Zig-zag Test Research Articles

Acute effect of injury-prevention-exercise-based warm-up vs. small-sided-game-based warm-up on speed performance in young amateur soccer players

Purpose: This study aimed to investigate the effects of an Injury-Prevention-Exercise (IPE)-based warm-up and a Small-Sided-Game (SSG)-based warm-up on subsequent speed performance in young soccer players. Method: Twelve male soccer players from the fourth division regional league in Algeria participated in the study. The participants completed both the IPE-based warm-up and the SSG-based warm-up in a counterbalanced order with a one-week interval between conditions. Linear and curved sprint performances, and change of direction (COD) speed, were assessed. Results: The results showed no significant differences between the two warm-up protocols in linear sprint performance (10m and 20m tests) or COD speed (zigzag test) (p > .05). However, in curved sprinting, the IPE-based warm-up demonstrated a significant improvement in the 8.5m curve sprint on the right side (p = .017, ES = -1.04). No significant differences were observed in the other curved sprint variables (17m on both sides and 8.5m on the left side). Conclusion: the findings suggest that the IPE-based warm-up may enhance speed performance in curved sprints. However, both warm-up protocols had similar effects on linear sprint performance and COD speed. Coaches and Strength and conditioning coaches should consider incorporating neuromuscular exercises in warm-ups to optimize curved sprint performance in young soccer players.

A temporal prediction model for ship maneuvering motion based on multi-head attention mechanism

In real-world maritime conditions, accurately predicting ship maneuvering motion over ultrashort periods can enhance the development of more precise vessel control algorithms. This study proposes a prediction model for ship maneuvering that utilizes a multi-head attention mechanism. To form a basis for this data-driven approach, we gathered training data from turning and zigzag tests of a ship conducted in natural sea environments. The model's predictive capability is assessed by comparing two strategies over a fixed 30-time-step forecast horizon: iterative multi-step forecasting (IMS) and direct multi-step forecasting (DMS). Notably, the model employs distinct attention layers to examine the temporal relationships among various motion variables across the three degrees of freedom in the output. Moreover, it uses separate attention layers to explore the distinct time response traits of the input motion states and control signals. The results demonstrate that different motion state variables display unique temporal correlations under different signal sequences, and the proposed network architecture effectively captures these temporal response traits.

Integrating Computational Fluid Dynamics for Maneuverability Prediction in Dual Full Rotary Propulsion Ships: A 4-DOF Mathematical Model Approach

To predict the maneuverability of a dual full rotary propulsion ship quickly and accurately, the integrated computational fluid dynamics (CFD) and mathematical model approach is performed to simulate the ship turning and zigzag tests, which are then compared and validated against a full-scale trial carried out under actual sea conditions. Initially, the RANS equations are solved, employing the Volume of Fluid (VOF) method to capture the free water surface, while a numerical simulation of the captive model test is conducted using the rigid body motion module. Secondly, hydrodynamic derivatives for the MMG model are obtained from the CFD simulations and empirical formula. Lastly, a four-degree-of-freedom mathematical model group (MMG) maneuvering model is proposed for the dual full rotary propulsion ship, incorporating full-scale simulations of turning and zigzag tests followed by a full-scale trial for comparative validation. The results indicate that the proposed method has a high accuracy in predicting the maneuverability of dual full-rotary propulsion ships, with an average error of less than 10% from the full-scale trial data (and within 5% for the tactical diameters in particular) in spite of the influence of environmental factors such as wind and waves. It provides experience in predicting the maneuverability of a full-scale ship during the ship design stage.

Implementation of Ball Feeling to The Results of Dribbling Agility in Football Games

This study aims to solve the problem of ball feeling on dribbling agility so that players have good dribbling quality and are right in the direction of the ball's goal. The sample of this study was football students aged 11-12 years in the Sumedang area, namely SSB Bina Putra Pamekar. The number of samples of this study was 16 football training participants, this research test consisted of 1 type, namely the zig-zag ball feeling test where the ball must remain controlled at a distance of feet, the speed test is the same as the zig-zag test with a distance of 5 meters. Lack of dribbling agility in the game of soccer, this ball feeling can have the right influence on dribbling agility in the soccer game. In line with the title of the research that the researchers took, this study uses the Experiment method with the research design using one group pretest-posttest design, because it is to determine the influence and magnitude of the influence of the results of the research taken. The results of research conducted by researchers that the implementation of ball feeling affects dribbling agility in football games, the magnitude of the influence is 0.02.

Effect of Sampling Rate in Sea Trial Tests on the Estimation of Hydrodynamic Parameters for a Nonlinear Ship Manoeuvring Model

This paper explores the impact of sampling rates during sea trials on the estimation of hydrodynamic parameters in a nonlinear manoeuvring model. Sea trials were carried out using an offshore patrol vessel and test data were collected. A nonlinear manoeuvring model is introduced to characterise the ship’s manoeuvring motion, and the truncated least squares support vector machine is employed to estimate nondimensional hydrodynamic coefficients and their corresponding uncertainties using the 25°–25° zigzag test. To assess the influence of the sampling rates, the training set is resampled offline with 14 sampling rates, ranging from 0.2 Hz to 5 Hz, encompassing a rate 10 times the highest frequency component of the signal of interest. The results show that the higher sampling rate can significantly diminish the parameter uncertainty. To obtain a robust estimation of linear and nonlinear hydrodynamic coefficients, the sampling rate should be higher than 10 times the highest frequency component of the signal of interest, and 3–5 Hz is recommended for the case in this paper. The validation is also carried out, which indicates that the proposed truncated least square support vector machine can provide a robust parameter estimation.

Effects of an 8-week pre-season targeted training on sprinting performance, agility and lower limb muscular asymmetries in elite soccer players.

The purpose of this study was to determine the effects of an 8 week targeted training program on speed, agility, and muscle asymmetries in soccer players. 32 elite soccer players were recruited for the study. Their age, body mass, and body height were 25.8 ± 7.3 years, 77.4 ± 11.1 kg, and 177.5 ± 9.8 cm, respectively. After the warm-up, participants performed two maximum 30 m sprints with a 5-minute rest interval between trials. After the linear sprint test, performed two repetitions of the COD randomized ZigZag test. The tests were performed at the beginning and at the end of the pre-season, which lasted for 8 weeks. EMG was measured bilaterally from the quadriceps, hamstrings, and gluteal muscles with shorts made of knitted fabric similar to elastic clothes. Athletes in the experimental group performed sport-specific targeted strength training based on movement patterns 4 times per week (Monday, Tuesday, Thursday, and Friday). The training included 6 bodyweight exercises (Bird Dog, Single-Leg Glute Bridge, Dead Bug, Side Plank, Reverse Lunge, and Clamshell), performed unilaterally in 5 sets of 10 repetitions of each exercise. The load progression included an additional set in each successive week of the experiment. The data analysis showed significant improvement in 5 m and 30 m sprints after applying the 8-week targeted training protocol. A statistically significant improvement in performance was also observed after the 8-week training period in case of COD, while the speed deficit also decreased significantly. The greatest improvements were observed during the COD test. As a result of repeated COD training over a period of 8 weeks, its technique was improved. Implementation of training methods, which target specific aspects of soccer in the pre-season training routines can improve key motor abilities for that sports discipline. A comprehensive training approach including speed, agility, and resistance training based on specific movement patterns should be applied by strength and conditioning practitioners in soccer teams to achieve peak physical performance and reduce injury risk due to the partial elimination of muscular asymmetries.

Maneuverability Performance of a KRISO Container Ship (KCS) with a Bulb-Type Wavy Twisted Rudder and Asymmetric Pre-Swirl Stator

The maneuverability performance of a KCS with energy-saving devices was investigated. A bulb-type wavy rudder and an asymmetric pre-swirl stator were used as energy-saving devices because their use resulted in considerable efficiency gain. A validated simulation method based on the maneuvering modeling group model was used for the simulation in this study. Turning circle, 10/10 zigzag, and 20/20 zigzag tests were simulated to compare various cases with and without a stator as well as conventional full-spade and bulb-type wavy rudders. Remarkable maneuverability performance was achieved, particularly with a bulb-type wavy rudder, and starboard–port unbalancing due to the one-directional propeller action was almost eliminated using these devices. The findings of this study will be useful in the development of more reliable autonomous maritime surface ships.

Study on the Manoeuvring Performance of a Fishing Vessel Based on CFD Simulation of the Hull Forms and Rudder Shapes

To evaluate manoeuvring performance of merchant ships, the mathematical modeling group (MMG) or computational fluid dynamics (CFD) simulations are used. However, it is difficult to use the MMG to evaluate the manoeuvring performance of fishing vessels, thus research using CFD simulations is necessary. Also, since the course-changing and turning ability is crucial in fishing operations, a rudder design suitable for fishing vessels is necessary. This study designs a rudder using National Advisory Committee for Aeronautics (NACA) airfoil sections and evaluates its manoeuvring performance. A CFD model is used to evaluate the manoeuvring performance of the fishing vessel, and turning and zig-zag tests are conducted. The effectiveness of using CFD simulations based on Reynolds averaged Navier-Stokes equations to assess the manoeuvring performance of fishing vessels was validated. No significant difference was found in the manoeuvring performance for hull forms and rudder designs for course-changing ability. However, the original hull form showed superior turning performance. Among five rudders with varying aspect ratios and shapes, the rudder with 5.5% aspect ratio had the best turning performance. Regarding the rudder design for fishing vessels, NACA airfoil was employed, and a rudder aspect ratio of 5.5% based on the immersed hull side area is recommended.

Anthropometric and Physical Profile Among the Different Age Groups of Tunisian Tennis Players

Background: The popularity of Tunisian tennis is on the rise, due to emerging players gaining global recognition, leading to growth and evolution in the sport. In order to optimize training and performance, coaches need valuable information on physical fitness and player profiling. Objectives: The study aimed to investigate the physical profile of Tunisian tennis players in different age groups ranging from 7 to 17 years. Methods: One hundred and one tennis players from the same team were assigned to six age groups (U9-U18); U9 (7.89 ± 0.32), U10 (8.88 ± 0.34), U11 (9.78 ± 0.43), U12 (10.81 ± 0.4), U14 (12.3 ± 0.73), and U18 (14.69 ± 0.95) and were assessed for standing long jump (SLJ), countermovement jump, medicine ball throw (MBT), various sprint distances, agility drills, 20m Shuttle run (20mSRT), and Sit and reach tests. Results: The results showed that U14 and U18 age groups demonstrated better performance than U9 and U10 in jump tests, while U18 and U14 outperformed only U9 in the MBT test. U11 showed better performance than U9 and U10 in sprints, sideways shuffle, and spider drill tests. U9 and U10 had lower performance than U12 in SLJ, 20m sprint, sideways shuffle, and zigzag tests, and U11 outperformed U9 in the SLJ test. U18 and U14 had higher VO2max than U10 and U11, while U12 was higher than U11 only. No difference in flexibility was reported. The centile estimates of physical performances among Tunisian tennis players provide a means to compare individual player test results with the standard performance levels of the group. Conclusions: In conclusion, this study found that 11–17-year-old players exhibited greater physical performance than 7–10-year-old players. However, no age effect was found for flexibility.

Acute Effects of Different Creatine Supplementation Methods on Anaerobic Performance

The aim of this study is to compare the acute effects of different creatine loading methods on anaerobic performance in soccer players. Totally 21 healthy male soccer players participated in this study. The study was conducted in a randomized and double-blind study design. Athletes were loaded with creatine on 3 different days. The different creatine supplementation methods were as follows; athletes took creatine supplement 4 times a day for 15 days, 4x5 grams for the first 5 days and 5 g for the following 10 days. In other creatin loading is took 0.3 grams of creatine per kg for 15 days. In other creatin loading is (placebo loading) received the same amount (Maltodextrine) for 15 days. Vertical jump, 10-30 m sprint test and agility test were performed on all subjects. The Shapiro-Wilk test was used for normality distribution of the data. Since parametric test assumptions were met, t-test for dependent groups and one-way analysis of variance test (ANOVA) for repeated measurements were used to compare dependent group differences. Significant differences were found for 10-30 m sprint, vertical jumping, zig zag test (p

An improved body force method for simulation of self-propulsion AUV with ducted propeller

The body force method (BFM) is an efficient computational method used for maneuvering simulations of marine vehicles with ordinary propellers. In this paper, an improved BFM is proposed to perform maneuvering simulations of a self-propelled AUV with a ducted propeller. Initially, the conventional BFM is applied to numerically investigate the open water performance of a ducted propeller(No. 19A+Ka4-70). However, significant prediction errors have been observed, which were mainly caused due to ignorance of the interaction between the duct and the propeller. To increase the prediction accuracy, an improved BFM is proposed to perform maneuvering simulations of the ducted propeller AUV by considering the mass flow correction. In addition, the external diameter of the actuator is proposed to be a function of real-time advance velocity. To investigate the efficacy of the proposed method, the simulated results have been compared with the model testing carried out in a towing tank and with the discretized propeller method. The proposed improved BFM is used to simulate the 20°/20° zigzag tests of AUV in both vertical and horizontal planes with different advance speeds. Simulated results, particularly propeller thrust, advance speed, pitch (or yaw), resistance, and especially duct thrust of AUV have significantly improved as compared to the conventional BFM. The improved BFM results were found in close agreement with discretized propeller method and thus, the proposed method is considered a highly efficient and computationally cost-effective method to perform maneuvering simulations of ducted-propeller marine vehicles. The present work can contribute to the fast optimization of the manoeuvrability of marine vehicles with ducted propeller.

Differences in Motor Abilities among Basketball Players in Relation to Biological Maturity

Basketball is a popular team sport with a combination of alternating and high-intensity activities. Physical characteristics related to age and maturity can be quite important for developing the career of a young athlete. The aim of this study was to determine the differences in motor skills among basketball players with regard to their biological maturity. Using the Mirwald equation, the total sample of participants was divided into three groups based on their biological maturity: early-maturing (postPHV), normally-maturing (midPHV), and late-maturing (prePHV). The sample of participants consisted of 51 basketball players (body height 171±12 cm; body weight 63±15.7 kg; BMI 21.3±3.8). Tests of speed (5, 10, 20m sprint), explosive power of the lower extremities (the countermovement jump with arm swing (CMJwas), the countermovement jump (CMJ), and the squat jump (SJ)), and agility (the t-test, zigzag, and slalom test) were evaluated. The one-factor ANOVA showed a statistically significant difference between groups in the slalom, t-test, and zig-zag test (p<0.05). On the sprint tests and tests assessing explosive power no difference was found. We can conclude that this group of participants showed equal performance in motor skills on most tests, regardless of their maturity status. The primary significance of this study is that it shows coaches the importance of understanding their players’ biological maturation for optimal selection, suitable training design, and a reduction in the risk of injury.

Peningkatan Kondisi Fisik Menggunakan Metode Contrast Training pada Atlet Paralayang Kabupaten Ciamis Menghadapi Porprov Jawa Barat 2022

The purpose of this study was to determine the impact of the contrast training method on physical conditions consisting of power, flexibility, agility, and balance. The research method used is experimental. The research design is a one-group pretest-posttest design is the research design used. The population used is the PGPI Paragliding Athletes in Ciamis Regency, totaling 15 sons, ranging in age from 16 to 20 years. The sampling technique is total sampling. Instrument test consists of vertical jump test, static flexibility test-shoulder & wrist, zig-zag test, and flamingo balance test. The results showed that the data from the vertical jump test results showed a significant increase in the significance value of 0.000 < 0.05. Static flexibility test-shoulder & wrist a significant increase proved the significance value of 0.000 < 0.05. The results of the zig-zag test data showed a significant increase in the significance value of 0.000 <0.05. The results of the flamingo balance test data showed a significant increase in the significance value of 0.028 < 0.05. Conclusion. A better and more appropriate contrast training method is given to paragliding athletes in Ciamis Regency. For coaches of physical condition to be able to apply the contrast training method by prioritizing training program innovations so that the physical condition of the athletes is getting better, especially their needs during matches.

Mathematical modeling of shallow water effects on ship maneuvering

An Abkowitz-type model was extended to improve the prediction of maneuvering dynamics of inland ships in deep and shallow waters. First, additional coupled rudder and speed related hydrodynamic derivatives were added to better capture hydrodynamic forces and moments. Second, higher order drift related hydrodynamic derivatives were implemented to more reliably predict longitudinal forces. Steady RANS-based captive model tests were performed to estimate speed-dependent hydrodynamic derivatives. Unsteady captive model tests, based on applying a novel Euler equations based numerical approach, were carried out to determine acceleration-dependent zero-frequency hydrodynamic derivatives. Executed were propulsion tests, rudder tests, coupled propulsion and rudder tests, rotating arm tests, drift tests, and coupled rotating arm and drift tests, all at five water depths to draft ratios of 1.43, 1.79, 2.00, 4.00, and 8.00. Tests at the ratio 1.79 were validated against physical captive model tests, and regression analyses estimated the hydrodynamic derivatives. At each water depth, a 45 deg turning circle test, a 35/10 zigzag test, and a 45/110 evasive action test were carried out. Turning circle maneuvers were significantly influenced by shallow water. Compared to deep water, in shallow water the tactical diameter increased from 1.6L to 2.6L, and the drift angle decreased from 21 deg to about 4 deg. Compared to turning circles maneuvers, effects on the zigzag and evasive action maneuvers were relatively small in shallow water. Drift angles and yaw rates in the simulated 45 deg turning circle and a 35/5 zigzag tests agreed favorably with full-scale trials of a similar ship; however, scale effects and the slightly different hull shapes led to different speed losses.

Direct CFD simulations of standard maneuvering tests for DARPA Suboff

Maneuvering abilities of underwater vehicles are one of the primary concerns for navies and in the civil field they provide great flexibility in working in confined environments. Numerical simulations of the motions of these vessels may be conducted via system-based or direct CFD approaches. In this study, we focus on direct CFD simulations of the benchmark DARPA Suboff AFF8 Configuration. The paper starts by showing the submarine's lack of course-keeping stability using the C-index. After validation of the numerical approach by self-propulsion tests (and the determination of the propeller rotation rate to achieve the required velocity), the results of an extensive set of standard maneuvering tests are presented. Turning circle, pullout and zig-zag tests confirm that the DARPA Suboff does not have course-keeping ability. The submarine leans to the starboard side at neutral rudder angle. The maneuvering indices are investigated with respect to changing rudder angle with turning circle tests. High residual yaw rates are found in both side turnings in the pullout tests and the zig-zag tests show the submarine's inadequacy in making sharp turns. Numerical simulations reveal that the DARPA Suboff has high turning ability but no course-keeping ability.

선박의 종경사와 횡경사 변화에 따른 조종특성

This study was conducted to analyse the changes in trim and heeling using Zig-zag test, at T/S SAE DONG BACK was used to examine the manoeuvrability according to the trim and heeling changes of the vessels. Regarding the Zig-zag test to observe the trim changes at the port and with starboard rudder angles of 10° and 20° at 0.30m, and 0.52m, the overshoot angle of starboard was 18% bigger than that of the port at the rudder angle of 10°, and the course changing ability was better than the turning ability at the rudder angle of 10°. The size of the turning circle, final diameter was 4-5% and the required time was 2-7% larger than the port at the trim of 0.52m and 0.30m. External forces and superstructures that are larger than those of general ships showed characteristics that affect turning performance. When the Zig-zag test was used to compare the heeling changes, the overshoot angle of the starboard was 12°-14° larger than that of the port at 0° with no heeling compared to the 3° heeling. As a result, the Turning ability of the vessel was satisfactory. Furthermore, the second overshoot angle at 3° heeling was 6° larger; thus, the port veering showed a better rudder effect than the starboard veering. Hence, the turning ability decreased and the course-changing ability increased as the trim change in the vessel increased. Regarding the values of the turning ability index, K′, and the course changing ability, T′, according to the Trim increased when the rudder angle was used on The larger the trim, the lower the turning ability and the higher the course change ability, and when the burp is low, the turning ability is good, but the course change ability is somewhat decreased.

Weighted multi-kernel relevance vector machine for 3 DOF ship manoeuvring modeling with full-scale trial data

In order to improve the accuracy of ship maneuvering state prediction, a nonparametric identification method based on weighted multi-kernel relevance vector machine (WMRVM) is proposed to establish the motion prediction models of the vessel YUKUN. The WMRVM is composed of weight parameters and different types of kernel functions. On the one hand, RVM provides probability interpretation, its kernel functions do not have to satisfy Mercer condition; on the other hand, WMRVM improves the prediction accuracy of single kernel RVM. Taking the vessel YUKUN as the research plant, the full-scale trials satisfy the requirements of maneuverability test. The 20°/20° zigzag test data and 30° turning test data are used as the generalization verification. The prediction results obtained by the proposed algorithm are compared with those obtained by RVM and support vector regression (ε-SVR). The results show that the proposed algorithm has higher prediction accuracy and better generalization. This research can lay the foundation for the application of RVM in ship maneuvering state prediction and online identification modeling.

Black-box modeling of ship maneuvering motion based on Gaussian process regression with wavelet threshold denoising

A system identification method based on Gaussian progress regression (GPR) combined with wavelet threshold denoising (WT) is proposed for identifying the black-box model of ship maneuvering motion. WT is applied for data preprocessing to filter out the noise in the collected data of ship motion; GPR is used for modeling with the denoised data. Two study objects are considered. One is the KVLCC1 tanker model for verifying the basic identification ability of the proposed method by utilizing the available data of zigzag tests. The other one is an unmanned surface vessel (USV) for further verifying the effectiveness and advantages of the proposed method by using the measured data of zigzag tests and turning test. For the KVLCC1, the results of the proposed method are compared with the experimental data, the results of the basic GPR model and the model identified by BPNN combined with WT. For the USV, the results of the proposed method are further compared with those of the model identified by GPR combined with lowpass filter and the model identified by BPNN combined with WT. It is shown that the proposed method is more suitable for modeling of ship maneuvering motion using limited and noisy data.

Change of Direction Deficit: A Promising Method to Measure a Change of Direction Ability in Adolescent Basketball Players.

The aims of this study were to determine the relationship between vertical jumping performance, linear speed, change of direction speed (CODs) time and the COD deficit (CODD) in adolescent basketball players and to analyze the CODD between faster and slower players based on linear speed performance. Thirty-eight male basketball players (age: 15.47 ± 0.51 years; body height: 185.19 ± 5.67 cm; body mass: 71.87 ± 7.29 kg) completed countermovement jumps (CMJ) with and without an arm swing, squat jumps (SJs), linear sprints at 20 m with split times at 5 and 10 m, the pro-agility test and the zig-zag tests. Furthermore, the CODD was calculated as the difference between the 20 m linear speed result and CODs time in both COD tests. Pearson and Spearman analyses were used to determine the correlations between power-speed-related variables and the CODD. Moreover, independent t-tests and Cohen's d effect size (ES) were used to analyze the differences between the faster and slower players in the CODD. Moderate to strong significant negative correlations were observed between the CODD in the pro-agility test and linear speed at 5 m, 10 m, and 20 m (r = -0.55 to -0.46), while moderate negative significant correlation was found between the zig-zag CODD and SJs (r = -0.37) as well as small positive significant correlation between the CODD in the zig-zag test and the eccentric utilization ratio (EUR) (r = 0.23). Additionally, faster basketball players displayed significantly higher CODD values performing the pro-agility test. In summary, these findings underline the complexity of COD performance and the importance of remodeling traditional training programs in basketball players.

Correlation between linear speed, change of direction speed and dribble deficit in male handball players

The aim of this study was to determine the relationship between linear sprint and change of direction (COD) speed using the novel approach of the Dribble Deficit (DD) among professional handball players. This study included 14 male professional handball players (age = 23.1 ± 3.43). Each player performed the following tests: a 10, 20 and 30 meter linear sprint; a zig-zag test; a slalom test and 4 × 5 agility test with and without a ball. A significant correlation was found between the DD at 10 m and the 10 m sprint with the ball (p < 0.05, r = 0.575). Additionally, the results showed that the values of dribble deficit during slalom test were related (p < 0.01) to the 20-m sprint with the ball (r = 0.767), the 30-m sprint with a ball (r = 0.765) and the slalom with a ball (r = 0.938). Regression analyses showed significant influence of the linear sprint at 10 m on DD (p = 0.02, R2 = 0.373), and the zig-zag test without ball on the DD (p = 0.004, R2 = 0.514). The results suggest that the linear sprint and zig-zag test used to evaluate COD movement speed are associated with and influence DD in professional handball players. Further research on DD is necessary in order to determine that DD is not influence by physical performance and how we can use it in the future to calculate the time required for dribbling.