Why do your legs tremble uncontrollably sometimes when rock climbing?


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Dear Straight Dope: I remember the first time I went rock-climbing back in high school, using ropes and experiencing some real exposure to heights. At one point, my legs were trembling uncontrollably in the middle of a pitch. I called for tension on the rope and everything turned out OK. Why would nature make you tremble uncontrollably when the direct result could be death? John Kenney

SDStaff Jillgat replies:

Hey teemsters, raise your scabby, abraded hand if you’ve done any technical rock climbing. Only seven of you? Okay, the rest of you talk amongst yourselves about whether fish fart while we address the issue of trembling legs, also known to climbers as “sewing machine leg,” “stitching,” “Elvis syndrome” and “death wobbles.” I’ll define some other climbing terms later for the rest of you who decide to stick with us.

Sewing machine leg is usually a pretty easy condition to alleviate unless the fear component is too high, too. It happens when you have all the weight on the ball of your foot with your heel lifted. This puts a lot of strain on your (probably already tired) calf muscle which causes it to reach a point of fatigue, whereupon the humiliating shakes begin. Relax and lower your heel and it will usually stop right away. And try not to reach so high that you’re stretched out like that.

What causes it, physiologically? Partly it’s just nature’s way of embarrassing you out of using bad climbing technique. One physical therapist told me about “activating and sensitizing gastroc muscle spindles [gastrocnemius = calf muscle] that work on a reflex loop.” Another one I spoke with talked about “overfiring of nerves due to hyperpolarization along the neuronal pathway responsible for supplying that particular muscle with electrical impulses to contract.” Climbers aren’t the only guys with their own language.

An answer from Erik van Dijk of Physical Therapy Associates helped me picture it a little better:

Particularly during rock climbing, the calf muscle is under constant demand to perform in carrying someone’s weight. During normal ambulation, there is a rest/contraction cycle during which the muscle contracts to propel the person forward. This is done alternately by both legs, giving a moment of rest and relaxation to the opposite leg. These phases are called push-off and swing-thru. The push-off phase causes the muscle to contract, the swing-thru phase causes the muscle to relax. When alternation of contraction and relaxation are not possible, the muscle fatigues quickly and responds with a cramp-like action, causing the foot to go up and down rapidly. Pushing the heel down breaks up the spastic contraction and lengthens the muscle so it can contract (shorten) again later in the cycle.

Now for that vocabulary lesson I promised, plus this tip: The purpose of the rope is to catch you if you fall, not to assist you in climbing. Unless you really are about to fall, it is often considered a wuss move to ask for “tension” on the rope from your belayer. If there is too much slack in the rope above you, you can say “up rope” which doesn’t have the same desperate connotation as “tension” (but is still used sometimes in panicky moments, as is “tight rope”). Yes, I’ve asked for tension on the rope with shaky voice as well as shaky legs while climbing, but not without having my partner respect me less in the morning.

The climber ties the rope to a harness around his or her waist and legs, and the “belayer,” the person holding the other end of the rope, protects you should you fall. A belayer can be above you reeling rope in as you approach or below you, feeding rope out if you are “leading.” When you get to the end of the rope (or reach your belayer above you), you’ve climbed a “pitch.” The length of long climbs is sometimes described by how many pitches they are. Longest climb I ever did was eighteen pitches. And I led nine of ’em. That was a very long day.

If you’re “leading” a climb, you’re placing “protection” in the form of “chocks” and “stoppers” (shaped pieces of metal that fit into cracks in the rock acting as anchors while you climb). The rope slides through carabiners (aluminum snap links) connected to your protection via nylon webbing, and back down to the belayer below you. If you fall, hopefully you will only fall a short distance and your protection and belayer will stop you. If you’ve climbed too high above your last placed protection, you’ll fall farther and sometimes, if your protection isn’t “bombproof,” the sudden force will cause all your chocks and stoppers to pull out in sequence as you speed to the ground. This is called “zippering” and the term for what you may end up doing is a “screamer” and final “cratering.” Presumably your goal is recreation, and this is obviously not that, so it’s a good idea to avoid it.

I haven’t climbed in a long time, so some of these terms may be outdated and I’m sure there are lots of new ones. But here are some of my favorites:

Barn Door – when a climber loses purchase with the hand and foot on one side and the other side, still on the rock, acts as a hinge as the body swings out away from the rock. Belay Betty or Belay Bob – the girlfriend or boyfriend of an addicted climber Cheese Grater – taking a fall and sliding down a slab of rock. You can imagine what this does to your skin. Crux – the hardest part or section of the climb Epic – a hike or climb that turns into a grueling, sometimes dangerous, adventure. Usually exaggerated in the telling, but exaggerations are not always necessary. Flailing – using bad form, frantically grabbing for holds Flash – to easily do a new climb one has never attempted before, without falling or having to repeat sections. Gripped – paralyzed with fear Gumby – a new climber Jam – to use your hand, foot or other body part as a wedge in the rock to pull yourself up. This accounts for a lot of the scabs and abrasions on climbers’ hands. Sew up – to place lots of protection on a climb, sometimes close together. This is what you might do to avoid zippering. But don’t run out of pro too soon! Thank God hold – after clinging to flakes and almost invisible nubbins on the rock, you come across this great bucket for your hand or ledge for your foot.

See you on the crags!

SDStaff Jillgat, Straight Dope Science Advisory Board

Send questions to Cecil via cecil@straightdope.com.