Why ski jumping's central dry-land drill is more than a warm-up: it predicts season performance and shows the same knee pattern that endangers cruciate ligaments.
The imitation jump is the only exercise in ski jumping that reproduces the take-off on land — and the only one with hard numbers behind it. In a laboratory study of ten elite jumpers using a force plate and motion analysis, the vertical take-off velocity in the imitation jump was related to season and competition performance on the hill — R = 0.718 [1]. For a dry-land drill that is a remarkably close relationship.
The second number is even more interesting. The stronger the tendency towards knee valgus — knees collapsing inwards under load — the worse the performance: R = 0.729 in the imitation jump, R = 0.685 in the squat [1].
That is the real reason this drill matters so much: the same movement quality that brings you distance protects your knee. Internal rotation at the knee is at the same time a risk factor for cruciate ligament injury [2]. Performance and prevention here are not a trade-off but the same number.
This section explains what the imitation jump is and what it measures — it is not a training plan and not instruction to jump at the hill. Set-up, volume and progression belong to coach and sports medicine.
It reproduces the transition from the deep in-run crouch into explosive extension — exactly the movement that decides everything on the hill: the take-off is the most important movement phase, because it sets flight speed, early flight angle, angular momentum and body position [5]. On land everything distracting falls away — speed, height, fear.
On the hill the force must be developed at the optimal moment at the optimal point of the table, and that window is fractions of a second long [5]. The take-off velocity perpendicular to the ramp sits at roughly 2 to 3 metres per second in elite jumpers [5] — a small number with large effect. The imitation jump is where this timing becomes repeatable a thousand times over.
Two quantities carry the drill: vertical take-off velocity — related to season performance in elite jumpers at R = 0.718 [1] — and knee control under load. Neither needs a competition hill. That is exactly why the drill is a diagnostic instrument and not just preparation.
When knees collapse inwards under load, it measurably costs performance (R = 0.729 in the imitation jump, R = 0.685 in the squat) [1]. And that same internal rotation at the knee is among the factors that, under high landing forces, favour a non-contact cruciate ligament injury [2]. One pattern, two bills — one paid in the results, the other in hospital.
Film from the front and look at three things: do the knees stay over the feet? Does extension come as one movement or in two portions? And is the sequence repeatable, or does one in five work? What you see there belongs in the conversation with your coach — the correction itself is training work, not self-diagnosis.
The imitation jump is a land drill — which is exactly why its load is easily underestimated. These are maximal jumping movements [4], and they add up. Volume, progression and rest belong in a plan owned by the coach and, where needed, sports medicine.
On movement quality: knee valgus is not a cosmetic flaw. Internal rotation at the knee is one of the factors that, under high ground reaction forces, favour a cruciate ligament injury [2]. Repeating it under fatigue trains in precisely the pattern that later becomes dangerous on the hill.
And the limit of this text: it explains and motivates, it never replaces supervised training in a club or at the hill — nor any medical or physiotherapeutic assessment. Separate understanding from execution: a good imitation jump does not make you hill-ready. The hill remains a matter of strict size progression under qualified guidance.
Judge your series by its repeatability, not by the best attempt. On the hill you get exactly one jump, and the force window is fractions of a second long [5] — what counts is the sequence you can call up under pressure, not your highlight. A practical rule from the data: when speed and leg axis conflict, the leg axis always wins — because valgus costs you both, performance [1] and cruciate ligament [2].
Essentially through jumping power, explosiveness and trunk stability, because the take-off is a maximal, precisely timed explosive leg extension from a deep crouch [4]. The methodological core is dry-land drills of the in-run crouch and the take-off movement [3], above all the imitation jump, whose vertical take-off velocity was related to season performance [1].
Mainly two things: vertical take-off velocity, related in ten elite jumpers to competition performance at R = 0.718, and control of the leg axis under load — more knee valgus went with worse performance (R = 0.729 in the imitation jump, R = 0.685 in the squat) [1].
Because it costs twice. It was associated with worse competition performance in elite jumpers [1], and the same internal rotation at the knee is among the factors that, under high landing forces, favour a non-contact cruciate ligament injury [2]. Performance and prevention point the same way here.
The movement itself is a land drill, but set-up, volume and correction belong in supervised training [3]. Without a view from the front you will not see your valgus, and without management maximal jumping movements add up quickly [4]. Filming yes, programming alone no.
Protecting the Knee and ACL: Why the Landing Carries the Risk — and How to Prevent It