Measuring Power in Skate Technique – How Much Work Goes Through the Poles?

We hope you’ve all had a great Christmas break – and that some of you, at least further north, have managed to get out on snow. In southern Sweden the snow is still missing, so we’ve been entertaining ourselves with some tests on the roller treadmill. We took the opportunity to look more closely at how pole force behaves when we skate ski (freestyle).

We often get questions about how we measure power in skate. It’s a very good question. Since we only measure in the poles, we are not directly capturing all of the body’s work. However, from roller treadmill tests we’ve seen that what we do measure is highly consistent. A skier using gear 3 (V2) has a certain proportion of total power going through the poles, and once we know that fraction we can estimate whole-body power. The key metrics and force curves are also excellent tools for technique feedback.

Figure 1 shows key metrics for eight 3-minute intervals in freestyle skating. Note how cadence goes down and impulse goes up in intervals 5–7 when the skier switches to gear 2 (V1).

Figure 1. Key metrics and power for eight 3-minute freestyle intervals in gear 2 and gear 3.

An interesting observation in Figure 1 is that pole power drops significantly in intervals 5–7, even though heart rate remains virtually unchanged. The explanation is of course that the plotted power shows only the contribution from the poles. By comparing with external power calculated from friction, speed, and incline, we can determine what share of total power passes through the poles in different skate gears – see Figure 2.

Figure 2. Proportion of total power going through the poles.

Figure 2 shows that about 75% of the power goes through the poles in gear 3 (V2), and about 35% in gear 2 (V1). An interesting detail is that the final interval in gear 3 has a slightly higher pole contribution, which may be a result of the skier’s legs fatiguing during the three preceding intervals.

Knowing the share of power from the poles is extremely useful for anyone who wants to use Skisens for intensity control in skate. We can use an algorithm to detect skate technique (gear) and then multiply by a compensation factor for the lower-body contribution, giving us whole-body power as illustrated in Figure 3. It is clear that heart rate reflects this corrected power very well.

Figure 3. Corrected whole-body power and heart rate for eight 3-minute freestyle intervals.

For deeper insight into skate technique, we can also look at the force curves. Figure 4 below shows pole force curves in gear 3 (V2), and Figure 5 shows the corresponding curves from gear 2 (V1).

Figure 4. Pole force curves in gear 3 (V2), 19 km/h and 3% incline.

Figure 5. Pole force curves in gear 2 (V1), 8% incline and 8.5 km/h with left-leg hang.

The force curves in Figure 4 show very good symmetry and closely resemble double-poling force curves, while the curves in Figure 5 are asymmetrical, as expected in gear 2 (V1). You can also see that pole contact time is longer in gear 2, which is natural given the lower speed. We will return later with a deeper analysis of how these force-curve shapes relate to skate technique, but for comparison we include double-poling curves at 19 km/h and 3% incline in Figure 6 below. These can be compared directly to Figure 4.

Figure 6. Pole force curves from double poling at 19 km/h and 3% incline.