Readers of Sportscience News last year were amongst the first to learn about the increasing use of a hinged skate by top speed skaters (Seiler, 1997). Dutch researchers invented the "klapshaats" over 13 years ago (for the history, see Koning, 1997). They were first referred to in English as slapskates, but after Nagano they look set to be called clapskates.

Traditional speed skates have the blade rigidly attached to the boot. Clapskates have a hinge located beneath the toes, allowing the ankle to plantarflex during push-off while the blade remains in full contact with the ice. A spring returns the blade to the heel of the boot once the blade is lifted off the ice, making a distinctive sound. Increased skating speeds should result with the new skate, because the calf muscles can now produce power during ankle plantar flexion. In addition to incorporating energy from a new muscle group, the knee extensors may produce more power because of increased leg extension (Ingen Schenau et al., 1987; Ingen Schenau et al., 1996).

The conservative attitudes of elite skaters prevented them from experimenting with the new skate for over a decade. A few elite skaters found they went faster near the end of the 1996-97 season with the new skate. During the summer of 1997, almost all of the international level skaters decided they needed to change to the clapskate to be competitive. Many skaters who won world-cup medals last season on traditional skates did not adapt well to the clapskate and turned in poorer performances this season. These athletes may have trained their neuromotor system so well using the traditional skate (no plantar flexion during push-off) that they couldn't untrain these motor control patterns. Skating technique appeared to improve throughout this season as the athletes adapted to the clapskate. World record times gradually declined throughout the season.

I have now taken a close look at changes in world records to see how effective clapskates have been. During the speed skating season, 10 of 10 senior men's and women's world records were broken or tied using the clapskate for the Olympic distances. The data for all events are shown in Table 1. The average lap times decreased 0.59 s (men) and 0.52 s (women). Changes in the world records represent average improvements of 1.9% (men) and 1.8% (women).

Table 1. World record times for Olympic distances in long-track speed skating at the end of the 1997 season (traditional skates) and after the 1998 Nagano Olympics (predominantly clapskates).
MEN
	500 m	1000 m	1500 m	5000 m	10000 m
1997	35.39	1:11.67	1:50.61	6:34.96	13:30.55
1998	35.39	1:10.16	1:47.87	6:22.20	13:15.33
decrease in lap time (s)	0.00	0.60	0.73	1.02	0.61
decrease in finish time (%)	0.0	2.1	2.5	3.2	1.9
WOMEN
	500 m	1000 m	1500 m	3000 m	5000 m
1997	38.69	1:17.65	1:59.30	4:09.32	7:03.26
1998	37.51	1:15.43	1:57.58	4:07.13	6:59.61
decrease in lap time (s)	0.94	0.89	0.46	0.18	0.15
decrease in finish time (%)	3.0	2.9	1.4	0.9	0.9

Slips at the start of the sprint events (500 m and 1000 m) are more common with the clapskate than with the traditional skate. Once the heel of the boot lifts off the rear support of the blade, the skater is balancing over a single point (the hinge). If the push-off force is not directed exactly through the hinge and perpendicular to the ice blade, the blade will slide forward or rearward. This slip was most evident on the first push-off at the start. In the sprints, where the start is critical, slips affected many skaters. In spite of any difficulties at the start, Catriona Lemay-Doan (Canada) was able to reduce the 500-m world record by 1.18 s over last season, while Hiroyasu Shimizu (Japan) was just able to tie the 500-m world record that he set in 1996 on traditional skates.

Are the improvements in performance due to the clapskates, or are such improvements typical for an Olympic year? To answer this question, I have compared the changes this season with those of the previous Olympic season, the Lillehammer Games of 1994. I used the previous Olympics rather than more recent seasons, because coaches plan training programs so the athletes peak for the Olympic Games. I chose the Lillehammer Olympics, because environmental conditions were similar to those in Nagano. The Albertville Olympics (1992) were contested outdoors, where ice and weather conditions were not favorable (no world records were set). I did not include the Calgary Olympics (1988), because the altitude and indoor ice apparently contributed to the number of world records broken (8 of 10).

During the '94 season, five out of five world records were set in the men's distances. Over the five Olympic distances for men, the average lap times decreased 0.22 s and the final times decreased 0.7% (Table 2, data from T. B. Hansen). Something special must have happened at Nagano: the improvement was more than twice that of the previous Olympic season.

Table 2. World-record times on traditional skates for Olympic distances in long-track speed skating at the end of the 1993 season and after the Lillehammer Olympics in 1994.
MEN
	500 m	1000 m	1500 m	5000 m	10000 m
1993	36.02	1:12.58	1:52.06	6:36.57	13:43.54
1994	35.76	1:12.43	1:51.29	6:34.96	13:30.55
decrease in lap time (s)	0.21	0.06	0.21	0.13	0.52
decrease in finish time (%)	0.7	0.2	0.7	0.4	1.6

Another equipment change could have improved times this season. The day before races began, the Dutch team got International Skating Union approval to wear three thin strips of rubber on their skin suits. One strip was worn over the head and one on each shin (Associated Press, 1998). The 2-mm strips are designed to slightly change the pattern of airflow behind the skater, resulting in less vortex production behind the head and legs and therefore reduced pressure drag. Other skaters, including Adne Sondrål, the Norwegian 1500-m record breaker, quickly applied these strips to their existing skin suits. Some athletes claimed these strips reduced lap times by 0.5 s. Previously, the slap-skate promoters claimed the new skate could reduce lap times by 0.5-1.5 s. More studies are required to sort out how much each of these new advances contributes to performance.

References

Associated Press (1998). Skaters say they've earned their stripes. http://cbc.sympatico.ca/news/archive/html/1998/02/09/go209d.html.

Hansen, T.B. (1998). Ice speed skating statistics. http://home.idgonline.no/hansens/skate.

Ingen Schenau, G.J. van, Boer, R.W. de, and Groot, G. de (1987). On the technique of speed skating. International Journal of Sports Biomechanics, 3, 419-431.

Ingen Schenau, G.J. Van, Groot, G. de, Scheurs, A. W., & Koning, J .J. de (1996). A new skate allowing powerful plantar flexions improves performance. Medicine and Science in Sports and Exercise, 28, 531-535.

Koning, J.J. (1997). Background to the slapskate: fifteen years of slapskate history, biomechanical backgrounds, first results and recent developments. Addendum to Seiler (1997). http://www.sportsci.org/news/news9703/slapxtra.htm.

Seiler, K.S. (1997). The new Dutch "slapskates": will they revolutionize speed skating? Sportscience News (Mar-Apr), http://www.sportsci.org/news/news9703/slapskat.htm.