Reliability of the High-speed Camera-based System (HSC-Kinovea) for lower-limb explosive strength endurance assessment in athletes

The present study verified the reliability of the high-speed camera-based system (HSC-Kinovea) in the lower-limb explosive strength endurance assessment in athletes. Eleven male volleyball players (21.8 ± 2.9 years; 186.3 ± 6.2 cm and 82.3 ± 11.0 kg) participated in the intermittent vertical jumping test in two days. The test was filmed and later analyzed using Kinovea 0.8.15 software to obtain the mean and peak power variables. Regarding reliability, the intra-class correlation coefficient, the typical error of measurements, and Bland-Altman plots were used. The method presented satisfactory values for inter and intra-class correlations (˃ 0.88). The typical values error of measurement presented in the inter-rater analysis was 0.95 W.kg-1 and 0.59 W.kg-1 for the peak and the mean power, respectively. In the intra-assessment analyses, the typical measurement error values were 7.02 W.kg-1 and 5.66 W.kg-1 (test-retest) and 1.59 W.kg-1 and 0.24 W.kg-1 (duplicates videos) for peak and average power, respectively. The HSC-Kinovea system is reliable for assessing the variables of the explosive strength endurance in athletes.

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Diferencias en el salto vertical y la velocidad de patada mae-geri entre karatekas internacionales y nacionales

Revista de Artes Marciales Asiáticas ◽

10.18002/rama.v8i1.835 ◽

2013 ◽

Vol 8 (1) ◽

pp. 13 ◽

Cited By ~ 1

Author(s):

Carlos Balsalobre-Fernández ◽

Víctor Martínez-Majolero ◽

Jorge Villacieros-Rodríguez ◽

Carlos María Tejero-González

Keyword(s):

Lower Limb ◽

High Speed ◽

National Level ◽

High Speed Camera ◽

International Level ◽

Warm Up ◽

Explosive Strength ◽

Counter Movement Jump ◽

High Level ◽

Effect Of Age

Aim: Lower limb explosive strength and mae-geri kicking velocity are fundamental in karate competition; although it is unclear whether these variables could differentiate the high-level athletes. The objective of this research is to analyze the differences in the mae-geri kicking velocity and the counter-movement jump (CMJ) between a group of international top level karateka and another group of national-level karateka.Methods: Thirteen international-level karateka and eleven national-level karateka participated in the study. After a standard warm-up, CMJ height (in cm) and mae-geri kicking velocity (in m/s) was measured using an IR-platform and a high-speed camera, respectively.Results: Proceeding with MANCOVA to analyze the differences between groups controlling the effect of age, the results show that the international-level karateka demonstrated significantly higher levels of CMJ than national-level competitors (+22.1%, F = 9.47, p = 0.006, η2 = 0.311). There were no significant differences between groups in the mae-geri kicking velocity (+5,7%, F=0.80; p=0.38; η2=0.03).Conclusion: Our data shows, first, the importance of CMJ assessment as a tool to detect talent in karate and, second, that to achieve international-level in karate it may be important to increase CMJ levels to values similar to those offered here.

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New Insights Into Utilizing Bistability for Energy Harvesting Under White Noise

Journal of Vibration and Acoustics ◽

10.1115/1.4029008 ◽

2015 ◽

Vol 137 (2) ◽

Cited By ~ 23

Author(s):

Qifan He ◽

Mohammed F. Daqaq

Keyword(s):

Potential Energy ◽

White Noise ◽

Time Constant ◽

Energy Function ◽

Average Power ◽

Potential Energy Function ◽

Constant Ratio ◽

Mean Power ◽

Potential Wells ◽

The Mean

This paper investigates the response of a bistable energy harvester to random excitations that can be approximated by a white noise process. Statistical linearization (SL), direct numerical integration of the stochastic differential equations, and finite element (FE) solution of the Fokker–Plank–Kolmogorov (FPK) equation are utilized to understand how the shape of the potential energy function influences the mean output power of the harvester. It is observed that, both of the FE solution and the direct numerical integration provide close predictions for the mean power regardless of the shape of the potential energy function. SL, on the other hand, yields nonunique and erroneous predictions unless the potential energy function has shallow potential wells. It is shown that the mean power exhibits a maximum value at an optimal potential shape. This optimal shape is not directly related to the shape that maximizes the mean square displacement even when the time constant ratio, i.e., ratio between the time constants of the mechanical and electrical systems is small. Maximizing the mean square displacement yields a potential shape with a global maximum (unstable potential) for any value of the time constant ratio and any noise intensity, whereas maximizing the average power yields a bistable potential which possesses deeper potential wells for larger noise intensities and vise versa. Away from the optimal shape, the average power drops significantly highlighting the importance of characterizing the noise intensity of the vibration source prior to designing a bistable harvester for the purpose of harnessing energy from white noise excitations. Furthermore, it is demonstrated that, the optimal time constant ratio is not necessarily small which challenges previous conceptions that a bistable harvester provides better output power when the time constant ratio is small. While maximum variation of the mean power with the nonlinearity occurs for smaller values of the time constant ratio, this does not necessarily correspond to the optimal performance of the harvester.

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Stability, spatial extension and extinction of an electric arc in aeronautical conditions of pressure under 540 V DC

The European Physical Journal Applied Physics ◽

10.1051/epjap/2019190029 ◽

2019 ◽

Vol 87 (3) ◽

pp. 30901

Author(s):

Romaric Landfried ◽

Mohamed Boukhlifa ◽

Thierry Leblanc ◽

Philippe Teste ◽

Jonathan Andrea

Keyword(s):

High Speed ◽

Electric Arc ◽

High Speed Camera ◽

Arc Length ◽

Electrode Gap ◽

Arc Current ◽

The Mean ◽

The Stability ◽

Energy Dissipated

This work deals with the characterization of DC electric arcs in aeronautical conditions of pressure (from 104 Pa to 105 Pa). Observations have been made with the help of a high speed camera and various characteristics of electric arc under 540 V DC have been studied: the stability arc length, the extinction gap, the arc duration and the mean energy dissipated in the arc. The arc current intensity range is 10–100 A. The obtained results show that the arc stability length, extinction electrode gap, arc duration and energy dissipation in the arc have a direct correlation with the pressure and the current in the circuit.

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Reader fatigue – Electroencephalography findings: A case study in students

Work ◽

10.3233/wor-205121 ◽

2021 ◽

pp. 1-6

Author(s):

Abbas Mohammadi ◽

Leila Nematpour ◽

Behzad Fouladi Dehaghi

Keyword(s):

Average Power ◽

Mental Fatigue ◽

Theta Band ◽

Mean Power ◽

Self Assessment ◽

Prolonged Duration ◽

The Mean ◽

Highly Correlated ◽

Reading Activities

BACKGROUND: Mental fatigue is usually accompanied by a sense of weariness, reduced alertness, and reduced mental performance, which can lead to accidents, decrease of productivity in workplace and several other health hazards. OBJECTIVE: The aim of this study was to assess mental fatigue of students while reading for a prolonged duration of time by application of electroencephalography (EEG). METHODS: Ten healthy students (27.57±3.4 years; 5 females and 5 males), participated in the study. The experimental design consisted of 5 blocks of 15-min length, in total 75 min for each participant. The experiment was done without any reading activities at the first block. In the following, participants studied the texts and corrected the mistakes. In each block EEG (beta, alpha, and theta power), and the Karolinska Sleepiness Scale (KSS) were recorded. RESULTS: The mean of the self-assessment of sleepiness by KSS from the first to final 15 minutes were 2.3, 3.4, 4.3, 5.2, and 6.1, respectively. The average power in the theta band decreased from 1.23μV2/Hz at the first 15-min period to 1.02μV2/Hz at the last 15-min period. Also, mean power in the alpha band decreased from 0.85μV2/Hz at the first 15-min period to 0.59μV2/Hz at the last 15-min period. Conclusion: The study showed that the KSS and EEG activity indicate sleepiness which were highly correlated, with both changing along with performance.

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Investigations into Balancing Peak-to-Average Power Ratio and Mean Power Extraction for a Two-Body Point-Absorber Wave Energy Converter

Energies ◽

10.3390/en14123489 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3489

Author(s):

Hayrettin Bora Karayaka ◽

Yi-Hsiang Yu ◽

Eduard Muljadi

Keyword(s):

Wave Energy ◽

Reference Model ◽

Average Power ◽

Full Scale ◽

Scale Model ◽

Second Phase ◽

Mean Power ◽

Point Absorber ◽

The Mean ◽

Body Point

The power harnessed by wave energy converters (WECs) in oceans is highly variable and, therefore, has a high peak-to-average power (PTAP) ratio. To minimize the cost of a WEC power take off (PTO) system, it is desirable to reduce the PTAP ratio while maximizing the mean power extracted by WECs. The important issue of how PTAP ratio reduction measures (such as adding an inertia element) can affect the mean power extracted in a reference model has not been thoroughly addressed in the literature. To investigate this correlation, this study focuses on the integration of the U.S. Department of Energy’s Reference Model 3, a two-body point absorber, with a slider-crank WEC for linear-to-rotational conversion. In the first phase of this study, a full-scale numerical model was developed that predicts how PTO system parameters, along with an advanced control algorithm, can potentially affect the proposed WEC’s PTAP ratio as well as the mean power extracted. In the second phase, an appropriate scaled-down model was developed, and extracted power results were successfully validated against the full-scale model. Finally, numerical and hardware-in-the-loop (HIL) simulations based on the scaled-down model were designed and conducted to optimize or make trade-offs between the operational performance and PTAP ratio. The initial results with numerical and HIL simulations reveal that gear ratio, crank radius, and generator parameters substantially impact the PTAP ratio and mean power extracted.

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Experimental Study of Turbulence and Entrained Air Characteristics in a Plunging Breaking Solitary Wave

International Journal of Ocean and Coastal Engineering ◽

10.1142/s2529807020500013 ◽

2020 ◽

Vol 03 (01n02) ◽

pp. 2050001

Author(s):

Lian Tang ◽

Yun-Ta Wu ◽

Onyx. W. H. Wai ◽

Pengzhi Lin

Keyword(s):

Solitary Wave ◽

Void Fraction ◽

High Speed ◽

Surf Zone ◽

Phase Speed ◽

Breaking Waves ◽

High Speed Camera ◽

Ensemble Averaging ◽

The Mean ◽

Entrained Air

The entrained air and turbulence characteristics under a breaking solitary wave on a 1:20 sloping beach are investigated through laboratory measurement. Free surface elevation is obtained from wave gauge measurements. Wave breaking process is captured in detail by a high-speed camera. The bubble image velocimetry (BIV) is used to measure the velocity and the fiber optic reflectometer (FOR) is used to capture instantaneous void fraction in the aerated region. The mean void fraction and velocities in the aerated region are obtained by ensemble averaging over 22 repetitions. Results show that the maximum mean void fraction is 0.6 in the collapsing cavity region and is 0.35 in the splash up region. The time series of the mean void fraction has good synchronization with the instantaneous images taken by high-speed camera. The maximum horizontal velocity occurs in the splash up region and reaches 1.17C shortly after the plunging jet hits the water surface, with C being the phase speed of the primary wave. The turbulence intensities over the entire aerated region are presented and discussed. The measured data can be used for the calibration and verification of the numerical model for aerated flows simulation under breaking waves in the surf zone.

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Comparisons of flow dynamics of dual-blade to single-blade beveled-tip vitreous cutters

Ophthalmic Research ◽

10.1159/000521468 ◽

2021 ◽

Author(s):

Makoto Inoue ◽

Takashi Koto ◽

Akito Hirakata

Keyword(s):

Salt Solution ◽

High Speed ◽

Lateral View ◽

Flow Dynamics ◽

High Speed Camera ◽

Mean Flow ◽

Cutting Rate ◽

The Mean ◽

Fluorescent Polymer ◽

End Results

Introduction: To compare the flow dynamics of the dual-blade to the single-blade beveled-tip vitreous cutters. Methods: The aspiration rates of balanced salt solution (BSS) and swine vitreous were measured for the 25-gauge and 27-gauge dual- and single-blade vitreous cutters. The flow dynamics of BSS and diluted vitreous mixed with fluorescent polymer at the maximal cutting rates and the reflux of BSS were measured in images obtained by a high-speed camera. The distal end of the cutter was defined as the head end. Results: The aspiration rates of BSS and vitreous by the 25- and 27-gauge dual-blade cutters were significantly higher than those of both single-blade cutters at the maximal cutting rate (all P≤0.01). The mean aspiration flow of BSS in front of the port from a lateral view was significantly faster for both dual-blade cutters than for both single-blade cutters (P=0.003, P=0.019). The angle of the mean flow of BSS of both dual-blade cutters was from the distal end (P<0.001, P<0.001) but that of the single blade-cutters was from the proximal end. The velocity and angle of the mean reflux flow of both types of cutters were not significantly different. The mean aspiration flow of diluted vitreous was significantly faster for 25-gauge dual-blade cutters with the angle more from the proximal end and 27-gauge dual-blade cutters more from the distal end than both single-blade cutters (P=0.018, P=0.048). Conclusion: The dual-blade beveled-tip vitreous cutters improve the efficiency of the vitrectomy procedures and maintain the distal aspirating flow by the beveled-tip.

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Studi Analisis Biomechanics Langkah Awalan (Footwork Step) Open Spike Dalam Bola Voli Terhadap Power Otot Tungkai

Jorpres (Jurnal Olahraga Prestasi) ◽

10.21831/jorpres.v14i1.19985 ◽

2018 ◽

Vol 14 (1) ◽

pp. 81-89

Author(s):

Danang Ari Santoso Santoso ◽

Edi Irwanto

Keyword(s):

High Speed ◽

Muscle Power ◽

Average Power ◽

Initial Step ◽

High Speed Camera ◽

Science Field ◽

Sports Science ◽

Calculation Results ◽

Leg Muscle ◽

Step Number

Biomechanic adalah bidang ilmu yang diterapkan pada ilmu olahraga untuk mempelajari gerak-gerak tubuh. Penelitian ini bertujuan untuk mendapatkan jumlah langkah awalan (footwork step) dalam spike bola voli yang menghasilkan power terbaik. Penelitian ini dilakukan dengan eksperimen. Jumlah langkah awalan yang divariasi adalah 0, 1, 2, dan 3 langkah. Subyek penelitian adalah atlet bola voli Universitas PGRI Banyuwangi. Pengukuran power otot tungkai dilakukan dengan menggunakan high-speed camera. Pengolahan data menggunakan software kinovea untuk mendapatkan data hasil power. Hasil perhitungan menunjukkan bahwa semakin banyak langkah awalan (footwork step) maka power rata-rata cenderung semakin naik. Power rata-rata maksimum terjadi pada 2 langkah awalan (footwork step) atlet 4 yaitu sebesar 2340,44 J/dt. Power rata-rata minimum terjadi pada 0 langkah awalan (footwork step) atlet 1 yaitu sebesar 1765,85 J/dt. Kecenderungan power maksimum terjadi pada langkah awalan sebanyak 2 langkah. Hasil analisis juga menunjukkan bahwa langkah awalan sebanyak 3 langkah cenderung menghasilkan power yang lebih kecil dibanding jumlah langkah awalan yang lain. Gerakan spike dalam bola voli merupakan gerakan yang dilakukan dengan cepat dalam waktu sesingkat mungkin. Pola ini membuat seorang atlet terbiasa menggunakan langkah awalan yang sedikit jumlahnya. Langkah awalan berjumlah 3 akan menyebabkan kecepatan gerak atlet menjadi berkurang sehingga mengurangi powernya.ABSTRACT Biomechanic is one of science field that applied to the sports science to study gestures. This study aims to obtain the number of step prefix (footwork step) in volleyball spike that produces the best power. This research is done by experiment. The number of prefix steps varied are 0, 1, 2, and 3 steps. The subjects of the study were volleyball athletes of Universitas PGRI Banyuwangi. Measurement of leg muscle power is done using a high-speed camera. Data processing using kinovea software to obtain data power results. The calculation results show that the more step prefix (footwork step) then the average power tends to increase. Maximum average power occurs in 2 step prefix (footwork step) athlete 4 that is equal to 2340,44 J/dt. Minimum average power occurs at 0 step of the athlete (footwork step) at 1 at 1765,85 J/dt. Maximum power trend occurs in 2 step prefix step. The analysis results also show that 3-step prefixes tend to produce less power than the number of other prefix steps. Spike movement in volleyball is a quick movement in the shortest possible time. This pattern makes an athlete accustomed to using a few prefix steps. The initial step number 3 will cause the speed of athlete's motion to be reduced so as to reduce its power.

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Hydrodynamics of swimming in the water boatman, Cenocorixa bifida

Canadian Journal of Zoology ◽

10.1139/z86-242 ◽

1986 ◽

Vol 64 (8) ◽

pp. 1606-1613 ◽

Cited By ~ 15

Author(s):

R. W. Blake

Keyword(s):

High Speed ◽

Forward Direction ◽

Added Mass ◽

Mean Value ◽

The Body ◽

Power Stroke ◽

Mass Force ◽

Mean Power ◽

Recovery Stroke ◽

The Mean

Locomotion of a small water boatman (Cenocorixa bifida, Corixidae) was investigated employing high-speed cinematography and hydromechanical modelling based on a blade-element approach. The animal is propelled by the synchronous rowing action of its hind legs. The propulsive cycle consists of a power stroke and a recovery stroke phase. Force, impulse, power, and hydromechanical efficiency were calculated for a representative power stroke during which the mean body velocity was about 8 cms−1. A distinction is made between quasi-steady resistive and unsteady inertial (added mass) forces. The mean and maximum resistive thrust forces were calculated to be about 2.4 × 10−5 and 5.7 × 10−5 N per limb, respectively. By equating the total impulse of the power stroke for both legs (2.4 × 10−6 N s) with that of the drag force acting on the body over the same period, a drag coefficient of approximately 1.07 is inferred for the body. This value is comparable to those obtained for certain insects that operate at similar Reynolds numbers to C. bifida. The unsteady added mass force that acts in the forward direction is positive (propulsive) over most of the stroke with a mean value of about 1.17 × 10−5 N per limb, corresponding to an impulse of approximately 5.9 × 10−7Ns. The total propulsive mean force and impulse acting in the forward direction amount to about 3.6 × 10−5N and 1.8 × 10−6N s per limb, respectively, so the impulse of the forwardly directed added mass force amounts to about half that of the resistive thrust force. The total work and mean power associated with generating the resistive thrust were calculated to be about 6.7 × 10−7 J and 1.33 × 10−5 W per limb, respectively. Dividing the mean body drag power (1.4 × 10−5 W) by the total mean resistive power from both legs gave a hydromechanical efficiency of 0.52. When the mean inertial power associated with moving the body (2.3 × 10−6 W) and the added mass power required to accelerate and decelerate the legs (1.95 × 10−5 W per limb) are taken into account, the power stroke propulsive efficiency falls to 0.42. Taking the energy required to power the recovery stroke into account gives an overall propulsive cycle efficiency of about 0.40. This value is about twice that calculated in a previous study for drag-based pectoral fin rowing in the angelfish and reasons for this are suggested.

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Articulatory Behavior Pre and Post Full-Mouth Tooth Extraction and Alveoloplasty

Journal of Speech Language and Hearing Research ◽

10.1044/jshr.2303.630 ◽

1980 ◽

Vol 23 (3) ◽

pp. 630-645 ◽

Cited By ~ 7

Author(s):

Gerald Zimmermann ◽

J.A. Scott Kelso ◽

Larry Lander

Keyword(s):

Control Subject ◽

High Speed ◽

Tooth Extraction ◽

Kinematic Parameters ◽

Experimental Conditions ◽

Mean Values ◽

Articulatory Movements ◽

The Mean ◽

Experimental Subjects ◽

Normal Speech

High speed cinefluorography was used to track articulatory movements preceding and following full-mouth tooth extraction and alveoloplasty in two subjects. Films also were made of a control subject on two separate days. The purpose of the study was to determine the effects of dramatically altering the structural dimensions of the oral cavity on the kinematic parameters of speech. The results showed that the experimental subjects performed differently pre and postoperatively though the changes were in different directions for the two subjects. Differences in both means and variabilities of kinematic parameters were larger between days for the experimental (operated) subjects than for the control subject. The results for the Control subject also showed significant differences in the mean values of kinematic variables between days though these day-to-day differences could not account for the effects found pre- and postoperatively. The results of the kinematic analysis, particularly the finding that transition time was most stable over the experimental conditions for the operated subjects, are used to speculate about the coordination of normal speech.

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