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Abstract Vestibular motion perception declines with age, increasing the risk of falling substantially. We performed a two-week perceptual learning intervention using a self-motion direction discrimination task (2800 training trials per person) on a 6 degrees of freedom motion platform in healthy older adults (n = 40, aged 70–88 yr). Linear inter-aural and angular roll tilt vestibular thresholds improved with training (95% credible interval for pre/post difference), suggesting altered sensitivity post-training. Moreover, improved perceptual abilities transfer to actual posture (reduced sway) and gait parameters. Passive self-motion discrimination training provides a new and promising way to counteract age-related sensory decline. It can reduce the risk of falling, and thereby maintain individual autonomy and quality of life.

Patellar tendon (PT) complaints are frequent in competitive alpine skiers and such complaints are characterized by a long-lasting affection. Since PTs are subject to maturation up to 1–2 years after growth spurt, this early career stage may be decisive for the further course of complaints. The aim of this study was to investigate the evolution of PT complaints and shear wave velocity patterns among competitive alpine skiers during a 4-year post-growth spurt follow-up. The PT complaints and SWV patterns of forty-seven skiers were analysed at baseline (i.e., immediately after their peak height growth at 13–15 years of age) and were re-analysed at 4-year follow-up. The PTs were scanned via three-dimensional SWE. Symptomatic skiers were identified based on pain sensation under loading and pressure-induced pain around the PT. The prevalence of PT complaints decreased from 29.8% at baseline to 12.8% at follow-up (Pearson’s χ2 = 9.429; p = 0.002). SWV decreased from the baseline assessment to the follow-up in the proximal and distal regions (p < 0.05). SWV coefficient of variation (CV) in the distal and mid-portion regions was greater at baseline than at follow-up (p < 0.05). At the follow-up assessment, compared to “healthy” skiers, “healed” skiers who recovered from PT complaints had lower SWVs in the proximal region (p = 0.020) and greater SWV CVs in the proximal region (p = 0.028). Moreover, symptomatic skiers had significantly greater SWV CVs in the mid-portion region than did “healthy” subjects with no history of PT complaints (p = 0.020). The average SWV was negatively correlated with the SWV (proximal: r = −0.74, p < 0.001; mid-portion: r = −0.37 p = 0.011; and distal: r = −0.58, p < 0.001). The occurrence of PT complaints decreased over a 4-year post-growth spurt follow-up. “Healed” skiers who were symptomatic at baseline had an even greater average decrease in the proximal and mid-portion SWV than “healthy” skiers with no history of PT complaints. This may lead to the hypothesis that PT complaints in adolescent skiers are not self-eliminating towards the end of adolescence, as at least structural irregularities appear to persist for several years after the onset of initial symptoms. Furthermore, “healed” and symptomatic tendons exhibited increased SWV variability, supporting the hypothesis that SWV CV may provide additional valuable information on the mechanical properties of PTs affected by overuse-related complaints.

Abstract The aim of this study was to investigate the reliability of panoramic ultrasound (US) imaging and agreement with magnetic resonance imaging (MRI) for assessing the average lumbar multifidus anatomical cross-sectional area between the lumbar vertebral bodies L3–L5 (i.e., LMF ACSAL3–L5). US and MRI scans of 20 male youth competitive alpine skiers were collected. To test the intra- and interrater reliability of US, transversal panoramic scans were analyzed on two different days by the same rater and the analysis of the first day was compared with the analysis of a second rater. To examine the agreement between US and MRI, Bland–Altman analysis was performed. Intrarater reliability was excellent, and interrater reliability was weak to good for both sides. The bias between MRI and US was − 0.19 ± 0.90 cm2 (2.68 ± 12.30%) for the left side and − 0.04 ± 0.98 cm2 (− 1.11 ± 12.93%) for the right side (i.e., for both sides US slightly overestimated LMF ACSAL3–L5 on average). The limits of agreement were − 1.95 to 1.57 cm2 (− 26.70 to 21.30%) for the left side and − 1.95 to 1.88 cm2 (− 26.46 to 24.24%) for the right side. Panoramic US imaging may be considered a method with excellent intrarater and weak to good interrater reliability for assessing LMF ACSAL3–L5. Comparison with MRI showed large individual differences in some cases, but an acceptable bias between the two imaging modalities.

Introduction Patellar tendinopathy is frequent in adolescent athletes and particularly accentuated in competitive alpine skiers (Fröhlich et al., 2020). Tendinopathies are characterized by long disease histories, and whether they can be healed completely is an open question (Kettunen et al., 2002). Three-dimensional (3D) shear wave elastography (SWE) has proven valuable in the early detection of tendinopathies (Götschi et al., 2023). The aims of this study were to (1) describe the longitudinal progression of patellar tendon complaint prevalence in competitive alpine skiers during adolescence, (2) compare the SWV patterns of skiers that were symptomatic four years ago with those with no history of patellar tendon complaints and (3) analyse whether shear wave velocity (SWV) average values correlate with SWV coefficient of variation (CV). Methods Forty-seven subjects were analysed in this 4-year follow-up study regarding their patellar tendon complaints and SWV patterns. Symptomatic and asymptomatic skiers were identified by clinical examinations including the criteria of pain sensation under loading and palpation-induced pain. SWV was determined by ultrasound-based 3D SWE. Prevalence differences were assessed using Pearson’s χ2 tests. Group differences in the SWV patterns were analysed using unpaired sample t tests. Correlations between SWV average and CV values were analysed by means of Pearson’s correlation coefficient. Results With proceeding adolescence, the prevalence of patellar tendon complaints significantly decreased from 29.8% at baseline assessment (13-16 years) to 12.7% at follow-up assessment (Pearson’s χ2 = 9.429; p = 0.002). Those skiers who were symptomatic at baseline but asymptomatic at the follow-up still had lower average SWV values and higher CVs than asymptomatic skiers with no history of patellar tendon complaints (p = 0.054 and p = 0.011, respectively). Furthermore, there was a significant negative correlation between the tendon SWV average values and their CVs (R = -0.55; p < 0.001). Discussion/Conclusion Despite the decreasing prevalence of patellar tendon complaints in youth competitive alpine skiers after their growth spurt, structural abnormalities appear to remain in asymptomatic subjects with a previous history of patellar tendinopathy, indicating potential long-term implications for mechanical tendon proprieties. The SWV average and CV values were negatively correlated, which underlines our hypothesis that a low SWV is associated with a high CV. This altogether may reflect the degenerative processes in patellar tendons affected by complaints in the early stages of a sports career. References Fröhlich, S., Peterhans, L., Stern, C., Frey, W. O., Sutter, R., & Spörri, J. (2020). Remarkably high prevalence of overuse-related knee complaints and MRI abnormalities in youth competitive alpine skiers: A descriptive investigation in 108 athletes aged 13-15 years. BMJ Open Sport & Exercice Medicine, 6(1), Aticle e000738. https://doi.org/10.1136/bmjsem-2020-000738 Götschi, T., Franchi, M. V., Schulz, N., Fröhlich, S., Frey, W. O., Snedeker, J. G., & Spörri, J. (2023). Altered regional 3D shear wave velocity patterns in youth competitive alpine skiers suffering from patellar tendon complaints – A prospective case–control study. European Journal of Sport Science, 23(6), 1068-1076. https://doi.org/10.1080/17461391.2022.2088404 Kettunen, J. A., Kvist, M., Alanen, E., & Kujala, U. M. (2002). Long-term prognosis for jumper’s knee in male athletes. A prospective follow-up study. The American Journal of Sports Medicine, 30(5), 689-692. https://doi.org/10.1177/03635465020300051001

Introduction: The mechanical properties of skeletal muscle are indicative of its capacity to perform physical work, state of disease, or risk of injury. Ultrasound shear wave elastography conducts a quantitative analysis of a tissue’s shear stiffness, but current implementations only provide two-dimensional measurements with limited spatial extent. We propose and assess a framework to overcome this inherent limitation by acquiring numerous and contiguous measurements while tracking the probe position to create a volumetric scan of the muscle. This volume reconstruction is then mapped into a parameterized representation in reference to geometric and anatomical properties of the muscle. Such an approach allows to quantify regional differences in muscle stiffness to be identified across the entire muscle volume assessed, which could be linked to functional implications.Methods: We performed shear wave elastography measurements on the vastus lateralis (VL) and the biceps femoris long head (BFlh) muscle of 16 healthy volunteers. We assessed test-retest reliability, explored the potential of the proposed framework in aggregating measurements of multiple subjects, and studied the acute effects of muscular contraction on the regional shear wave velocity post-measured at rest.Results: The proposed approach yielded moderate to good reliability (ICC between 0.578 and 0.801). Aggregation of multiple subject measurements revealed considerable but consistent regional variations in shear wave velocity. As a result of muscle contraction, the shear wave velocity was elevated in various regions of the muscle; showing pre-to-post regional differences for the radial assessement of VL and longitudinally for BFlh. Post-contraction shear wave velocity was associated with maximum eccentric hamstring strength produced during six Nordic hamstring exercise repetitions.Discussion and Conclusion: The presented approach provides reliable, spatially resolved representations of skeletal muscle shear wave velocity and is capable of detecting changes in three-dimensional shear wave velocity patterns, such as those induced by muscle contraction. The observed systematic inter-subject variations in shear wave velocity throughout skeletal muscle additionally underline the necessity of accurate spatial referencing of measurements. Short high-effort exercise bouts increase muscle shear wave velocity. Further studies should investigate the potential of shear wave elastography in predicting the muscle’s capacity to perform work.

Lower extremity injuries are common in competitive alpine skiers, and the knee and lower leg are often affected. The hamstring muscles, especially the biceps femoris long head (BFlh), can stabilize the knee and the hip and may counteract various adverse loading patterns during typical mechanisms leading to severe lower extremity injuries. The aim of the present study was to describe BFlh morphology in youth competitive alpine skiers in relation to sex, age and biological maturation and to investigate its association with the occurrence of traumatic lower extremity injuries in the upcoming season. 95 youth skiers underwent anthropometric measurements, maturity offset estimations and ultrasound assessment, followed by 12-months prospective injury surveillance. Unpaired t tests showed that the two sexes did not differ in BFlh morphology, including fascicle length (Lf), pennation angle (PA), muscle thickness (MT) and average anatomical cross-sectional area (ACSAavg). In contrast, U16 skiers had longer fascicles than U15 skiers (9.5 ± 1.3 cm vs 8.9 ± 1.3 cm, p < 0.05). Linear regression analyses revealed that maturity offset was associated with Lf (R2 = 0.129, p < 0.001), MT (R2 = 0.244, p < 0.001) and ACSAavg (R2 = 0.065, p = 0.007). No association was found between maturity offset and PA (p = 0.524). According to a binary logistic regression analysis, ACSAavg was significantly associated with the occurrence of traumatic lower extremity injuries (Chi-square = 4.627, p = 0.031, RNagelkerke2 = 0.064, Cohen f = 0.07). The present study showed that BFlh morphology is age- and biological maturation-dependent and that BFlh ACSAavg can be considered a relevant modifiable variable associated with lower extremity injuries in youth competitive alpine skiers.

Patellar tendon (PT) complaints are frequent in competitive alpine skiers and such complaints are characterized by a long-lasting affection. Since PTs are subject to maturation up to 1-2 years after growth spurt, this early career stage may be decisive for the further course of complaints. The aim of this study was to investigate the evolution of PT complaints and shear wave velocity patterns among competitive alpine skiers during a 4-year post-growth spurt follow-up. The PT complaints and SWV patterns of forty-seven skiers were analysed at baseline (i.e., immediately after their peak height growth at 13-15 years of age) and were re-analysed at 4-year follow-up. The PTs were scanned via threedimensional SWE. Symptomatic skiers were identified based on pain sensation under loading and pressure-induced pain around the PT. The prevalence of PT complaints decreased from 29.8% at baseline to 12.8% at follow-up (Pearson's 2 = 9.429; p = 0.002). SWV decreased from the baseline assessment to the follow-up in the proximal and distal regions (p < 0.05). SWV coefficient of variation (CV) in the distal and mid-portion regions was greater at baseline than at follow-up (p < 0.05). At the follow-up assessment, compared to "healthy" skiers, "healed" skiers who recovered from PT complaints had lower SWVs in the proximal region (p = 0.020) and greater SWV CVs in the proximal region (p = 0.028). Moreover, symptomatic skiers had significantly greater SWV CVs in the mid-portion region than did "healthy" subjects with no history of PT complaints (p = 0.020). The average SWV was negatively correlated with the SWV (proximal: r = -0.74, p < 0.001; mid-portion: r = -0.37 p = 0.011; and distal: r = -0.58, p < 0.001). The occurrence of PT complaints decreased over a 4-year post-growth spurt follow-up. "Healed" skiers who were symptomatic at baseline had an even greater average decrease in the proximal and mid-portion SWV than "healthy" skiers with no history of PT complaints. This may lead to the hypothesis that PT complaints in adolescent skiers are not self-eliminating towards the end of adolescence, as at least structural irregularities appear to persist for several years after the onset of initial symptoms. Furthermore, "healed" and symptomatic tendons exhibited increased SWV variability, supporting the hypothesis that SWV CV may provide additional valuable information on the mechanical properties of PTs affected by overuse-related complaints. [ABSTRACT FROM AUTHOR]

Motion platforms are used to study human behavior and brain function during passive motions. The software for controlling motion platforms is typically developed by the respective laboratories. Such customized, closed source solutions make replications of studies or multi-center collaborations difficult. Therefore, we developed PlatformCommander, an open-source software package for interfacing two often used motion platform models (6DOF2000E., MB-E-6DOF). The software includes a server implementing the interaction with the motion platform and additional devices, and a client application, connecting to the server and controlling experiments. PlatformCommander is ideal for the synchronization of data from different sources with high temporal precision.

IntroductionGene polymorphisms are associated with athletic phenotypes relying on maximal or continued power production and affect the specialization of skeletal muscle composition with endurance or strength training of untrained subjects. We tested whether prominent polymorphisms in genes for angiotensin converting enzyme (ACE), tenascin-C (TNC), and actinin-3 (ACTN3) are associated with the differentiation of cellular hallmarks of muscle metabolism and contraction in high level athletes.MethodsMuscle biopsies were collected from m. vastus lateralis of three distinct phenotypes; endurance athletes (n = 29), power athletes (n = 17), and untrained non-athletes (n = 63). Metabolism-, and contraction-related cellular parameters (such as capillary-to-fiber ratio, capillary length density, volume densities of mitochondria and intramyocellular lipid, fiber mean cross sectional area (MCSA) and volume densities of myofibrils) and the volume densities of sarcoplasma were analyzed by quantitative electron microscopy of the biopsies. Gene polymorphisms of ACE (I/D (insertion/deletion), rs1799752), TNC (A/T, rs2104772), and ACTN3 (C/T, rs1815739) were determined using high-resolution melting polymerase chain reaction (HRM-PCR). Genotype distribution was assessed using Chi2 tests. Genotype and phenotype effects were analyzed by univariate or multivariate analysis of variance and post hoc test of Fisher. P-values below 0.05 were considered statistically significant.ResultsThe athletes demonstrated the specialization of metabolism- and contraction-related cellular parameters. Differences in cellular parameters could be identified for genotypes rs1799752 and rs2104772, and localized post hoc when taking the interaction with the phenotype into account. Between endurance and power athletes these concerned effects on capillary length density for rs1799752 and rs2104772, fiber type distribution and volume densities of myofibrils (rs1799752), and MSCA (rs2104772). Endurance athletes carrying the I-allele of rs1799752 demonstrated 50%-higher volume densities of mitochondria and sarcoplasma, when power athletes that carried only the D-allele showed the highest fiber MCSAs and a lower percentage of slow type muscle fibers.DiscussionACE and tenascin-C gene polymorphisms are associated with differences in cellular aspects of muscle metabolism and contraction in specifically-trained high level athletes. Quantitative differences in muscle fiber type distribution and composition, and capillarization in knee extensor muscle explain, in part, identified associations of the insertion/deletion genotypes of ACE (rs1799752) with endurance- and power-type Sports.

Background: Conventional forms of endurance training based on shortening contractions improve aerobic capacity but elicit a detriment of muscle strength. We hypothesized that eccentric interval training, loading muscle during the lengthening phase of contraction, overcome this interference and potentially adverse cardiovascular reactions, enhancing both muscle metabolism and strength, in association with the stress experienced during exercise. Methods: Twelve healthy participants completed an eight-week program of work-matched progressive interval-type pedaling exercise on a soft robot under predominately concentric or eccentric load. Results: Eccentric interval training specifically enhanced the peak power of positive anaerobic contractions (+28%), mitigated the strain on muscle’s aerobic metabolism, and lowered hemodynamic stress during interval exercise, concomitant with a lowered contribution of positive work to the target output. Concentric training alone lowered blood glucose concentration during interval exercise and mitigated heart rate and blood lactate concentration during ramp exercise. Training-induced adjustments for lactate and positive peak power were independently correlated (p < 0.05, |r| > 0.7) with indices of metabolic and mechanical muscle stress during exercise. Discussion: Task-specific improvements in strength and muscle’s metabolic capacity were induced with eccentric interval exercise lowering cardiovascular risk factors, except for blood glucose concentration, possibly through altered neuromuscular coordination.

Background: The lumbar multifidus (LMF), as a dynamic stabilizer of the lumbar spine, may play an important role in the prevention of overuse-related back complaints. Hypothesis: LMF morphology is associated with trunk stability and differs between symptomatic and asymptomatic skiers. Study Design: Cohort study. Level of Evidence: Level 3. Methods: A total of 85 youth skiers (28 females, mean age, 14.7 ± 0.7 years; 57 males, mean age, 14.9 ± 0.5 years) underwent anthropometric assessments, an estimation of biological maturation, a magnetic resonance imaging- and ultrasound-based examination of LMF morphology, and a biomechanical quantification of deadbug bridging stabilization performance. Athletes were categorized as symptomatic if they had registered at least 1 significant overuse-related back complaint episode in the 12 months before the main examination. Results: Male skiers showed a greater LMF size (ie, anatomical cross-sectional area [ACSA]) than female skiers, except for vertebral body L5, where no difference was found (8.8 ± 1.8 cm2 vs 8.3 ± 1.4 cm2, P = 0.18). Conversely, female skiers displayed longer fascicles than male skiers (5.8 ± 0.8 cm vs 5.4 ± 0.8 cm, P = 0.03). Skiers aged under 16 years (U16) skiers had greater values for LMF size and fascicle length than U15 skiers. Maturity offset was associated with L5 LMF size (R 2 = 0.060, P = 0.01), fascicle length (R 2 = 0.038, P = 0.04), and muscle thickness (R 2 = 0.064, P = 0.02). L5 LMF size was associated with trunk stability (R 2 = 0.068, P = 0.01). Asymptomatic skiers showed on average a 12.8% greater value for L5 LMF size compared with symptomatic skiers (P = 0.04). Conclusion: There are sex- and age-related differences in LMF morphology in youth competitive alpine skiers. Moreover, the ACSA at the level of the lumbar vertebral body L5 undergoes changes during biological maturation, shows a small, but significant association with trunk stability, and differs between symptomatic and asymptomatic skiers with back complaints. Clinical Relevance: The observed association of muscle structure (ie, L5 LMF ACSA) with functional aspects (ie, trunk stabilization capacity) and clinical representation (ie, overuse-related back complaints) further highlights the important role of the multifidus muscle for training and injury prevention in youth competitive alpine skiers around the growth spurt. [ABSTRACT FROM AUTHOR]