دراسة : العلاقة بين طول الذراع ومشط القدم/Foot and Forearm Comparison

Foot and Forearm Comparison
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Wed, 03/03/2010 - 00:18 — Bethany CalabreseComparison of the Foot and Forearm Length in Humans
Abstract
The human forearm length is believed to be equal to the human foot length in the same individual. In order to test this belief, an experiment was performed in order to compare the lengths of the right forearm and the left foot of the same human. A detailed methods section was composed so that another person could read it and perform the same tasks. A reader, named Dan, was assigned to perform the methods and construct an identical figure as the original one produced. In comparing the two figures, 24 differences were found between them. The controls in the experiment and the detail of the methods described were responsible for the similarities between the two figures. By adding more controls to the experiment, as well as being even more specific in the methods description, a better figure could be produced by the reader. Some of the differences were not only due to inadequate numbers of controls and insufficient detail in the writing, but were also a result of the reader incorrectly following the methods described. Although some differences existed between the two figures produced in the experiment, the figures were successful in proving that forearm length is equal to foot length in humans.
Introduction
The human body has always been of great interest to me. While speaking with a group of friends, one of them mentioned that the human forearm should be equal in length to the human foot. Therefore, I decided to look further into this statement and test it out using my own arm and foot. The length of the forearm can be obtained by measuring the distance from the wrist to the elbow. The length of the foot is measured from the heal to the tip of the furthest extending toe. By taking measurements of these two body parts, my goal was to test this belief for legitimacy.
This experiment involves taking pictures of a living organism, specifically a human (Homo sapien). The body shape in humans can vary greatly. Humans grow throughout development and are constantly changing in shape and size. While our bodies develop, the lengths of our arms and feet progressively get longer until we grow out of adolescence. Therefore, comparison of a human forearm to a human foot is an example of comparing two living body parts of a living organism.
The lengths of the forearm and foot are dependant upon an individual's growth pattern. Many adolescents grow at different rates, with a most notable difference between boys and girls. During adolescence, growth may not be as uniform as one may think. This could lead to different foot and forearm lengths at different stages of development. One stable length would be common between these two body structures once adulthood is met (Cameron et al. 1982). It is also important to note that the human forearm and foot have other similarities besides length. For example, circulatory similarities between the forearm and foot have allowed for such procedures as bilateral foot construction using radial forearm flaps to be successfully completed (Hallock 1987). Therefore these two body structures can be easily compared and used to help each other when needed.
Considering the fact that my methods were going to be followed by another person, I attempted to choose
an interesting topic that anyone could relate to. I also wanted to perform an experiment that could be replicated without much difficulty. Therefore, I set up the experiment so that it could be completed in any place as long as the correct backdrop was used. I also chose common materials that were easily attainable.
Methods
First the right forearm was measured. A black marker was used to make a 2cm line across the inside of the right wrist. Another 2cm line was made along the crease of the forearm directly opposite the elbow of the right arm. The right arm was then extended straight out from the body cavity with the palm facing forward and fingers extended. This was done in front of a white poster board. The ruler was then held by the thumb and index finger of the left hand along the center of the inside of the right forearm with the 0cm position over the mark on the wrist and the other end of the ruler extending over the elbow crease. A picture was taken of this setup (and later cropped so that the area from the tips of the fingers to the bicep was contained in the image and the thumb was facing up). The length of the forearm was then noted by using the ruler and the mark along the elbow crease.
Next, the left foot was measured. This was done by placing the white poster board on the floor and putting the bare foot on top of it while sitting in a chair. The ruler was then placed along the inside of the left foot (to the right of the left foot) so that it was almost touching the foot. The 0cm position of the ruler was aligned with the very back of the heal and the opposite end extended past the toes. While keeping the foot in this position and then pulling the knee to the left, a picture was taken from directly above the foot and ruler (and the picture of this setup was later cropped to contain an image with the length just a little longer than the ruler and the width a little wider than the foot and ruler combined). The length of the foot was then noted by using the ruler and the furthest extending toe.
Lastly, the length of the right forearm was compared to the length of the left foot. The left foot was traced on a piece of white copy paper with a black marker. The marker and ruler were then used to draw a straight line from the back of the heal to the end of the longest toe. Two dots were drawn where the ends of the line met the end of the heal and the end of the toe. The poster board was then placed on a table and the foot tracing was placed on top of it. The right forearm was then placed next to the tracing (about 2cm to the right of the big toe) with the palm facing upwards. The fingers were extended, the wrist was positioned next to the end where the traced toes were and the elbow crease was positioned next to the heal. The mark on the wrist was then aligned with the dot on the toes of the tracing and the mark on the elbow crease was aligned with the mark on the heal of the tracing. A picture was taken from directly above this setup (and was later cropped so that the area from the center of the palm to the bicep was in view). The lengths of both the left foot and right arm were compared with each other in this position.
The cropped pictures were then formed into a composite figure using Inkscape. All pictures and captions had minimal white space between them. The picture of the right arm being measured was placed along the top of the page with the fingers on the left side of the page and the bicep on the right side of the page. This picture was labeled a.
The picture of the left foot being measured was then placed under the picture of the right arm being measured and on the left side of the page. The toes were pointing towards the top of the page. It was labeled b.
The picture of the foot and arm comparison was then placed under the picture of the right arm being measured and on the right side of the page. It was directly next to the picture of the left foot being measured and a similar size as it also. The toes and fingers were pointing towards the top of the page. It was labeled c.
The labels of each picture were placed in the top left corner of each with no background so that the image could be seen behind the letters. The letters were Arial and size 40 font. A caption was then placed under pictures b and c that ran the width of the bottom of these two pictures. The caption stated "Figure 1: A study comparing the relationship between arm and foot length was pictorially depicted using the images of (a) the right arm measurement, (b) the left foot measurement, and (c) a comparison of the right arm and left foot". The font of this text was Arial and size 12.
Results
Dan followed my methods in order to create an identical figure. He did so without seeing my original figure. In examining the two figures, 24 total differences were observed between them. The most prominent difference was the fact that a different arm and foot was used in the images of my figure than in the images of Dan's figure. This can be determined by the differences in forearm and foot length, finger and toe length, and the overall shape of the arm and foot in each figure. The toenails in my figure are painted pink, while the toenails in Dan's figure are not painted. The right ring finger in my figure is wearing a ring, while the right ring finger in Dan's figure does not have a ring on it. Clothing is not seen in my figure, but the white shirtsleeve and gray pant leg of Dan's clothes can be seen in his figure. A different ruler is also used in the two images. My image contains a wider ruler with lettering in a different font and size than Dan's. The brands on the rulers are also different. The background in the two figures differs as well. The background in my figure is a dull white poster board, whereas Dan's is a shinier white poster board.
Four labeling differences were found between the two figures. My figure contains lowercase letters and his figure contains capital letters. The letters in my figure are closer to the left and top sides of the individual images than Dan's figure. My figure also contains a caption along the bottom of the lower two images, whereas his does not contain a caption. The spacing between the images is larger in my figure than in Dan's figure.
There are five differences in image a. The ruler is being held by its center in my image and by its end in his. The ruler is also held along the inside of the right arm in my image, but below the right arm in Dan's image. My fingers are more spread out, while Dan's are closer together. The image is also cropped differently in each figure. My image contains much less white space around the right arm, half of my left hand, and a short area of my right bicep. Dan's image contains much more white space, his entire left hand, half of his left forearm, and a longer portion of his left bicep. My image does not have a glare on the poster board, but Dan's image does contain a glare above the right forearm.
Image b and c are reversed in the two figures. Image b in my figure contains a similar picture to image c in Dan's figure, whereas image c in my figure contains a similar picture to image b in Dan's figure.

When comparing image b in my figure with image c in Dan's figure, three differences were found. A glare can be seen in my figure on the ruler at the three-inch mark. Dan's image contains a glare directly next to the very center of the inside of his left foot. My figure contains a reflection of a lamp on the top end of the ruler and Dan's image does not have a reflection in it. More of the poster's white space is seen in my image than in his also.
When comparing image c in my figure to image b in Dan's figure, five differences were found. The images are cropped differently in each figure. My image contains a small portion of white space, the half of my right palm closest to the right forearm, and a short area of my right bicep. Dan's figure contains a large amount of white space, his entire right hand, and his entire right bicep all the way to his shoulder. My image does not contain any portion of my head, but Dan's image contains a small portion of his head in the top right corner. My image also has no white space besides the poster board in the background, but Dan's image contains a four-inch section of white concrete wall along the bottom of the image, below the white poster board. The direction of the arm is different between the two images also. My image contains the palm at the top and the bicep at the bottom, whereas Dan's image contains the palm on the left side and the bicep on the right side. A shadow can also be seen to the right side of the right arm in my image, but no shadow is seen in his image.
Discussion
There were five controls in this experiment in order to receive a similar outcome within the figures. This included the fact that the arm and foot were from a human being so that the overall shapes of each were similar. The left foot and right forearm were used throughout the images as well. A white poster board was used as the background. A black marker was used to make the markings on the right forearm and to trace the left foot. The ruler contained measurements in centimeters.
In order to improve the outcome of this experiment, more factors could be controlled. For example, the arm and foot of a specific human could be measured. In doing so, the arm and foot would be the same in both figures. The camera used could also be specified so that the same one was used to take the pictures for both images. For example, the camera from the Biology Computer Resource Center at Umass Amherst could be used so that the images would be of the same quality and focus. The pictures could also be taken within a certain area of a specific room, such as the side lab table of the Biology Computer Resource Center. This would cause the lighting to be the same and glares and reflections to be similar as well.
The detail of the methods section could also be improved to yield better results. More specificity could be used to describe the dimensions of cropping the pictures and the actual amount of area of the objects within pictures. Better explanations of font use, size of the letters, and dimensions of letter placement would also allow the reader to more accurately construct the figure.
Some of the 24 differences found between the figures were due to incorrect following of the methods described. For example, the methods section states, "the picture of the left foot being measured was then placed under the picture of the right arm being measured and on the left side of the page", yet Dan placed the image of his left foot being measured on the right side of the page. Consequently, this caused Dan's image of his foot and arm comparison to also be in the wrong position. The caption of the figure was also not included in Dan's figure even though the methods section stated that it should be placed below the images. Therefore, some differences are due to incorrectly following the directions, rather than inaccuracy in explaining the methods used.
Acknowledgements
Bethany Calabrese was responsible for completing the original figure. I would like to thank Dan Greenwood for following my methods and completing a figure based upon the methods section of this experiment.
References
Cameron N, Tanner J, Whitehouse R. 1982. A longitudinal analysis of the growth of limb segments in adolescence. Informa Healthcare [Internet]. [cited 2010 March 10];9(3):[211-220 p.]. Available from: http://informahealthcare.com/doi/abs...14468200005701
Hallock, G. 1987 December. Simultaneous Bilateral Foot Reconstruction Using a Single Radial Forearm Flap. Plastic and Reconstructive Surgery Journal of the American Society of Plastic Surgeons [Internet]. [cited 2010 March 10];80(6):[836-838 p.]. Available from: http://journals.lww.com/plasreconsurg/Citation/1987/12000/Simultaneous_B...


http://bcrc.bio.umass.edu/courses/sp...arm-comparison