Catapult start likely improves sprint start performance

2021 ◽  
pp. 174795412110151
Author(s):  
Ryu Nagahara ◽  
Sam Gleadhill
Keyword(s):  
Effect Size ◽  
Force Production ◽  
Technical Training ◽  
Ground Reaction Forces ◽  
Control Effect ◽  
Forward Motion ◽  
Sprint Time ◽  
Reaction Forces ◽  
External Power

Sprint technical training, named the catapult start, is defined as partner assisted pulling of the hip backward at the set position and during block clearance, released by the forward motion of the athlete. This study investigated the characteristics of the catapult start and its influence on the following sprint start performance. Fourteen male sprinters performed a single 15-m control, catapult, and post-catapult sprint starts, during which ground reaction forces (GRFs) were measured using force platforms. All measured GRF variables during the block clearance, except for the impulses and mean forces on the front block and ratio of force for the rear block, were greater in the catapult start than the control (effect size [ES]=0.52–2.09). Waveform analyses revealed that the rear block anteroposterior GRF was greater for the catapult start than the control during the initial, middle and final phases (0 to 20%, 40 to 61% and 95 to 100%) of block clearance, while the rear block ratio of force was greater for the catapult start until 13% of block clearance. The catapult start resulted in greater rear block ratio of force (ES = 0.28), faster 10-m sprint time (ES = 0.31) and greater average horizontal external power during the initial 10-m (ES = 0.25) at the post-catapult trial. The results suggest that the catapult start can be accompanied with greater force production mainly for the rear block regardless of direction during the block clearance, and it can improve post-catapult sprint start performance in terms of the rear block ratio of force and 10-m sprint time.

Associations between ground reaction force waveforms and sprint start performance

2019 ◽  
Vol 14 (5) ◽  
pp. 658-666 ◽  
Author(s):  
Steffi L Colyer ◽  
Philip Graham-Smith ◽  
Aki IT Salo
Keyword(s):  
Reaction Force ◽  
Statistical Parametric Mapping ◽  
Force Production ◽  
Mass Motion ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Specific Training ◽  
Force Vector ◽  
Reaction Forces ◽  
External Power

Ground reaction forces produced on the blocks determine an athlete’s centre of mass motion during the sprint start, which is crucial to sprint performance. This study aimed to understand how force waveforms are associated with better sprint start performance. Fifty-seven sprinters (from junior to world elite) performed a series of block starts during which the ground reaction forces produced by the legs and arms were separately measured. Statistical parametric mapping (linear regression) revealed specific phases of these waveforms where forces were associated with average horizontal external power. Better performances were achieved by producing higher forces and directing the force vector more horizontally during the initial parts of the block phase (17–34% and 5–37%, respectively). During the mid-push (around the time of rear block exit: ∼54% of the block push), magnitudes of front block force differentiated performers, but orientation did not. Consequently, the ability to sustain high forces during the transition from bilateral to unilateral pushing was a performance-differentiating factor. Better athletes also exhibited a higher ratio of forces on the front block in the latter parts of unilateral pushing (81–92% of the block push), which seemed to allow these athletes to exit the blocks with lower centre of mass projection angles. Training should reflect these kinetic requirements, but also include technique-based aspects to increase both force production and orientation capacities. Specific training focused on enhancing anteroposterior force production during the transition between double- to single-leg propulsion could be beneficial for overall sprint start performance.

scholarly journals The Effect of First-Step Techniques from the Staggered Stance in American Football

2017 ◽  
Vol 01 (02) ◽  
pp. E69-E73
Author(s):  
Nikolas Knudsen ◽  
Thomas Andersen
Keyword(s):  
Reaction Time ◽  
Random Order ◽  
American Football ◽  
Football Players ◽  
Ground Reaction Forces ◽  
Time Analysis ◽  
Sprint Time ◽  
Reaction Forces ◽  
Force Profiles ◽  
Time Linear

AbstractThe purpose of this study was to evaluate 3 different starting techniques from the staggered stance with regards to sprint time, reaction time, linear impulse and power. 11 male amateur American football players volunteered to participate in a testing session consisting of twelve 5 m sprints, 4 in each technique (normal (NORM), backwards false step (BFS) and forwards false step (FFS)) in random order. Sprint starts were performed on force plates to investigate ground reaction forces, reaction time and total sprint time. Analysis showed significant differences in sprint times, with NORM (1.77±0.10 s) being faster than FFS (1.81±0.12 s) and BFS (2.01±0.13 s), and FFS being faster than BFS, although no differences were found in reaction time. In terms of mean force and power, NORM (331.1±39.2N, 542.2±72.3W) and FFS (320.8±43.2N, 550.9±81.4W) were significantly larger than BFS (256.9±36.2N, 443.5±61.1W). This indicates that when starting from a staggered stance, the BFS is inferior to the others and should be avoided. However, since the force profiles of the NORM and the FFS were similar, the differences in sprint time could arise from a technique bias towards the NORM start.

Force-Velocity-Power Profiling During Weighted-Vest Sprinting in Soccer

2019 ◽  
Vol 14 (6) ◽  
pp. 747-756 ◽  
Author(s):  
Jorge Carlos-Vivas ◽  
Elena Marín-Cascales ◽  
Tomás T. Freitas ◽  
Jorge Perez-Gomez ◽  
Pedro E. Alcaraz
Keyword(s):  
Effect Size ◽  
Power Output ◽  
Field Method ◽  
Maximum Power ◽  
Soccer Players ◽  
Total Force ◽  
Ground Reaction Forces ◽  
Time Data ◽  
Reaction Forces ◽  
Force Velocity

Purpose: To describe the load–velocity relationship and the effects of increasing loads on spatiotemporal and derived kinetic variables of sprinting using weighted vests (WV) in soccer players and determining the load that maximizes power output. Methods: A total of 23 soccer players (age 20.8 [1.5] y) performed 10 maximal 30-m sprints wearing a WV with 5 different loads (0%, 10%, 20%, 30%, and 40% body mass [BM]). Sprint velocity and time were collected using a radar device and wireless photocells. Mechanical outputs were computed using a recently developed valid and reliable field method that estimates the step-averaged ground-reaction forces during overground sprint acceleration from anthropometric and spatiotemporal data. Raw velocity–time data were fitted by an exponential function and used to calculate the net horizontal ground-reaction forces and horizontal power output. Individual linear force–velocity relationships were then extrapolated to calculate the theoretical maximum horizontal force (F0) and velocity and the ratio of force application (proportion of the total force production that is directed forward at sprint start). Results: Magnitude-based inferences showed an almost certain decrease in F0 (effect size = 0.78–3.35), maximum power output (effect size = 0.78–3.81), and maximum ratio of force (effect size = 0.82–3.87) as the load increased. The greatest changes occurred with loads heavier than 20% BM, especially in ratio of force. In addition, the maximum power was achieved under unloaded conditions. Conclusions: Increasing load in WV sprinting affects spatiotemporal and kinetic variables. The greatest change in ratio of force happened with loads heavier than 20% BM. Thus, the authors recommend the use of loads ≤20% BM for WV sprinting.

Amputee Locomotion: Ground Reaction Forces During Submaximal Running With Running-Specific Prostheses

2016 ◽  
Vol 32 (3) ◽  
pp. 287-294 ◽  
Author(s):  
Brian S. Baum ◽  
Hiroaki Hobara ◽  
Yoon Hyuk Kim ◽  
Jae Kun Shim
Keyword(s):  
Three Dimensional ◽  
Force Production ◽  
Acute Injury ◽  
Ground Reaction Forces ◽  
Control Subjects ◽  
Prosthetic Limbs ◽  
Function Loss ◽  
Reaction Forces ◽  
Musculoskeletal Function ◽  
And Control

Individuals with lower extremity amputation must adapt the mechanical interactions between the feet and ground to account for musculoskeletal function loss. However, it is currently unknown how individuals with amputation modulate three-dimensional ground reaction forces (GRFs) when running. This study aimed to understand how running with running-specific prostheses influences three-dimensional support forces from the ground. Eight individuals with unilateral transtibial amputations and 8 control subjects ran overground at 2.5, 3.0, and 3.5 m/s. Ten force plates measured GRFs at 1000 Hz. Peak and average GRFs and impulses in each plane were compared between limbs and groups. Prosthetic limbs generated reduced vertical impulses, braking forces and impulses, and mediolateral forces while generating similar propulsive impulses compared with intact and control limbs. Intact limbs generated greater peak and average vertical forces and average braking forces than control subjects’ limbs. These data indicate that the nonamputated limb experiences elevated mechanical loading compared with prosthetic and control limbs. This may place individuals with amputation at greater risk of acute injury or joint degeneration in their intact limb. Individuals with amputation adapted to running-specific prosthesis force production limitations by generating longer periods of positive impulse thus producing propulsive impulses equivalent to intact and control limbs.

scholarly journals The effect of graded knee brace at two angles of 60 and 30 degrees on the frequency spectrum of ground reaction forces in individuals with genu valgum during landing

2021 ◽  
Vol 43 (2) ◽  
pp. 220-229
Author(s):  
AmirAli Jafarnezhadgero ◽  
Arefeh Mokhtari Malek Abadi ◽  
Ali Yadegar ◽  
Farshad Ghorbanloo ◽  
Aydin Valizadeh Orang
Keyword(s):  
Frequency Spectrum ◽  
Effect Size ◽  
Genu Valgum ◽  
Ground Reaction Forces ◽  
Median Frequency ◽  
Force Frequency ◽  
Frequency Content ◽  
Knee Brace ◽  
High Effect ◽  
Reaction Forces

Background: Genu valgum is a postural malalignment in the knee joint. This malalignment is accompanied by altered mechanical forces in the tibiofemoral and patellofemoral joints. The purpose of this study was to investigate the effect of using a graded knee brace in two angles of 60 and 30 degrees on the frequency spectrum of ground reaction forces in individuals with genu valgum during landing. Methods: The present study was semi-experimental. Twenty non-athlete male students with genu valgus (age range: 20-30 years) were volunteered to participate in the study. The landing task was done during three conditions including without a knee brace, with a brace at two 30 and 60 degrees of flexion from a height of equal to 30 cm. Bertec force plate was used to record ground reaction forces. Fourier transform was used to calculate ground reaction force-frequency content during both landing conditions with and without a knee brace. Results: The results of this study showed a significant reduction in the frequency content with a power of 99.5% in the mediolateral direction (P=0.02; high effect size) and vertical direction (P=0.075; high effect effect) during landing with a knee brace at 60 degrees of flexion angle compared with without knee brace condition. Also, the median frequency component in the mediolateral direction (P=0.019; low effect size) and in the anterior-posterior direction (P=0.019; high effect effect) showed a significant decrease during wearing a knee brace compared with without it. Conclusion: Regarding the decreasing of median frequency after using the knee brace, it might be effective in the reduction of injury rate in individuals with genu valgum. However, further study warranted to better establish this issue.

Maximum single leg force production: cockroaches righting on photoelastic gelatin

1995 ◽  
Vol 198 (12) ◽  
pp. 2441-2452 ◽  
Author(s):  
R Full ◽  
A Yamauchi ◽  
D Jindrich
Keyword(s):  
Body Mass ◽  
High Speed ◽  
Neural Control ◽  
Force Production ◽  
Video Camera ◽  
Ground Reaction Forces ◽  
Geometric Scaling ◽  
Unit Body Weight ◽  
Reaction Forces ◽  
Muscle Force Production

Integrating studies of mechanics, neural control and isolated muscle function are possible using arthropod legs. To evaluate leg performance, we measured the ground reaction forces generated by individual legs of the six-legged cockroach Blaberus discoidalis (3.1 g), during an emergency behavior, righting or over-turning. We used a photoelastic method to measure the forces generated by individual legs simultaneously. A gelatin track placed between crossed polarizing filters was illuminated from below, and a high-speed video camera recorded the stress-induced optical signals from above. The size and skew of the optical patterns were found to be related to the magnitude and direction of the force. We discovered that the ground reaction forces generated during the righting behavior of the death-head cockroach were eight times greater than those observed during high-speed running, supporting the possibility that relative leg forces (leg force per unit body weight) during running and maximal leg activity differ more in small arthropods than in larger vertebrates. Non-geometric scaling of relative leg force (i.e. scaling to less than body mass-0.33), along with the reduced force-generating ability of a single leg in animals with many legs, may help to explain why the maximum relative leg force production by six-legged cockroaches, as well as by some other small insects, can be similar to the relative single leg forces produced by two- and four-legged vertebrates that are almost 1000 times more massive. Leg number and body mass alone, however, appear to be insufficient to explain the variation observed in relative leg force production at a given body mass, because enormous diversity in musculo-skeletal parameters exists. The maximal relative leg force of the cockroach B. discoidalis during righting was at the low end of a 100-fold variation observed for smaller insects wedging (pushing through a small crevice) and pulling loads. Thus, this cockroach can be characterized as a moderately strong insect with the capacity for relatively high speed. Results from the present study question the predictive strength of the simple geometric scaling arguments involving a strength:weight ratio as they are applied to small arthropods and encourage further consideration of the importance of leg number, muscle force production and mechanical advantage in the derivation of general principles of leg performance.

scholarly journals Differences in ground reaction waveforms between elite senior and junior academy sprinters during the block phase and first two steps

2020 ◽  
Vol 15 (3) ◽  
pp. 418-427
Author(s):  
Philip Graham-Smith ◽  
Steffi L Colyer ◽  
Aki IT Salo
Keyword(s):  
Force Production ◽  
Foot Force ◽  
Junior Athletes ◽  
S 100 ◽  
Reaction Forces ◽  
External Power ◽  
Senior Athletes ◽  
Mass Displacement ◽  
The Difference ◽  
Maximal Effort

The block start and initial steps following block exit are fundamental aspects of sprinting and their development is key to junior athletes’ progression. This study assessed the difference in force production between elite senior (including two sub-10 s 100-m sprinters) and junior academy sprinters during the block phase and the first two steps of a sprint. Thirty-seven male sprinters (17 senior, 20 junior) performed a series of maximal effort 20–40 m acceleration from blocks on an indoor track, with the ground reaction forces produced during the block phase and first two steps measured using force platforms. Senior athletes produced better block-phase performances (average horizontal external power; 15.52 ± 1.48 W/kg, M ±  SD) compared with the juniors (12.37 ± 2.21 W/kg; effect size ± 90% confidence interval = 1.28 ± 0.38). However, force production during the initial two steps was comparable across groups. Specifically, senior athletes exhibited higher relative force production and ratio of forces during the early (∼15–35%) block phase and higher anteroposterior forces during the transition from bilateral to unilateral pushing (58–62% of the block phase). Front foot force production was also found to differentiate senior and junior groups at rear block exit (∼55% of the block phase). This may be a required response to the greater centre of mass displacement in order to prevent over-rotation in the senior athletes during the front block pushing phase. Collectively, these results indicate that the progression of junior athletes is non-uniform across the block phase and subsequent two contacts, which should be considered when attempting to progress junior athletes towards senior ranks.

3D Printed Passive Compliant and Articulating Prosthetic Ankle Foot

2017 ◽  
Author(s):  
Millicent Schlafly ◽  
Tyagi Ramakrishnan ◽  
Kyle Reed
Keyword(s):  
United States ◽  
3D Printing ◽  
Sagittal Plane ◽  
The United States ◽  
Computer Assisted ◽  
Ground Reaction Forces ◽  
Forward Motion ◽  
Human Ankle ◽  
Reaction Forces ◽  
3D Printed

The human ankle is crucial to mobility as it counteracts the forces and moments created during walking. Around 85% of the 1.7 million people in the United States living with limb loss are transtibial (below knee) and transfemoral (above knee) amputees who are missing their ankle and require a prosthetic. This paper presents the Compliant and Articulating Prosthetic Ankle (CAPA) foot, a solution that uses torsional springs to store and release energy at three different locations on the mechanism, assisting in forward motion. The CAPA foot utilizes 3D printing and allows for the full ankle range of motion in the sagittal plane. Testing was performed with the CAPA foot on the Computer Assisted Rehabilitation Environment on an able-bodied person wearing a prosthetic simulator. Compared to the conventional non-articulating Solid Ankle Cushioned Heel foot, the CAPA foot is shown to better mimic the ground reaction forces and ankle angles of a healthy gait.

scholarly journals A Novel and Safe Approach to Simulate Cutting Movements Using Ground Reaction Forces

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2631 ◽  
Author(s):  
Amelia Lanier ◽  
Brian Knarr ◽  
Nicholas Stergiou ◽  
Thomas Buchanan
Keyword(s):  
Force Control ◽  
Cruciate Ligament ◽  
Knee Injuries ◽  
Force Production ◽  
Ground Reaction Forces ◽  
Control Task ◽  
Significant Difference ◽  
Reaction Forces ◽  
Anterior Cruciate ◽  
Force Profiles

Control of shear ground reaction forces (sGRF) is important in performing running and cutting tasks as poor sGRF control has implications for those with knee injuries, such as anterior cruciate ligament (ACL) ruptures. The goal of this study was to develop a novel and safe task to evaluate control or accurate modulation of shear ground reaction forces related to those generated during cutting. Our approach utilized a force control task using real-time visual feedback of a subject’s force production and evaluated control capabilities through accuracy and divergence measurements. Ten healthy recreational athletes completed the force control task while force control via accuracy measures and divergence calculations was investigated. Participants were able to accurately control sGRF in multiple directions based on error measurements. Forces generated during the task were equal to or greater than those measured during a number of functional activities. We found no significant difference in the divergence of the force profiles using the Lyapunov Exponent of the sGRF trajectories. Participants using our approach produced high accuracy and low divergence force profiles and functional force magnitudes. Moving forward, we will utilize this task in at-risk populations who are unable to complete a cutting maneuver in early stages of rehabilitation, such as ACL deficient and newly reconstructed individuals, allowing insight into force control not obtainable otherwise.

scholarly journals Running ground reaction forces across footwear conditions are predicted from the motion of two body mass components

2019 ◽  
Vol 126 (5) ◽  
pp. 1315-1325 ◽  
Author(s):  
Andrew B. Udofa ◽  
Kenneth P. Clark ◽  
Laurence J. Ryan ◽  
Peter G. Weyand
Keyword(s):  
Ground Reaction Force ◽  
Lower Limb ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Vertical Ground Reaction Force ◽  
Time Patterns ◽  
Foot Strike ◽  
Reaction Forces ◽  
Vertical Ground ◽  
Force Time

Although running shoes alter foot-ground reaction forces, particularly during impact, how they do so is incompletely understood. Here, we hypothesized that footwear effects on running ground reaction force-time patterns can be accurately predicted from the motion of two components of the body’s mass (mb): the contacting lower-limb (m1 = 0.08mb) and the remainder (m2 = 0.92mb). Simultaneous motion and vertical ground reaction force-time data were acquired at 1,000 Hz from eight uninstructed subjects running on a force-instrumented treadmill at 4.0 and 7.0 m/s under four footwear conditions: barefoot, minimal sole, thin sole, and thick sole. Vertical ground reaction force-time patterns were generated from the two-mass model using body mass and footfall-specific measures of contact time, aerial time, and lower-limb impact deceleration. Model force-time patterns generated using the empirical inputs acquired for each footfall matched the measured patterns closely across the four footwear conditions at both protocol speeds ( r2 = 0.96 ± 0.004; root mean squared error  = 0.17 ± 0.01 body-weight units; n = 275 total footfalls). Foot landing angles (θF) were inversely related to footwear thickness; more positive or plantar-flexed landing angles coincided with longer-impact durations and force-time patterns lacking distinct rising-edge force peaks. Our results support three conclusions: 1) running ground reaction force-time patterns across footwear conditions can be accurately predicted using our two-mass, two-impulse model, 2) impact forces, regardless of foot strike mechanics, can be accurately quantified from lower-limb motion and a fixed anatomical mass (0.08mb), and 3) runners maintain similar loading rates (ΔFvertical/Δtime) across footwear conditions by altering foot strike angle to regulate the duration of impact. NEW & NOTEWORTHY Here, we validate a two-mass, two-impulse model of running vertical ground reaction forces across four footwear thickness conditions (barefoot, minimal, thin, thick). Our model allows the impact portion of the impulse to be extracted from measured total ground reaction force-time patterns using motion data from the ankle. The gait adjustments observed across footwear conditions revealed that runners maintained similar loading rates across footwear conditions by altering foot strike angles to regulate the duration of impact.

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