Reliability of Xsens IMU-Based Lower Extremity Joint Angles during In-Field Running.

The Xsens Link motion capture suit has become a popular tool in investigating 3D running kinematics based on wearable inertial measurement units outside of the laboratory. In this study, we investigated the reliability of Xsens-based lower extremity joint angles during unconstrained running on stable (asphalt) and unstable (woodchip) surfaces within and between five different testing days in a group of 17 recreational runners (8 female, 9 male). Specifically, we determined the within-day and between-day intraclass correlation coefficients (ICCs) and minimal detectable changes (MDCs) with respect to discrete ankle, knee, and hip joint angles. When comparing runs within the same day, the investigated Xsens-based joint angles generally showed good to excellent reliability (median ICCs > 0.9). Between-day reliability was generally lower than the within-day estimates: Initial hip, knee, and ankle angles in the sagittal plane showed good reliability (median ICCs > 0.88), while ankle and hip angles in the frontal plane showed only poor to moderate reliability (median ICCs 0.38-0.83). The results were largely unaffected by the surface. In conclusion, within-day adaptations in lower-extremity running kinematics can be captured with the Xsens Link system. Our data on between-day reliability suggest caution when trying to capture longitudinal adaptations, specifically for ankle and hip joint angles in the frontal plane.

Do Bernstein's Stages of Learning Apply after Stroke? A Scoping Review on the Development of Whole-Body Coordination after Cerebrovascular Accidents.

Stroke is one of the leading causes of disability around the world, presenting unique challenges in motor development during the rehabilitation process. Based on studies in movement and sports science, thorough knowledge has accumulated on the development of movement skills. Through the works of Nikolai Bernstein, it has been established that when learning new skills, people tend to first simplify coordination by 'freezing' their degrees of freedom, after which they start building efficiency by 'releasing' specific degrees of freedom. If a similar pattern of development can be established post-stroke, it would imply that lessons learned in sports skill acquisition can also be implemented to optimize stroke rehabilitation. The current scoping review aims to assess whether the Bernsteinian freezing-to-releasing stages of learning also apply to developing whole-body movement skills after stroke. To this end, we systematically screened the existing literature for studies involving a longitudinal measure of whole-body coordination after a stroke. Only five articles met the criteria for inclusion, indicating a gap in research on this topic. Based on the observations within these articles, we could neither confirm nor reject whether the freezing-to-releasing process can apply after a stroke. We could, however, hypothesize a detailed description of the freezing-to-releasing process, which can be assessed in future works.