Jos de Koning sports scientist

Attachment by Jos de Koning -movement scientist and skater

What makes skating very special is that you push yourself against a contact point that is in motion during the push off. Because of this and because of the possibilities and the limitations that are determined by the material, you have to push off sideways when skating. Your body has a speed in an oblique direction, and by pushing you sideways against your skate you bend that direction in another direction, obliquely forward in the other direction. In another way you can't skate any faster. This means that a skater will always go back and forth, never straight ahead.

The desire to go even harder has always resulted in two major limitations. In order to reduce the air resistance encountered by the skater as much as possible, he must keep his torso bent forward. As a result, he can only use the extension possibilities that the hip joints normally offer to a limited extent.

To ensure that the skate does not bury itself in the ice during the take-off, the foot must be kept horizontal as much as possible. This means that the extension possibilities that the ankle joints normally offer can only be used to a limited extent.

Science is trying to figure out which factors determine performance in speed skating. The following factors play a role:

The take-off angle should be as large as possible. 

The take-off angle is the angle made by the take-off leg with respect to the vertical at the time of the take-off. It turns out that this angle determines measurable performance up to the very highest level.

Measurements have been taken according to knee angle

It turns out that the knee angle at which a skater rides also partly determines performance, but is hardly trainable. Incidentally, high-speed film images show that the knee angle gradually increases during the entire sliding phase, with a peak in stretching speed between 130 and 160 degrees. The skate already comes off the ice at a knee angle of 160 degrees, this is due to a combination of the mass inertia of the body away from the take-off point, while during the last part of the stretch the pushing power approaches zero.

The skater provides power through the push-off. 

This ability serves to cope with air resistance and ice friction. As long as the skater can deliver more power than he loses overcoming air resistance and ice friction, he can accelerate. However, the air resistance increases squared with the speed, so quite quickly an equilibrium is reached and as soon as the skater can deliver less power due to fatigue than he has to overcome in relation to his speed, he will lose speed.

Toppers have to deal with a power loss of ± 80% due to air resistance, and ± 20% due to ice friction. With recreational users, the ratio is more towards 50/50 simply because their speed is a lot lower. Relatively speaking, recreationists therefore suffer a lot more from poorly maintained ice than very good skaters.

The air resistance in relation to the knee angle. 

A competitive skater loses ± 5 seconds on the 1500 meters if he would sit only a few degrees less deep. A positive effect can also be expected from sitting deeper, but that turns out to be almost impossible to train.

The air resistance in relation to the trunk position. 

A competitive skater quickly wins 5 seconds in the 1500 meters by lowering his torso 8 to 10 degrees. Because the shift of the lzp is a cosine function of the torso angle, you do not have to worry that you will hang too much in front. This would be the case with skaters who normally keep their torso fairly upright.

Oxygen absorption capacity in relation to performance. 

A reasonably positive effect can be achieved here at longer distances, not yet at 1500 meters. An increase in the oxygen absorption capacity of ± 20% (a lot of training) only gives a gain of a few seconds on the 1500 meters. This is largely due to the fact that the 1500 meters are completed in ± 2 minutes, while the aerobic part of the energy system is only just getting started.

Height in relation to performance. 

A 1500 meters at 1000 meters gives a gain of 6 seconds.

Ice temperature in relation to performance. 

Ice slides best at an ice temperature of 6 to 7 degrees below 0.