January 4th, 2012 08:32pm
Nate
Summary:
This article reports on 20 subjects who walking on Mainline Ballast, Walking Ballast, and No Ballast. Measurement were taken using a motion capture system and two force plates to measure kinematics and kinetics as well as surface EMG. THey found that subjects walk slower and took shorter steps on the ballast surfaces. It is assumed this was an effort to be more cautious while walking on a irregular surface. It was also noted based on the results obtained from the EMG measurement that co-contraction increased. It is assumed that this was in order to increase the stability of the joints. This increase in co-contraction increased overall muscle activation. The potential result is an increase in localized muscle fatigue and and increase in the compressive for at these joints.
Reference:
Federal Railroad Administration. (2011). Joint Loading and Muscle Activity in the Lower Body While Walking on Ballast. U.S. Department of Transportation (pp. 1–4). Washington, DC. Retrieved from http://www.fra.dot.gov/rpd/downloads/RR_Joint_Loading_and_Muscle_Activity.pdf
May 23rd, 2011 11:25am
Nate
Summary:
This article came to some interesting and what I believe to be useful conclusions about the use of skin markers during motion analysis. By comparing skin marker set to a marker set using bone pins the following conclusions were made. Using skin markers motions other than flexion/extension at the knee produce substantial errors. When looking at markers at the Ankle Joint Complex (AJC) motions are less error prone. Thus skin markers can be used for plantar/dorsal flexion, inversion/eversion, or adduction/abduction motions.
The comment was made that significant challenges prevent the creation of a skin motion error reduction model. This is a result of the subject specific amount of adipose tissue and it mobility. Therefore when using skin markers the results should be interpreted with caution.
Reference:
Reinschmidt, C., van den Bogert, A. J., Lundberg, A., Nigg, B. M., Murphy, N., Stacoff, A., & Stano, A. (1997). Tibiofemoral and tibiocalcaneal motion during walking: external vs. skeletal markers. Gait and Posture, 6(2), 98-109. doi:10.1016/S0966-6362(97)01110-7
January 20th, 2011 04:51pm
Nate
This semester I am taking a Functional Anatomy class that includes dissection. To put it in the words of one of the people in lab “I think I have learned more in the last hour than I have in the last several months”. I had to agree that the hands on experience of actually seeing and touching brought a much greater understanding of how the muscles of the human body work together to produce motion. I am excited to see what the rest of the semester will bring.
January 10th, 2011 05:17pm
Nate
Today was the first day of Spring Semester 2011. This semester I will have three challenging classes that I am really looking forward to: Anatomy, Human Movement, and a System Safety classes. I also have quite a bit to do to get caught up on my research. I am looking forward to it and hope to post often on the progress that I am able to make each week.
December 11th, 2010 04:32pm
Nate
Yet another semester has come and almost gone, all but the 40% of your grade exam that comes at the end. It has been a long time since I have had a cumulative final but this semester I have one it is going to be interesting figuring out how to cover all the material. I am sure it is going to just take hours of dedicated study to push through and hope that something sticks.
March 17th, 2009 03:16am
Nate
Ground Reaction Forces During Human Locomotion on Railroad Ballast
Journal of Applied Biomechanics, 207, 23, 322-329 (link)
Wade, Redfern
Rationale:
The literature currently provides few if any discussions regarding the dynamics of locomotion on surfaces that are either rocky or uneven. Not all occupational settings or the activities of daily living involve level, smooth firm surfaces, and a large percentage of work-related injuries are associated with work that is done on altered surfaces. In 2004 the Railroad reported that walking was the cause of 14.9% and 19.3% of all railroad worker injuries and days absent, respectively.
Hypothesis:
The purpose of this study was to determine the feasibility of using force plates to measure accurately the ground reaction forces (GRF) during gait on ballast surfaces.
Methods:
1. Used a known magnitude of vertical and shear loads at the surface of the ballast to verify that the magnitude of forces being applied at the force plate was equivalent
2. Comparisons of the magnitude and timing of the GRF data during locomotion on a level surface with GRF data of locomotion on ballast of varying depths wer made
3. n = 5 ( four male, one female – age: 22-25 mean 23.6 ± 1.4)
Exclusion Criteria:
- A history of or current neurological or orthopedic disease
- Any difficulty that would impede normal walking
- Any cardiopulmonary condition
- Osteoporosis
- Balance or dizziness problems
- Pregnancy
Setup:
- Each subject was given the same brand and model of polyvinyl chloride hard-soled shoes with new socks.
- 5 m wide/ 8.5m long vinyl tile walkway GRF measured at 1,080 Hz.
- Ballast surface conditions consist of 1 1/4in. marble ballast covering the walkway surface at two depths of approximately 2.5 in. or 4 in.
- Indoor outdoor carpet placed between ballast and vinyl flooring to act as a binder of the ballast to adhere to the floor surface with minimal movement between teh ballast and the floor surface.
- Statics loads of 2.114. N and 511.5 N placed at five locations on each force plate.
- Then the static load was pulled horizontally to provide shear force to the surface of the ballast until movement was initiated and continued following the initiation of movement until exiting the force plate.
- Human Gait:
- Five subjects walked at self selected pace on the three surface types, vinly tile, 63.5 mm ballast, 101.6 mm ballast
- Total of 25 trials performed with in each condition of each subject.
- 20 N threshold set to determine heal strike and toe off.
- GRF data were filtered using a 4th order zero lag butterworth digital low-pass filter with a cutoff frequency set at 25 hz.
- GRF peak values normalized to body mass
- Anterior-posterior shear were recorded as the maximum from 0 to 50% stance and 5 to 100 % stance
-Medial-lateral shear was recorded as the maximum and minimum from 0 to 100% stance
-Significance was set at alpha level of p ≤ .05
Results:
Shear forces (AP and ML) measured by the force plate generated by pulling horizontally on the two static loads showed slight systematic difference, preceding and following the initiation of movement, from the load cell measurements between 63.5 mm and 101.6 mm ballast conditions; however, these differences were not statistically significant.
The three-component part GRF time history curves during walking on the no-ballast condition, the 63.5 mm ballast condition, and the 101.6 mm ballast condition showed very similar GRF time history curves and nonsignificant difference in shear and normal forces.
Discussion:
Tee study indicates that a traditional 6-degree-of-freedom force plate system embedded in a walkway can provide accurate GRF measures of individuals walking over rough, uneven surfaces, specifically ballast.
Strengths:
Weaknesses:
This method is only truly validated for loading in the approximate center of the force plates.
February 25th, 2009 02:11pm
Nate
The compiler treats all letters typed in math mode as variables so it puts them in italics and ignores all spaces. In order to type text while in math mode you must use one of the following commands.
In addition to this I found that the compiler doesn’t treat the text in super/subscript correctly. So in order to adjust the font size I had to additionally include the \scriptsize command. This reduced the font size to match the other text in the super/subscript.
Example:
References:
Getting Started with LaTeX – David R. Wilkins
February 18th, 2009 08:23pm
Nate
I have had a really hard time making the time to sit down and post thoughts related to what I am doing toward my major. That is hopefully until today. I have found a pretty slick little app called blogo that I am hoping will make the process of post to this blog a lot easier. I guess only time will tell.
