## 1 Introduction  
Infantile cerebral palsy (CP) is the most common cause of motor development disorders in early childhood. It is defined as non-progressive damage to the developing brain that leads to impaired posture and movement, resulting in activity limitations [1]. The severity of CP ranges from mild forms such as unilateral spastic cerebral palsy with mild spasticity, contractures and limitations of sensitivity and fine motor skills to severe disabilities in which the entire body is affected and which often have a mixed form of spasticity and dyskinesia [2]. The severity of motor disorders in people with CP depends on the location, severity and timing of the damage [3]. In addition to motor impairments, individuals may also experience issues with cognition, speech, vision and sensory function, as well as dysfunctions of the autonomic system, behavioral issues, pain and epilepsy [4]. Within the rehabilitation of children with CP, evaluation therapy outcomes are crucial for assessing the effectiveness of interventions [5]. Various instruments are used to assess changes in gross motor functions, which involve movements of the arms, legs and trunk, such as crawling, walking and running [6]. The Gross Motor Function Measure (GMFM) is a standardized instrument for the assessment of gross motor functions in children and adolescents with motor impairments, particularly those with cerebral palsy. It is commonly used in rehabilitation settings to monitor progress [7]. However, the implementation of the GMFM can present challenges for both the examiner and the child or adolescent. For instance, proper administration requires training and experience to ensure consistent and accurate assessments [8]. Additionally, securing the cooperation of participants can be difficult, as the test involves numerous tasks that can be mentally and physically exhausting [8; 9]. Repeated testing may also be psychologically stressful, especially for children aware of their motor limitations [10]. The GMFM-66 is a shortened version of the original GMFM-88. With only 66 items, it enhances efficiency and reduces completion time while preserving its established validity and reliability. [PERSON] et al. reported Intraclass Correlation Coefficients (ICCs) greater than 0.96 in their reliability assessments. They evaluated consistency over time (ICC = 0.966, \(n\) = 228), between random samples (ICC = 0.976, \(n\) = 115), and between samples intentionally biased for ability (ICC = 0.975, \(n\) = 536) [11]. It is considered the gold standard for measuring gross motor function in children with CP [12]. To further reduce test burden, two abbreviated versions have been developed: the GMFM-66-IS and the GMFM-66 B&C [13; 14]. One study found both shortened versions to yield accurate results compared to the full GMFM-66, especially in children with spastic CP, with the GMFM-66-IS showing better accuracy in unilateral spastic CP. However, it is recommended to retain the full GMFM-66 when evaluating longitudinal changes [13]. A new study has developed a shortened version of the GMFM-66 (rGMFM) that utilizes artificial intelligence to accurately predict the full score in both individual assessments and over time. This method initially uses seven test items to predict the GMFM-66 score, potentially increasing assessment efficiency. However, the method has not yet been integrated into software, and thus, the rGMFM is not currently available for clinical use [15]. In addition to assessing gross motor skills, gait analysis plays a critical role in the rehabilitation of children and adolescents with CP. Instrumented Gait Analysis (IGA) allows for the objective measurement of gait parameters such as step length, step width, walking speed and gait symmetry. These quantitative data form the basis for detailed gait assessments and can inform therapy planning. When performed repeatedly, gait analysis also allows for monitoring therapeutic progress [16]. There is now a wide variety of IGA systems on the market.