Josef Kröll
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View article: Validation of a Sensor-Based Dynamic Ski Deflection Measurement in the Lab and Proof-of-Concept Field Investigation
Validation of a Sensor-Based Dynamic Ski Deflection Measurement in the Lab and Proof-of-Concept Field Investigation Open
Introduction: Ski deflection is a performance-relevant factor in alpine skiing and the segmental and temporal curvature characteristics (m−1) along the ski have lately received particular attention. Recently, we introduced a PyzoFlex® ski …
View article: Effect of Additional Loads on Joint Kinetics and Joint Work Contribution in Males and Females Performing Vertical Countermovement Jumps
Effect of Additional Loads on Joint Kinetics and Joint Work Contribution in Males and Females Performing Vertical Countermovement Jumps Open
This study aimed to investigate the effect of additional loads and sex on countermovement jump (CMJ) joint kinetics during the entire take-off impulse in males and females. Twelve female and 13 male sport students performed vertical counte…
View article: Simple foot strike angle calculation from three-dimensional kinematics: A methodological comparison
Simple foot strike angle calculation from three-dimensional kinematics: A methodological comparison Open
A simple and accurate method of determining foot strike angle (FSA) during running can simplify data collections and validations of wearable sensors. The purpose of this study was to determine the validity of two simplified methods for est…
View article: Curvature Detection with an Optoelectronic Measurement System Using a Self-Made Calibration Profile
Curvature Detection with an Optoelectronic Measurement System Using a Self-Made Calibration Profile Open
So far, no studies of material deformations (e.g., bending of sports equipment) have been performed to measure the curvature (w″) using an optoelectronic measurement system OMS. To test the accuracy of the w″ measurement with an OMS (Quali…
View article: Perceptions of experts on key injury risk factors in alpine ski racing as a function of stakeholder role and associated level of competition
Perceptions of experts on key injury risk factors in alpine ski racing as a function of stakeholder role and associated level of competition Open
Objectives (1) To update experts’ priorities of perceived key injury risk factors in alpine ski racing based on a framework and list derived 10 years ago, (2) to identify additionally emerging risk factors since then and (3) to compile a l…
View article: A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model
A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model Open
The ski deflection with the associated temporal and segmental curvature variation can be considered as a performance-relevant factor in alpine skiing. Although some work on recording ski deflection is available, the segmental curvature amo…
View article: Foot Strike Angle Prediction and Pattern Classification Using LoadsolTM Wearable Sensors: A Comparison of Machine Learning Techniques
Foot Strike Angle Prediction and Pattern Classification Using LoadsolTM Wearable Sensors: A Comparison of Machine Learning Techniques Open
The foot strike pattern performed during running is an important variable for runners, performance practitioners, and industry specialists. Versatile, wearable sensors may provide foot strike information while encouraging the collection of…
View article: Does enhanced footwear comfort affect oxygen consumption and running biomechanics?
Does enhanced footwear comfort affect oxygen consumption and running biomechanics? Open
Comfort as an essential parameter for running footwear is gaining importance in footwear research and development, and has also been proposed to decrease injury rate and improve metabolic demand in the paradigm of the comfort filter. The a…
View article: Foot strike angle calculation during running based on in-shoe pressure measurements
Foot strike angle calculation during running based on in-shoe pressure measurements Open
The foot strike angle (FSA) is a common biomechanical parameter in the analysis of human running. It can be used for shoe recommendation purposes by classifying runners into foot strike patterns (Z...
View article: A Magnet-Based Timing System to Detect Gate Crossings in Alpine Ski Racing
A Magnet-Based Timing System to Detect Gate Crossings in Alpine Ski Racing Open
In alpine skiing, intermediate times are usually measured with photocells. However, for practical reasons, the number of intermediate cells is limited to three–four, making a detailed timing analysis difficult. In this paper, we propose an…
View article: In-field measurement of vertical and horizontal forces in ski-jumping: Evaluation of a portable two-dimensional force plate
In-field measurement of vertical and horizontal forces in ski-jumping: Evaluation of a portable two-dimensional force plate Open
Various methods for measuring ground reaction forces during ski-jumping have been developed and applied. The main limitations of the current systems are the restriction to the measurement of single phases (parts of the in-run and take-off)…
View article: Acute Effects of an Ergometer-Based Dryland Alpine Skiing Specific High Intensity Interval Training
Acute Effects of an Ergometer-Based Dryland Alpine Skiing Specific High Intensity Interval Training Open
Introduction: To establish an alpine ski racing (ASR) specific dryland high intensity training protocol (HIT), we set out to analyze cardiorespiratory and metabolic responses of three ASR specific HIT modes using a ski ergometer compared w…
View article: Reducing the back overuse-related risks in alpine ski racing: let’s put research into sports practice
Reducing the back overuse-related risks in alpine ski racing: let’s put research into sports practice Open
It is well recognised in alpine ski racing (ASR) that the risk of traumatic injuries is high.1 Yet, so far the nature and causation of ASR-related back overuse injuries have received little attention.2 During adolescence, competitive alpin…
View article: Comfort assessment of running footwear: Does assessment type affect inter‐session reliability?
Comfort assessment of running footwear: Does assessment type affect inter‐session reliability? Open
Assessing comfort of running footwear reliably is challenging. The purpose of this study was to compare the intra‐rater reliability between different assessment types, to calculate intra‐individual reliability scores and to evaluate the ef…
View article: The role of path length‐ and speed‐related factors for the enhancement of section performance in alpine giant slalom
The role of path length‐ and speed‐related factors for the enhancement of section performance in alpine giant slalom Open
Knowing how to enhance alpine skiing performance is essential for effective coaching. The purpose of this study was to explore the role of path length‐ and speed‐related factors for performance enhancement, while skiing on a homogeneously …
View article: Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety
Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety Open
External forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness. In order to establish appropriate physical conditioning regimes, which ade…
View article: Standing Height as a Prevention Measure for Overuse Injuries of the Back in Alpine Ski Racing: A Kinematic and Kinetic Study of Giant Slalom
Standing Height as a Prevention Measure for Overuse Injuries of the Back in Alpine Ski Racing: A Kinematic and Kinetic Study of Giant Slalom Open
Background: In alpine ski racing, typical loading patterns of the back include a combined occurrence of spinal bending, torsion, and high peak loads. These factors are known to be associated with high spinal disc loading and have been sugg…
View article: Functional calibration for trunk, lower- and upper-limb fixed inertial sensors v1
Functional calibration for trunk, lower- and upper-limb fixed inertial sensors v1 Open
Calibration procedure for functionally aligning inertial sensors fixed to the shanks, thighs, trunk (e.g. sacrum, sternum), head, arms, and forearms / wrists. The movements were originally designed for analyzing skiing movements where the …
View article: The Use of Body Worn Sensors for Detecting the Vibrations Acting on the Lower Back in Alpine Ski Racing
The Use of Body Worn Sensors for Detecting the Vibrations Acting on the Lower Back in Alpine Ski Racing Open
This study explored the use of body worn sensors to evaluate the vibrations that act on the human body in alpine ski racing from a general and a back overuse injury prevention perspective. In the course of a biomechanical field experiment,…
View article: Functional calibration for trunk and lower limb fixed inertial sensors v2
Functional calibration for trunk and lower limb fixed inertial sensors v2 Open
Calibration procedure for functionally aligning inertial sensors fixed to the shanks, thighs, and trunk (e.g. sacrum, sternum). The movements were originally designed for analyzing skiing movements where the person is wearing ski boots. Ho…
View article: Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running
Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running Open
To enhance running performance in heel-toe running, a leaf spring structured midsole shoe (LEAF) has recently been introduced. The purpose of this study was to investigate the effect of a LEAF compared to a standard foam midsole shoe (FOAM…
View article: Joint Inertial Sensor Orientation Drift Reduction for Highly Dynamic Movements
Joint Inertial Sensor Orientation Drift Reduction for Highly Dynamic Movements Open
Inertial sensor drift is usually corrected on a single-sensor unit level. When multiple sensor units are used, mutual information from different units can be exploited for drift correction. This study introduces a method for a drift-reduce…
View article: How to Prevent Injuries in Alpine Ski Racing: What Do We Know and Where Do We Go from Here?
How to Prevent Injuries in Alpine Ski Racing: What Do We Know and Where Do We Go from Here? Open
Alpine ski racing is known to be a sport with a high risk of injury and a high proportion of time-loss injuries. In recent years, substantial research efforts with regard to injury epidemiology, injury etiology, potential prevention measur…
View article: Course Setting as a Prevention Measure for Overuse Injuries of the Back in Alpine Ski Racing
Course Setting as a Prevention Measure for Overuse Injuries of the Back in Alpine Ski Racing Open
Background: A combination of frontal bending, lateral bending, and torsion in the loaded trunk has been suggested to be a mechanism leading to overuse injuries of the back in Alpine ski racing. However, there is limited knowledge about the…
View article: A Return to Skiing Envelope of Function for Anterior Cruciate Ligament Reconstructed Elite Alpine Ski Racers
A Return to Skiing Envelope of Function for Anterior Cruciate Ligament Reconstructed Elite Alpine Ski Racers Open
Elite alpine ski racing comprises bidirectional turning with forceful concentric but predominantly eccentric contractions that create large quadriceps muscle loading and hamstrings/quadriceps muscle co-contraction (4, 10). Ski racing also …
View article: Alpine ski racing gate crossing detection using magnetometers
Alpine ski racing gate crossing detection using magnetometers Open
Keywords: gate crossing ; inertial sensors ; magnetometers ; timing ; validation Reference EPFL-CONF-224327 Record created on 2017-01-10, modified on 2017-05-10