Subject: Slapskate history and background
Date: 20 Feb 1997

Dear speedskating enthusiasts

It is clear that speed skating on slapskates is a big issue this winter. Many skaters have tried them and even more people have an opinion about skating or not skating on these skates. Please find an article about the backgrounds and history of the slapskate. Hopefully it will give you some interesting information on this topic.

Jos J. de Koning.
Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam

BACKGROUND TO THE SLAPSKATE: Fifteen years of slapskate history, biomechanical backgrounds, first results and recent developments

Prelude and theory

The idea that a skate which allows an ankle extension might improve performance in speed skating emerged within the Faculty of Human Movement Sciences of the Vrije Universiteit (Free University), Amsterdam and was based on biomechanical research on various types of leg extension as occur, for example, in speed-skating, running and jumping. This faculty has paid attention to speed skating for almost 20 years now, resulting in 3 PhD-theses, about 50 scientific papers, more than 40 papers for practitioners and an extensive 'Handbook of competitive speed-skating'.

In 1978, Gerrit Jan van Ingen Schenau started a study on biomechanical and physiological aspects of speed-skating which resulted in 1981 in a PhD-thesis entitled 'A power balance applied to speed-skating'. Based on research probing specific properties of the gliding technique (skaters push off while the skate continues to glide in forward/slightly sideways direction), it became clear that skaters suppress a powerful ankle extension in order to prevent the tip of the gliding skate from scratching through the ice, or even worse, that it might be pushed into the ice in such a way that one looses balance. Clearly, this suppression of a powerful ankle extension limits the ankle extensor's contribution to propulsion, when compared to the powerful ankle extensions as occur in running or jumping.

The slapskate was described as possible solution for this problem as early as 1982 in a series of papers by Van Ingen Schenau on behalf of the journal of a local speed-skating club ('Alkemade'). During a reception in 1983 where Gerrit Jan and his colleague in the speed-skating research Gert de Groot discussed the backgrounds of muscular pain in the tibialis anterior (lies in front of the shin bone) with two instrument-makers, Wim Schreurs and Hans Meester, Gerrit Jan proposed the idea of the slapskate as a solution to this problem. Most skaters who have difficulties in suppressing the ankle extensor activity use this muscle to oppose the action of the ankle extensors. Together with the expected role of the ankle extensors in work enhancement, these ideas convinced the four reception participants that the slapskate had to be built and they agreed to proceed with project as co-inventors. However, the project didn't become reality until additional knowledge about the significance of an explosive ankle extension emerged. As described in more detail in Van Ingen Schenau et al., 1996 (see references, previous article), two newly discovered phenomena appeared to strongly support the slapskate idea:

a. From a high -speed film analysis of 10 participants in the female World Championships in the former Karl Marx Stadt in 1983, it was discovered that skaters loose contact with the ice far before the knee is fully extended. This could be explained by the fact that the velocity difference between hip- and ankle joint can only be increased during the first part of knee extension and will always go to zero as the knee approaches full extension.

b. Results from parallel research on intermuscular coordination supervised by Van Ingen Schenau in the early eighties made it clear that in the vertical jump a specific coordination between knee and ankle prevents jumpers from loosing contact with the ground too early. Precisely at the instant that the velocity difference between hip and ankle can no longer increase (for the same reason as in the speed-skating push off), jumpers appear to start a powerful ankle extension which results in a further increase of the trunk velocity. In particular the ankle extensor muscle which runs over the knee- and the ankle joint (the gastrocnemius) appeared to play a particular role in this coordination: it allows the knee extensor muscles to support the ankle extension in this last phase of the push off. In order to demonstrate the impressive significance of this mechanism, a mechanical model was constructed ('Jumping Jack') which shows that not only the calf muscles but also the knee extensors are utilized much more effectively in a push off which includes a powerful ankle extension than in a skating-like push off For this reason one might state that Jumping Jack is in fact the spiritual father of the slapskate.

Based on these insights, the first slapskates were designed by Wim Schreurs and Hans Meester in the 1984/1985 skating season. The first official slapskate-time was realized by the former sprinter Ron Ket during a 500 m race (40.63 s, opening 10.20 s) specially organized for the press in February, 1985. Shortly before this race, a Dutch patent application was formulated and registered as number 8500483 by the Dutch Patent Office. The Inventors Center in Rotterdam brought the inventors in contact with the Viking skate factory who appeared interested in the rights, which resulted in a European patent application. During this process it became clear that the editor of the Dutch journal 'Fiets' (means: 'Bicycle'), Guus van de Beek, had comparable ideas. This led to a quintet of inventors with respect to the European patent application. Unfortunately for the inventors, the research of the European Patent Office into the uniqueness of the general idea of a moving shoe relative to the blade showed that between 1894 and 1997 as many as 5 former patents based on the same general idea were granted. Although these patents mainly concerned figure skates and obviously never were applied in practice, this meant that a protection of the general idea was not possible. Consequently, the applicants decided not to go through with the patent application. It should be noted, however, that at present this has been an advantage in the sense that continuing research can be performed entirely independently, that is without any financial bonds, from skate factories.

With respect to the name of this new skate, it should be stressed that this name is based on the verb 'to slap' which means that the slapskate is meant to enable the skater 'to slap on' an extra amount of work to his/her work per stroke. Note, however, that this extra work is not for free. One has to have the physical capacity to increase the work per stroke and the mean power output in order to skate faster. This is in sharp contrast to benefits based on reductions of air- or ice frictional forces and may have as a consequence that not all skaters will be able to skate faster on slapskates.

First experiences

During the period 1985-1987 several designs and constructions were realized and tested by a number of skaters. This resulted in a version which has been for sale by Viking since 1987. Remarkably, the test skaters were quite favorable towards the slapskates, but it was observed that if they had to skate a real important competition, they appeared to fall back to their old pattern of coordination. As long as they were consciously involved with their technique, the extra degree of freedom was clearly utilized, but during those important competitions the hinged skate hardly opened. Since these test skaters were all 25 years and older, we concluded that it is quite difficult to automize the newly required coordination. (This conclusion, however, seems to be falsified by recent top skaters of the same age such as Niemann, Veldkamp and Zijlstra). Though the Dutch coach Henk Gemser was very interested at that time to try to find a number of junior skaters, his appointment as coach of a national senior team prevented him to realize these plans.

In 1986, Jos de Koning entered the speed-skating research group as a PhD-student. Jos was (and is), in contrast to the inventors, a competitive speed-skater himself and was soon convinced that our theory had to work in practice. In short time he broke all his personal best times by many seconds. In that time a number of other skaters of regional level showed a comparable progress as well, but top skaters remained skeptic. In all those years prior to the onset of the breakthrough in 1994, both Jos and Gerrit Jan discussed the advantages of the slapskate at various international and national congresses and coaching clinics. Remarkably, they never received negative responses. Obviously, the elite skaters were all waiting for a proof at the top level. We would not qualify this attitude as conservative, however. Top skaters are quite aware what their competitive ranking is on normal skates, while it could not be guaranteed that their position would improve when switching over to the slapskate. As a matter of fact the scientists always stressed that skaters and their coaches are entirely responsible for their choice in this respect. In retrospect it is clear that all interested top skaters simply waited for other top skaters to prove that the slapskate really improves performance. This is a position which is quite understandable, given the enormous effort skaters have to devote to their sport to reach the national or international top.

The breakthrough

In 1988 a student, Erik van Kordelaar, started his study at our faculty. Erik was skating at sub-top level and became impressed by the theory behind the slapskate. Despite some hesitation expressed by Gerrit Jan because of the experiences with the previous test skaters of Erik's age, Erik took the risk and switched over to the slapskate in the skating season 1990/1991. In short time he made considerable improvements. The next season (1992/1993) he became coach of the regional junior selection of Zuid-Holland and impressed his colleague Dick de Bles and their juniors with his own improvements. The following season 1994/1995 his colleague Dick and 11 junior skaters switched over. Their astonishing results were described in the 1996 MSSE paper. The first two Dutch champions mentioned in that paper were Andre Vreugdenhil and Raymond Barendse. Based on these results many other junior skaters and a few senior skaters took this step in 1995/1996; especially in the regional selection Friesland under supervision of the coach Sijtje van der Lende. From all the male junior A-skaters in the Netherlands, about 50% were already skating on slapskates that season. Their improved performances finally convinced three Dutch senior female skaters (de Jong, de Loor and Zijlstra) who introduced (1996/1997) the slapskate at the international level of senior elite skaters. Despite the achievements of these and other senior skaters very recently (Gunda Niemann, Bob de Jong etc.) it should be stressed that the 11 junior skaters and their coaches Erik van Kordelaar and Dick de Bles are to be judged as the true pioneers in practice who placed the slapskate at the national and international agenda.

Estimated benefit of the slapskate

It is quite understandable that coaches as well as journalists always want to know what we (the research group at the Vrije Universiteit) think about the maximal possible benefit of skating on the slapskate. Though at present we do not have decisive evidence about this benefit, theoretical considerations as well as achievements deduced from practice seem to indicate that this benefit lies in the order of magnitude of 0.5 at the 500m to more than 1 second per lap at the longest distances. The theoretical considerations are based on the assumption that the slapskate might allow the skater to reach a contribution of the ankle extension in the total work per stroke comparable to what is observed in jumping and running. This estimation predicts a benefit of 1 - 1.5 seconds per lap. In this estimation a prolonged knee extension is not included, suggesting that this theoretical benefit might prove to be an underestimation. If we express the progress of the 11 junior skaters in the 94/95 test group in seconds per lap, we get 0.6 s /lap at the 500 m to 1.2 s/lap at the 3000 m. It can not be excluded, however, that other factors (related to being the pioneers) might also have played a role that season. From the juniors in the following

(1995/1996) season and the present achievements of senior skaters at the European and World Championships, it appears that most of the observed progress falls within the range of 0.1-0.5 s/lap at the 500 m to 0.5-1.4 s/lap at the longer distances. Since the 500 m seems to require the longest time for adaptation, it remains to be seen whether the results realized at the 500m at present might prove to be an underestimation of the actual benefit after sufficient training.

Recent and future developments

Triggered by the results of the pioneers described in the enclosed paper, a number of others besides Viking have also developed slapskates. The most well-known factory in this respect is Interraps, who developed the so-called Rotrax-skate. This skate is based on an idea of Bert Otten, who is a human movement scientist at the State University of Groningen. In this skate a sophisticated mechanism creates a virtual axis of rotation which moves in forward direction as a function of ankle extension. Despite considerable advertisement and publicity, this skate is only scarcely used by skaters at national level and, as far as we know, not by skaters at international level (although many of them have tried the Rotrax). Since a few national skaters (i.e. Klein Hesselink) are skating quite fast on the Rotrax skates, it is not clear at present why the Rotrax is not more widely accepted.

With respect to future developments, it should finally be noted that we successfully applied for a grant from the Netherlands Foundation of Scientific Research. This will allow us to focus our attention toward the physiological and biomechanical backgrounds of skating on various types of slapskates. This research is supervised by Gerrit Jan van Ingen Schenau and Jos de Koning. Jos was appointed in a staff position at our faculty by 1993 and is in fact the principle investigator of our continuing speed skating research (including more issues than the slapskate). On the basis of the grant we appointed Han Houdijk as a PhD-student for the period 1996-2000. Han will devote his entire research to the optimization of the slapskate. This season, Han and Jos have collected data of the kinematics, oxygen consumption and lactate production of skaters on Viking slapskates, Rotrax slapskates and normal skates. From these data, we hope to improve our understanding of the influence of (the differences in) ankle extension in speed-skating. This might possibly lead to other types of slapskates in the future.

For more information about the history, backgrounds and present development of our ideas concerning the slapskate, don't hesitate to contact us.

Gerrit Jan van Ingen Schenau
Professor in Biomechanics
phone (work): 020 4448481
phone (home): 071 3314502

Jos de Koning
Associate professor in Biomechanics and Exercise Physiology
phone (work): 020 4448517
phone (home): 0172 603740

Han Houdijk
PhD-student slapskate project
phone (work): 020 4448504
phone (home): 076 5205332

Mail address: Dept. Kinesiology, Faculty of Human Movement Science, Free University, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands

February, 1997

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