What are the core rules in Cross-Country Skiing?

Relay: exchange zones are 30 m long. Body contact (tag) required for valid exchange.

Section 5: Rules of Play

Skating movements strictly prohibited on flat and uphill terrain; both skis must remain in the set tracks
Herringbone (V-step without glide) permitted on steep uphills only
Snowplow permitted for downhill braking
Stepping out of the track to pass is permitted; the overtaking skier must return to a track after passing
Double-poling (using only arms without kick) is permitted as a classic technique
Technique violations detected by controllers stationed along the course with video equipment

Any technique permitted, including skating (V-skate, marathon skate) and classic movements
No set tracks on the course; athletes choose their own line within the groomed corridor
Overtaking: the athlete being overtaken must yield the preferred line when the faster athlete comes alongside

First half raced in classic technique; second half in free technique
Transition zone: athletes remove classic skis and boots, switch to skating equipment. No time added; clock runs continuously.
All equipment must be pre-positioned in the transition zone before the race starts
Athletes must complete the classic leg before entering the transition zone

Men: 4×10 km (legs 1–2 classic, legs 3–4 free). Women: 4×5 km (same technique order).
Exchange: body contact (hand tag) required for a valid exchange in the 30 m exchange zone
All teams start simultaneously (mass start for the first leg)
Leg order and technique for each leg are pre-determined by the organizers

An athlete being overtaken must move to one side and yield the fastest line
In classic races, the overtaken athlete must leave the track within 15 m of the faster athlete coming alongside
Deliberate obstruction is a violation subject to time penalty or DSQ
In sprint heats, athletes may not make lateral movements to block overtaking

Skating movements strictly prohibited on flat and uphill terrain; both skis must remain in the set tracks
Herringbone (V-step without glide) permitted on steep uphills only
Snowplow permitted for downhill braking
Stepping out of the track to pass is permitted; the overtaking skier must return to a track after passing
Double-poling (using only arms without kick) is permitted as a classic technique
Technique violations detected by controllers stationed along the course with video equipment

Any technique permitted, including skating (V-skate, marathon skate) and classic movements
No set tracks on the course; athletes choose their own line within the groomed corridor
Overtaking: the athlete being overtaken must yield the preferred line when the faster athlete comes alongside

First half raced in classic technique; second half in free technique
Transition zone: athletes remove classic skis and boots, switch to skating equipment. No time added; clock runs continuously.
All equipment must be pre-positioned in the transition zone before the race starts
Athletes must complete the classic leg before entering the transition zone

Men: 4×10 km (legs 1–2 classic, legs 3–4 free). Women: 4×5 km (same technique order).
Exchange: body contact (hand tag) required for a valid exchange in the 30 m exchange zone
All teams start simultaneously (mass start for the first leg)
Leg order and technique for each leg are pre-determined by the organizers

An athlete being overtaken must move to one side and yield the fastest line
In classic races, the overtaken athlete must leave the track within 15 m of the faster athlete coming alongside
Deliberate obstruction is a violation subject to time penalty or DSQ
In sprint heats, athletes may not make lateral movements to block overtaking