Upper arc vs lower arc in a snowboard carve: why the hard parts are opposite

“Why is the lower arc always slower than the upper arc?” After watching a carving DVD, 西西 says, sleep didn’t come that night until 2 a.m.

The DVD is a conversation among several top riders. 西西 summarised a few of their points in a post; this post joins those to 西西’s other notes on where to apply pressure and on edging and pressure, to look at the shape of a carved turn.

This post is for you if you:

• can already carve, but feel you lose a lot of speed in the lower arc
• want to know why some riders shape the turn like a “heart” rather than a circle
• often hear “apply pressure in the upper arc” and aren’t sure what it means

First, where this comes from. The DVD material is 西西’s account; the riders are not named here, and we won’t supply names for them. The rest is 西西’s own summary. All of it is personal opinion, not an official JSBA position, and there is no measured data on how large the external force is in each part of the turn. KAKU’s earlier post didn’t address that question, so Part 4 didn’t cover it; everything in this post comes from 西西.

The heart-shaped turn: all the work goes into the upper arc

First, the terms. This post follows the usage in 西西’s posts: from turn entry until the fall line (the steepest natural line down the slope) is the upper arc; past the fall line, the second half, where the turn comes back uphill, is the lower arc. 西西 doesn’t define “upper arc”; this is how we read 西西’s usage.

According to 西西’s account, the DVD’s first point is that the lower arc has lots of external force and slows you down by nature. So strong riders don’t ride a “circle”. They shape the turn like a “heart”.

Cut a heart in half and look: the top half curls up, the bottom half runs smooth.

As relayed by 西西

In other words, these riders put their work only into the upper arc to make the turn shape; past the part that curls up, they run the lower part straight down the hill with the board flat.

The second point is that the two halves are hard in exactly opposite ways:

• Lower arc: lots of external force. Don’t misuse internal force here. Rather than actively applying pressure, hold on and get the turn shape right, and you’ve won.
• Upper arc: no external force. Internal force alone controls direction and edging, and the body has to make many fine movements.

If a “da-da-da” bounce appears as you exit the turn, then according to 西西’s account the edge isn’t gripping the snow. In that moment, press the upper body down lightly for an instant, edge once, and the edge change settles.

The DVD also covers another way of riding: one type of rider uses “the board’s deformation”. They stamp on the board hard enough to bend it severely; ease off the legs slightly and the board springs back hard. What they think about is not releasing pressure but “when the board rebounds, I need to stay steady, not get thrown off, and change edges while I’m at it.”

Key point: the upper arc uses internal force to shape the turn; the lower arc has lots of external force, so hold on. This is the view 西西 relays.

Where you apply pressure decides what your speed does

In another post, 西西 sets out how the place you apply pressure relates to speed:

• Apply pressure in the upper arc and you speed up.
• Apply pressure near the fall line and you can steady your speed.
• Apply pressure where the turn comes back uphill and you slow down.

西西 says the up-and-down movement of the centre of mass is the core of carving technique; at high speed especially, this movement produces a feeling like being catapulted. Speaking of certification exams, 西西 also says controlling the turn shape is the key, and that pressure in the upper arc is especially important.

Read this order alongside the earlier post on crouching: what crouching and rising change is the moment at which pressure shows up.

In yet another post, 西西 describes how the first and second halves of a long turn feel different:

• In the first half, pressure comes mainly “passively”, from external forces such as centrifugal force. The body doesn’t actually work very hard; it just goes with the speed and the centrifugal force, and pressure reaches the board on its own.
• In the second half, external forces grow and get more complicated, and you need to actively use muscle strength, that is, internal force, to maintain or adjust the pressure.

There is a gap here we have to be honest about. The DVD account says the upper arc has no external force and relies entirely on internal force; the long-turn post says the first half is pressured passively by centrifugal force and takes little effort. Whether the “first half” and the “upper arc” here are the same part of the turn, and under what conditions each statement holds, 西西 doesn’t explain, and we have no verified data. So we set them side by side and don’t reconcile them on 西西’s behalf.

Key point: apply pressure in the upper arc to speed up, near the fall line to steady your speed, where the turn comes back uphill to slow down; on the external force in each part of the turn, the two posts don’t agree.

Edging and pressure are results

The last point is about “how to handle edging and pressure”. 西西 relays that in this episode of the programme 滑力, 青木玲 interviewed several top riders with the same question: how do you handle edging and pressure in snowboard carving?

The consensus:

Rather than treating edging or pressure as two separate actions you make on purpose, see them as "results" the body produces naturally as it follows the board through a particular turn shape.

The programme's consensus, as relayed by 西西

This fits the order above: decide first what turn shape you want to ride, and edging and pressure follow from it. That link is our reading; 西西’s posts don’t say it. To practise, the edging process is covered in stalled edge changes and edge angle.

Who this post is not for

• Riders who can’t yet carve consistently: read what carving is first. You won’t need these turn-shape trade-offs for now.
• Anyone who wants numbers for “how much external force, how much pressure”: the sources don’t give any, and this post won’t make them up.

How these ideas map onto the snow is best checked with someone watching you ride. For the Snowboard Progression Lesson in Hokkaido, see the courses page; to sign up, you need to be able to link turns consistently. For 西西’s qualifications, see 西西’s profile. The previous part covered where to look when carving on steep slopes.

This post draws on 西西's Threads posts and teaching notes. The DVD and programme content is 西西's account; we have not checked it against the original programmes, and the riders in that account are not named. These are personal views, not official JSBA positions.