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Fig. 1. (A) The skates used in the present study, from the left: the bone skates,
the first wooden skates with a metal blade, the skates used in the 15th and
18th century, and the modern conventional ice skates. Details can be found in
the text. (B) `Winter landscape with iceskaters' 1608, a painting by Hendrick
Avercamp (15851634). Reproduced with permission from The Rijksmuseum,
Amsterdam, The Netherlands.