Dominik Fohrmann

Background: Functional performance test (FPT) results have rarely been analysed for sex-specific differences among professional ballet dancers yet. Therefore, this study aims to assess the FPT results of professional female and male ballet dancers, analyse sex-specific differences, describe the number of dancers meeting predefined thresholds, and present the prevalence of lower limb asymmetries in selected FPTs. Methods: Professional ballet companies in Germany were invited to participate in this study via word-of-mouth. An extensive health & performance screening was provided to the voluntarily participating dancers, which included eight FPTs. Solely dancers on sick leave were excluded. The selected FPTs focused on stability (balance error scoring system (BESS)), muscular endurance & strength (heel-rise test, Bunkie test, and closed kinetic chain upper extremity stability test (CKCUEST)), and hop performance (vertical-hop test, figure-of-eight-hop test, side-hop test, and speedy jump test). Differences in the FPT results between sexes, limb asymmetries in the FPTs (determined by the Limb Symmetry Index (LSI)), and the number of dancers achieving predefined thresholds were analysed with independent-samples t -test, and Chi²-tests, respectively. Results: Data from 115 dancers from four classical ballet companies were included in the analysis. The FPT results differed between sexes: while female dancers performed better than male dancers in the heel-rise test ( p = .019), males excelled in the CKCUEST ( p <.001), Bunkie Copenhagen plank ( p = .004), vertical-hop test ( p <.001), figure-of-eight-hop test ( p <.001), and side-hop test ( p <.001). Lower limb asymmetries greater than 15% were most prevalent in the vertical-hop test (30%) and the side-hop test (24%), and least prevalent in the figure-of-eight-hop test (1%). Conclusion: This is the first study that analysed sex-specific differences in FPT results of professional ballet dancers from multiple companies. It contributes to the broader understanding of the basic physical performance skills for ballet, presenting the current training status of dancers from four professional ballet companies. The majority of muscular endurance & strength tests and hop performance tests revealed significant differences between male and female dancers, with many dancers showing notable limb asymmetries. Overall, the results demonstrated a lower performance level compared to athletes in other sports.

Background: Functional leg axis deviations, particularly dynamic knee valgus (DKV), are considered key risk factors for lower-extremity injuries. In physiotherapy practice there are no standardized tools to quantitatively assess functional leg axis deviations within a treatment session. While application-based 2D analyses offer accessible options, the agreement between manual and automated, AI-based Human Pose Estimation (HPE) methods remains underexplored. Here, the aims were to investigate the intra- and inter-rater reliability of a manual application-based method (PhysioMaster®); to quantify the agreement between two AI-based HPE models (OpenPose, BlazePose); and to explore which functional test, Single-Leg Squat (SLS), Single-Leg Hop for Distance (SLH), or Single-Leg Landing (SLL), elicits the most pronounced leg axis deviations. Methods: Sixteen healthy adults (8 females) performed three standardized single-leg tasks (SLS, SLH, SLL) with each leg. Knee angles in the frontal plane were measured from monocular video images using the PhysioMaster® application (two raters × two ratings) and compared with automated 2D analyses using OpenPose and BlazePose. Reliability and agreement were evaluated using Intraclass Correlation Coefficients, Lin’s Concordance Correlation Coefficient (CCC), and Bland–Altman analyses. Linear Mixed Model (LMM) analyses were carried out to explore which functional task would be the most effective. Results: The PhysioMaster® application showed excellent intra- and inter-rater reliability across all tests (ICC ≥ 0.95). OpenPose demonstrated excellent agreement with manual application-based measurements (CCC = 0.95; Bias = 0.87°; LoA = –4.32° to 6.05°), while BlazePose achieved good agreement (CCC = 0.89; Bias = –0.67°; LoA = –8.76° to 7.42°). LMM analyses revealed that all three tasks significantly evoked knee angle deviations. The SLL evoked the largest valgus angles (Estimate = –8.29°, p < .001), while the SLS elicited the highest varus angles (Estimate = 7.92°, p < .001). Conclusion: Both, manual application-based and AI-based 2D methods, provided reliable and largely consistent assessments of knee valgus angles in the frontal plane during functional testing. OpenPose achieved the best agreement with manual application-based reference values, and the SLL was the most suitable task for detecting DKV. While the results support the integration of manual application-based and AI-assisted posture analysis into clinical physiotherapy, further research on concurrent validity of all three methods used against 3D motion capture is needed.

Background: Advanced footwear technology (AFT) can enhance long-distance running performance by improving running economy (RE). However, the range of the individual improvements is large. Different intra-individual responses in running biomechanics may account for some of the variation. Thus, this randomized within-subject crossover study aimed to identify biomechanical factors associated with changes in RE when running with different AFT models. Methods: Twenty-two trained long-distance runners (50% female) ran multiple 5-minute running bouts at their season’s best marathon pace (15.0 ± 2.3 km⸱h ^− 1 ) while wearing three standardized AFT models (Nike Air Zoom Alphafly Next% 2, Puma Fast-R Nitro Elite v1, Asics Metaspeed Sky+). During each condition, gas exchange data and three-dimensional kinematics and spatiotemporal variables were acquired. RE was determined as the energetic cost of transport. We used two complementary model selection strategies (Akaike Information Criterion model averaging and least absolute shrinkage and selection operator) to identify biomechanical parameters associated with intra-individual differences in RE, and a repeated measures ANOVA to compare RE between shoes at the group level. Results: Across shoe conditions, shorter ground contact time was significantly associated with lower energetic cost of transport (β = 0.025, 95% CI [0.010, 0.040], t(42) = 3.33, p = 0.002), reflecting a ~ 1% improvement in RE per 4 ms decrease. We did not find group-level differences in RE between shoe conditions ( p = 0.246). Conclusions: AFT models that reduced runners’ individual ground contact time were associated with improved RE. This effect appears to depend on the individual athlete-shoe interaction since no single AFT model stood out as an overall optimum. These findings can help determine optimal footwear for athletes. Future studies should investigate the interaction of AFT properties and individual biomechanics to identify further RE improvements through footwear individualization.

Hugs are an important nonverbal social-affective behavior that plays a crucial role in romantic relationships. Unfortunately, little is known about how movement biomechanics during hugging relate to relationship status and personality factors. To address these open questions, the present proof-of-principle project focused on three-dimensional movement analyses of hugs in different imagined emotional situations (positive, negative, or neutral) provoked by auditory instructions in participants (n = 60) who were either in romantic relationships or platonic friendships. Videos of hugs were recorded using 14 high-frequency video cameras and analyzed using three-dimensional markerless motion capture software. From the raw motion data, various biomechanical parameters were computed (e.g., the distance between the feet or the pelvises of the participants or the duration of the embraces). Personality traits were assessed with a questionnaire. Results showed that romantic partners hugged longer than platonic friends. Moreover, while there was an overall rightward bias for the hugging hand, romantic couples hugged more often leftward than platonic friends. In addition, both groups hugged less rightward in emotional situations compared to neutral situations. Also, individuals with higher neuroticism preferred a larger distance during hugging, while individuals with higher conscientiousness preferred shorter distances to their hugging partners. These findings show that biomechanical features of embraces obtained from markerless movement analyses differ according to the relationship status and personality. This shows that markerless movement analysis is a valuable tool in social-affective neuroscience of two-person interactive non-verbal behaviors like social touch.

Lower body positive pressure treadmills (LBPPTs) offer precise body weight unloading for injury rehabilitation and performance training in runners. This study investigated biomechanical changes during running at varying body weight support (BWS) levels (0%–80%) in competitive runners, including sex‐specific responses. Twenty‐six runners (age: 33.6 ± 9.8 years; 15 female, 11 male) completed randomized 3‐min running bouts at 12 km/h across nine BWS levels. Spatiotemporal parameters, plantar force, peak tibial acceleration, and running stability were measured using pressure insoles and inertial sensors placed at the tibia and foot. Our results revealed significant reductions in step rate (b = −0.24 steps•min⁻¹/%BWS, p < 0.001), normalized ground contact time (b = −0.001 1/%BWS, p < 0.001), maximum plantar force (b = −0.010 BW/%BWS, p < 0.001), and peak tibial acceleration (b = −0.03 g/%BWS, p < 0.001) with increased BWS. Swing time increased (b = 1.50 ms/%BWS, p < 0.001), while stance time decreased (b = −0.41 ms/%BWS, p < 0.001). Running stability showed marginal changes (foot: b = −0.001 1/%BWS, p = 0.017; tibia: b = 0.001 1/%BWS, p = 0.009). Sex differences were observed in step rate (b = −6.79 steps•min⁻¹, p = 0.045) and maximum plantar force (b = −0.128 BW, p = 0.034), but there were no significant sex × BWS interaction effects for any of the investigated parameters. Findings from this study highlight the effectiveness of LBPPTs for reducing musculoskeletal loading while revealing associated gait changes. Athletes, therapists, and coaches should consider individual biomechanical responses to optimize rehabilitation and performance strategies. Future research should explore long‐term adaptations and injury prevention outcomes.

Objective: To describe the incidence and characteristics of injuries and illnesses that occurred during the 54th Nordic World Ski Championships in Planica (Slovenia) 2023, including the disciplines of cross-country skiing, Nordic combined and ski jumping. Methods: In this prospective cohort study, national medical teams and the medical team of the local organiser collected data on a daily basis on all new, exacerbated or recurrent injuries and illnesses of the registered athletes using the IOC consensus recommendations. Results: There were 596 registered athletes (250 women, 346 men), all with access to medical services. The national medical teams covered 347 (58.2%) athletes with a response rate of 77.1%. A total of 24 injuries, corresponding to an incidence rate of 4.0 per 100 athletes (95% CI, 2.5 to 5.6), and 15 illnesses, corresponding to an incidence rate of 2.5 per 100 athletes (95% CI, 1.3 to 3.8), were reported. The lower extremities were the most common injury location (58.3%), and every second injury in this category was a knee injury. The predominant injury types were joint sprains/ligament tears (25.0%) and contusions/bruises (25.0%). A total of three concussions (12.5% of all injuries) were reported, all of them in ski jumping. Among the illnesses, infections (73.3%) were the most common aetiology, and the respiratory system (53.3%) was the most frequently affected organ system. Conclusion: Special attention should be given to knee injuries in all disciplines and concussions in ski jumping. A high proportion of the recorded illnesses were of infectious origin. The reduction in hygiene regulations after the COVID-19 pandemic could have contributed to this.

Aim was to evaluate alterations of the non‐linear short‐term scaling exponent alpha1 of detrended fluctuation analysis (DFAa1) of heart rate (HR) variability (HRV) as a sensitive marker for assessing global physiological demands during multiple running intervals. As a secondary analysis, agreement of ECG‐derived respiratory frequency (EDR) compared to respiratory frequency (RF) derived from the metabolic cart was evaluated with the same chest belt device. Fifteen trained female and male long‐distance runners completed four running bouts over 5 min on a treadmill at marathon pace. During the last 3 min of each bout gas exchange data and a single‐channel ECG for the determination of HR, DFAa1 of HRV, EDR and RF were analyzed. Additionally, blood lactate concentration (BLC) was determined and rating of perceived exertion (RPE) was requested. DFAa1, oxygen consumption, BLC, and RPE showed stable behaviors comparing the running intervals. Only HR (p < 0.001, d = 0.17) and RF (p = 0.012, d = 0.20) indicated slight increases with small effect sizes. In addition, results point towards inter‐individual differences in all internal load metrics. The comparison of EDR with RF during running revealed high correlations (r = 0.80, p < 0.001, ICC_3,1 = 0.87) and low mean differences (1.8 ± 4.4 breaths/min), but rather large limits of agreement with 10.4 to −6.8 breaths/min. Results show the necessity of EDR methodology improvement before being used in a wide range of individuals and sports applications. Relationship of DFAa1 to other internal load metrics, including RF, in quasi‐steady‐state conditions bears the potential for further evaluation of exercise prescription and may enlighten decoupling mechanisms during prolonged exercise bouts.

Purpose: This study aimed to compare running economy across habituated and nonhabituated advanced footwear technology (AFT) in trained long-distance runners. Methods: A total of 16 participants completed up to six 5-minute trials in 1 to 3 pairs of their own habituated shoes and 3 different and standardized AFTs at individual marathon pace. We measured oxygen uptake and carbon dioxide production and expressed running economy as oxygen uptake (in milliliters oxygen per kilogram per minute), oxygen cost of transport (oxygen per kilogram per minute), energetic cost (in watts per kilogram), and energetic cost of transport (in joules per kilogram per kilometer). We used linear mixed-effect models to evaluate differences. Relative shoe weight and shoe mileage (distance worn during running) were covariates. Results: Forty-eight standardized and 29 individual AFT conditions were measured (mileage 117.0 [128.8] km, range 0–522 km; 25 habituated 135.7 [129.2] km, range 20–522 km; 4 nonhabituated 0 [0] km, range 0–0 km). Rating of perceived exertion, blood [La], and respiratory exchange ratio ranged from 9 to 15, 1.11 to 4.54 mmol/L, and 0.76 to 1.01. There was no effect for habituation on energetic cost of transport (t_habituation = −.232, P = .409, b = −0.006; 95% CI, −0.058 to 0.046) or other running economy metrics. Neither shoe weight nor shoe mileage had an effect. Conclusions: Our results suggest that habituation to AFTs does not result in greater benefits in the use of AFTs. This means that implementation in training may not be needed, even if we cannot rule out any other possible benefits of habituation at this stage, such as adaptation of the musculoskeletal system.