Browsing by Author "Hoerzer, Stefan"

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    Footwear Decreases Gait Asymmetry during Running
    (PLoS ONE, 2015-10-21) Hoerzer, Stefan; Federolf, Peter A; Maurer, Christian; Baltich, Jennifer; Nigg, Benno M
    Previous research on elderly people has suggested that footwear may improve neuromuscular control of motion. If footwear does in fact improve neuromuscular control, then such an influence might already be present in young, healthy adults. A feature that is often used to assess neuromuscular control of motion is the level of gait asymmetry. The objectives of the study were (a) to develop a comprehensive asymmetry index (CAI) that is capable of detecting gait asymmetry changes caused by external boundary conditions such as footwear, and (b) to use the CAI to investigate whether footwear influences gait asymmetry during running in a healthy, young cohort. Kinematic and kinetic data were collected for both legs of 15 subjects performing five barefoot and five shod over-ground running trials. Thirty continuous gait variables including ground reaction forces and variables of the hip, knee, and ankle joints were computed for each leg. For each individual, the differences between the variables for the right and left leg were calculated. Using this data, a principal component analysis was conducted to obtain the CAI. This study had two main outcomes. First, a sensitivity analysis suggested that the CAI had an improved sensitivity for detecting changes in gait asymmetry caused by external boundary conditions. The CAI may, therefore, have important clinical applications such as monitoring the progress of neuromuscular diseases (e.g. stroke or cerebral palsy). Second, the mean CAI for shod running (131.2 ± 48.5; mean ± standard deviation) was significantly lower (p = 0.041) than the CAI for barefoot running (155.7 ± 39.5). This finding suggests that in healthy, young adults gait asymmetry is reduced when running in shoes compared to running barefoot, which may be a result of improved neuromuscular control caused by changes in the afferent sensory feedback.
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    Selected Methodological Approaches to Identify Functional Groups in Running
    (2017-12-21) Hoerzer, Stefan; Nigg, Benno M.; Edwards, William Brent; Stefanyshyn, Darren J; Von Tscharner, Vinzenz; Bertram, John E. A.; Brüggemann, Gert-Peter
    A footwear construction typically produces different biomechanical, physiological, and/or perceptual responses for different groups of individuals. Consequently, a given insert or shoe can be beneficial for one group, but ineffective or even detrimental for another group. This observation represents a key challenge in the attempt to develop athletic footwear constructions that improve athletic performance, reduce the risk of movement-related injuries, and/or enhance comfort. A functional group is a collection of individuals with the same functional solutions when executing a locomotion task, and when reacting to a locomotion task intervention, such as footwear. It was speculated that tailoring footwear constructions to the functional solutions of these groups might help to develop footwear that promotes comfort, health, and/or performance. Before footwear constructions can be matched to functional groups, the groups have to be identified. To date, however, no systematic methodological approach exists to identify functional groups. Therefore, the main objective of this doctoral thesis was to develop and test methodological approaches that lead to the identification of functional groups in running. The first approach applied pattern recognition techniques to running kinematics in order to identify functional groups. The second approach combined footwear comfort with kinematic and muscle activity data collected during running to identify functional groups. The results showed that both tested approaches successfully identified functional groups. The main finding of this thesis is therefore that functional groups can be identified (1) by utilizing pattern recognition techniques, and (2) by isolating individuals who choose the same footwear as comfortable and excluding all individuals from this groups who do not share the same biomechanical solutions. Therefore, this PhD research provides a set of tools that can be utilized to identify functional groups in order to gain a better understanding about their specific functional solutions, biological characteristics, and footwear requirements.