Winter is here and the Wisma Ski Classics series are now in full swing! Since we at Racefox love data and try to understand what’s happening, we could not resist looking at Ski Power for Tord-Asle Gjerdalen in La Diagonela across different types of terrain. We looked at flat, easy downhill, uphill and his excellent sprint. We know that this is a little nerdy, but here we go.
First let's quickly recap what Ski Power is. How fast you ski depends on how often you perform a stroke (frequency) and how much force you generate in each stroke to generate speed. Then you also want to ski as energy efficient as possible - that is, you ski in a certain speed minimizing waste of energy and power! Your speed is approximately proportional to the force of each stroke multiplied by the frequency (measured as the number of strokes per minute). We can say that we are getting close to a power measure for double poling in the same way as you talk about effect in cycling. We call it Ski Power! While your actual speed depends on the conditions, the Ski Power you develop depends solely on your efforts.
Now let's look at some numbers from Tord's race.
We start with the data from the complete race. Tord performed just over 7,000 strokes and had an average Ski Power of 582. He had an average attack and frequency of 11 and 53 strokes per minute. His average heart rate was about 87% of the maximum heart rate.
If you compare this with a regular skier who performs Vasaloppet’s 90 km in about 6 hours, this skier will have a Ski Power of about 400. Tord thus has almost 50% higher Ski Power which is a lot because when you complete Vasaloppet in 6 hours that means that you are really fit and strong.
In flat terrain, the attack and frequency go up compared to the average. In this type of terrain Tord skied very fast which is also emphasized by the high pulse.
Of course, Tord goes downhill with larger and longer strokes to be able to generate speed and consequently both attack and frequency are lower.
Here it’s apparent that Tord changes his strategy. He increases frequency and reduces attack somewhat compared to when in flat terrain, which is a text book example of positive strategy. His pulse is almost at maximum. Regardless of technique, it is grueling since you have to lift your entire body weight. It cannot be compensated with technique it’s just hard work.
Here we arrive at the most fascinating part of the analysis, that is how fast he can ski at the end of the race given that’s on the back of 3 hours of intensive skiing. Tord’s Ski Power increases by over 30%. The frequency is just over 60 and the attack is at 13. It is so impressive to be able to respond in this way when your body is so tired.
|Max Ski Power||779|
In summary, we see that Tord adapts his technique to the terrain with great care, he paces his race very well and saves enough energy for a high intensity finish. A real master class in skiing!
P.S. We have calculated Ski Power as an average for the last 100 strokes to avoid transients. D.S.