IMPROVING THE ACCURACY OF LOW-COST GNSS BY FUSION WITH INERTIAL AND MAGNETIC SENSORS IN ALPINE SKI RACING

For analysing performance in alpine ski racing, an accurate estimation of the skier's centre of mass trajectory and speed is indispensable. However, the sole use of low-cost GNSS might not be accurate enough to detect meaningful differences. The aim of this study was to introduce a new system that can improve the accuracy of a low-cost GNSS to an acceptable level. To this end, the data obtained by low-cost GNSS was fused with data form inertial sensors and position information of permanent magnets buried into the snow surface along the ski track. This fusion improved the system's accuracy from 2m to 0.5m. Despite the added sensing technologies, the system remained simple and was easy to use. Further improvements are possible and a technical validation of the system could be a major aim for the future

Sidecut radius and the mechanics of turning—equipment designed to reduce risk of severe traumatic knee injuries in alpine giant slalom ski racing.

Background: There is limited empirical knowledge about the effect of ski geometry, particularly in the context of injury prevention in alpine ski racing. We investigated the effect of sidecut radius on biomechanical variables related to the mechanics of turning. Methods: During a field experiment, six European Cup level athletes skied on three different pairs of giant slalom (GS) skis varying in sidecut radii (30 m, 35 m and 40 m). Using a video-based three-dimensional (3D) kinematic system, a 22-point body segment model of the athletes was reconstructed in 3D, and the variables ground reaction force, centre of mass (COM) speed, COM turn radius, ski turn radius, edge angle, fore/aft position and skid angle were calculated. Results: While steering out of the fall line after gate passage, ground reaction force significantly differed between the 30 m and 40 m skis and between the 35 m and 40 m skis. These differences were mainly explainable by larger COM turn radii when skiing on the 40 m ski. During the same turn phase, significant differences in ski turn radius also were found, but there were no differences in edge angle, fore/aft position and skid angle. Summary: The sidecut-induced reduction in ground reaction force and the sidecut-induced increase in centre of mass and ski turn radius observed in this study provides indirect evidence of reduced self-steering of the ski. Self-steering plays a central role in the mechanism of anterior cruciate ligament rupture in alpine ski racing

A New Training Assessment Method for Alpine Ski Racing: Estimating Center of Mass Trajectory by Fusing Inertial Sensors With Periodically Available Position Anchor Points

In this study we present and validate a method to correct velocity and position drift for inertial sensor-based measurements in the context of alpine ski racing. Magnets were placed at each gate and their position determined using a land surveying method. The time point of gate crossings of the athlete were detected with a magnetometer attached to the athlete’s lower back. A full body inertial sensor setup allowed to track the athlete’s posture, and the magnet positions were used as anchor points to correct position and velocity drift from the integration of the acceleration. Center of mass (CoM) position errors (mean ± standard deviation) were 0.24 m ± 0.09 m and CoM velocity errors were 0.00 m/s ± 0.18 m/s. For extracted turn entrance and exit speeds the 95% limits of agreements (LoAs) were between −0.19 and 0.33 m/s. LoA for the total path length of a turn were between −0.06 and 0.16 m. The proposed setup and processing allowed estimating the CoM kinematics with similar errors than known for differential global navigation satellite systems (GNSS), even though the athlete’s movement was measured with inertial and magnetic sensors only. Moreover, as the gate positions can also be obtained with non-GNSS based land surveying methods, CoM kinematics may be estimated in areas with reduced or no GNSS signal reception, such as in forests or indoors

Cortical Bone Thickness, Base Osteophyte Occurrence and Radiological Signs of Osteoarthritis in the Fingers of Male Elite Sport Climbers: A Cross-Sectional 10-Year Follow-Up Study

Background: Sport climbing places high mechanical loads on fingers. In 2012, our research group demonstrated adaptations of climbers' cortical bones with the presence of osteophytes compared to non-climbing controls. Objectives: 1) To investigate 10-year changes in cortical bone thickness, base osteophyte occurrence and radiological signs of osteoarthritis in the fingers of elite male sport climbers with more than 25 years of climbing history and 2) to compare cortical bone thickness, base osteophyte occurrence and radiological signs of osteoarthritis between male sport climbers and age-matched controls at the 10-year follow-up. Methods: All 31 elite sport climbers who participated in both the baseline and 10-year follow-up assessments (follow-up rate 100%) were examined by means of X-rays. Cortical bone thickness, presence of osteophytes and signs of osteoarthritis according to Kellgren-Lawrence were obtained and compared to the baseline values 10 years earlier and to age-matched controls at the follow-up (n = 15). Results: Significantly increased cortical bone thickness over the past 10 years was observed in climbers (mean absolute difference with 95% CI:0.98 mm (0.77 mm, 1.19 mm); p <0.001). Moreover, compared to age-matched controls, climbers had significantly thicker cortical bone at the 10-year follow-up (mean absolute difference with 95% CI:0.86 mm (0.61 mm, 1.12 mm); p <0.001). In climbers, osteophytes and clear signs of osteoarthritis were mainly seen in DIP joints. Signs of osteoarthritis according to Kellgren-Lawrence were more prevalent than 10 years before in most joints. In lateral radiographs, base osteophytes were not significantly more prevalent than 10 years before in most of the joints. The percentage of climbers who had osteophytes in any DIP (PIP) joint increased from 93.5% (67.7%) at baseline to 100% (74.2%) at the 10-year follow-up. The percentage of climbers who had clear signs of osteoarthritis according to Kellgren-Lawrence in any DIP (PIP) joint increased from 12.9% (9.7%) at baseline to 74.2% (64.5%) at 10-year follow-up. Only a few such degenerative changes were found in age-matched controls. Conclusion: An accumulation of repetitive climbing-related stress to the fingers of elite sport climbers over the career may induce lifelong mechano-adaptation of the cortical bone thickness of all phalanges. At the 10-year follow-up, a further significant increase in radiographic signs of osteoarthritic changes was observed

Nonoperative Treatment of Finger Flexor Tenosynovitis in Sport Climbers—A Retrospective Descriptive Study Based on a Clinical 10-Year Database

The aim of this study was to describe the nonoperative treatment outcomes of finger flexor tenosynovitis in sport climbers and to evaluate the association with baseline measures and therapy contents. Sixty-five sport climbers (49 males, mean age 34.1 years) diagnosed with tenosynovitis of the finger flexors were retrospectively asked about injury triggers, therapy contents and outcomes. Pulley thickness was measured by ultrasound. All patients were initially treated conservatively, and only one of the patients needed further therapy (single injection with hyaluronic acid); none of them underwent surgical treatment. The most frequently applied therapy was climbing-related load reduction (91%). The treatment resulted in a statistically significant reduction in pain intensity during climbing (before/after therapy ratio [Visual Analog Scale (VAS)/VAS] = 0.62, 95% CI = 0.55, 0.68). The average duration of the symptoms was 30.5 weeks (range 1-120 weeks). In a multiple linear regression analysis, initial daily life pain intensity and a climbing level higher than 7b according to the French/sport grading scale were the only predictive parameters for the relative change in pain intensity and symptom duration, respectively. All patients were able to resume climbing, with 75% regaining or even exceeding their initial climbing level. The good to excellent outcomes and no correlation between particular therapy contents and therapy outcome may suggest that finger flexor tenosynovitis in sport climbers has a favorable natural course without requiring invasive therapy. However, further cohort studies and, ultimately, randomized controlled trials are needed to conclusively confirm our promising observations

Sport and exercise recommendations for pregnant athletes: a systematic scoping review

ObjectivesTo analyse the available evidence and identify gaps in current knowledge regarding physical activity volume and intensity and their effects on pregnancy outcomes in female athletes.DesignScoping review.Data sourcesA structured literature search of three electronic databases (Embase, PubMed and Web of Science) was conducted on 25 February 2022, and a rerun search was conducted on 8 September 2022.Eligibility criteriaStudies were eligible if they contained information on the relevant population (ie, elite or competitive amateur female athletes), intervention/exposure (ie, minimum of 10 hours of sport per week) and fetal and maternal outcomes. Eligible comparators included female recreational athletes and pregnant non-exercisers.Risk of biasThe risk of bias was evaluated with the National Institutes of Health (National Heart, Lung and Blood Institute) quality assessment tool.ResultsThe results revealed a discrepancy between the number of original research papers and the number of reviews and recommendations derived from them. The identified studies focused primarily on pregnant recreational athletes. Sixteen clinical studies met the inclusion criteria. No adverse effects on maternal or fetal outcomes were reported. Only during performance tests involving acute intensive exercise with the mother exercising at more than 90% of her maximal heart rate did some fetuses experience decelerations in heart rate.Summary/conclusionA lack of high-quality studies and direct evidence on pregnant elite and competitive amateur female athletes is evident. Further prospective observational cohort studies are needed using new monitoring methods (eg, non-invasive, wireless monitoring systems) aiming to gain a broader understanding of the stress tolerance of pregnant athletes and fetuses during exercise. Following that, interventional studies with stress tests in laboratory settings should be conducted. Therefore, technology plays a decisive role in gaining new knowledge and providing evidence-based recommendations on this topic.PROSPERO registration numberCRD42022309541

Addressing the unresolved challenge of quantifying skiing exposure-A proof of concept using smartphone sensors

In epidemiological studies related to winter sports, especially alpine skiing, an unresolved methodological challenge is the quantification of actual on-snow activity exposure. Such information would be relevant for reporting meaningful measures of injury incidence, which refers to the number of new injuries that occur in a given population and time period. Accordingly, accurate determination of the denominator, i.e., actual "activity exposure time", is critical for injury surveillance and reporting. In this perspective article, we explore the question of whether wearable sensors in combination with mHealth applications are suitable tools to accurately quantify the periods in a ski day when the skier is physically skiing and not resting or using a mechanical means of transport. As a first proof of concept, we present exemplary data from a youth competitive alpine skier who wore his smartphone with embedded sensors on his body on several ski days during one winter season. We compared these data to self-reported estimates of ski exposure, as used in athletes' training diaries. In summary, quantifying on-snow activity exposure in alpine skiing using sensor data from smartphones is technically feasible. For example, the sensors could be used to track ski training sessions, estimate the actual time spent skiing, and even quantify the number of runs and turns made as long as the smartphone is worn. Such data could be very useful in determining actual exposure time in the context of injury surveillance and could prove valuable for effective stress management and injury prevention in athletes

USING INERTIAL SENSORS FOR RECONSTRUCTING 3D FULL-BODY MOVEMENT IN SPORTS – POSSIBILITIES AND LIMITATIONS ON THE EXAMPLE OF ALPINE SKI RACING

The present study investigates if inertial sensors could be used for reconstructing 3D full body movements in sports. On the example of alpine ski racing, it was demonstrated that inertial sensors allow computing meaningful parameters related to a skier’s overall posture. While some parameters were obtained with sufficient accuracy and precision, others were not obtained reliably using inertial sensor-based systems. Main error sources were discussed and it was found that an accurate and precise functional calibration is most important for short duration measurements. In cases where it is not possible fixing inertial sensors to all relevant body segments (e.g. skis and arms) their orientations could be estimated. In this case parameter validity needs to be carefully verified, as even strongly related parameters may show different validities, as demonstrated in this study