Learning the scrub means starting small: push the bike sideways at take-off, straighten it before landing. 5 stages with milestones and safety.
The honest answer first: a scrub is a jump kept low. You push the bike sideways at take-off, stay over the bike with your body and straighten the bike again before landing. This is not a beginner skill, and there is no association or study description of the technique itself that we have read. Everything about execution below is scene practice and therefore carries no source number.
What it builds on is documented. BASPO, the Swiss Federal Office of Sport, names a small table (no gap between take-off and landing) a few metres long as ideal for practising jumps [1]. And it describes as the top aim of a controlled flight phase that neither front nor rear wheel may sag [2].
Why is the scrub demanding? Because it changes the flight phase, in which you can correct the least. In a video analysis of 534 mountain bike crashes, 64.4 percent of over-the-bars crashes followed poor jump landings [3], and a fall during a jump doubled the odds of head impact (odds ratio 2.2) [4].
How hard is it? It belongs to the skills that take months to years (experience-based), and it is practised only on a jump you already fully control.
A scrub is the art of flying less, not of being further away from the ground.
Ten clean landings in a row with eyes over the take-off to the landing [1]. Both wheels land at the same time or the front wheel slightly earlier, the legs absorb.
Milestone: ten out of ten clean, without a correction in the air.
Roll straight and tilt the bike sideways under your body, on the lawn and without take-off (see bike-body separation). Your upper body stays calm (practice).
Milestone: you tilt the bike 20 degrees left and right, your head stays in the middle.
On the small table you push the bike only a few degrees sideways at take-off. Then you straighten it again, long before landing (practice).
Milestone: five jumps in which the bike is straight at landing and both wheels touch down together.
Increase the lean only a little at a time, on the same jump at the same speed. BASPO names varying the approach speed as the most important element in drops [2]. So never change speed and lean at the same time (practice).
Milestone: you can see the lean and the return before landing on the video.
Only when the first jump is clean ten times do you transfer it to a second, similar table. Do not move to another type, for example with a gap (practice).
Milestone: two different table jumps, five clean scrubs each.
The scrub is safety-critical. Mistakes happen in the air and show at landing: in the bike park study of 274 injured riders, 20.8 percent were due to jump landings, fractures made up 52 percent and about a quarter were evacuated by helicopter (TRANSFER: bike park, not trail) [6]. Severe injuries are more common in downhill, influenced by rider skill and trail design [7].
Practise only on small, known jumps. The decision whether to jump follows the product of fall probability and injury probability: experienced riders declined ramps at about 13 percent on average (pilot study, ramps) [8]. A helmet cut serious head injuries among cyclists by about 60 percent [9], a figure for cycling in general. This guide explains and motivates, it does not replace supervised training or a coach.
Ride the first scrubs in your head on the ground. On the lawn, imagine where the bike lies and when you straighten it. Then simulate it in bike-body separation, without take-off. If you have automated the return to a straight landing, you are already half safe on the jump (practice).
A jump kept low in which you push the bike sideways at take-off and straighten it again before landing. The technique rests on scene practice, not on an association description (practice).
When you land a small table cleanly ten times in a row and can tilt the bike under your body. As a practice jump, BASPO names a small table a few metres long [1].
Yes, because mistakes hurt at the landing. A fall during a jump doubles the odds of head impact (odds ratio 2.2) [4]. Keep jumps small and controllable.
More protection than helmet and gloves makes sense. DIMB lists protectors as additional equipment [5]. Protectors do not replace technique or progression.
Tabletop on a Mountain Bike: Laying the Bike Flat Sideways in the Air