Force Motion Research Articles

Tribo-dynamic modeling method and application to three-dimensional flexible PRL system

Research on the tribo-dynamics of the piston-cylinder liner (PCL) and piston ring-cylinder liner (PRCL) is vital due to their role in generating over 50 % of total engine friction loss and the impact on carbon emissions. Traditional studies, hindered by the structural and functional differences between pistons and rings, required separate simulation models, often overlooking crucial coupling characteristics. A unified tribo-dynamics modeling method for the piston-ring-liner (PRL) system is proposed in this paper, integrating the ring pack and piston into one multi-body system. This article models with global coordinates, unifying the form of governing, film thickness, and load equations of discontinuous lubrication domains for more efficient dynamics-lubrication coupling. The described method is applied to a marine engine, and the new tribology characteristics discovered after calculations are exhibited. It shows how piston deformation impacts ring tribology, indicating that increased profile height reduces the squeezing effect by allowing more ring movement. Additionally, ring assembly position significantly affects tribology parameters' circumferential distribution. Installing the ring with the end gap facing the piston pin side should be avoided, as it maximizes the negative impact of elastic force and secondary motion, deteriorating lubrication.

Whole Body Control of Mobile Manipulators With Series Elastic Actuators for Cart Pushing Tasks.

Human-centered environments provide affordance for the use of two-handed mobile manipulators. Yet robots designed to function in and physically interact with such environments are not yet capable of meeting human users' requirements. This work proposes a whole body control framework of a two-handed mobile manipulator driven by series elastic actuators (SEAs) for cart pushing tasks. A whole body dynamic model for an integrated mobile platform and on-board arms is revealed, which takes into account the interaction forces with the cart. Then, the explicit force/position control of the mobile manipulator is performed. It enables the robot to interact dynamically with the environment while providing motion, i.e., the manipulators provide both output force control and motion control for pushing a cart. To cope with the highly nonlinear system dynamics and parameter variation of a SEA-driven mobile manipulator, this work proposes an adaptive robust controller based on a novel integral barrier Lyapunov function for cart pushing tasks by considering model uncertainty. The proposed controller enables the mobile manipulator to complete cart pushing tasks by regulating the position and output force of the mobile base and arms. The experimental results show the effectiveness of this approach in cart pushing tasks.

Improved multi-layer wavelet transform and blind source separation based ECG artifacts removal algorithm from the sEMG signal: in the case of upper limbs.

Introduction: Surface electromyogram (sEMG) signals have been widely used in human upper limb force estimation and motion intention recognition. However, the electrocardiogram(ECG) artifact generated by the beating of the heart is a major factor that reduces the quality of the EMG signal when recording the sEMG signal from the muscle close to the heart. sEMG signals contaminated by ECG artifacts are difficult to be understood correctly. The objective of this paper is to effectively remove ECG artifacts from sEMG signals by a novel method. Methods: In this paper, sEMG and ECG signals of the biceps brachii, brachialis, and triceps muscle of the human upper limb will be collected respectively. Firstly, an improved multi-layer wavelet transform algorithm is used to preprocess the raw sEMG signal to remove the background noise and power frequency interference in the raw signal. Then, based on the theory of blind source separation analysis, an improved Fast-ICA algorithm was constructed to separate the denoising signals. Finally, an ECG discrimination algorithm was used to find and eliminate ECG signals in sEMG signals. This method consists of the following steps: 1) Acquisition of raw sEMG and ECG signals; 2) Decoupling the raw sEMG signal; 3) Fast-ICA-based signal component separation; 4) ECG artifact recognition and elimination. Results and discussion: The experimental results show that our method has a good effect on removing ECG artifacts from contaminated EMG signals. It can further improve the quality of EMG signals, which is of great significance for improving the accuracy of force estimation and motion intention recognition tasks. Compared with other state-of-the-art methods, our method can also provide the guiding significance for other biological signals.

Effects of Short-Term Hand Tractor Operation on Upper Limb Responses of Users

ABSTRACT Objectives Continuous exposure to hand-arm vibration integrated with poor posture and forceful movements are known causes of musculoskeletal disorders (MSD). In most related studies, force and vibration levels in experimental research is controlled. This study aims to determine how actual hand tractor field operation can affect the upper limb of users. It intends to characterize upper limb muscle activation applied during actual hand tractor usage. Lastly, it determines the immediate impacts on hand strength and perceived upper limb discomfort after the operation. Methods We recruited 15 farm operators with a mean working experience of 20.1 ± 12.2 years. They were asked to operate a hand tractor on paddy fields for at most 8 minutes. Handle vibration was measured using a tri-axial accelerometer. The total unweighted vibration acceleration was computed and used to represent the handle vibration magnitude. Muscle activation was measured using surface electromyography (sEMG). Six sEMG sensors were attached to the dominant and non-dominant side of the extensor carpi radialis (ECR), bicep, and deltoid. Pre- and post-task hand strength and subjective discomfort rating were also taken. Results The total unweighted handle vibration acceleration is 17.45 ± 7.53 m/s2. This exceeds the allowable safe value. Meanwhile, the percentage of maximum voluntary contraction (% MVC) of the muscles ranged from 6% to 14% with the ECR having a significantly higher activation (p < .05) than the bicep and deltoid. The post-task grip strength of the dominant hand was lower than its pre-task value (p < .01) while that of the non-dominant side did not vary significantly. There is a modest trend of higher hand discomfort of the non-dominant side on post-task than pre-task rating (p < .10). Although, overall, the perceived discomfort ranged from none to mild discomfort. Conclusion In conclusion, the study showed an indication that the effects of vibration on humans are evident even at mild muscle exertion, with the exertion predominantly concentrated on the distal arm area clearly affecting grip strength and hand discomfort. In such cases, future recommendations can revolve around the improvement of the hand tractor handle grip to impose grip comfort and ease.

A novel method for accurate division of the gait cycle into seven phases using shank angular velocity

BackgroundAccurate detection of gait events is crucial for gait analysis, enabling the assessment of gait patterns and abnormalities. Inertial measurement unit (IMU) sensors have gained traction for event detection, mainly focusing on initial contact (IC) and toe-off (TO) events. However, effective detection of other key events such as heel rise (HR), feet adjacent (FA), and tibia vertical (TBV) is essential for comprehensive gait analysis. Research questionCan a novel IMU-based method accurately detect HR, TO, FA, and TBV events, and how does its performance compare with existing methods? MethodsWe developed and validated an IMU-based method using cumulative mediolateral shank angular velocity (CSAV) for event detection. A dataset of nearly 25,000 gait cycles from healthy adults walking at varying speeds and footwear conditions was used for validation. The method’s accuracy was assessed against force plate and motion capture data and compared with existing TO detection methods. ResultsThe CSAV method demonstrated high accuracy in detecting TO, FA, and TBV events and moderate accuracy in HR event detection. Comparisons with existing TO detection methods showcased superior performance. The method's stability across speed and shoe variations underscored its robustness. SignificanceThis study introduces a highly accurate IMU-based method for detecting gait events needed to divide the gait cycle into seven phases. The effectiveness of the CSAV method in capturing essential events across different scenarios emphasizes its potential applications. Although HR event detection can be further improved, the precision of the CSAV method in TO, FA, and TBV detection advance the field. This study bridges a critical gap in IMU-based gait event detection by introducing a method for subdividing the swing phase into its subphases. Further research can focus on refining HR detection and expanding the method’s utility across diverse gait contexts, thereby enhancing its clinical and scientific significance.

Forced surge motion of a floating bridge pontoon to evaluate the hydrodynamic damping properties

Dedicated model tests were carried out to investigate the hydrodynamic force coefficients in surge for a pontoon that is designed to support a floating bridge. The experiments were carried out by oscillating the pontoon at various Keulegan–Carpenter (KC) numbers and oscillation periods in forced motion. A pontoon designed for the floating bridge in Bjørnarfjorden, Norway, is investigated herein. Several numerical simulations are performed to supplement the experiments. The estimated damping coefficients in surge are of significant importance at the first horizontal resonant mode of the floating bridge, which may be excited due to swell sea in the fjord. The first horizontal resonant mode of the floating bridge is around 15–16 s. The model tests were conducted with and without turbulence triggers. A finding from the model tests were that turbulence triggers did not prove to be necessary to eliminate model scale effects in oscillatory flow.The KC-dependent added mass and damping coefficient in oscillatory flow is investigated. The added mass and damping coefficients are clearly KC-dependent. The wave radiation damping in surge is small at the tested oscillation periods, and the damping in surge is dominated by the damping due to flow separation.Numerical simulations using a hybrid potential flow-CFD solver with linear free-surface conditions, PVC3D, are carried out with both linear and nonlinear body-boundary conditions. The simulations with nonlinear body-boundary conditions predict the hydrodynamic force coefficients with reasonable accuracy, whilst the simulations with linear body-boundary conditions fail to predict the hydrodynamic coefficients with the desired accuracy — both used to investigate the viscous damping which arises due to flow separation along the pontoon body.

Glenohumeral internal rotation deficit: insights into pathologic, clinical, diagnostic, and therapeutic characteristics.

Overhead athletes undergo significant biomechanical adaptations due to repetitive overhead movements, primarily affecting the glenohumeral joint. These adaptations can lead to glenohumeral internal rotation deficit (GIRD), which is characterized by posterior capsule stiffness that results in glenohumeral joint translation and a shift in the center of gravity. The severity of GIRD is dependent upon the presence of asymmetry between gained external and lost internal rotation, which is defined clinically as an asymmetry exceeding 20º; this reduces the total range of motion compared to the unaffected limb or baseline measurements. Diagnosis is challenging, as it can be mistaken for chronic scapular adaptations. To mitigate misdiagnosis, a high clinical suspicion is crucial in overhead athletes, especially those who began performing forceful overhead movements before closure of growth plates. Periodic physical examinations should establish baseline values for glenohumeral rotation and track changes in glenohumeral motion to aid in diagnosis. Symptoms of GIRD include shoulder pain, stiffness, and decreased force exertion. Magnetic resonance imaging is the preferred imaging method for evaluating GIRD and assessing concomitant soft tissue pathologies. Untreated GIRD can lead to rotator cuff strength imbalances. Treatment mainly involves conservative measures, such as physical therapy, to improve internal rotation and alleviate posterior tightness. Surgical interventions are considered when symptoms persist despite conservative treatment with physical therapy or in the presence of concomitant pathologies.

Explicit solution framework and new insights of 3-DOF linear flutter considering various frequency relationships

Different engineering structures, e.g., long-span bridges, bundled conductors, and cable-supported photovoltaic modules, exhibit various frequency relationships among different degrees of freedom (DOFs). Despite extensive research, the initiation mechanisms of flutter remain somewhat ambiguous for a 3-DOF system considering heaving-lateral-torsional motions, especially when frequencies are close among different DOFs. This study introduced an explicit eigenvalue solution framework for tackling the 3-DOF linear flutter problem by utilizing matrix perturbation methods, enabling the extraction of modal damping and frequency solutions for all possible frequency scenarios. These solutions explicitly clarified the influence mechanism of all flutter derivatives (aerodynamic damping and stiffness), structural frequencies, and mechanical dampings. Important flutter derivatives, flutter risk level, and sensitivity level to mechanical damping and to frequency detuning were summarized in a table for all frequency scenarios, providing a panoramic perspective on flutter instability and the coupling mechanism. Numerical studies were conducted on a thin plate, the Akashi Kaikyo Bridge, and an eight-bundled conductor to examine the proposed explicit solutions. The results showed that approaching frequencies can amplify the coupling effect among different DOFs by half an order, but this does not necessarily mean the system is more prone to flutter. A system where the torsional frequency approximates the heaving/lateral frequency is expected to face a higher flutter risk if given significant torsional-related aerodynamic stiffness (H3*, P3*). Evidently, this high risk exhibits insensitivity to mechanical damping and small frequency-detuning. Though usually ignored in bridge flutter analysis, drag force and lateral motion could exert noticeable influence in a minority of cases, e.g., more than 10 m/s decrease of critical wind speed for the Akashi Kaikyo Bridge at large angles of attack. The proposed explicit solution framework provides a systematic view and new insights into the flutter initiation mechanism, serving as a reference in the design and studies of various engineering structures with different frequencies and coupling features.

Prevalence of occupational co-exposure to biomechanical factors and neurotoxic chemicals in French workers.

Little is known about occupational co-exposure. The objective was to assess the prevalence of exposure and co-exposure to biomechanical factors and neurotoxic chemicals in French workers in 2017. Data from the French representative survey SUMER 2017 (SUrveillance Médicale des Expositions aux Risques professionnels) were analyzed. A total of 25 118 workers were included. Exposure to 4 biomechanical factors (manual handling of loads, forceful joint exertion, repetitive movements, and hand-arm transmitted vibrations) and 18 neurotoxic chemicals (n-hexane, perchloroethylene, trichloroethylene, etc.) were assessed using a questionnaire during face-to-face interviews with occupational physicians. Among men, 22.9% were exposed to at least one biomechanical factor and 10.2% were exposed to at least one neurotoxic chemical, mainly single exposures. Among women, 10.8% were exposed to at least one biomechanical factor and 3.1% were exposed to at least one neurotoxic chemical, also mainly single exposures. Occupational co-exposure to biomechanical factors and neurotoxic chemicals was observed among 4.8% of men and 0.7% of women. Workers under 30 yr old, blue-collar workers and those working in small companies were more co-exposed than other workers. In men, the prevalence of co-exposure was higher in the construction sector compared to other economic activities. This study stresses the importance of considering multiple occupational exposures while the current prevention measures are designed to focus on preventing occupational factors individually.

1D manipulator with vibration impact drive, based on which it is possible to create orthogonal manipulators and robots of any dimension

Manipulator of the investigated type may move according to a straight line. It has an advantage in the fact that by choosing geometrical parameters of the manipulator it is possible to achieve its effective operation. This is presented by using analytical and graphical methods. The performed research shows that manipulators with vibration impact drives have some positive qualities. In their structure it is not necessary to include the self-stopping mechanism. In the conservative case of the system static position of equilibrium of the impact pair can be with negative, zero or positive tightening. In the case of zero tightening eigenfrequency and period of the system does not depend on the quantity of motion of impact excitation. In the case of harmonic forced excitation resonant motions take place in the vicinity of the eigenfrequency of the conservative system with zero tightening. Analytical – numerical calculations contribute to the creation of manipulators and robots with vibration impact drives.

Underestimation of the tidal force and apsidal motion in close binary systems by the perturbative approach: Comparisons with non-perturbative models

Context. Stellar deformations play a significant role in the dynamical evolution of stars in binary systems, impacting the tidal dissipation and the outcomes of mass transfer processes. The prevalent method for modelling the deformations and tidal interactions of celestial bodies solely relies on the perturbative approach, which assumes that stellar deformations are minor perturbations to the spherical symmetry. An observable consequence of stellar deformations is the apsidal motion in eccentric systems, which has be observationally determined across numerous binary systems. Aims. Our objective is to assert the reliability of the perturbative approach when applied to close and strongly deformed binary systems. Methods. We have developed a non-perturbative 3D modelling method designed to account for high stellar deformations. We focus on comparing the properties of perturbatively deformed stellar models with our 3D models, particularly in terms of apsidal motion. Results. Our research highlights that the perturbative model becomes imprecise and underestimates the tidal force and rate of apsidal motion at a short orbital separation. This discrepancy primarily results from the first-order treatment in the perturbative approach, and cannot be rectified using straightforward mathematical corrections due to the strong non-linearity and numerous parameters of the problem. We have determined that our methodology affects the modelling of approximately 42% of observed binary systems with measured apsidal motion, introducing a discrepancy greater than 2% when the normalised orbital separation verifies q−1/5a(1 − e2)/R1 ≲ 6.5 (q is the mass ratio of the system, a is its semi-major axis, e is its orbital eccentricity and R1 is the radius of the primary star). Conclusions. The perturbative approach underestimates tidal interactions between bodies up to ∼40% for close low-mass binaries. All the subsequent modelling is impacted by our findings, in particular, the tidal dissipation is significantly underestimated. As a result, all binary stellar models are imprecise when applied to systems with a low orbital separation, and the outcomes of these models are also affected by these inaccuracies.

Global rotation of skyrmion bags under vertical microwave fields

Magnetic skyrmion bags are composite topological spin textures with arbitrary topological charges. Here, we computationally study the transient rotational motion of skyrmion bags, which is characterized by a global rotation of inner skyrmions around the central point. Distinct from conventional rotational modes found in skyrmions, the observed rotation is a forced motion associated with the breathing mode induced solely by vertical microwave fields. The driving force behind this rotation originates from the interactions between outer and inner skyrmions, with the angular velocity determined by the phase difference resulting from their asynchronous breathing behaviors. It is also found that skyrmion bags with larger skyrmion numbers are more conducive to the occurrence of the rotation. Our results are useful for understanding the cluster dynamics of complex topological spin textures driven by dynamic fields.

Direct numerical simulation of supersonic nanoparticles flow in free-molecule regime using the angular coefficient method

We employ molecular flow methods to numerically simulate the supersonic nanoparticles flow in free-molecule regime. To streamline the computational complexity, interaction forces between the gas and solid particles are disregarded. We first develop a discrete phase model (DPM) method that integrates the non-rigid body collision model, enabling an accurate simulation of nanoparticle diffusion under the influence of the drag force and Brownian motion force. The nanoparticles considered in this study have sizes below 10 nm, and the accuracy of the DPM method is verified by comparing its results with experimental data. Subsequently, we theoretically and numerically investigate the transmission probability and number density of N2 molecules flowing through two-dimensional (2D) channels and three-dimensional (3D) tubes by using the angular coefficient (AC) method and the direct simulation Monte Carlo (DSMC) method. The findings indicate that as the diameter of the nanoparticle (dp) decreases to 1 nm, the diffusion coefficient (D) and the root mean square displacement (x) of nanoparticles approach the N2 molecules. The microscopic velocity of most N2 molecules falls within the range of 62–1400 m/s, and the macroscopic velocity of N2 flow falls within the range of Ma = 1.28–1.35. In contrast to the DSMC method, the AC method exhibits enhanced accuracy even with a reduced number of grids and obviates the process for large-scale sampling. Additionally, the solution time required by the AC method is approximately 1/10 and 1/13–1/32 of the DSMC method in 3D cylindrical tubes and 2D channels, respectively. Moreover, the AC method demonstrates superior adaptability when dealing with complex geometries.

The Physics of a Rope Dart: Mass, Force, and Circular Motion

The Physics of a Rope Dart: Mass, Force, and Circular Motion

The dynamic properties and performance of the bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolator

Aiming to effectively isolate disturbance vibrations for heavy machines with low frequencies, a novel bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolation (I-DAVI) isolator is proposed, which consists of a primary supporting bellows container and an additional inerter subsystem comprising horizontal bellows and inertial mass, and the incompressible oil liquid is filled in the vacuum of both bellows as the working medium. First of all, the mathematic model of the presented I-DAVI device is established, and then the vibration transmissibility for the systems under force excitation and motion excitation are derived. The relevant results indicate that the anti-resonance appears at specific frequency, creating near-zero energy transmission and significantly reducing vibration transmission to the base or machines. Through the nondimensionalization analysis, the four parameters including the inertial mass ratio, damping ratio, ratio of effective cross-section areas, and number of the inerter subsystem completely dominate the isolation characteristics of the proposed device. Subsequently, a comparison study is carried out between systems with and without inertial mass located at the end of the additional horizontal bellows, and furthermore the operating mechanism of the I-DAVI is explained clearly. It is proven that the inerter-based DAVI isolator exhibits high static and low dynamic stiffness characteristics, which cause the resonance frequency of the isolation system to shift toward lower frequency without changing the static bearing stiffness and also reduce the peak value of the transmissibility. The further numerical simulation verifies that the optimal isolation effectiveness at the anti-resonance frequency is attributed to the dynamic equilibrium between the elastic restoring force of the primary bellows and the internal hydraulic pressure. In practice, the bellows-type hydraulic inerter-based I-DAVI isolator device investigated in this study is suitable for machines with the narrowband low-frequency vibration, such as the marine turbines.

Development of Ethno-STEM-Loaded Digital Science Teaching Materials the Process of Making Traditional Sidoarjo Snacks Material of Force and Object Motion to Train Science Literacy in Elementary School Students

This study aims to develop digital science teaching materials with Ethno-STEM content to train elementary students' scientific literacy. The research method used is the ADDIE Research and Development (R&amp;D) model (Analyze, Design, Development, Implementation and Evaluation). The results of the feasibility of digital science teaching materials obtained a percentage of 92.42% with very feasible criteria. The effectiveness of digital science teaching materials was declared effective by the results of the paired t-test which showed that there was an average difference in the pretest and posttest data, and the n-gain results scored 0.40 with the criteria of being effective. The results of the student response questionnaire after the learning process obtained a percentage of 90.35%; as well as the results of the teacher's response questionnaire after the learning process obtained a percentage of 90.62%. The results of student and teacher responses obtained very positive criteria. The conclusions of this study are that digital science teaching materials with Ethno-STEM content are effective in training scientific literacy for grade IV elementary school students.

The effects of workplace intervention programs to manage work-related musculoskeletal pain among poultry slaughterhouse workers: A randomized controlled trial

Background: The prevalence rate of work-related musculoskeletal pain (WMSP) among poultry slaughterhouse workers (PSW) has been reported in the shoulder, arm, and hand due to the involvement of repetitive and forceful upper limb movements. An intervention program is needed to reduce upper limb pain and improve upper limb functions among PSW. Objectives: This study aimed to investigate the effectiveness of workplace intervention programs on musculoskeletal pain, upper limb functions, and work ability among PSW. Materials and methods: A total of 48 participants (21 males and 27 females) who met the inclusion criteria were recruited into the study. The participants were allocated into two groups: The workplace intervention group (WIG, N=24; 10 males; 14 females) and the control group (CG, N=24; 11 males; 13 females). The WIG performed the exercise training with elastic resistance bands (ERB) and stretching exercises for eight weeks, and the CG did not perform any activity. The Visual Analogue Scale (VAS), shoulder reach flexibility test, active range of motion (AROM), the disability of the Arm, Shoulder, and Hand (KKU-DASH), and Thai Work Ability Index (Thai WAI) were used as outcome evaluations. The two-way analyses of variance (ANOVAs) with repeated measures (group x time) were used for statistical analyses, and the statistical significance was set at p&lt;0.05. Results: Approximately 79.1% (N=19) of the participants in WIG reported significantly decreased pain intensity of upper limb 3.06 (0.83 to -5.4) in the right side (p&lt;0.01) and 1.96 (1.6 to -5.6) in the left side (p&lt;0.001) after the 8-week intervention. Meanwhile, shoulder flexibility in WIG significantly increased (p&lt;0.001) to around 3.55 cm. (0.67 to 8.20) on the right side and 5.61 cm. (2.0 to 10.67) on the left side. For AROM in WIG, neck flexion, lateral neck flexion, neck rotation, and left shoulder flexion significantly increased (p&lt;0.05), as well as KKU-DASH and Thai WAI scores (p&lt;0.001). There was no significant difference within-group in all variables in CG. Conclusion: The workplace intervention program significantly reduced upper limb pain and increased neck movement and shoulder flexion among PSW. The training programs also improved work ability and reduced disability with upper extremity musculoskeletal conditions among PSW.

Applying Bayesian optimization to predict parameters in a time-domain model for cross-flow vortex-induced vibrations

As the demand for harvesting offshore energy increases worldwide, the need for slender structures, such as marine risers and power cables, will increase. The dominating loads for deep water applications will primarily be caused by current-structure interactions, where vortex-induced vibrations (VIV) are known to be a challenging response type to handle correctly during design. Semi-empirical time-domain models are promising for VIV prediction, but uncertainties related to simplifications in the hydrodynamic load model and empirical parameters lead to over-conservative designs, where the parameters are estimated from model tests within a relatively low Reynolds number range. The aim of this paper is to present an efficient tool to estimate empirical hydrodynamic parameters directly from test data. To illustrate the method, the hydrodynamic parameters were estimated from pure cross-flow VIV model tests in a steady current with Reynolds numbers in the range of 40,000-120,000. The parameters were updated sequentially by using a Bayesian optimization framework, with the aim of minimizing an objective function that incorporates the response errors between time-domain VIV simulations and model test data. It is shown that three empirical parameters can be obtained simultaneously, resulting in small response errors but the optimal parameters were overly sensitive to variations in the flow velocity. The optimal parameters were used to reconstruct the drag amplification related to cross-flow VIV and in forced motion simulations to illustrate how the parameters in the load model would map into the traditional formulation in terms of the added mass and excitation coefficient.

Comparison of Various Devices Used in the Evaluation of Vertical Jump Height

This study aimed to compare force plate, motion analysis, and mobile application methods for calculating vertical jump height. Twenty-nine male college students (age: 22.4 ± 1.0 years; height: 178.1 ± 6.2cm; body weight: 71.2 ± 8.0 kg) voluntarily participated in the study. Two countermovement jumps (CMJ) with 1-minute intervals on a force platform (BERTEC 4060-10) were performed. The countermovement jump performances were captured using an iPhone 11 (Apple Inc., USA). The experimental setup involved using three high-speed cameras, specifically the My Jump 2 and SIMI Motion 7.5. Obtained results from hip displacement (HD) data with motion analysis system showed that participants had significantly lower vertical jump height calculated from motion capture (p = 0.01; -8.3 ± 3.86, 95%CI; MyJump2-SIMI_HD = 1.24/3.30). It was also found that calculations from left and right foot displacement were higher than My Jump 2 results (95%CI; MyJump2-SIMI_RF = 0.66/2.93) and 95%CI (MyJump2-SIMI_LF) = (-0.63/2.65). In contrast, force plate calculations, known as the gold standard in the literature, were very similar to My Jump (95%CI; MyJumpII-FP) = (2.38/4.01). The findings indicate that the My Jump 2, used for assessing vertical jump height, may be a reliable alternative for determining vertical jump height instead of setting up gold standard methods. Individuals' athletic performance abilities and birth, gender, and sports preferences should be considered. Finally, when coaches or sports scientists intend to measure CMJ, My Jump 2 application can be recommended as a laboratory application as well as a practical and valid measurement method, especially for field applications.

Correlation of Body Mass Index and Work Profile on Hand Grip Strength and Endurance in Healthy Adults

Background and need of research: Hand Grip Strength (HGS) is an integral part of performing precise and refined fine motor activities. Many professions necessitate lifting and holding heavy loads with a proportionately static grip or repetitive or forceful gripping movements. Hence it is important to consider measurement of handgrip endurance (HGE) as an important component of assessment of physical performance. Most of studies have shown that HGS and BMI is associated with mortality and cardiovascular disease. So, need of this study is to fulfill the lacunae of literature. Method: A cross-sectional study-conducted on 80 healthy adults(age:18-40) after obtaining Institutional Ethical Committee clearance. Participants who met with the inclusion criteria were invited for study. BMI was calculated using the formula weight(kg)/height(m)2.HGS and HGE were measured in office worker and labourer using hand grip dynamometer. Results: Mean age, BMI, strength and endurance of office worker is (32.78+5.96), (26.15+5.36), (29.04+9.34), (44.63+28.53) and labourer is (32.47+4.46), (25.35+3.33), (37.26+8.57), (32.82+29.44) respectively. Spearman correlation test was used for analysis. Significant negative correlation (r=-0.507, p&lt;0.05) is found between labourer BMI and HSG and very weak correlation found between BMI and HGE (r=-0.010, p&gt;0.05). Weak and very weak correlation found between office worker’s BMI, HGS and HGE (r=-0.274, p&gt;0.05 and r=0.110, p&gt;0.05) respectively. Conclusion and clinical implication: There is significant negative correlation found between BMI and grip strength in labour group. This result supports that HGS can be effective tool for predicting physical fitness. Moreover, through normative value of HGS, clinician can detect low level of physical fitness at early stage in order to prevent future health problems. Keywords: BMI, hand grip strength, hand grip endurance, work profile