The ski tuck: torso forward, knees together, poles under your arms. Wind-tunnel numbers, steps and why speed control comes before top speed.
The tuck is the deep, aerodynamic riding position: knees bent, torso far forward, arms bent, poles under your armpits. It makes you smaller for the wind and therefore faster – but only where you can control that speed. The honest answer up front: the tuck is a speed tool, not a must.
How much it brings was shown by wind-tunnel measurements on two world-class skiers: for every degree the torso gets steeper, drag rises by about 0.8 %, and by about 1.2 % per degree of steeper thigh [1]. Extrapolated to ten degrees that is roughly 8 % more drag – my own extrapolation, the study measures per degree. This applies to racers (TRANSFER), but it shows the principle: every degree counts.
How hard is it? The position is quickly learned by a skier with a secure straight run. The hard part is the decision: when to go in, when to get out. How long you need for this, no study tells.
Run straight in the basic stance, shins lightly against the boot. When that runs calmly, go lower. Milestone: you run straight for 30 seconds without wobbling. This time is an experience value, not a study value.
Bend your knees and tip the torso forward from the hip. The back stays long, not round. The flatter the torso, the less drag [1] – but only as flat as your forward view allows.
In the deep tuck, the lower legs alone account for up to 40–50 % of the total drag [1]. So: knees tight, calves together, and the knees fill the gap behind the armpits.
Bend your elbows. In a high tuck, arm position alone makes a 17–21 % difference in drag between an open and a closed posture [2]. Guide the poles backwards under your armpits: they make up only about 2 % of the cross-sectional area in the tuck and up to just under 5 % in higher positions [3]. Not much – but their position varied by a good quarter in the same skiers in the tuck [3]. So guide them deliberately close.
Look beyond your ski tips, not at them. You must see obstacles and other skiers early (practice).
Get out of the tuck before crests, traverses, narrow spots and people. Milestone: you rise from the tuck and are in the basic stance before you lose control – not after.
Close the gap. The wind-tunnel data are clear: the flatter the torso and the tighter the knees, the smaller the area [1]. Try it on a flat run-out with side video: is there a visible gap between upper arm, thigh and torso? Then close it with your knees.
A second trick: the difference between open and closed arms in the high tuck is larger than between different forearm angles in the low tuck (only up to 2.8 % there) [2]. If you want to change just one thing: close the arms.
You bend your knees, tip the torso forward from the hip, bend your arms and guide the poles backwards under your armpits. Knees and calves stay tight, the back long and your gaze far ahead. The flatter the torso and the tighter the posture, the smaller the area for the wind [1][2][3].
Because you present less area to the wind. In wind-tunnel measurements on two top skiers, drag rose by about 0.8 % per degree of steeper torso and about 1.2 % per degree of steeper thigh. These are racer values (TRANSFER), but they show the principle: every degree counts, especially in torso and knees [1].
Only on free, open slopes and only at a speed you control. FIS Rule 2 requires you to adapt speed and way of skiing to your ability, the terrain and traffic density. Advanced skiers already average 44.5 km/h without a tuck – in a tuck you get even faster [4][5].
Close to the body, backwards under the armpits. In the tuck the poles make up about 2 % of the cross-sectional area, in higher positions up to just under 5 %. Their position varies a lot from run to run – so guide them deliberately close so they do not add drag or hinder you in a fall [3].
Skating 1:2 (V1): The Uphill Technique in Cross-Country