scholarly journals The Effects of External Loads and Muscle Forces on the Knee Joint Ligaments during Walking: A Musculoskeletal Model Study

2021 ◽  
Vol 11 (5) ◽  
pp. 2356
Author(s):  
Carlo Albino Frigo ◽  
Lucia Donno
Keyword(s):  
Knee Joint ◽  
Cruciate Ligament ◽  
Musculoskeletal Model ◽  
Optimization Approach ◽  
Muscle Forces ◽  
Collateral Ligaments ◽  
Flexion Extension ◽  
Lateral Collateral Ligaments ◽  
Gastrocnemius Muscles ◽  
External Loads

A musculoskeletal model was developed to analyze the tensions of the knee joint ligaments during walking and to understand how they change with changes in the muscle forces. The model included the femur, tibia, patella and all components of cruciate and collateral ligaments, quadriceps, hamstrings and gastrocnemius muscles. Inputs to the model were the muscle forces, estimated by a static optimization approach, the external loads (ground reaction forces and moments) and the knee flexion/extension movement corresponding to natural walking. The remaining rotational and translational movements were obtained as a result of the dynamic equilibrium of forces. The validation of the model was done by comparing our results with literature data. Several simulations were carried out by sequentially removing the forces of the different muscle groups. Deactivation of the quadriceps produced a decrease of tension in the anterior cruciate ligament (ACL) and an increase in the posterior cruciate ligament (PCL). By removing the hamstrings, the tension of ACL increased at the late swing phase, while the PCL force dropped to zero. Specific effects were observed also at the medial and lateral collateral ligaments. The removal of gastrocnemius muscles produced an increase of tension only on PCL and lateral collateral ligaments. These results demonstrate how musculoskeletal models can contribute to knowledge about complex biomechanical systems as the knee joint.

scholarly journals Understanding Covalent Grafting of Nanotubes onto Polymer Nanocomposites: Molecular Dynamics Simulation Study

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2621
Author(s):  
Seunghwa Yang
Keyword(s):  
Molecular Dynamics ◽  
Load Transfer ◽  
Cell Model ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Covalent Grafting ◽  
Modelling Strategies ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
External Loads

Here, we systematically interrogate the effects of grafting single-walled (SWNT) and multi-walled carbon nanotubes (MWNT) to polymer matrices by using molecular dynamics (MD) simulations. We specifically investigate key material properties that include interfacial load transfer, alteration of nanotube properties, and dispersion of nanotubes in the polymer matrix. Simulations are conducted on a periodic unit cell model of the nanocomposite with a straight carbon nanotube and an amorphous polyethylene terephthalate (PET) matrix. For each type of nanotube, either 0%, 1.55%, or 3.1% of the carbon atoms in the outermost nanotubes are covalently grafted onto the carbon atoms of the PET matrix. Stress-strain curves and the elastic moduli of nanotubes and nanocomposites are determined based on the density of covalent grafting. Covalent grafting promotes two rivalling effects with respect to altering nanotube properties, and improvements in interfacial load transfer in the nanocomposites are clearly observed. The enhanced interface enables external loads applied to the nanocomposites to be efficiently transferred to the grafted nanotubes. Covalent functionalization of the nanotube surface with PET molecules can alter the solubility of nanotubes and improve dispersibility. Finally, we discuss the current limitations and challenges in using molecular modelling strategies to accurately predict properties on the nanotube and polymers systems studied here.

scholarly journals Associations between Well-Being State and Match External and Internal Load in Amateur Referees

2021 ◽  
Vol 18 (6) ◽  
pp. 3322
Author(s):  
Eñaut Ozaeta ◽  
Javier Yanci ◽  
Carlo Castagna ◽  
Estibaliz Romaratezabala ◽  
Daniel Castillo
Keyword(s):  
External Load ◽  
Contact Time ◽  
Well Being ◽  
Ground Contact ◽  
Internal Load ◽  
Match Play ◽  
Power Meter ◽  
Ground Contact Time ◽  
Training Impulse ◽  
External Loads

The main aim of this paper was to examine the association between prematch well-being status with match internal and external load in field (FR) and assistant (AR) soccer referees. Twenty-three FR and 46 AR participated in this study. The well-being state was assessed using the Hooper Scale and the match external and internal loads were monitored with Stryd Power Meter and heart monitors. While no significant differences were found in Hooper indices between match officials, FR registered higher external loads (p < 0.01; ES: 0.75 to 5.78), spent more time in zone 4 and zone 5, and recorded a greater training impulse (TRIMP) value (p < 0.01; ES: 1.35 to 1.62) than AR. Generally, no associations were found between the well-being variables and external loads for FR and AR. Additionally, no associations were found between the Hooper indices and internal loads for FR and AR. However, several relationships with different magnitudes were found between internal and external match loads, for FR, between power and speed with time spent in zone 2 (p < 0.05; r = −0.43), ground contact time with zone 2 and zone 3 (p < 0.05; r = 0.50 to 0.60) and power, speed, cadence and ground contact time correlated with time spent in zone 5 and TRIMP (p < 0.05 to 0.01; r = 0.42 to 0.64). Additionally, for AR, a relationship between speed and time in zone 1 was found (p < 0.05; r = −0.30; CL = 0.22). These results suggest that initial well-being state is not related to match officials’ performances during match play. In addition, the Stryd Power Meter can be a useful device to calculate the external load on soccer match officials.

scholarly journals Electromechanical Response of Smart Ultra-High Performance Concrete under External Loads Corresponding to Different Electrical Measurements

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1281
Author(s):  
Min Kyoung Kim ◽  
Huy Viet Le ◽  
Dong Joo Kim
Keyword(s):  
Electrical Resistivity ◽  
High Performance ◽  
High Performance Concrete ◽  
Steel Slag ◽  
Measurement Methods ◽  
Electrical Measurements ◽  
Ultra High Performance Concrete ◽  
Ac Measurement ◽  
External Loads ◽  
Functional Fillers

This study investigated the electromechanical response of smart ultra-high-performance concretes (smart UHPCs), containing fine steel slag aggregates (FSSAs) and steel fibers as functional fillers, under external loads corresponding to different measurement methods. Regardless of different measurement methods of electrical resistance, the smart UHPCs under compression showed a clear reduction in their electrical resistivity. However, under tension, their electrical resistivity measured from direct current (DC) measurement decreased, whereas that from alternating current (AC) measurement increased. This was because the electrical resistivity, from DC measurement, of smart UHPCs was primarily dependent on fiber crack bridging, whereas that from AC measurement was dependent on tunneling effects.

Agreement and reliability of magnetic, angular rate, and gravity (MARG) sensors to assess multiple body segment’s external loads during off-road running

2021 ◽  
pp. 175433712199698
Author(s):  
Daniel Rojas-Valverde ◽  
José Pino-Ortega ◽  
Rafael Timón ◽  
Randall Gutiérrez-Vargas ◽  
Braulio Sánchez-Ureña ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Angular Rate ◽  
Wearable Sensors ◽  
Intraclass Correlation ◽  
Principal Component ◽  
Test Reliability ◽  
Data Set ◽  
Body Segments ◽  
External Loads ◽  
Good Agreement

The extensive use of wearable sensors in sport medicine, exercise medicine, and health has increased the interest in their study. That is why it is necessary to test these technologies’ efficiency, effectiveness, agreement, and reliability in different settings. Consequently, the purpose of this article was to analyze the magnetic, angular rate, and gravity (MARG) sensor’s test-retest agreement and reliability when assessing multiple body segments’ external loads during off-road running. A total of 18 off-road runners (38.78 ± 10.38 years, 73.24 ± 12.6 kg, 172.17 ± 9.48 cm) ran two laps (1st and 2nd Lap) of a 12 km circuit wearing six MARG sensors. The sensors were attached to six different body segments: left (MPLeft) and right (MPRight) malleolus peroneus, left (VLLeft) and right (VLRight) vastus lateralis, lumbar (L1-L3), and thorax (T2-T4) using a special neoprene suit. After a principal component analysis (PCA) was performed, the total data set variance of all body segments was represented by 44.08%–70.64% for the 1st PCA factor considering two variables, Player LoadRT and Impacts, on L1-L3, respectively. These two variables were chosen among three total accelerometry-based external load indicators (ABELIs) to perform the agreement and reliability tests due to their relevance based on PCAs for each body segment. There were no significant differences between laps in the Player LoadRT or Impacts ( p > 0.05, trivial). The intraclass correlation and lineal correlation showed a substantial to almost perfect over-time test consistency assessed via reliability in both Player LoadRT and Impacts. Bias and t-test assessments showed good agreement between Laps. It can be concluded that MARGs sensors offer significant test re-test reliability and good agreement when assessing off-road kinematics in the six different body segments.

scholarly journals Comparison between Continuous and Fractionated Game Format on Internal and External Load in Small-Sided Games in Soccer

2020 ◽  
Vol 17 (2) ◽  
pp. 405 ◽  
Author(s):  
Luís Branquinho ◽  
Ricardo Ferraz ◽  
Bruno Travassos ◽  
Mário C. Marques
Keyword(s):  
Confidence Intervals ◽  
External Load ◽  
Continuous Method ◽  
Soccer Players ◽  
Professional Soccer ◽  
Game Format ◽  
Physical Impact ◽  
Mean Differences ◽  
External Loads

This study aimed to identify the effects of continuous and fractionated game formats on internal and external load in small-sided games in soccer. Twenty male professional soccer players participated in the study performing the same exercise (5 vs. 5 players) continuously (1 × 24 min) and in a repeated/fractioned manner (2 × 12 min, 4 × 6 min, and 6 × 4 min). A comparison between playing conditions was assessed by means of standardized mean differences calculated with combined variance and respective confidence intervals of 90%. The limits for the statistics were 0.2, trivial; 0.6, small; 1.2, moderate; 2.0, large; and >2.0, very large. The results indicate that the use of the continuous method seems to present the tendency of less physical impact on the internal and external loads compared to the fractionated method. In addition, the higher number of exercise repetitions in the fractionated method was found to increase the external load compared to the continuous method. This study showed that application of small-sided games by the fractionated method tends to result in higher training loads.

Behavioural study of a reinforced analogical soil under external loads

1996 ◽  
Vol 14 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Amina Benrabah ◽  
Jacques Gielly ◽  
Farimah Masrouri
Keyword(s):  
Behavioural Study ◽  
External Loads

Meso-Mechanics Analysis of Concrete: Generation of Random Aggregate Structure

2008 ◽  
Vol 400-402 ◽  
pp. 363-370
Author(s):  
Shao Fei Jiang ◽  
Zhao Qi Wu ◽  
Yun Fei Qiu
Keyword(s):  
Random Sampling ◽  
Progressive Failure ◽  
Aggregate Structure ◽  
Numerical Examples ◽  
Random Aggregate ◽  
Mechanics Analysis ◽  
Statistical Sense ◽  
Controlling Measures ◽  
External Loads ◽  
Aggregate Particles

In this paper, a new analytical method is proposed to generate concrete random aggregate structure (RAS) in meso-scopic level. This method is particular useful for the progressive failure of concrete under various external loads. In the meso-mechanics level, the concrete is taken as the composite material consisting of aggregate, mortar and interface between them. As a result, it is generated a random aggregate structure in which the shape, size and distribution of the aggregate particles resemble real concrete in the statistical sense using the Monte Carlo random sampling principle in this paper, and the method proposed can generate both regular aggregate particles and irregular ones in 2-Dimmension. It is should be noted that vector concept and some controlling measures are also proposed to avoid generating aggregate particles not consistent with real ones. Numerical examples are simulated to validate the proposed method finally.

Nonlinear ultrasonic imaging method for closed cracks using subtraction of responses at different external loads

Ultrasonics ◽  
2011 ◽  
Vol 51 (6) ◽  
pp. 661-666 ◽  
Author(s):  
Yoshikazu Ohara ◽  
Satoshi Horinouchi ◽  
Makoto Hashimoto ◽  
Yohei Shintaku ◽  
Kazushi Yamanaka
Keyword(s):  
Ultrasonic Imaging ◽  
Imaging Method ◽  
Nonlinear Ultrasonic ◽  
External Loads

Robust Stress Check Formula of Lifting Padeye

2010 ◽  
Vol 54 (01) ◽  
pp. 34-40
Author(s):  
Zhou Bo ◽  
Liu Yujun ◽  
Ji Zhuoshang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Accurate Method ◽  
Offshore Structures ◽  
Structure Design ◽  
Stress Calculation ◽  
Check Method ◽  
External Loads ◽  
Actual Stress ◽  
Element Method

Lifting padeyes are widely used in the construction of offshore structures and ships. It has been shown that the traditional check method cannot reflect the realistic value and distribution of actual stress on the padeyes. A more accurate method for the padeye stress calculation is essential and important for promoting the safety of the padeyes. In this paper, a new check formula is proposed based on the analysis of deformation and external loads distribution on lifting padeyes. The results of finite element method and the solutions of traditional check formula and new check formula are compared. It is shown that, by applying the stress check formula derived in the paper, the value and the location of the dangerous stresses occurred can be evaluated easily and exactly. The safe reliability of structure design can be improved significantly.

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