Mastering Skinfold Measurements: Body Composition Assessment (Part II)
Measurement Sites: How to Find Them
The locations and names of the various folds have changed over time. The methods listed here are selected in an attempt to make locating the site as reproducible as possible so that you obtain the most sensitive body composition monitor possible.
Suprailiac
The usual description of this site is "a diagonal fold just above the iliac crest." When I first read that, I nearly blew a fuse. The iliac crest or, "hip bone," can be felt starting a few inches away from the navel and sweeping in a long arc out to the side of the body and around back to the sacrum. Just where did these jokers mean? If I measure closer to my navel, I get a small number. If I measure out at the very fattest part of the love handles, I get a big number. So, where? And if you look at pictures on the web or in articles, they differ from each other and, in some cases, the text differs from the photo. Well, take a calming breath. Here's how to do it. The method presented here has the advantage of being very repeatable.
You're going to measure directly above a bump on the front of your hip bone: The iliac crest is a ridge of bone along the top of your pelvis. In the photo, the dashed line marks the top of the hip bone as it sweeps up and over the side of the body and then descends downwards. The cross marks the location of a raised bump where the hip bone seems to disappear (because it curves inwards).
(Suprailiac Measurement Site)
There are three ways to find this spot. The first is to just feel for the bump. Once you've experienced locating it accurately once, you can find it easily but, how do you confirm you have the right place? Here are two methods.
Method 1:
• Standing, put your right leg up on a chair with your knee bent and your right thigh roughly parallel to the floor. Place your hand on top of your right thigh and follow the mid-line back to your hip bone.
• Feel the hip bone along the crease between your thigh and torso with your finger tips and discover the following features: As you move your fingertips towards your groin you will feel a place where your fingers fall off of the hip bone and sink into soft tissue. Okay, now move back, away from the groin, along the crease, and you'll feel your fingers come back up onto the hip bone. As you come up onto the hip bone and move just a bit further away from the groin, you'll feel your fingers fall into a valley, but still be feeling bone. Thus, you've just found a ridge of bone along your hip and located where it crosses the crease between leg and torso. Place your index finger on the peak of that ridge right at the crease between your thigh and your torso. Without moving your hand, put your foot down on the floor.
• Your index finger is now sitting on the landmark for taking the measurement. With your thumb, reach up and grab a roll of skin. Play a bit and you'll see that the fold of skin naturally wants to fall along a diagonal rather than parallel to the floor. That's the skinfold you want. Your index finger will move up off of the landmark about an inch when taking the fold, but it will start vertically above the landmark.
(Method 1 For Finding The Suprailiac Site)
Method 2:
This method is fast but first you need to do a little experiment: Sit in a chair, feet flat on the floor. Place your fingertips in the crease between your right leg and your torso in the vicinity of your hip bone. Move as if you are crossing your legs, putting your right foot on your left knee. This is a twisting movement rather than simply lifting the knee.
If you have trouble, it may be helpful to think of your leg below the knee as a golf club and you are moving as if you were putting a golf ball with your foot. The moment you start to move, you will feel a muscle pop up under your fingertips. Keeping the tension on in the muscle, follow the muscle all the way up to where it meets the hip.
Keep going up, following the tendon all the way to the very crest of the hip. If you go even a little further, your fingertip will leave the hip bone and sink into soft tissue. You have just found the origin of the sartorius muscle along the iliac crest. This is your landmark.
Now that you've learned where the sartorius originates on the iliac crest, here is the method:
• Standing, place your fingertips on your hip bone in the crease between your right thigh and torso.
• Pretend your right foot is a golf club and putt an imaginary ball away from you, 45 degrees off to the left. You will feel the sartorius pop up just as you did in the experiment.
• Locate the origin of the sartorius on the iliac crest with your pointer finger. This is your landmark.
• With your thumb, reach up grab a roll of skin. Play a bit and you'll see that the fold of skin naturally wants to fall along a diagonal rather than parallel to the floor. That's the skinfold you want. Your index finger will move up off of the landmark about an inch when taking the fold, but it will start vertically above the landmark.
(Method 2 For Finding The Suprailiac Site)
Abdomen (Umbilicus)
• Make a vertical fold 2 inches (5 cm) to the right of your navel (umbilicus).
• Measure below the pinch at the level of the navel. If you are working alone and find it difficult to apply the calipers below your fingers, you may pinch above them at the level of the navel.
Thigh:
• Sit with your feet flat on the floor, knees bent at roughly 90 degrees.
• Locate the top of your kneecap (patella) and also locate the bump on your hip bone used for the suprailiac site, as indicated in the photo and described above.
• Grab a vertical skinfold at the midpoint on the thigh, halfway between these two landmarks (the cross in the photo). Take the fold at the midpoint vertically and also at the midpoint side to side (midline of the thigh).
It can be difficult to raise this fold in some people. If you have trouble, trying sitting on a bench or floor with your legs out straight or, sitting in the chair, place your hands under the thigh and lift up on the belly of the hamstrings, relieving the tension at the skinfold site. The thigh measurement most often employed is taken standing, but the seated version is presented here hoping it is easier to self-teach and easier to do in difficult cases.
(Thigh Measurement Site)
Tricep
• Locate the midpoint between the shoulder and the elbow, over the tricep. To be more precise, locate the bony bump at the end of your scapula at the shoulder (acromion process). In the photo, the horizontal line follows a ridge you can easily feel. At the end is a bony bump, marked with the vertical hash. Find the midpoint between that bump and the tip of the elbow long the midline of the tricep.
• Gather a vertical fold along the midline of the tricep
(Triceps Measurement Site)
Bicep
• Locate and mark the tricep site.
• With the arm hanging loosely by the side, mark the bicep at the same vertical level as the tricep measurement.
• Looking from the front, locate the midline over the belly of the bicep. Gather a vertical fold there for the measurement.
The site may not appear to be centered vertically over the bicep, but this is the site to use. Notice that, as you flex and extend your elbow, the belly of the bicep moves up and down.
(Biceps Measurement Site)
Subscapular
• The scapula (shoulder blade) appears roughly triangular in shape. Explore the right scapula and locate its bottom border. Feel along the border, moving towards the spine, and discover the inferior angle, the place where the approximately horizontal bottom edge and approximately vertical edge of the triangular scapula meet. This is your landmark. In the photo, the blue pen line follows the edge of the scapula. The cross hatch is at the inferior angle. (I moved after we marked the lines, so they are a little off in the photo). Notice that my hand is behind my back. This helps make the scapula stand out.
(Subscapular Measurement Site)
• Place your index finger tip on the apex and reach diagonally downwards and towards the spine with your thumb to gather a diagonal fold of skin that parallels the bottom of the shoulder blade. Pay attention to reach the same distance each time in order to get consistent results.
(How to pinch the Subscapular Measurement Site)
Axillary Fold
• Gather a vertical fold at the crease above your right armpit. In the photo, there are two creases, one nearly vertical with a blue line next to it and another at a slant. The vertical crease is the one to use.
(Axillary Measurement Site)
Pectoral (chest)
• For men, locate the midpoint between your armpit (the axillary crease, described above) and nipple along the border of your right pectoral muscle. For women, locate the point one third of the distance.
• Gather a fold of skin at the midpoint along the border of the pectoralis. The fold will be a diagonal fold following the angle of the border of the muscle.
Story Sticks
Cabinetmakers use story sticks to do their work faster and more accurately. A story stick is just a piece of wood with all the measurements needed to build a project laid out upon it. Measurement errors disappear because re-measuring isn't needed. Distances are simply transferred from the story stick when needed.
You can make a story stick for your skinfold measurements from a small piece of wood, like a paint stirring stick. Use a ruler or tape to locate the skinfolds described above and mark them on yourself or partner. Hold the end of the story stick against the landmark for a fold and transfer the mark from your body to the stick. For example, for the tricep fold, locate the acromion process and use a ruler to locate and mark the tricep site, as described above.
Then, place the end of the story stick against the acromion process and transfer the mark at the tricep site over to the story stick. In the future, you do not need to use a ruler for this site. Just put the story stick against the bone, find the mark on the story stick, and you are ready to measure. You can place all your measurements onto one stick. To avoid mistakes, clearly mark the end of the stick that goes against the landmark. My stick has an arrow at the reference end plus a heavy black line.
(Stroy Stick)
Conclusion
In this article, you have learned how to select an appropriate caliper, how to gather and measure a skinfold, how to locate the most important measurement sites, and how to use the results to monitor changes in body composition. There are many skinfold methods to use, varying by which sites are measured and how the thicknesses are converted to fat percentage (or simply summed). The most important thing is to select a method for yourself and then be as precise as you can be.
