[1] Lulea Univ Technol, Dept Hlth Sci, Paediat Physiotherapy & Motor Control, Hedenbrovagen, SE-96136 Boden, Sweden
[2] Karolinska Inst, Dept Neurotec, Motor Control & Phys Therapy Res Lab, Stockholm, Sweden
[3] Univ Cent Hosp Helsinki, Dept Child Neurol, Helsinki, Finland
[4] Umea Univ, Dept Community Med & Rehabil Physiotherapy, Umea, Sweden