The Forces Exerted on the Substrate by Walking and Stationary Crickets

1980 ◽  
Vol 85 (1) ◽  
pp. 263-279 ◽  
Author(s):  
Jack Harris ◽  
Helen Ghiradella
Keyword(s):  
The Body ◽  
Peak Force ◽  
Vertical Force ◽  
Step Frequency ◽  
Oscillatory Mechanism ◽  
Lower Magnitude ◽  
Stationary Period

1. The gait and the protraction/retraction ratios (P/R ratios) for the cricket are described. They are essentially the same as for the cockroach and the grasshopper. 2. The vertical forces exerted on the substrate by all six legs of walking and stationary crickets are measured. On the basis of the ‘forceprints’ obtained and differences in P/R ratios among the legs of different thoracic segments, it is pointed out that all segments are not functionally identical. Specifically, the greater irregularity of the forceprints of the prothoracic legs, and the lower magnitude of peak force exerted on the substrate by the prothoracic legs suggest that the prothoracic legs are more involved in balancing or searching than in propulsion. 3. The metathoracic legs exert an increased vertical force on the substrate just before the initiation of protraction. This increase correlates with an extension of the leg apparently through extension of the femoraltibial joint. 4. A slight decrease in the force exerted on the substrate by the mesothoracic legs occurs when the leg is at right angles to the body. 5. Placing or lifting one mesothoracic leg does not affect the force exerted by the contralateral mesothoracic leg in a regular way. This argues against mechanical interactions between the legs and in favour of theories invoking central generation of pattern. 6. At a stepping frequency of below 2 steps s−1 the shapes of the forceprints of all legs are no longer repetitive. Also, below 2 steps s−1 there is an increase in the variability of the peak force exerted on the substrate. It is possible that the animal switches to a more sensory sensitive mode below a step frequency of 2s−1. 7. During stationary periods the forces exerted on the substrate continue to show oscillations which may be metachronal. This suggests a mechanism whereby a central oscillatory mechanism can account for the behaviour of an animal starting to walk following such a stationary period.

Characteristics of Eight Irish Dance LandingsConsiderations for Training and Overuse Injury Prevention

2021 ◽  
Vol 25 (1) ◽  
pp. 30-37
Author(s):  
Sarah Klopp Christensen ◽  
Aaron Wayne Johnson ◽  
Natalie Van Wagoner ◽  
Taryn E. Corey ◽  
Matthew S. McClung ◽  
...  
Keyword(s):  
Large Range ◽  
Force Plate ◽  
Three Dimensional ◽  
The Body ◽  
Peak Force ◽  
Warm Up ◽  
Dance Training ◽  
Rise Rate ◽  
Dance Movements ◽  
Reaction Forces

Irish dance has evolved in aesthetics that lead to greater physical demands on dancers' bodies. Irish dancers must land from difficult moves without letting their knees bend or heels touch the ground, causing large forces to be absorbed by the body. The majority of injuries incurred by Irish dancers are due to overuse (79.6%). The purpose of this study was to determine loads on the body of female Irish dancers, including peak force, rise rate of force, and impulse, in eight common Irish hard shoe and soft shoe dance movements. It was hypothesized that these movements would produce different ground reac- tion force (GRF) characteristics. Sixteen female Irish dancers were recruited from the three highest competitive levels. Each performed a warm-up, reviewed the eight movements, and then performed each movement three times on a force plate, four in soft shoes and four in hard shoes. Ground reaction forces were measured using a three-dimensional force plate recording at 1,000 Hz. Peak force, rise rate, and vertical impulse were calculated. Peak forces normalized by each dancer's body weight for each of these variables were significantly different between move- ments and shoe types [F(15, 15)= 65.4, p < 0.01; F(15, 15) = 65.0, p < 0.01; and F(15, 15) = 67.4, p < 0.01, respectively]. The variable years of experience was not correlated with peak force, rise rate, or impulse (p > 0.40). It is concluded that there was a large range in GRF characteristics among the eight movements studied. Understanding the force of each dance step will allow instructors to develop training routines that help dancers adapt gradually to the high forces experienced in Irish dance training and competitions, thereby limiting the potential for overuse injuries.

The Vertical Mean Force and Moment of Submerged Bodies Under Waves

1971 ◽  
Vol 15 (03) ◽  
pp. 231-245 ◽  
Author(s):  
C. M. Lee ◽  
J. N. Newman
Keyword(s):  
Free Surface ◽  
Added Mass ◽  
Cross Sectional Area ◽  
The Body ◽  
Slender Body ◽  
Longitudinal Distribution ◽  
Vertical Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Mean

A neutrally buoyant slender body of arbitrary sectional form, submerged beneath a free surface, is free to respond to an incident plane progressive wave system. The fluid is assumed inviscid, incompressible, homogeneous and infinitely deep. The first-order oscillatory motion of the body and the second-order time-average vertical force and pitching moment acting on the body are obtained in terms of Kochin's function. By use of slender-body theory for a deeply submerged body, the final expressions for the mean force and the moment are shown to depend on the longitudinal distribution of sectional area and added mass and on the amplitude and the frequency of the ambient surface waves. The magnitude of the mean force for various simple geometric cylinders is compared with that of a circular cylinder of equal cross-sectional area. The mean force on a nonaxisymmetric body is often approximated by replacing the section with circular profiles of equivalent cross-sectional area. A better scheme of approximation is presented, based on a simple way of estimating the two-dimensional added mass. It is expected that the effect of the cross-sectional geometry on mean vertical force and moment will be more significant when the body is very close to the free surface.

Kinematic Mechanics Analysis of Takeoff in Pre-Jumping for Sports Aerobics

2014 ◽  
Vol 1014 ◽  
pp. 157-160 ◽  
Author(s):  
Zi Xin Zhu
Keyword(s):  
Influencing Factors ◽  
Mechanical Model ◽  
Angular Speed ◽  
The Body ◽  
Dynamics Analysis ◽  
Vertical Force ◽  
Bending Angle ◽  
Mechanics Analysis ◽  
Light Pole

Takeoff is important to a variety of difficult movements for sports aerobics. The paper analyzes the kinematic mechanics of takeoff in pre-jumping for the sport. It first discusses the importance of takeoff in sports aerobics, and finds that the mechanics theory can be utilized to analyze the forces produced in the process of takeoff. Then, the dynamics analysis of takeoff in pre-jumping is completed to reveal the change of the vertical force and expound the sports process from the aspect of mechanics. Subsequently, the body for the athlete is simplified a two-light-pole mechanical model. On the basis of this, the mechanics analysis of vertical force in pre-jumping is done to find the influencing factors for vertical force. The results show that the vertical force produced by the takeoff in pre-jumping suffers from the factors of the weight, length of leg, bending angle of knee, and angular speed of leg rotation, etc.

Biology and physics of locust flight. III. The aerodynamics of locust flight

1956 ◽  
Vol 239 (667) ◽  
pp. 511-552 ◽  
Keyword(s):  
Body Weight ◽  
Posterior Part ◽  
Slow Motion ◽  
Middle Part ◽  
The Body ◽  
Vertical Force ◽  
Aerodynamic Forces ◽  
Locust Flight ◽  
Lift And Drag ◽  
Wing Stroke

A proper understanding of how locusts fly must be based upon knowledge of how the wings are moved. A desert locust was suspended from a balance and placed in an air stream so that it flew under nearly the same conditions as during natural forward flight. Four stroboscopic slow-motion films were selected for measurement. The movements of the wings, i.e. their positions, velocities and accelerations, were then calculated in sufficient detail to show how these quantities vary with time during one complete wing stroke. The aerodynamic lift and drag of the entire natural wing were measured in a wind tunnel with the wing arranged in different positions relative to the flow. By placing it in the boundary layer of the tunnel, the wind speed was graded from tip to base in approximately the same way as during the actual flight. There is therefore no error due to scale effect or to the induced drag. In most respects the wings resemble ordinary, slightly cambered airfoils. Their characteristics are given as polar diagrams. The kinematic and aerodynamic analyses make it possible to calculate the forces which act upon the locust at any instant of time. It is here necessary to presuppose that the non-stationary flight situations are essentially similar to a sequence of stationary situations. For locusts, this presupposition is justified: (i) from theoretical estimates of the quantitative effect of non-stationary flow; and (ii) from control measurements of the average thrust and lift produced during flight. It was found that the calculated vertical force, when averaged over an entire wing stroke, equalled the average reduction in body weight, as measured directly on the flight balance. Similarly, the average thrust of the wings corresponded to the drag of the body. The analysis shows how the aerodynamic forces vary during the wing stroke. The hindwings are responsible for about 70 % of the total lift and thrust. About 80 % of the lift is produced during the downstroke. During flight at normal lift the angles of attack (middle part of wing) are small during the upstroke and vary between 10 and 15° during the downstroke. When the lift was larger or smaller than the body weight these figures increased or decreased respectively. The forewings are peculiar in two ways: (i) during the middle part of the downstroke a true flap (the vannus) is put into action; (ii) during the upstroke the proximal part has a Z-shaped cross-section and gives but little lift and drag. The hindwings are characteristic in that the posterior part (vannus) is flexible and becomes moulded by the wind, increasing the angle of attack at which stalling occurs to about 25°. Since both the movements of the wings relative to the body and the aerodynamic forces are known at any instant, the exchange of power with the surrounding air can be calculated. The moments of inertia of the wing mass being known, the power for accelerating the wings can also be estimated. The sum of these contributions is the power which passes the wing fulcrum; this estimate is used in a later paper (part IX) where the energetics of flight is discussed in detail. The diagrams are correct to scale. The restriction of freedom caused by the suspension is discussed, together with the possible errors of a stationary analysis.

Effects of Fatigue on Running Mechanics: Spring-Mass Behavior in Recreational Runners After 60 Seconds of Countermovement Jumps

2015 ◽  
Vol 31 (6) ◽  
pp. 445-451 ◽  
Author(s):  
Gabriela Fischer ◽  
Jorge L.L. Storniolo ◽  
Leonardo A. Peyré-Tartaruga
Keyword(s):  
Center Of Mass ◽  
Force Plate ◽  
Vertical Displacement ◽  
Step Length ◽  
Vertical Force ◽  
Step Frequency ◽  
Mass Model ◽  
Vertical Stiffness ◽  
Recreational Runners ◽  
Running Mechanics

The purpose of this study was to investigate the effects of acute fatigue on spring-mass model (SMM) parameters among recreational runners at different speeds. Eleven participants (5 males and 6 females) performed running trials at slower, self-selected, and faster speeds on an indoor track before and after performing a fatigue protocol (60 s of countermovement jumps). Maximal vertical force (Fmax), impact peak force (Fpeak), loading rate (LR), contact time (Tc), aerial time (Ta), step frequency (SF), step length (SL), maximal vertical displacement of the center of mass (ΔZ), vertical stiffness (Kvert), and leg work (Wleg) were measured using a force plate integrated into the track. A significant reduction (–43.1 ± 8.6%; P < .05) in mechanical power during jumps indicated that the subjects became fatigued. The results showed that under fatigue conditions, the runners adjusted their running mechanics at slower (≈2.7 ms–1; ΔZ –12% and SF +3.9%; P < .05), self-selected (≈3.3 ms–1; SF +3%, SL –6.8%, Ta –16%, and Fmax –3.3%; P < .05), and faster (≈3.6 ms–1 SL –6.9%, Ta –14% and Fpeak –9.8%; P < .05) speeds without significantly altering Kvert (P > .05). During constant running, the previous 60 s of maximal vertical jumps induced mechanical adjustments in the spatiotemporal parameters without altering Kvert.

scholarly journals Energetically optimal running requires torques about the centre of mass

2012 ◽  
Vol 9 (73) ◽  
pp. 2011-2015 ◽  
Author(s):  
James R. Usherwood ◽  
Tatjana Y. Hubel
Keyword(s):  
Large Body ◽  
The Body ◽  
Moment Of Inertia ◽  
Mechanical Work ◽  
Vertical Force ◽  
Centre Of Mass ◽  
Pitch Moment ◽  
Tail Structure ◽  
Reaction Forces ◽  
Long Head

Bipedal animals experience ground reaction forces (GRFs) that pass close to the centre of mass (CoM) throughout stance, first decelerating the body, then re-accelerating it during the second half of stance. This results in fluctuations in kinetic energy, requiring mechanical work from the muscles. However, here we show analytically that, in extreme cases (with a very large body pitch moment of inertia), continuous alignment of the GRF through the CoM requires greater mechanical work than a maintained vertical force; we show numerically that GRFs passing between CoM and vertical throughout stance are energetically favourable under realistic conditions; and demonstrate that the magnitude, if not the precise form, of actual CoM-torque profiles in running is broadly consistent with simple mechanical work minimization for humans with appropriate pitch moment of inertia. While the potential energetic savings of CoM-torque support strategies are small (a few per cent) over the range of human running, their importance increases dramatically at high speeds and stance angles. Fast, compliant runners or hoppers would benefit considerably from GRFs more vertical than the zero-CoM-torque strategy, especially with bodies of high pitch moment of inertia—suggesting a novel advantage to kangaroos of their peculiar long-head/long-tail structure.

scholarly journals Improving the Stability of the Passenger Vehicle by Using an Active Stabilizer Bar Controlled by the Fuzzy Method

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Tuan Anh Nguyen
Keyword(s):  
High Speed ◽  
Control Method ◽  
Spatial Dynamics ◽  
The Body ◽  
Vertical Force ◽  
Dynamics Model ◽  
Track Dynamics ◽  
The Difference ◽  
Lift Off ◽  
The Stability

The rollover phenomenon is a particularly dangerous problem. This phenomenon occurs when the driver travels at high speed and suddenly steers. Under the influence of centrifugal force, the body vehicle will be tilted and cause the wheels to lift off the road. To solve this problem, the method of using an active stabilizer bar has been proposed. The active stabilizer bar is controlled automatically by a previously designed controller. The performance of the active stabilizer bar depends on the selected control method. Previous research often only used a half-car dynamics model combined with a linear single-track dynamics model to simulate the vehicle’s oscillation. In addition, most of the research focuses only on the use of linear control methods for the active stabilizer bar. Therefore, the performance of the stabilizer bar is not guaranteed. This paper focuses on establishing the model of spatial dynamics combined with the nonlinear double-track dynamics model that fully describes the vehicle’s oscillation most accurately. Besides, the fuzzy control method is proposed to control the operation of the hydraulic stabilizer bar. This is a completely novel model, and it is suitable for the actual traveling conditions of the vehicle. Also, simulations are done based on different scenarios. The results of the paper showed that the values of the roll angle, the difference in the vertical force at the wheels, and the displacement of the unsprung mass were significantly reduced when the vehicle used the active stabilizer bar, which is controlled by an intelligent control method. Therefore, the stability and safety of the vehicle have been guaranteed. This result will be the basis for performing other more complex research in the future.

scholarly journals Combining wearable sensor signals, machine learning and biomechanics to estimate tibial bone force and damage during running

2020 ◽  
Author(s):  
Emily Matijevich ◽  
Leon R. Scott ◽  
Peter Volgyesi ◽  
Kendall H. Derry ◽  
Karl Zelik
Keyword(s):  
Machine Learning ◽  
Injury Risk ◽  
Wearable Sensors ◽  
Reaction Force ◽  
The Body ◽  
Machine Learning Algorithms ◽  
Peak Force ◽  
Tibial Bone ◽  
Bone Damage ◽  
Damage Estimates

There are tremendous opportunities to advance science, clinical care, sports performance, and societal health if we are able to develop tools for monitoring musculoskeletal loading (e.g., forces on bones or muscles) outside the lab. While wearable sensors enable non-invasive monitoring of human movement in applied situations, current commercial wearables do not estimate tissue-level loading on structures inside the body. Here we explore the feasibility of using wearable sensors to estimate tibial bone force during running. First, we used lab-based data and musculoskeletal modeling to estimate tibial force for ten participants running across a range of speeds and slopes. Next, we converted lab-based data to signals feasibly measured with wearables (inertial measurement units on the foot and shank, and a pressure-insole) and used these data to develop two multi-sensor algo rithms for estimating peak tibial force: one physics-based and one machine learning. Additionally, to reflect current running wearables that utilize foot impact metrics to infer musculoskeletal loading or injury risk, we estimated tibial force using the ground reaction force vertical average loading rate (VALR). Using VALR to estimate peak tibial force resulted in a mean absolute percent error of 9.9%, which was no more accurate than a theoretical step counter that assumed the same peak force for every running step. Our physics-based algorithm reduced error to 5.2%, and our machine learning algorithm reduced error to 2.6%. Further, to gain insights into how force estimation accuracy relates to overuse injury risk, we computed bone damage expected due to peak force. We found that modest errors in tibial force translated into large errors in bone damage estimates. For example, a 9.9% error in tibial force using VALR translated into 104% error in bone damage estimates. Encouragingly, the physics-based and machine learning algorithms reduced damage errors to 41% and 18%, respectively. This study highlights the exciting potential to combine wearables, musculoskeletal biomechanics and machine learning to develop more accurate tools for monitoring musculoskeletal loading in applied situations.

scholarly journals Mechanical Force System of Double Key Loop With Finite Element Analysis 

2020 ◽  
Author(s):  
Jiali Liu ◽  
Duanqiang Zhang ◽  
Linyu Xu ◽  
Senxin Cai ◽  
Jinquan Guo ◽  
...  
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Vertical Force ◽  
Element Analysis ◽  
Force System ◽  
Anterior Teeth ◽  
Lower Magnitude ◽  
Type 3

Abstract Background: The mechanics of double key loop (DKL) was not well defined and this finite element study was designed to explore its force system.Methods: Simplified 3-dimensional finite element model of single and double key loops with archwire between lateral incisor and second premolar was established in Ansys Workbench. Activation in Type-1 (retraction at distal end), Type-2 (retraction at distal key) and Type-3 (Type-2 plus ligation between keys) were simulated. The vertical force, load/deflection ratio and moment/force ratio of stainless steel and TMA loops were calculated and compared.Results: Double key loop generated about 40% force of single key loop. Type-2 loading of DKL showed higher L/D ratio than in Type-1 loading with similar M/F ratio. Type-3 loading of DKL showed the highest M/F ratio with similar L/D ratio as single key loop. The M/F ratio in Type-3 loading increased with the decrease of retraction force. DKL of TMA produced about 40% of force and moment compared to those of SS in all loading types. When activated at equal distance bellow 1mm, the M/F ratio of SS and TMA DKL with equal preactivation angle were almost the same. Conclusion: M/F ratio on anterior teeth increases with preactivation angle and deactivation of DKL. M/F ratio at certain distance of activation depends mainly on preactivation angle instead of wire material. TMA is recommended as substitute of SS in DKL for lower magnitude of force.

scholarly journals Mechanical demands of the two-handed hardstyle kettlebell swing in novice older adults: an exploratory profile

2021 ◽  
Author(s):  
Neil J. Meigh ◽  
Wayne A. Hing ◽  
Ben Schram ◽  
Justin W.L. Keogh
Keyword(s):  
Older Adults ◽  
Community Dwelling ◽  
Peak Force ◽  
Vertical Force ◽  
Physically Active ◽  
Paired Samples ◽  
Significant Difference ◽  
Exercise Effect ◽  
Males And Females ◽  
Force Time

Background: Understanding the mechanical demands of an exercise and its technique increases clinical confidence when assessing the benefits and risks of a prescribed exercise. This study profiles the mechanical demands of the hardstyle kettlebell swing in novice older adults and compares peak force with kettlebell deadlifts. These data will help therapists choose the most appropriate kettlebell exercise (deadlifts or swings) and weights for progressing kettlebell training for older adults. Methods: Thirty-five insufficiently physically active, community-dwelling males and females (59-79 years) were recruited. Two-handed hardstyle swings were performed with 8-16 kg and deadlifts with 8-24 kg and 8-32 kg for females and males, respectively. Ground reaction forces (GRFs) were obtained from a floor-mounted force platform. Force-time curves (FTCs), peak force, forward force relative to vertical force, rate of force development (RFD) and swing cadence were investigated. Peak GRF was compared by exercise and by sex, with RFD reported for swings. Results: For kettlebells weights up to 16 kg, paired samples T-tests show a large exercise effect (δ > 1.4) with peak force significantly higher for swings than deadlifts. Data shows: (i) significantly higher peak force during swings than deadlifts (δ = 1.77), reaching 4.5 (1.0) N.kg-1, (ii) peak force during an 8 kg swing was greater than a 32kg deadlift, (iii) no significant difference in normalised peak force between males and females performing kettlebell swings, but a moderately large effect size during deadlifts (males > females, δ = 0.69), (iv) mean RFD of 19.9 (4.7) N.s-1.kg-1 with a very weak, positive correlation with kettlebell weight (y = 14.4 + 0.32𝑥), and trivial or non-significant effect of sex, (v) mean forward force equal to 5.5% of vertical force during swings, increasing from 3.8 (1.6) % with 8 kg to 1.7 (2.6) % with 16kg. Conclusion: Where GRF is a therapeutic target, kettlebell swings with an 8 kg kettlebell could have similar effects to much heavier deadlifts (>24 kg). Compared to kettlebell deadlifts, the performance of kettlebell swings may be an easier, more convenient, and more appealing option for older adults in a primary care setting or at home. The hardstyle swing with 8 kg has the potential to produce double bodyweight in GRF and might be a suitable exercise to improve lower limb RFD and physical function in older adults. Findings from this study were used to inform the BELL Trial, a pragmatic clinical trial of kettlebell training with older adults. www.anzctr.org.au ACTRN12619001177145.

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