effect on whether you choose to fight or take flight, it's based on instinct, past experiences and situational awareness.

For example the gazelle has just as much adrenaine circulating as the cheetah who is chasing it...

Iain

In reply to IainMunro:

Being scared at a crux isn't situational awareness?? It's certainly related to fear in some way. Equally it certainly isn't due to fatigue as it can happen when there is none.

In reply to Cragrat Rich:


Based on what theory? Adrenaline primes your muscles to work beyond normal levels and have more strength rather than less, seems a bit counter intuitive

I have had disco leg not only when a bit scared but also on long uncomfortable belays in winter and at least a couple of times after pushing myself a bit too hard cycling up hill on my bike.

It doesn't seem to have any useful purpose which suggests there is not a direct association with adrenaline.

Iain

In reply to Offwidth:


Yes it is as it determines whether you fight (climb on) or take flight (climb down)

Iain

In reply to Offwidth:


PS you may have misunderstood the point of my post. Someone above was suggesting that as adrenaline levels tail off you take flight instead of fight. I was saying that it's a fight OR flight response and that other factors (instinct, situation awareness etc etc) determine your response rather than actual levels of the hormone

Iain

In reply to IainMunro:

It's not based on a theory Iain. It's based on my experience.

So (in my case anyway) it's based on Fact!


Have you ever experienced disco-leg where you have truely committed yourself upwards onto crux footholds, at the limit of your lead grade onsight, where a fall would be very serious Iain?
Not being funny, just wondering?
It's not really the same as riding your bike up a hill!

In reply to Lupine Lacuna: The fact that it can be relieved by lowering the heal suggests that it is more physiological than psychological.

Al

In reply to IainMunro: You seem rather young to be an expert on the complexities of the physiological effects of hormones.

In reply to Cragrat Rich:


I have had disco leg in several pretty uncomfortable situations, worst of them in winter. I could list them if you really wanted but the consequence of a fall in at least a few instances doesn't bear thinking about (a long run out pitch on the Ben above a mediocre belay springs to mind), the fact both you and I are hear suggests that when it really matters adrenaline kicks in and you pull it out the bag. If there is a direct relationship between adrenaline and disco leg then the more scared you are the worst it would get then you'd fall. How did you manage to climb the moves when you were genuinely scared?


Explain why fatigue causes the same effect as disco leg in non-life threatening situation (long belays perched on front points for example?)

Not wanting to get into an argument, I just don't understand this "direct link" with adrenaline. Perhaps I missed out that chapter of my physiology teaching

Iain

In reply to Offwidth:


I'm 2 months off receiving my MBChB, out of intrest what's your background in physiology?

Iain

In reply to Lupine Lacuna: What a great question! We really need a climbing neurologist with a past degree in exercise physiology perhaps!? Personally I get it when I drink too much coffee at the beginning of a climbing day but also sometimes when very fatigued, both situations at different ends of central nervous system drive and muscular fatigue. It's almost certainly a local muscular response affected by neural drive but probably also born from the clonus reflex. From memory we all have clonus until about 3 months of age and some retain a mild degree of it throughout life which is considered on the outskirts of very normal without CNS injury. I would imagine these people would be slightly more regular disco leggers at the crag. A more orthodox answer is it's your leg trying to find a stable position in space but mis-coordinating due to an altered CNS/local fatigue in a clonus like pattern. Interested in others takes on this as it's not my speciality and I am largely speculating.k

In reply to IainMunro:

He's got you there

In reply to IainMunro:

You don't need your uni notes Iain. The direct link between fear, adrenelin and disco leg comes from shitting yourself due to the prospect of falling off a rock face whilst being stood on small footholds above gear!! Errr Hello!!

I don't know ought about winter/alpine stuff, the only thing i've done is the Matterhorn, but I still can't imagine that the disco leg you've experienced riding your bike or standing on your front points for too long is a different kind to the 'classic' rock climbers 'disco leg' which the thread is discussing maybe?

In reply to IainMunro: I daresay the link is the central nervous system/upper motor neurones...

In reply to Cragrat Rich: The only time I have had disco leg - I wasn't in a scared situation. But I was in a position where my leg was tensed up for longer than was healthy.

In reply to IainMunro:

I dont recall claiming one (or any expertise on hormones) but I'm an academic surrounded by sports scientists and human biologists and have friends who are doctors and consultants.

In reply to Cragrat Rich:


That's the point.

In reply to Bellie

With all due respect - Aren't you just a walker??

What were you doing... Posing for an artist on a trig point

In reply to Offwidth:

Is this going to end with you both getting your nobs out?

In reply to Cragrat Rich:


You are still here to tell the tale and have presumably climbed on through on these occassions? Backing up the argument that adrenaline kicks in giving you extra strength to overcome the disco leg and deal with the task in hand?

In my experience the prospect of falling off becomes very real at times when you get disco leg and you then become even more scared but the occurrence of disco leg is not directly proportional to fear anymore than fatigue in my experience.


No it's exactly the same.

Iain

In reply to Cragrat Rich: I had disco leg in my arm last week coming round from surgery. Felt the same, wobbled the same too. I wasn't on my bike.

In reply to Cragrat Rich:

It is definately related to the body's stress response - aka Fight or Flight. I have had the exact same response during situations where I have percieved to be in danger such as being followed or recieving aggression towards me. Also I have also had the same elvis legs in other highly anxious situations such as waiting to get onto flights or during past panic attacks.

This is due to blood rushing into your muscles in order to deal with the perceieved threat or to prepare for survival (such as running away). The same response as sweaty palms (for grip), hyperventilating (to allow increased oxygen flow and heart rate), dilated pupils (more responsive eye sight)

In reply to Offwidth:


As an academic I assume you believe in evidence based practise and would be able to back up your adrenaline theory with a bit of science. Discuss it with your friends, they might be able to shed some more light on it.

I still believe it's due to fatigue and mis-firing of the nerves involved in muscle contraction. I have only a basic understanding of human physiology but the adrenaline theory simply doesn't fit.

Iain

In reply to Cragrat Rich:

The muscle fatigue you get from standing about in crampons etc which give the leg tremble is 100% different from elvis legs you get in a dangerous situation. I have experienced both.

In reply to Cragrat Rich: Lol... no am now climbing and experienced it on a crag. I am sure there will be times when I am crapping myself and get it too!.

But am actually interested in the question, as it eventually stopped me from completing a route as I kept getting it when trying to do moves. Perhaps I was subconsciously a bit scared as well? but it may have been due to it being the end of the day though and my legs had said enough is enough!

In reply to IainMunro: I don't have an adrenaline based theory. I have just often watched fit and strong climbers with no likely fatigue get disco leg when they got scared. Where is your fatigue based model for these folk?

In reply to IainMunro:

You are wrong then. Fight or Flight is a universally accepted response and your thoughts are never going to change this. Sorry.

I have suiffered panic attacks for the best part of a decade (in remission now thankfully) and I know the symptoms of Fight or Flight very well. These 1000000% creep their head when I am in potentially dangerous situations while climbing (but for genuine reasons unlike panic attacks which have no real dangerous external stimuli)

In reply to Milesy:


Is it though or is it the way you perceive it? Disco leg on a belay ledge is a nuisance whilst disco leg above poor gear and a rubbish belay is terrifying. The actual process seems the same (spasm of the calf relieved by stretching the muscle) but the way it effects me depends on my situation.

This is an interesting discussion

Iain

In reply to Lupine Lacuna:

It's adrenaline acting on the Beta 2 Adrenoceptor, causing an increase in the muscle spindle discharge and increased contraction of the muscle fibres.

I have a PhD in molecular pharmacology whilst we are waving willies.

In reply to Offwidth:


I presume you read my original response at the top of this thread?

Iain

In reply to Milesy:


Sorry, my post read wrong. I was agreeing with the above! I think I used the words 'can't imagine' it's different, when I mean't 'I imagine it is different'

In reply to Kid Spatula:

It's been a while since I had a bout of the dreaded sewing machine leg, but when I get it, it's always in the leg which doesn't have much weight on it, but is awkwardly positioned - high and sideways usually, so it can't (in my case) be due to muscle fatigue - the other leg is holding most of the weight.

FWIW I failed A level chemistry, so you're going need 20-20 vision to spot mine being waved...

In reply to Kid Spatula:


Am I right in saying that the effect of adrenaline on the B2 adrenoceptor will also trigger glycogenolysis providing more readily available glucose to overcome the stressful situation and speed up muscle contraction?

Interested as to why it is relieved by stretching the muscle and why it's only the calf that is effected? I thought the tremor associated with the stress responce was more widespread effecting the whole body?

Is my fatigue theory completely unplausible?

Iain

In reply to 999thAndy:

Exactly. It's nowt to do with fatigue.

In reply to Cragrat Rich:

Just to clarify (as it is indeed an interesting subject for a change)

I have no qualifications of any kind at all in physiology or similar, but when I put loads of weight on my back in a gym and train my calf muscles by repeatedly pressing up and down onto my toes, I have hadly managed to induce any kind of calf spasm resembling rock climbers disco leg.

However, when I rocked up onto the crux footholds of Gronf at Chevin Buttress, my belaying wife did very quickly become very concerned for my well being, since my leg was spasming up and down so much that I could barely keep it on the rock and I was looking at decking out fairly messily.

It is quite remarkable to this thread for me that my next statement to her was 'Shiiiiiiit, I've got masses of adreneline running through me'

(Can I have a First Class Honors degree for that little gem of scientific research & development)

In reply to 999thAndy:


i.e. the muscle is being stressed in an unusual manner and fatiguing quicker because you are not used to holding that particular position? The leg doing most of the work is not actually working particularly hard.

What will fatigue quicker the arm holding the shopping bag out at shoulder height or the arm with the shopping bag held on a locked off straight arm by your side?

Iain

In reply to IainMunro:

The triggering of glycogenolysis will take time though. Adrenaline and noradrenaline will spike once the stress response kicks in causing large scale muscle contractions and the use of a whole boat load of ATP.

By stretching the muscle you are essentially "overrding" the action of the adrenaline I reckon.

I don't think it's anything to do with fatigue in the case of disco leg as I usually get it due to crapping my pants rather than being knackered.

The fatigue leg wobble is probably due to the adrenaline/acetylcholine balance shifting towards the latter.

In reply to Kid Spatula:


I just don't understand why it doesn't happen everytime I get scared and only when I'm stuck on a move for a moment. I certainly suffer from a similar problem when frontpointing for prolonged periods when I'm out of shape (early season) or at the end of a long day. I've found that keeping hydrated helps reduce the problem.

Iain

In reply to IainMunro:

Perhaps I wasn't clear enough in my original post, when I get a shaky leg the leg doing the shaking is usually just being 'dabbed' for balance, the shaking usually eases if I put more load on the leg, even if I remain in the same position.

I agree with others that this probably more likely to be related to the central nervous system than (directly) a chemical effect. To back this up, I also have almost no background in physiology/biology! Indeed, I base my opinion on a little experience with neuroscience and control systems. Outwardly, the kind of behaviour that the leg exhibits is very similar to a poorly tuned feedback control system - e.g. overshoot/oscillation.

Maintaining a position on the points of your toes, requires your brain has to continuously balance our weight through tension of the calves (by measuring the angle/height of the foot at the heal). Under normal circumstances our subconsciousness handles this without issue, but it's possible that the performance of the closed loop degrades in a stressful/fatigued state - either because of a signalling issue in the central nervous system or because the brain is functioning sub-optimally.

It's a very interesting question anyway!

J

In reply to IainMunro: could it not be a little of both: muscle fatigue/adrenaline.

I get the beta-adrenergic idea, but should we not also consider that in many cases your calf is usually in that halfway stage of contraction and relaxation. Physiologically we aren't used to being in that position for a long time, there could be all sorts of feedback loops and short circuiting happening.

Yes I'm being non-scientific, my PhD was in molecular neuroendocrinology so I know just enough to know that I know nothing about physiology. There, that's my bit of willy waving.

In reply to Lupine Lacuna:

not sure if the connection to fear has been explained by anyone as haven't time to read all the way down. In case not I think ...

...the reason it's connected to fear, and also quite often to being a 'punter/beginner/etc' by some, is because you're not trusting your feet and therefore over tensing. This is particularly noticeable on slabs, as you get better at them once the leg starts to shake you can simply relax a bit and it goes. When you're worried any slight movement will make your foot slip off you can't relax.
It's a bit like over gribbing with your hands causing pump.

In reply to Scarab9: Bit like a tank slapper on a motorbike then... relax your grip and it goes, tighten it and you'll soon be out of control

In reply to orge:

I agree with the poor feedback control idea.

You get a similar oscillation effect when you first try slacklining. Or doing one leg balance positions in yoga. So it maybe has something to do with proprioception.

In reply to Lupine Lacuna: The only times I have experienced disco leg are when I am run out and climbing at or near my limit, as someone said above it seems to come on when stationary (working out a sequence or placing gear), oddly I find getting a bomber runner in does more to relieve it than heel stretches ...my theory is that it is mostly a psychological phenomenon that ocurs when you stop moving and the fear of your situation kicks in, but this is just based on personal experience and has no scientific grounding.

In reply to Lupine Lacuna:

I may be somewhat inferior in the degree willy waving contest, with only an almost completed BSc in human anatomy, but I thought I would take a stab at answering the question.

The following is relatively quickly researched and even more hastily written; a full list of references can be provided if anyone would like to read further into the subject. I have potentially barked up the wrong tree entirely but my suggestion is:

Motoneurons are capable of continuing to fire repetitively after stimulation by a brief, excitatory synaptic input (self-sustained firing). This self sustained firing (SSF) is the result of the activation of persistent inward calcium and sodium currents (PICs), which are themselves influenced by both serotonin and norepinephrine(adrenaline). Adrenaline and serotonin are monoamines which arise mainly from the brain stem; their levels are significantly elevated during periods of excitement or stress. Activation of 5HT2 and ¦Á-1 receptors, serotonin and adrenaline receptors respectively, on the motorneuron facilitate these low-voltage activated PICs producing sustained depolarisations, also referred to as plateau potentials.

These plateau potentials allow motor units, recruited through even slight stimulation, to continue to fire in a self-sustained manner following the removal of the excitatory stimulus; the stimulus usually needs to be present for ¡Ý2s however repeated activation or further increases in adrenaline, or serotonin, reduce this requirement.

Plateau potentials are primarily seen in type I motor neurons, whose units are recruited first in a muscular contraction and are relatively resistant to fatigue, though larger units can demonstrate the same effect.

The high serotonin concentrations demonstrated during 'central fatigue' may trigger an increase in plateau potentials and hence SSF, as might extracellular accumulation of K+, synonymous with fatiguing contractions. Increased extracellular [k+] decreases the concentration gradient and so reduces K+ transport out of the cell. High intracellular [K+] leads to further activation of plateau potentials and gradually increases motor unit depolarisation generating a stronger and stronger contraction.

The above would suggest that both adrenaline and serotonin levels may be responsible for disco leg while muscular fatigue is also an entirely plausable contributing factor. Experiments on this phenomenon have made use of caffeine and amphetamines to stimulate greater adrenaline release.

In reply to melonmike: ... which means that?

In reply to Rob Exile Ward:

Fear(adrenaline), potentially in combination with muscular fatigue, can result in disco leg.

In reply to melonmike:
Interesting topic. I think as mentioned that it has more physiological than fear induced basis. Dropping heel relieves it.

Isometric muscle contraction could prevent effective perfusion and prevent ATP regeneration for myosin head binding. The muscle (gastrosoleus group) fatigues and tries to relax. When heel dropped muscle is stretched and cannot contract..?

Catecholamine influence is apparent but not main factor??

In reply to melonmike:

I think you are confusing the two functions of adrenaline.

The physiological processes you described earlier happen within synapses (the junction between nerve cells) in the central nervous system where adrenaline acts as a neurotransmitter ie it is involved in neurological control.

Adrenaline also acts as an endocrine hormone when it is released into the bloodstream in response to psychological states such as fear ie fight or flight response.

Disco leg is a failure of neurological control, same as standing on one leg and closing your eyes.

This process will be intensified by fear and fatigue and reduced by repetitive practice/motor learning.

In reply to Lupine Lacuna:

Its probably some kind of activity-specific intention tremor.

In reply to Lupine Lacuna:

Do you think there may be a few different phenomena at work here rather than just one?

Personally, I find that there is no correlation between whether or not I get disco leg and how nervous / in extremis I am. On the other hand, my parents dog gets disco-body while lying in his bed if he hears thunder...

In reply to IainMunro: I'm with you here, I think the main cause of disco leg is some sort of fatigue from being in one position. I do think fear comes in and that can tire you quicker or cause the shakes which I'm not sure is strictly disco leg.

Also re the others on flight/ flight adrenalin, adrenalin is for both, it'll help you run quicker, ignore pain, run when you should be immobilised etc.

PhD in marine invertebrate physiology, so not a strict physiologist but more than a cursory understanding.

In reply to Milesy:

Yeah, so this is what I'm saying. I think much of the arguments here are about 2 different but similar reactions, with different causes.

Be an interesting sports science project. Maybe you could use adrenalin suppressors or boosters (I'm sure ethics would be an issue) to test and compare situations.