The interconnection between trunk control, leg muscle strength and selectivity for gait capacity in children with CP was shown. It indicates the significance of these impairments in gait assessment and, potentially, rehabilitation. Implications for Rehabilitation Trunk control was the strongest predictor for gait capacity in a regression model with lower extremity spasticity, muscle strength and selectivity and age as independent variables. Lower extremity muscle strength, selectivity, and trunk control explained a similar amount of gait capacity variance which is higher than that explained by lower extremity spasticity. Lower extremity muscle strength and selectivity correlated strongly with trunk control. Therefore, we cautiously suggest that a combined trunk control and lower extremity training might be promising for improving gait capacity in children with CP (Gross Motor Function Classification System level I-III), which needed to be tested in future intervention-studies.

RESULTS SCALE scores differed significantly between the less and more affected leg (p<0.001) and between most leg joints. Total SCALE scores differed significantly between GMFCS levels I and II. Correlations with Fugl-Meyer Assessment, Manual Muscle Test, and Modified Ashworth Scale were 0.88, 0.88, and -0.55 respectively. Intraclass correlation coefficients were all above 0.9, with the minimal detectable change below 2 points.INTERPRETATION The SCALE appears to be a valid and reliable tool to assess selective voluntary movement control of the legs in children with spastic CP.With an incidence of 2 to 3 per 1000 in Europe, cerebral palsy (CP) is the most common motor disorder in childhood. 1 Depending on the severity and location of the congenital brain lesion, the appearance of positive and negative motor signs are heterogeneous.2 Positive motor signs are associated with an involuntarily increased frequency or magnitude of muscle activity (i.e. hypertonia), whereas negative signs are characterized by insufficient muscle activity (i.e. muscle weakness) and their control (i.e. selective voluntary motor control [SVMC]).2 Impaired SVMC has been defined as the inability 'to isolate the activation of muscles in a selected pattern in response to demands of a voluntary movement or posture'.2 It is one of the most common motor impairments of the lower extremity in children with spastic CP.2,3 As impaired SVMC can be caused by a reduction of corticospinal drive as well as by increased input of descending subcortical pathways, consensus about its exact pathophysiological nature is still lacking.2-4 Although in comparison to other motor signs (e.g. hypertonia, muscle strength) improving SVMC has received little attention in the past decades, recent studies have indicated the importance of SVMC in relation to motor performance. [5][6][7] The results of several studies suggest that a loss of SVMC interferes much more with motor performance, such as walking, than, for instance, hypertonia and contractures. [5][6][7] Furthermore, impaired selective activation can initiate and worsen a vicious cycle of limited active movement, joint contractures, hampered motor function, and diminished activity, thereby causing pain and appearance of secondary deformities in children with CP.8 Although the clinical importance of physiological muscle activation is obvious, routinely assessing selectivity is rare in the clinical environment, which, in turn, hampers evaluation of therapy-induced changes in SVMC. This lack of clinical assessment might be explained by the fact that testing SVMC is challenged by the coexistence of other motor signs. For instance, besides impaired SVMC, increased muscle tone or a lack of muscle strength, range of motion, sensory awareness, or stability in other joints can also result in limitations of movement quality.

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