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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Hans Essers (Maastricht University)
Anneliek Peters (University of Groningen)
Kenneth Meijer (Maastricht University)
Alessio Murgia (University of Groningen)

Abstract:
Facioscapulohumeral Dystrophy (FSHD) is a progressive muscle-wasting disease, which leads to declines in upper extremity functionality. Although the scapulohumeral joint’s stability and functionality are affected, evidence on possible muscle control alterations in FSHD individuals is still lacking. From previous findings it was observed that FSHD persons had a decreased muscle activity of the scapula rotators, Serratus Anterior and Trapezius Ascendens, during humeral elevation in the sagittal and frontal plane. Moreover almost half of the FSHD participants had greater elevations in the sagittal plane than the frontal plane, while no such difference was shown in healthy control participants. The aim of this study is to investigate if the differences in muscle activity, in FSHD participants, are accompanied by a higher elevation in the sagittal than in the frontal plane. Upper arm kinematics and electromyograms of eight upper extremity muscles were recorded during humeral elevation in the sagittal and frontal plane in ten FSHD participants (Brooke scale 3-4). Maximum normalized muscle activities were extracted from electromyograms and peak humeral elevations were derived from kinematic data. The main outcomes were the differences in maximal muscle activities and humeral elevations, between the sagittal and frontal plane respectively. An independent-samples Mann-Whitney U test was used to test for significant group differences at alpha: 0.05. Four FSHD participants elevated the humerus higher in the sagittal plane (range: 21-54°, p<0.05) compared to the remaining six who did not show any difference (range: -11-3°). Activations were on average 4.3±2.0 times larger in the sagittal plane for the Serratus Anterior muscle (p<0.05). For the remaining six FSHD participants the same muscle was activated comparably in both planes (1.4±1.0 times in the sagittal compared to the frontal plane). The remaining seven muscles did not show any significant group differences. Higher humeral elevations were characterized by a higher activity of the scapula rotator Serratus Anterior. This greater activation of the scapular muscle accompanied by an increase in kinematic performance suggests a better preserved muscle quality in an otherwise clinically identical population. Future research should investigate whether this muscle activity difference between humeral elevation planes is underlined by differences in muscle control.