In skiathlon, athletes change skis in the middle of the race because the event combines two completely different techniques—classic and skate—that each require different equipment to be fast and fair.

What is a skiathlon?

A skiathlon is a cross‑country race done half in classic style and half in skate (freestyle) style, with a mandatory equipment change in the middle. The race usually starts in classic, then after a set distance skiers enter a pit zone, switch skis (and sometimes poles), and continue in skating technique to the finish.

Why they change skis

The short version: classic skis and skate skis are built differently, so using one pair for both styles would be slow and unbalanced.

Key reasons:

  • Different ski construction
    • Classic skis are longer with a “wax pocket” under the foot for grip wax or skins, so you can kick and glide in tracks and on climbs.
* Skate skis are shorter and fully glide‑oriented, with no grip zone, optimized for side‑to‑side skating pushes on packed snow.
  • Technique demands
    • Classic style needs grip underfoot to push straight back, especially on climbs and in set tracks.
* Skate style relies on edging and glide, and any grip wax or skin would drag and be noticeably slower.
  • Speed and fairness
    • If athletes tried to do both halves on one compromise ski, someone’s setup would be badly disadvantaged in at least one half.
* Requiring a change lets everyone race the classic portion on proper classic skis and the skate portion on proper skate skis, which keeps the focus on fitness, technique, and tactics rather than on who gambled best on a “hybrid” ski.

How the change works in the race

  • The race is mass‑start in classic; after the classic distance (e.g., 15 km of a 30 km race), skiers enter a transition pit.
  • They must switch to a second pair of skis that are prepared specifically for skating, then exit the pit and finish the remaining distance in skate style.
  • The transition itself is tactical: a fast, clean ski change can gain a few seconds, while a fumble can cost positions.

Extra angle: waxing and conditions

While the main reason is the classic vs skate design difference, the mid‑race change also helps with waxing in difficult or changing snow. Teams can prepare the skate pair with glide structures and waxes ideal for higher speed and possibly different snow than at the start, which can decide small margins late in the race.

TL;DR: They change skis in skiathlon because the race switches from classic to skate technique, and each style needs its own specialized ski to maximize speed, maintain fairness, and showcase athlete performance rather than equipment compromise.

Information gathered from public forums or data available on the internet and portrayed here.