Human movements are characterized by highly non-linear and multi-dimensional interactions within the motor system. Therefore, the future of human movement analysis requires procedures that enhance the classification of movement patterns into relevant groups and support practitioners in their decisions. In this regard, the use of data-driven techniques seems to be particularly suitable to generate classification models. Recently, an increasing emphasis on machine-learning applications has led to a significant contribution e.g. in increasing the classification accuracy. In order to ensure the generalizability of the machine-learning models, different data preprocessing steps are usually carried out to process the measured raw data before the classifications. In the past, various methods have been used for each of these preprocessing steps. However, there are hardly any standard procedures or rather systematic comparisons of these different methods and their impact on the classification accuracy. Therefore, the aim of this analysis is to compare different combinations of commonly applied data preprocessing steps and test their effects on the classification accuracy of gait patterns.A publicly available dataset on intra-individual changes of gait patterns was used for this analysis. Forty-two healthy subjects performed 6 sessions of 15 gait trials for one day. For each trial, two force plates recorded the three-dimensional ground reaction forces (GRF). The data was preprocessed with the following steps: GRF filtering, time derivative, time normalization, data reduction, weight normalization and data scaling. Subsequently, combinations of all methods from each individual preprocessing step were analyzed and compared with respect to their prediction accuracy in a six-session classification using Support Vector Machines, Random Forest Classifiers and Multi-Layer Perceptrons. 1 arXiv:1911.04335v1 [cs.LG] 11 Nov 2019 Burdack et al. Data Preprocessing in Gait ClassificationThe results indicate that filtering GRF data and a supervised data reduction (e.g., using Principal Components Analysis) lead to increased prediction accuracies of the machine-learning classifiers. Interestingly, the weight normalization and the number of data points (above a certain minimum) in the time normalization does not have a substantial effect. In conclusion, the present results provide first domain-specific recommendations for commonly applied data preprocessing methods and might help to build more comparable and more robust classification models based on machine learning that are suitable for a practical application.
The aims of this study were (a) to assess and correlate interval shuttle run test (ISRT) performance, maximum oxygen uptake (V[Combining Dot Above]O(2)max), running economy (RE), running velocity at the first rise in blood lactate concentrations above baseline (vLT) and running velocity at 4 mmol·L(-1) blood lactate concentration (v4) in professional soccer players and (b) to investigate whether a correlation exists between the respective results of time to exhaustion (T(lim)) from continuous and intermittent endurance tests, respectively. Eleven male professional field soccer players (mean ± SD: age 23.8 ± 3.0 years, V[Combining Dot Above]O(2)max 58.2 ± 4.9 ml·kg(-1)·min(-1)) completed a continuous Incremental Test with lactate measurements to determine vLT and v4, a continuous Ramp Test with gas exchange analysis to determine V[Combining Dot Above]O(2)max and RE, and an intermittent ISRT to determine intermittent endurance capacity during the first week of preseason preparation. There were significant correlations between ISRT performance and V[Combining Dot Above]O(2)max (r = 0.70, p < 0.05), and between T(lim) in both continuous endurance tests (r = 0.89, p < 0.01). Between all other variables no significant correlations were found overall (best r = 0.60, p > 0.05). The assessment of all values of V[Combining Dot Above]O(2)max, RE, vLT, and v4 should be included when investigating aerobic endurance performance among groups or over time in professional soccer players. Although V[Combining Dot Above]O(2)max, RE, vLT, and v4 have been regarded as important factors of aerobic performance in endurance related sports, the present data revealed that V[Combining Dot Above]O(2)max was the only factor, which correlated with intermittent endurance capacity in professional soccer players. Hence, V[Combining Dot Above]O(2)max should be increased through soccer-specific training interventions including universal agility components. The T(lim) in continuous and intermittent endurance tests differs and is therefore an independent endurance performance factor in professional soccer players.
Abstract:The researches which investigated the effects of core training on skill performance for badminton players are in sufficient. The current study aimed to examine the effects of core stability training on dynamic balance and smash stroke velocity and accuracy performance. Twenty badminton players under 19 years were divided into two groups, core training group (n = 10) and control group (n = 10). Core stability training group completed 8 weeks training programme, while control group did only their badminton traditional training. The effectiveness of core stability training intervention was assessed by performing core stability tests with four positions, dynamic balance test and forehand smash stroke performance test. Significant improvement was obtained only in the training group for core muscle endurance, total reached distance of three directions in star excursion balance test and smashing velocity and accuracy variables (p < 0.05). Consequently, eight weeks core stability training provides an improvement for maintained optimum lower limbs dynamic balance and increased the performance level of smash stroke in young badminton players.
Repeated sprint training is usually performed in team sports, but its combination with blood flow restriction has a lake datum existing on the intense response to this type of training. This study aims to determine the acute effect of repeated sprint training in combination with blood flow restriction on the strength, anaerobic and aerobic performance in basketball. Twenty-four basketball players participated in current study were divided into two groups. They performed twelve on-court sessions; each consists of 3 sets of 8 repetitions of 20-sec and 4-min rests. Strength (1-RM bench press and half-squat), anaerobic, aerobic measurements were tested before the beginning of the study and two days followed by the training intervention period. The results presented a small increase in upper maximum strength (bench press) and anaerobic (Suicide Run) variables (ES 0.2 to 0.5) in (RST-BFR) group. In addition, there is a large increase in lower body maximum strength (half-squat) and aerobic capacity (VO 2max ) variables. In comparison, the control group reported a small increase only in the aerobic capacity (VO 2max ) (ES = 0.26), otherwise trivial effect size was observed in other variables. The t-test reported a significant difference between both groups (p < 0.05) after the (RST) with blood flow restriction on the lower body maximum strength (half-squat) and the aerobic capacity (VO 2max ) measured variables.
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