Comment on “Soft-tissue contributions to impact forces simulated using a four-segment wobbling mass model of forefoot-heel landings”

Rotational falls are a serious cause of injury and death to horse and rider, particularly in the cross-country phase of eventing. The forces involved when horses galloping cross-country strike an immovable fence are unknown. The objective of this study was to mathematically model those forces using existing kinematic data measured from jumping horses. Data were obtained from published research using motion capture to measure mechanics about the center of gravity of the jumping horse at take-off. A convenience method from video evidence of rotational falls was used to estimate time of collision (Δt). A point mass model using equations of impulse-momentum and incorporating key variables was systematically implemented in Matlab (r2016a). The mean collision time (Δt=0.79s) produced horizontal, vertical, and resultant impact forces of 8,580, 8,245, and 12,158 N, respectively. Reference curves of impact forces were created for ranges of relevant input variables including collision time. Proportional relationships showed that shorter impact duration led to higher magnitude of force transfer between horse and obstacle. This study presents a preliminary range of collision forces based on a simplified model and numerous assumptions related to input variables. Future research should work to build upon these estimates through more complex modelling and data collection to enhance applicability for the design of cross-country safety devices.

Download Full-text

Effect of Surrogate Surface Compliance on the Measured Stiffness of Snowboarding Wrist Protectors

Proceedings ◽

10.3390/proceedings2020049084 ◽

2020 ◽

Vol 49 (1) ◽

pp. 84

Author(s):

Gemma Leslie ◽

Weizhuo Wang ◽

Keith Winwood ◽

Chris Liauw ◽

Nick Hamilton ◽

...

Keyword(s):

Soft Tissue ◽

Bending Stiffness ◽

Bend Test ◽

Effective Stiffness ◽

Wrist Injuries ◽

Wrist Extension ◽

Surrogate Surface ◽

Impact Forces ◽

Compliant Layer ◽

Torque Values

Wrist injuries have been reported to account for 35%–45% of snowboarding injuries. Snowboarding wrist protectors are designed to limit impact forces and prevent wrist hyperextension. The absence of a standard for snowboarding wrist protectors makes it hard to identify models offering an adequate level of protection. Wrist surrogates are well suited for testing and benchmarking wrist protectors. This study investigated the effect of introducing a soft tissue simulant onto an otherwise stiff wrist surrogate on the bending stiffness of snowboarding wrist protectors. A compliant surrogate (stiff core and 3 mm thick silicone layer) and a comparable stiff surrogate were fabricated. Two snowboarding wrist protectors were tested on each surrogate, under three strapping conditions, following a bend test to ~80° wrist extension. The introduction of a compliant layer to the wrist surrogate gave higher torque values for a given wrist extension angle, increasing protector effective stiffness, relative to a rigid surrogate.

Download Full-text

Component Inertia Modeling of Segmental Wobbling and Rigid Masses

Journal of Applied Biomechanics ◽

10.1123/jab.22.2.148 ◽

2006 ◽

Vol 22 (2) ◽

pp. 148-154 ◽

Cited By ~ 14

Author(s):

Marianne J.R. Gittoes ◽

David G. Kerwin

Keyword(s):

Soft Tissue ◽

Maximum Error ◽

The Body ◽

Whole Body ◽

Uniform Density ◽

Mass Model ◽

Novel Approach ◽

Geometric Solids ◽

Inertia Parameters ◽

Inertia Model

A modification to an existing mathematical model is described, which permits the determination of subject-specific inertia parameters for wobbling and rigid masses of female body segments. The model comprises segment-specific soft tissue, bone, and lung components. A total of 59 geometric solids (40 soft tissue, 17 bone, 2 lung) were used to represent the body components. Ninety-five anthropometric measurements were collected from 7 female participants and were used to develop and evaluate the model. The success of the model is evaluated using predicted mass and mass distribution. The overall absolute accuracy in predicted whole body mass was better than 3.0%, with a maximum error of 4.9%. The appropriateness of the cadaver-based density values used in the model is addressed and the accuracy of the component inertia model in relation to uniform density models is discussed. The model offers a novel approach for determining component inertia parameters, which have been used successfully in a wobbling mass model to produce realistic kinetic analyses of drop-landings.

Download Full-text

Interactive Effects of Mass Proportions and Coupling Properties on External Loading in Simulated Forefoot Impact Landings

Journal of Applied Biomechanics ◽

10.1123/jab.25.3.238 ◽

2009 ◽

Vol 25 (3) ◽

pp. 238-246 ◽

Cited By ~ 6

Author(s):

Marianne J. R. Gittoes ◽

David G. Kerwin

Keyword(s):

Interactive Effects ◽

Upper Body ◽

External Loading ◽

Mass Model ◽

Mass Proportion ◽

Rigid Mass ◽

Coupling Stiffness ◽

The Individual ◽

Stiffness And Damping ◽

Wobbling Mass

This study aimed to gain insight into the individual and interactive effects of segmental mass proportions and coupling properties on external loading in simulated forefoot landings. An evaluated four-segment wobbling mass model replicated forefoot drop landings (height: 0.46 m) performed by two subjects. A comparison of the peak impact forces (GFzmax) produced during the evaluated landing and further simulated landings performed using modified (±5% perturbation) mass proportions and coupling properties was made. Independent segmental mass proportion changes, particularly in the upper body, produced a prominent change in GFzmax of up to 0.32 bodyweight (BW) whereas independent mass coupling stiffness and damping alterations had less effect on GFzmax (change in GFzmax of up to 0.18 BW). When combining rigid mass proportion reductions with damping modifications, an additional GFzmax attenuation of up to 0.13 BW was produced. An individual may be predisposed to high loading and traumatic and overuse injury during forefoot landings owing to their inherent inertia profile. Subject-specific neuromuscular modifications to mass coupling properties may not be beneficial in overriding the increased forces associated with larger rigid mass proportions.

Download Full-text

The Role of Footwear on Impact Forces and Soft Tissue Vibrations during Active and Passive Landings

IFMBE Proceedings - 6th World Congress of Biomechanics (WCB 2010). August 1-6, 2010 Singapore ◽

10.1007/978-3-642-14515-5_41 ◽

2010 ◽

pp. 159-162 ◽

Cited By ~ 1

Author(s):

W. J. Fu ◽

Y. Liu ◽

M. F. Ruan ◽

S. T. Wei

Keyword(s):

Soft Tissue ◽

Impact Forces

Download Full-text

Wobbling Mass Influence on Impact Ground Reaction Forces: A Simulation Model Sensitivity Analysis

Journal of Applied Biomechanics ◽

10.1123/jab.20.3.309 ◽

2004 ◽

Vol 20 (3) ◽

pp. 309-316 ◽

Cited By ~ 22

Author(s):

Matthew T.G. Pain ◽

John H. Challis

Keyword(s):

Ground Reaction Force ◽

Reaction Force ◽

Joint Torque ◽

Model Parameters ◽

Vertical Ground Reaction Force ◽

Mass Model ◽

Heel Pad ◽

Precise Knowledge ◽

Vertical Ground ◽

Wobbling Mass

Wobbling mass models have been used to gain insight into joint loading during impacts. This study investigated the sensitivity of a wobbling mass model of landing from a drop to the model's parameters. A 2-D wobbling mass model was developed. Three rigid linked segments designed to represent the skeleton each had a second mass attached to them, via two translational nonlinear spring dampers, representing the soft tissue. Model parameters were systematically varied one at a time and the effect this had on the peak vertical ground reaction force and segment kinematics was examined. Model output showed low sensitivity to most model parameters but was sensitive to the timing of joint torque initiation. Varying the heel pad stiffness in the range of stiffness values reported in the literature had the largest influence on peak vertical ground reaction force. The analysis indicated that the more proximal body segments had a lower influence on peak vertical ground reaction force per unit mass than the segments nearer the contact point. Model simulations were relatively insensitive to variations in the properties of the connection between wobbling masses and the skeleton. If the goal is to examine the effects of wobbling mass on the system, this insensitivity is an advantage, with the proviso that estimates for the other model parameters and joint torque activation timings lie in a realistic range. If precise knowledge about the motion of the wobbling mass is of interest, however, this calls for more experimental work to precisely determine these model parameters.

Download Full-text