106 Chapter 7 the seven publications on (non-)pharmacological interventions to ameliorate gait problems in people with HSP. 4-10 This demonstrates the need for consensus on how to assess gait capacity in HSP, a need that has previously been recognized and extends beyond people with HSP. 11 However, reaching such a consensus is difficult, specifically for people with HSP, as no outcome measures have yet been validated. In this thesis, we have provided novel insights into outcome measures useful for assessing gait capacity in this population. As in most other studies, we assessed gait capacity using overground lab-based assessments and clinical testing. We demonstrated that people with HSP scored poorer on the requirement stepping than healthy controls, which was in line with the literature. 12,13 To this end, we recorded spatiotemporal gait parameters. Such spatiotemporal parameters can easily and quickly be obtained with the GAITRite® system (GAITRite Gold, CIR Systems, PA, USA). This pressure-sensitive, 3-meter walkway automatically calculates the spatiotemporal parameters after a person has walked across the mat. A more elaborate analysis is required to assess to which extent impairments in bodily functions impact stepping in HSP. Such an analysis often consists of a marker-based, 3D gait analysis and surface electromyography. Although this assessment is more time-consuming and costly, it provides an empirical basis for the underlying mechanisms causing stepping problems. For example, spasticity of the hamstring muscles may interfere with full knee extension at the end of the swing phase, hampering optimal step length. We also demonstrated that people with HSP scored poorer on dynamic balance than healthy controls. We used the clinical Mini-BESTest and novel biomechanical measures of gait stability, such as Foot Placement Deviation (FPD) and Local Dynamic Exponents (LDEs). These biomechanical measures provide detailed information about dynamic balance control and potentially overcome some of the methodological limitations of clinical testing (e.g., the subjective interpretation by clinicians, floor and ceiling effects, or large minimal clinically detectable differences). However, from a practical viewpoint, assessing biomechanical gait stability measures requires sophisticated methods and expensive equipment. Biomechanical measures are still challenging to obtain and interpret and, thus, unfeasible for clinical practice. Furthermore, they do not seem to differentiate between fallers and non-fallers in people with HSP (chapter 6). To fully capture balance from a clinical and theoretical perspective, testing should incorporate items that assess: 1) steady-state balance (i.e., during unperturbed standing), 2) proactive balance (i.e., when anticipating a predictable perturbation), and 3) reactive balance (i.e., when responding to an unpredictable perturbation). To this end, the Mini-BESTest is a valuable tool for assessing balance in clinical practice and research: it incorporates steady-state, proactive, and reactive balance items, is quick to perform, requires few attributes, and has little ceiling effect. Unlike the biomechanical measures, the Mini-BESTest seems
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