COMPARISON OF THREE DIFFERENT MEASUREMENT SYSTEMS TO ASSESS THE VERTICAL JUMP HEIGHT

ABSTRACT Introduction: The numerous instruments used to measure jump height use different technologies and calculations that can provide variable results. Objective: This study compared the countermovement jump (CMJ) height assessed with a wearable 3D inertial measurement unit (IMU), using flight time and the numerical integration method with a force platform and photocells. Methods: Forty CMJs were analysed, starting from an upright standing position with the hands placed on the waist. Twenty healthy volunteers completed 2 CMJs, which were simultaneously assessed using an IMU placed on the subject's sacrum, a force platform (considered the gold standard method) and photocells. The maximum height of each CMJ was measured. Results: The results showed a significant overestimation (p<0.001) in jump height for the IMU using the numerical integration method when compared to the force platform (+7 cm). Excellent intraclass correlation coefficients (ICCs) were obtained with the flight time equations for the different types of measurement equipment. Fair to good ICCs were obtained with the IMU using the numerical integration method and force platform. Conclusion: In conclusion, the jump height obtained with the IMU using the numerical integration method showed the poorest agreement compared to the force platform. Level of evidence III; Prospective comparative study.

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Assessing Interlimb Jump Asymmetry in Young Soccer Players: The My Jump 2 App

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2019-0981 ◽

2021 ◽

Vol 16 (1) ◽

pp. 19-27

Author(s):

Matheus Barbalho ◽

Ana Francisca Rozin Kleiner ◽

Bianca Callegari ◽

Ramon Costa de Lima ◽

Givago da Silva Souza ◽

...

Keyword(s):

Correlation Coefficient ◽

Intraclass Correlation Coefficient ◽

Intraclass Correlation ◽

Flight Time ◽

Mobile App ◽

Force Platform ◽

Soccer Players ◽

Drop Jump ◽

Time Asymmetry ◽

Gold Standard Method

Background: Jumps are important evaluation tools for muscle strength and power and for interlimb asymmetries. Different jump tests are well related to athletic performance, prediction of injury risk, and common motor gestures of several sports such as soccer. Low-cost mobile applications (apps) have gained popularity for this measure. The authors hypothesized that the My Jump 2 app would be a valid tool to assess drop-jump performance and interlimb asymmetry in soccer players. Methods: Eleven male soccer players took part in this study (18.2 [1.3] y, 69.9 [9.5] kg, 174 [6.6] cm). The athletes performed each test twice on a force plate (gold-standard method), while the jumps were recorded through the mobile app. Measures with the My Jump 2 app were applied by 2 evaluators, independently and in duplicate (interrater and intrarater reliability). The agreement analysis between both evaluations was done using an intraclass correlation coefficient and Bland–Altman plots. Results: Compared with the force platform, the app tested showed excellent reliability for the drop jump’s flight time and interlimb asymmetry (intraclass correlation coefficient > .98). For interlimb contact-time asymmetry, the values were 18.4 (9.9) and 19.1 (9.9) milliseconds for the My Jump 2 app and the force platform, respectively (P = .88). For flight-time asymmetries, the values were 389.7 (114.3) and 396.8 (112.5) milliseconds for the My Jump 2 app and the force platform, respectively (P = .88). Conclusion: The My Jump 2 app is a valid tool to assess drop-jump and interlimb asymmetry in soccer players.

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Numerical Integration Method for Stability Analysis of Milling With Variable Spindle Speeds

Journal of Vibration and Acoustics ◽

10.1115/1.4031617 ◽

2015 ◽

Vol 138 (1) ◽

Cited By ~ 18

Author(s):

Ye Ding ◽

Jinbo Niu ◽

LiMin Zhu ◽

Han Ding

Keyword(s):

Differential Equation ◽

Stability Analysis ◽

Numerical Integration ◽

Integration Method ◽

Transcendental Equation ◽

Spindle Speed ◽

Machining Parameters ◽

Numerical Integration Method ◽

Stability Diagrams ◽

Time Period

A semi-analytical method is presented in this paper for stability analysis of milling with a variable spindle speed (VSS), periodically modulated around a nominal spindle speed. Taking the regenerative effect into account, the dynamics of the VSS milling is governed by a delay-differential equation (DDE) with time-periodic coefficients and a time-varying delay. By reformulating the original DDE in an integral-equation form, one time period is divided into a series of subintervals. With the aid of numerical integrations, the transition matrix over one time period is then obtained to determine the milling stability by using Floquet theory. On this basis, the stability lobes consisting of critical machining parameters can be calculated. Unlike the constant spindle speed (CSS) milling, the time delay for the VSS is determined by an integral transcendental equation which is accurately calculated with an ordinary differential equation (ODE) based method instead of the formerly adopted approximation expressions. The proposed numerical integration method is verified with high computational efficiency and accuracy by comparing with other methods via a two-degree-of-freedom milling example. With the proposed method, this paper details the influence of modulation parameters on stability diagrams for the VSS milling.

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The Numerical Methods of Peridynamics Theory Used in Failure Analysis of Materials

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1030-1032.223 ◽

2014 ◽

Vol 1030-1032 ◽

pp. 223-227

Author(s):

Lin Fan ◽

Song Rong Qian ◽

Teng Fei Ma

Keyword(s):

Differential Equation ◽

Integral Equation ◽

Numerical Integration ◽

Integration Method ◽

Equation Of Motion ◽

Numerical Integration Method ◽

Volume Integral ◽

Volume Integral Equation ◽

Method Of Molecular Dynamics ◽

Classic Theory

In order to analysis the force situation of the material which is discontinuity,we can used the new theory called peridynamics to slove it.Peridynamics theory is a new method of molecular dynamics that develops very quickly.Peridynamics theory used the volume integral equation to constructed the model,used the volume integral equation to calculated the PD force in the horizon.So It doesn’t need to assumed the material’s continuity which must assumed that use partial differential equation to formulates the equation of motion. Destruction and the expend of crack which have been included in the peridynamics’ equation of motion.Do not need other additional conditions.In this paper,we introduce the peridynamics theory modeling method and introduce the relations between peridynamics and classic theory of mechanics.We also introduce the numerical integration method of peridynamics.Finally implementation the numerical integration in prototype microelastic brittle material.Through these work to show the advantage of peridynamics to analysis the force situation of the material.

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