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Skater's Cramp: A Possible Task‐Specific Dystonia in Dutch Ice Skaters
Author(s) -
Nijenhuis Beorn,
Schalkwijk Aron H.P.,
Hendriks Sharon,
Zutt Rodi,
Otten Egbert,
Tijssen Marina A.J.
Publication year - 2019
Publication title -
movement disorders clinical practice
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.754
H-Index - 18
ISSN - 2330-1619
DOI - 10.1002/mdc3.12799
Subject(s) - speed skating , dystonia , physical medicine and rehabilitation , medicine , range of motion , interquartile range , ankle , psychology , physical therapy , surgery , neuroscience , simulation , engineering
Background Skater's cramp is an involuntary lower leg movement in skilled speed skaters. We aim to evaluate whether skater's cramp is compatible with task‐specific dystonia. Methods A case‐control study tested 5 speed skaters exhibiting symptoms of skater's cramp and 5 controls. Affected skaters completed a standardized questionnaire and neurological examination. Video analyses included skating normally, intensely, and with extra mass around the skater's ankles. An Inertial Motion Capturing (IMC) device mounted on both skates provided angular velocity data for both feet. Results Median time of onset of skater's cramp occurred after 12 (range 3–22) years of speed skating. Skater's cramp appeared as task specific; its onset was sudden and correlated to stress and aberrant proprioception. Symptoms presented acutely and consistently during skating, unilaterally in 4 and bilaterally in 1 skater. Visually, skater's cramp was an active, patterned, and person‐specific jerking of a skater's foot, either exo‐ or endorotationally. It presented asymmetrically, repeating persistently as the foot neared the end of the swing phase. The skater's affected leg had a longer swing phase (median, 1.37 [interquartile range {IQR}, 0.35]/1.18 [IQR, 0.24] seconds; P < 0.01), a shorter glide phase (median, 1.09 [IQR, 0.25]/1.26 (IQR, 0.29) seconds; P < 0.01), and higher angular velocity during the jerking motion. Symptoms remained constant irrespective of speed or extra mass around the ankle ( P > 0.05). No significant differences between legs were detected in the control group. Conclusions Observed clinical, visual, and kinematic data could be an early and tentative indication of task‐specific dystonia.