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The study objective is to test general- and sport-specific adaption during a single training on the Flexibility Trainer. The device is designed to trigger residual muscle tone decreases of the hip-joint muscles by providing (nearly) isokinetic resistance during a full range of motion strength training in adduction/abduction and flexion/extension direction. Static hip flexion and abduction as well as kinematics of double side kicks were analysed on 15 participants before and after training (or rest for controls) to assess general flexibility and sport-specific movement range. Tests were recorded by a Vicon® motion capturing system. Static hip flexion and abduction as well as leg vector spreading angles (VSA) at different nodes of the kick were selected to determine adaptions of active and passive flexibility. Normalised hip joint moments, movement velocities and VSA were calculated to evaluate the training with the device. ANOVAs with 4-repeated measures and Friedman tests were performed to identify time differences and Bonferroni post-hoc test to identify between-subject effects. Significant differences were found for both static flexibility tests (Flexion = 13.65%; Abduction = 9.94%) and the VSA at specific action phases (≤15.15%). Results indicate that short-term adaptions when training with the Flexibility Trainer are exceeding comparable literature showing improved flexibility and sport-specific performance. [ABSTRACT FROM AUTHOR]

The work investigates the relationship between the leg spread and hip joint flexibility during kicking action of highly skilled martial artists. Vector-based spreading angles (VSAs), as a simplified way to assess kick execution patterns and movement ranges, are proposed. The first VSA measures the angle between the two femur vectors (i.e., upper leg spread), whereas the second describes the full-leg spread. The proposed measures were applied to 3D motion analysis performed on 33 participants at various skill levels who executed double side kicks and performed two static flexibility tests (hip joint flexion and abduction). Statistical analysis showed that the proposed parameters differentiate between skill levels. Both VSAs and VSA rate of change showed high Pearson correlation to the quality of execution (the average of 10 subjective kickboxing experts' evaluation scores) at critical instants of the kick execution , i.e., during the first leg elevation and kick (angles: ρ > 0.8; p < 0.001). In addition, they significantly correlated to maximum static hip abduction at any instant (ρ = 0.37–0.69; p < 0.05). The work established that both static and dynamic joint flexibility contribute to high-performance levels and could be used for initial selection and assessment of training effectiveness. [ABSTRACT FROM AUTHOR]

To identify the relationship between load and the number of repetitions performed to momentary failure in the pin press exercise, the present study compared different statistical model types and structures using a Bayesian approach. Thirty resistance-trained men and women were tested on two separate occasions. During the first visit, participants underwent assessment of their one-repetition maximum (1-RM) in the pin press exercise. On the second visit, they performed sets to momentary failure at 90%, 80% and 70% of their 1-RM in a fixed order during a single session. The relationship between relative load and repetitions performed to failure was fitted using linear regression, exponential regression and the critical load model. Each model was fitted according to the Bayesian framework in two ways: using an across-subjects pooled data structure and using a multilevel structure. Models were compared based on the variance explained (R2) and leave-one-out cross-validation information criterion (LOOIC). Multilevel models, which incorporate higher-level commonalities into individual relationships, demonstrated a substantially better fit (R2: 0.97–0.98) and better predictive accuracy compared to generalised pooled-data models (R2: 0.89–0.93). The multilevel 2-parameter exponential regression emerged as the best representation of data in terms of model fit, predictive accuracy and model simplicity. The relationship between load and repetitions performed to failure follows an individually expressed exponential trend in the pin press exercise. To accurately predict the load that is associated with a certain repetition maximum, the relationship should therefore be modelled on a subject-specific level. [ABSTRACT FROM AUTHOR]

The study was designed to investigate the validity of different technologies used to determine movement velocity in resistance training. Twenty-four experienced powerlifters (18 male and 6 female; age, 25.1 ± 5.1 years) completed a progressive loading test in the squat, bench press, and conventional deadlift until reaching their 1 repetition maximum. Peak and mean velocity were simultaneously recorded with 4 field-based systems: GymAware (GA), FitroDyne (FD), PUSH (PU), and Beast Sensor (BS). 3D motion capturing was used to calculate specific gold standard trajectory references for each device. GA provided the most accurate output across exercises (r = 0.99-1, ES 5 -0.05 to 0.1). FD showed similar results for peak velocity (r = 1, standardized mean bias [ES] = -0.1 to -0.02) but considerably less validity for mean velocity (r = 0.92-0.95, ES = -0.57 to -0.29). Reasonably valid to highly valid output was provided by PU in all exercises (r = 0.91-0.97, ES = -0.5 to 0.28) and by BS in the bench press and for mean velocity in the squat (r 5 0.87-0.96, ES 5 -0.5 to -0.06). However, BS did not reach the thresholds for reasonable validity in the deadlift and for peak velocity in the squat, mostly due to high standardized mean bias (ES 5 -0.78 to -0.63). In conclusion, different technologies should not be used interchangeably. Practitioners who require negligible measurement error in their assessment of movement velocity are advised to use linear position transducers over inertial sensors. [ABSTRACT FROM AUTHOR]

A technique in Martial Arts is often indicated by an athlete's preceding actions, which potentially enables an opponent to detect or counter it. Prior to kicks, fighters attain balance and ease leg elevation by re-distributing their weight (WRT) or ease following sequences by elevating COM (CET). The aim of this study was to define such movements and to compare them by their duration and motion amplitude. The kick preceding actions and regular fighting movements of a kicking combination performed by 44 fighters across different skill levels (advanced to world leading) were compared. The initiation action start was determined by the moment during the preparatory phase, when a joint angle significantly exceeds or subceeds a specific threshold (3Sd). Descriptive statistics and qualitative analysis were used to summarise movement types, durations, and amplitudes. T- and Wilcoxon tests were performed to analyse differences in movement start and amplitude between WRT and CET, while Friedman- and Dunn-Bonferroni tests were used between body segments. Results showed that WRTs start earlier, happen more often, and are more subtle than CETs. Furthermore, proximal segments tend to move earlier [Sequence: COM; torso; hips> arms; knees] and with less movement amplitude [Sequence: arms > hips; knees > torso]. [ABSTRACT FROM AUTHOR]

Prolonged sitting is a risk factor for several diseases and the prevalence of worksite-based interventions such as sit-to-stand workstations is increasing. Although their impact on sedentary behaviour has been regularly investigated, the effect of working in alternating body postures on cognitive performance is unclear. To address this uncertainty, 45 students participated in a two-arm, randomised controlled cross-over trial under laboratory conditions. Subjects executed validated cognitive tests (working speed, reaction time, concentration performance) either in sitting or alternating working postures on two separate days (ClinicalTrials.gov Identifier: NCT02863731). MANOVA results showed no significant difference in cognitive performance between trials executed in alternating, standing or sitting postures. Perceived workload did not differ between sitting and alternating days. Repeated measures ANOVA revealed significant learning effects regarding concentration performance and working speed for both days. These results suggest that working posture did not affect cognitive performance in the short term. Practitioner Summary: Prior reports indicated health-related benefits based on alternated (sit/stand) body postures. Nevertheless, their effect on cognitive performance is unknown. This randomised controlled trial showed that working in alternating body postures did not influence reaction time, concentration performance, working speed or workload perception in the short term. [ABSTRACT FROM AUTHOR]

The double side kick is a frequently used technique in pointfighting on which most offensive kicking techniques are based on. The aim of the study was to identify parameters, e.g., trunk and leg positions, durations and velocities that affect successful technique execution. 44 fighters, male and female, including European and World champions, participated in the research. The participants performed double side kicks to a punching bag with the target at chest level. 10 international experts scored (1–10 points; interrater correlation ICC (3,1): 0.952) videos of the best individual trial for quality of technique execution. Based on the average of the scores participants were categorised into 2 equally sized groups. For kinematic data acquisition, a Vicon 3D-motion capturing system was used. The normalised knee height of the kick leg (KHK), normalised absolute distance to the frontal shoulder (DKS) at the end of both chambering phases, the horizontal velocity during both chambering phases (KEV), the durations of all 6 functional phases and total duration, were analysed. KHK1, KHK2, DKS1 and DKS2, total duration as well as 4 out of 6 phase durations and KEV1 showed significant differences between groups in two-sided t-test or Mann–Whitney U-test for not normally distributed variables. [ABSTRACT FROM PUBLISHER]

The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the system's transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the system's transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athlete's heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) system's difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of −0.46–7.35%. The study indicates the examined system's sufficient accuracy for time-motion analysis in basketball. [ABSTRACT FROM PUBLISHER]

The overall goal of the present study was to illustrate the potential of artificial intelligence (AI) techniques in sports on the example of weight training. The research focused in particular on the implementation of pattern recognition methods for the evaluation of performed exercises on training machines. The data acquisition was carried out using way and cable force sensors attached to various weight machines, thereby enabling the measurement of essential displacement and force determinants during training. On the basis of the gathered data, it was consequently possible to deduce other significant characteristics like time periods or movement velocities. These parameters were applied for the development of intelligent methods adapted from conventional machine learning concepts, allowing an automatic assessment of the exercise technique and providing individuals with appropriate feedback. In practice, the implementation of such techniques could be crucial for the investigation of the quality of the execution, the assistance of athletes but also coaches, the training optimization and for prevention purposes. For the current study, the data was based on measurements from 15 rather inexperienced participants, performing 3-5 sets of 10- 12 repetitions on a leg press machine. The initially preprocessed data was used for the extraction of significant features, on which supervised modeling methods were applied. Professional trainers were involved in the assessment and classification processes by analyzing the video recorded executions. The so far obtained modeling results showed good performance and prediction outcomes, indicating the feasibility and potency of AI techniques in assessing performances on weight training equipment automatically and providing sportsmen with prompt advice. [ABSTRACT FROM AUTHOR]

The jumping front-leg axe-kick is a valid attacking and counterattacking technique in Taekwondo competition (Streif, 1993). Yet, the existing literature on this technique is sparse (Kloiber et al., 2009). Therefore, the goal of this study was to determine parameters contributing significantly to maximum linear speed of the foot at impact. Parameters are timing of segment and joint angular velocity characteristics and segment lengths of the kicking leg. Moreover, we were interested in the prevalence of proximal-to-distal-sequencing. Three-dimensional kinematics of the kicks of 22 male Taekwondo-athletes (age: 23.3 ± 5.3 years) were recorded via a motion capturing system (Vicon Motion Systems Limited, Oxford, UK). The participants performed maximum effort kicks onto a rack-held kicking pad. Only the kick with the highest impact velocity was analysed, as it was assumed to represent the individual's best performance. Significant Pearson correlations to impact velocity were found for pelvis tilt angular displacement (r = 0.468, p < 0.05) and for hip extension angular velocity (r = -0.446, p < 0.05) and for the timing of the minima of pelvis tilt velocity (r = -0.426, p < 0.05) and knee flexion velocity (r = -0.480, p < 0.05). Backward step linear regression analysis suggests a model consisting of three predictor variables: pelvis tilt angular displacement, hip flexion velocity at target contact and timing of pelvic tilt angular velocity minimum (adjusted R² = 0.524). Results of Chi-Squared tests show that neither for the leg-raising period (χ² = 2.909) of the technique, nor for the leg-lowering period a pattern of proximal-to-distal sequencing is prevalent (χ² = 0.727). From the results we conclude that the jumping front-leg axe-kick does not follow a proximal-to-distal pattern. Raising the leg early in the technique and apprehending the upper body to be leant back during the leg-lowering period seems to be beneficial for high impact velocity. Furthermore, striking by extending the hip rather than by flexing the knee could raise impact velocity. [ABSTRACT FROM AUTHOR]