Learn the underbar: leg guidance, hip swing and hand change in six stages — with the sitting test for gap size and honest, checkable safety limits.
In the underbar you do not go over an obstacle, you go through it: you jump legs first into a gap — typically between two railing bars — grab the upper bar in flight, pull yourself through with a hip swing and land on the other side. The order is always legs, hips, hands. Think head first and you will hit the bar with your head.
The underbar is the move that proves parkour is not jumping but reading space.
That is exactly its appeal, too: a review describes adaptability to unfamiliar environments as the core of the sport — and notes that many of these specific techniques have barely been studied scientifically so far [1]. The underbar is one such case: there is no force-plate data on it. What you read here is therefore deliberately split into documented numbers and declared practice.
The good news: the underbar is one of the few parkour moves you can learn almost entirely from standing and in slow motion. Expect one to two weeks to the basic shape on a wide gap and several weeks to a fluid pass out of a run. Experience values, not study figures.
Climb slowly through the gap once, no jump. If shoulders and hips pass comfortably, the gap is suitable. Then pad the upper bar.
Milestone: three passes without bumping anything, each under five seconds.
Sit on the lower bar, grip the upper one above you, push your legs forward through the gap and lower yourself under control on the other side. This is the underbar in slow motion.
Milestone: 10 repetitions with no contact on either bar.
Hang from the upper bar and swing your straight legs calmly forward and back with a braced core. That swing is the drive that will later carry you through the gap.
Milestone: 10 controlled swings with no arched back and no hanging shoulders.
Take off two-footed half a step before the railing, legs first through the gap, hands grabbing the upper bar, hips following, set down under control.
Milestone: 10 passes where neither heel nor head touches a bar.
Now add speed. The hands grip briefly, pull and release again — the underbar is a pull-through, not a hang. Look through the gap at your landing spot.
Milestone: 8 out of 10 attempts with a silent landing and no stop at the railing.
Finally out of a jog and with changing gaps: narrower, higher, wider, different material. In a cross-sectional study traceurs showed clearly larger eccentric knee extension torques than gymnasts and strength athletes [2]; it does not show that variation is the reason — as a training idea, variety still makes sense.
Milestone: the same underbar on three different railings, each time running on.
The underbar has a different risk profile from any vault: the danger is not the ground but the metal around you. In a survey of 161 practitioners, 24.7 percent of injuries hit the upper limb, and the most common diagnoses overall were sprains (22.3 percent) and contusions (21.1 percent) [4] — exactly the two categories a failed underbar produces.
The rest of the statistics stay reassuring: in a survey of 180 traceurs the self-reported rate of ankle or knee injuries averaged 1.7 per 1000 training hours [5]. This move is manageable if you keep the order.
This guide explains and motivates, but it does not replace supervised training. The underbar puts your head between two solid bars — the first attempts belong on a padded gym railing and under the eyes of someone who can judge the gap size for you.
Before every new railing, run the sitting test: sit on the lower bar, grip the upper one and slide yourself slowly through once. If you fit through comfortably while seated, you will fit in flight — and at the same time you learn how stable the bars are, how much grip the material has and where your head has to go. The test takes ten seconds and replaces guessing. Anything you cannot manage seated, you certainly cannot manage with a run-up — only faster.
Rule of thumb from practice: you must be able to step through comfortably while standing, without contorting yourself. Anything narrower is not progress but risk — the typical underbar injuries are shoulder and hip contusions and they almost always come from gaps that are too tight. There are no scientific measurements for this; it is experience knowledge.
Because your torso tips too late. The legs lead, the torso lays back, and the head follows last — not the other way round. Practise the seated slide-through until that order comes automatically, and pad the upper bar with pipe insulation during the learning phase.
Yes, as soon as speed is involved. The grip keeps your hips up and turns a fall-through into a pull-through. Without it your heel drags on the lower bar and the landing becomes uncontrolled — exactly the hard landings that produced 5.2 body weights on the force plate (traditional landing) instead of 3.2 for the precision landing [3].
It causes fewer accidents than any jump with height, but it produces the typical contact injuries: contusions and sprains, which together made up the largest share in the survey of 161 practitioners [4]. With a big enough gap, a checked railing and a flat landing area the risk is small and easy to control.
Best on gym railings or gymnastics bars whose spacing you can set yourself. Outdoors, solid barrier railings with a wide gap and flat ground on both sides work well. Avoid mesh fences, bars with vertical struts and anything that wobbles — here the material decides more about your safety than your technique does.
Rail Balance: Standing Still on a Bar or Ledge