scholarly journals The Relationship of Gymnastics Experience and Hand Placement Technique on Peak Ground Reaction Forces Through the Elbow

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Saskia Richter
Keyword(s):  
Ground Reaction Forces ◽  
Reaction Forces ◽  
Relationship Of ◽  
The Relationship ◽  
Placement Technique

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals The Common Science Misconceptions in Indonesia Junior High School Students

2018 ◽  
Vol 2 (1) ◽  
pp. 21-24
Author(s):  
Putri Anjarsari
Keyword(s):  
High School Students ◽  
Junior High School ◽  
Junior High ◽  
School Students ◽  
Study Program ◽  
Science Misconceptions ◽  
Descriptive Research ◽  
Reaction Forces ◽  
Relationship Of ◽  
The Relationship

Identifying and correcting the mistake that students make about science concept is very important. The main purpose of this article is to analyse some publications about common science misconceptions in some science topics in junior high schools. Misconceptions are erroneous perceptions of what is universally accepted. The misconception identification in this research is based on the descriptive research using some journal publications in Indonesia university which is held science education study program. Study found that : the concept of photosynthesis,  respirations, the relationship of photosynthesis and respirations, force (action and reaction forces) , and Newton laws are most frequently investigated as misconceptions of science. Students’ interest and learning environments are some reasons of students’ misconceptions.

Normalization of Ground Reaction Forces

2006 ◽  
Vol 22 (3) ◽  
pp. 230-233 ◽  
Author(s):  
David R. Mullineaux ◽  
Clare E. Milner ◽  
Irene S. Davis ◽  
Joseph Hamill
Keyword(s):  
Loading Rate ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Newtonian Mechanics ◽  
Covariate Effect ◽  
Loading Rates ◽  
Reaction Forces ◽  
Explained Variance ◽  
Dimensionality Theory ◽  
The Relationship

The appropriateness of normalizing data, as one method to reduce the effects of a covariate on a dependent variable, should be evaluated. Using ratio, 0.67-nonlinear, and fitted normalizations, the aim of this study was to investigate the relationship between ground reaction force variables and body mass (BM). Ground reaction forces were recorded for 40 female subjects running at 3.7 ± 0.18 m·s–1 (mass = 58 ± 6 kg). The explained variance for mass to forces (peak-impact-vertical = 70%; propulsive-vertical = 27%; braking = 40%) was reduced to < 0.1% for mass to ratio normalized forces (i.e., forces/BM1) with statistically significantly different power exponents (p < 0.05). The smaller covariate effect of mass on loading rate variables of 2–16% was better removed through fitted normalization (e.g., vertical-instantaneous-loading-rate/BM0.69±0.93; ±95% CI) with nonlinear power exponents ranging from 0.51 to 1.13. Generally, these were similar to 0.67 as predicted through dimensionality theory, but, owing to the large confidence intervals, these power exponents were not statistically significantly different from absolute or ratio normalized data (p > 0.05). Further work is warranted to identify the appropriate method to normalize loading rates either to mass or to another covariate. Ratio normalization of forces to mass, as predicted through Newtonian mechanics, is recommended for comparing subjects of different masses.

Association of Step Width with Accelerated Sprinting Performance and Ground Reaction Force

2017 ◽  
Vol 38 (07) ◽  
pp. 534-540 ◽  
Author(s):  
Ryu Nagahara ◽  
Mirai Mizutani ◽  
Akifumi Matsuo ◽  
Hiroaki Kanehisa ◽  
Tetsuo Fukunaga
Keyword(s):  
Reaction Force ◽  
Step Width ◽  
Male Athletes ◽  
Phase Profile ◽  
Body Velocity ◽  
Reaction Forces ◽  
Relationship Of ◽  
The Relationship ◽  
Calculated Average ◽  
Step Section

AbstractThis study aimed to describe changes in step width (SW) during accelerated sprinting, and to clarify the relationship of SW with sprinting performance and ground reaction forces. 17 male athletes performed maximal-effort 60 m sprints. The SW and other spatiotemporal variables, as well as ground reaction impulses, over a 52 m distance were calculated. Average values for each 4 steps during acceleration were calculated to examine relationships among variables in different sections. The SW rapidly decreased up to the 13th step and slightly afterward during accelerated sprinting, showing a bilinear phase profile. The ratio of SW to the stature was significantly correlated with running speed based on average values over the 52 m distance and in the 9th–12th step section during accelerated sprinting. The SW ratio positively correlated with medial, lateral and mediolateral impulses in all step sections, except for medial impulse in the 17th–20th step section. These results indicate the importance of wider SW for better sprinting performance, especially in the 9th–12th step section. Moreover, the wider SW was associated with larger medial impulse and smaller lateral impulse, suggesting that a wide SW contributes to the production of greater mediolateral body velocity during accelerated sprinting.

scholarly journals The relationship between neck angles and ground reaction forces in schoolchildren during backpack carriage

2020 ◽  
Vol 12 (1) ◽  
pp. 1-9
Author(s):  
Dalia Mohammed Mosaad ◽  
Amr Almaz Abdel-aziem
Keyword(s):  
Body Weight ◽  
Negative Correlation ◽  
Force Plate ◽  
Ground Reaction Forces ◽  
Weight Changes ◽  
Strong Negative Correlation ◽  
Significant Difference ◽  
Reaction Forces ◽  
Analysis System ◽  
The Relationship

SummaryStudy aim: This study aimed to examine the effect of carrying backpacks on neck posture and ground reaction forces (GRFs) and to investigate the relationship between neck angles and GRFs during backpack carriage in schoolchildren.Material and methods: The craniohorizontal angle (CHA), craniovertebral angle (CVA), sagittal shoulder posture (SSP) and GRFs were measured in right-handed schoolchildren (14 male and 12 female) with mean age 10.17 ± 1.15 years during loaded and unloading conditions. The Qualisys motion analysis system with a force plate was used to assess the neck angles and GRFs.Results: During backpack carriage there was a significant increase in the CHA (p = 0.001), significant decrease in the CVA and SSP (p = 0.001, 0.016 respectively), no significant difference in the normalized (scaled to body weight) vertical GRFs (p > 0.05), and a significant increase in the anterior braking and posterior propulsive GRFs (p = 0.035, 0.002 respectively) compared to the unloading condition. While carrying a backpack there was a moderate negative correlation between the SSP and first vertical GRF (r = –0.464) and a strong negative correlation with the second vertical GRF (r = –0.571) and the posterior propulsive GRF (r = –0.587).Conclusion: Carrying a backpack weighing 15% of the child’s body weight changes the head posture and increases the normalized value of the anterior-posterior shear force. During backpack carriage, decreasing the SSP is associated with increasing the load acceptance, thrusting and posterior propulsive forces. Increasing the shearing force may lead to development of postural abnormities. Consequently, the ideal backpack weight should be considered by parents and teachers.

scholarly journals The metabolic cost of overcoming air resistive forces in distance running

2021 ◽  
Author(s):  
Edson Soares da Silva ◽  
Rodger Kram ◽  
Wouter Hoogkamer
Keyword(s):  
Aerodynamic Drag ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Metabolic Power ◽  
Resistive Force ◽  
Drag Forces ◽  
Reaction Forces ◽  
Time Savings ◽  
Resistive Forces ◽  
The Relationship

AbstractWe lack a mechanistic understanding of the relationship between aerodynamic drag forces and metabolic power during running. Further, the energetic and time savings possible from reducing aerodynamic drag (drafting) are still unclear due to the different methods previously assumed for converting from force reductions to metabolic power savings. Here, we quantified how small horizontal impeding forces (equivalent to aerodynamic forces) affect metabolic power and ground reaction forces over a range of velocities in competitive runners. In three sessions, 12 runners completed six 5-minute trials with 5 minutes of recovery in-between. We tested one velocity per session (12, 14 and 16 km/h), at three horizontal impeding force conditions (0, 4 and 8 N). On average, metabolic power increased by 6.13% per 1% body weight of horizontal impeding force but varied considerably between individuals. With greater horizontal impeding force, braking impulses decreased while propulsive impulses increased (p < 0.001). Across running velocities, the changes in braking and propulsive impulses with greater impeding force were correlated (r = -0.97; p < 0.001), but were not related to individual changes in metabolic power. We estimate that at ∼2-hour marathon pace, overcoming air resistive force comprises 8.52% of the gross metabolic power on average.

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