Search Results

You are looking at 1 - 10 of 193 items for :

  • "sensitivity analysis" x
  • Refine by Access: All Content x
Clear All
Restricted access

Estimating the Maximum Isometric Force-Generating Capacity of Wheelchair Racing Athletes for Simulation Purposes

Amy R. Lewis, William S.P. Robertson, Elissa J. Phillips, Paul N. Grimshaw, and Marc Portus

optimal force chosen in this research was established from performing a sensitivity analysis on the influence of the optimal force value on outputs (using values of 10, 50, 75, 100, 150, 200, and 1000 N). Generalized forces at the joint are calculated as follows: ∑ m = 1 n [ a m f ( F m 0 , l m , v m

Restricted access

Experimental Simulation of an Airborne Movement: Applicability of the Body Segment Parameter Estimation Methods

Young-Hoo Kwon

The purpose of this study was twofold: (a) to investigate the effect of the method of body segment parameter (BSP) estimation on the accuracy of the experimental simulation of a complex airborne movement; and (b) to assess the applicability of selected BSP estimation methods in the experimental simulation. It was hypothesized that different BSP estimation methods would provide different simulation results. A sensitivity analysis was performed to identify the BSP items and segments responsible for the inter-method differences in the simulation accuracy. The applicability of the estimation methods was assessed based on the simulation results and the number of anthropometric parameters required. Ten BSP estimation methods classified into 3 groups (4 cadaver-based, 4 gamma mass scanning-based, and 2 geometric) were employed in a series of experimental simulations based on 9 double-somersault-with-full-twist H-bar dismounts performed by 3 male college gymnasts. The simulated body orientation angles were compared with the corresponding observed orientation angles in computing the simulation errors. The inclination and twist simulation errors revealed significant (p < .05) differences among the BSP estimation groups and methods. It was concluded that: (a) the method of BSP estimation significantly affected the simulation accuracy, and more individualized BSP estimation methods generally provided more accurate simulation results; (b) the mass items, and the lower leg and thorax/ abdomen were more responsible for the intermethod differences in the simulation accuracy than other BSP items and segments, respectively; (c) the ratio methods and the simple regression methods were preferable in simulation of the somersaulting motion due to the fewer anthropometric parameters required; (d) the geometric models and the cadaver-based stepwise regression method were superior to the other methods in the simulation of the complex airborne motion with twist.

Restricted access

Using Monte Carlo Simulation to Propagate Processing Parameter Uncertainty to the Statistical Analyses of Biomechanical Trajectories

Todd C. Pataky

consideration is given to the biomechanical meaning of these results. The Figure  2 and 3 results represent a relatively straightforward sensitivity analysis wherein MC simulation iterations are completely independent. Other approaches to the problem of processing parameter uncertainty also exist. For

Restricted access

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

Matthew T.G. Pain and John H. Challis

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.

Restricted access

Material Property Sensitivity Analysis on Resonant Frequency Characteristics of the Human Spine

Li-Xin Guo, Zhao-Wen Wang, Yi-Min Zhang, Kim-Kheng Lee, Ee-Chon Teo, He Li, and Bang-Chun Wen

The aim of this study is to investigate the effect of material property changes in the spinal components on the resonant frequency characteristics of the human spine. Several investigations have reported the material property sensitivity of human spine under static loading conditions, but less research has been devoted to the material property sensitivity of spinal biomechanical characteristics under a vibration environment. A detailed three-dimensional finite element model of the human spine, T12– pelvis, was built and used to predict the influence of material property variation on the resonant frequencies of the human spine. The simulation results reveal that material properties of spinal components have obvious influences on the dynamic characteristics of the spine. The annulus ground substance is the dominant component affecting the vertical resonant frequencies of the spine. The percentage change of the resonant frequency relative to the basic condition was more than 20% if Young’s modulus of disc annulus is less than 1.5 MPa. The vertical resonant frequency may also decrease if Poisson’s ratio of nucleus pulposus of intervertebral disc decreases.

Restricted access

Effects of Exercise on Sleep in Older Adults: An Overview of Systematic Reviews and Meta-Analyses

Felipe Fank, Franciele da Silva Pereira, Leandro dos Santos, Marco Túlio de Mello, and Giovana Zarpellon Mazo

exercise on overall sleep quality revealed moderate heterogeneity ( I 2  = 37%). This outcome was considered the most important in the present overview since it was the most frequently explored by the primary studies. Thus, to explore the results of this variable more robust, sensitivity analysis was

Restricted access

Convergent Validity, Reliability, and Sensitivity of a Running Test to Monitor Neuromuscular Fatigue

Cédric Leduc, Jason Tee, Mathieu Lacome, Jonathon Weakley, Jeremy Cheradame, Carlos Ramirez, and Ben Jones

week reliability procedure was undertaken on sessions 2 and 3. Each session was preceded by 2 days of no lower body training; as such, a physiological and nonfatigued state was expected. The sensitivity analysis aimed to assess the ability of the different RLI to detect meaningful change over a typical

Restricted access

The Effect of Physical Activity Bout Patterns on Metabolic Syndrome Risk Factors in Youth: National Health and Nutrition Examination Survey 2003–2006

David A. White, Youngha Oh, and Erik A. Willis

. Not surprisingly, our sensitivity analysis revealed some differences in outcomes depending on which cut point and MET value for MVPA were applied, suggesting that not all MVPA cut points are the same and may provide different outcomes The Freedson/Saint-Maurice cut points also showed a significant

Restricted access

Cost-Utility of an Exercise Referral Scheme Versus Doing Nothing in Flemish Adults: Exploring the Impact of Key Assumptions

Amber Werbrouck, Masja Schmidt, Koen Putman, Steven Simoens, Nick Verhaeghe, and Lieven Annemans

regarding cost-effectiveness are not robust. Figure 3 (A) Probabilistic sensitivity analysis with 5000 iterations. The gray dots represent the probabilistic results; the black dot represents the deterministic result; the error bars show the 95% credibility interval. (B) Cost-effectiveness acceptability

Restricted access

Attributes, Trade-Offs and Choice: A Conjoint Analysis of Sport Management Programs

Gonzalo A. Bravo, Doyeon Won, and Mauricio Ferreira

Trade-offs in consumer choice become central to understanding how choice actually occurs. This study examines the trade-offs sport management students are willing to make in order to select the program of their choice. Sport management undergraduate students (N = 498) participated in a full-profile conjoint experiment asking them to rate 18 program-choice scenarios resulted from the factorial design of seven attributes and nineteen levels. Results at the aggregated level indicated that program environment was the most important attribute in choosing a sport management graduate program, followed by program reputation, graduate assistantship, cost/tuition, NCAA affiliation, program length, and location. Given these results, a sensitivity analysis illustrated that students were willing to make trade-offs among program characteristics, particularly pay more for a program with better reputation. Results from the current study are valuable and informative for sport management programs for setting market boundaries and selecting what to promote when advertising to attract prospective students.