Skisens Summary of Vasaloppet Week 2020 – Power Data, Glide Friction & Performance Analysis

Vasaloppet Week 2020 is over, and everyone who raced one or several events has now had a week to recover and reflect. The Vasaloppet organization can also finally breathe out after a winter full of challenges.

Skisens participated in the first race, Vasaloppet-30, as well as the grand finale — the “Real” Vasaloppet. These two events highlighted the extremes of this year’s Vasaloppet Week. Vasaloppet-30, along with Öppet Spår and several other races, took place under perfect, lightning-fast conditions. The main Vasaloppet, however, just like in 2019, brought heavy snowfall and slow tracks. The toughest conditions of the week hit the two most high-profile races: Tjejvasan and Vasaloppet.

We previously reported on the excellent conditions during Vasaloppet-30 and how those times could have translated to the tougher, rain-soaked conditions in Tjejvasan. Here we present measured data from Vasaloppet — a race without rain but with heavy snowfall that made the landscape beautiful, yet the tracks significantly slower according to Skisens measurements.

Part 1: My Vasaloppet 2020 Analyzed Through Skisens Power Data

For the second year in a row, I skied Vasaloppet with the Skisens power grips. In 2019, as previously reported, the data recording unfortunately stopped after about 25 minutes. This year I captured everything.

Notice in Figure 1 that heart rate follows power very closely over longer time periods. This confirms the quality of the measurement — and also reminds us why power is far superior to heart rate for intensity control. Heart rate reacts with significant delay, as shown in the segment from the start to Smågan.

Looking at how the race developed, Figure 1 shows that I held things together fairly well up to just after Risberg. The segment between Risberg and Evertsberg is often my weakest — and this year was no exception. Short and steep climbs left me suddenly tired in the upper body.

Up to ~40 km:
– Average power: ~180 W
– Average HR: 146 bpm

Remaining ~50 km:
– Average power: 132 W
– Average HR: 125 bpm

Overall:
– Average power: 158 W
– Average HR: 134 bpm

Table I shows that heart rate in the start climb is 12 bpm higher than later segments at the same power — likely adrenaline and the chaotic mass start.

My placing development is shown below.

Part 2: Vasaloppet 2020 Compared Using Skisens Power & Glide Data

To understand performance demands, we estimate glide friction using measured pole force and the barometer-based elevation profile.

By iterating against the mechanical power balance described in our Vasaloppet 2019 report, we estimate an average glide friction coefficient of 0.038.

Using this, we calculate required power for different finishing times and compare them to Öppet Spår 2020, where friction was just 0.022.

We also compare these to skierg benchmarks.

Part 3: Medal Difficulty and Advancement Between Start Waves

In 2020, only 1,712 skiers achieved medal time — far below the long-term average.

Advancing start waves was also unusually difficult.

Only 3 skiers advanced from Wave 1 to Wave 0 — the lowest in 7 years.

Summary

This complete pole-force and power dataset from Vasaloppet’s 90 km course is a milestone for Skisens. It gives unprecedented insight into:

– physical demands
– glide-friction impact
– pacing and fatigue patterns
– power needed for medals
– wave advancement difficulty

Vasaloppet 2020 was tough: slow tracks, low medal rate, difficult advancement.
Next year, Skisens aims to have athletes in every start wave for even deeper analysis.

Dan Kuylenstierna
Skisens AB