Issue link: https://www.massageandbodyworkdigital.com/i/121374
THE SCIENCE oF MoVEMENT exploring Technique Axial Compression Tests to Assess Lines of Force The center of gravity (COG) of a mass is that point around which all parts are exactly balanced: it is the same as the center of weight. The line of gravity (LOG) is the direction of gravity's force; it is, basically, a plumb line. Our uniquely upright skeleton aligns the body along a single vertical axis. The COG in the skull lies several inches behind the "third eye" on the forehead, slightly above, and between, the eyebrows. The COG in the chest lies several inches above the diaphragm, anterior to the 10th thoracic vertebra, midway between front and back, below the heart. The COG in the pelvis lies behind and below the navel, directly in front of the sacrum. It is usually lower on women, because of greater width and weight in the pelvic girdle. In optimal posture, the COG of each weight-bearing body part aligns as closely to the LOG as possible (Image 1, page 107). This allows gravity to flow through the center of a standing body. When a person demonstrates optimal posture, all the weight-bearing joints of the spine and lower limbs extend. Joints in the extended position are "joint neutral" because they are straight, neither bent nor twisted. Joint neutral serves as a reference point for optimal skeletal alignment and muscular balance. Mary Ann Foster is the author of Therapeutic Kinesiology: Musculoskeletal Systems, Palpation, and Body Mechanics (Pearson Publishing, 2013). She can be contacted at mafoster@somatic-patterning.com. Caution: Do not perform this test on anyone who has pain and/or a spinal disk problem. Make sure to press down only for an instant. Do not hold sustained pressure. use this simple compression test to assess the alignment of the thorax over the pelvis and legs. it will help your partner feel how compression translates through the joints from the shoulders to the feet, and feel when the upper body balances over the lower body and the base of support. 1. have your partner stand comfortably with her feet under her hips. have her sense where on her feet she feels her weight is balanced. stand behind your partner and lightly and quickly press down on both shoulders, then release. 2. Press lightly and release several times. the joints should feel springy. ask your partner where in her body she feels the compression. if her body masses stack vertically, it will go all the way to her feet. wherever the spine chronically bends (usually in the lower back), compression pools. Most people feel the low back bend, which indicates that the thorax is behind, rather than over, the base of support (image a). 3. next, have your partner subtly sway back and forth, keeping both her feet flat and shifting her weight from heels to toes and back (image B). tell your partner to sense the place where it feels like her thorax comes over her pelvis and stop there. then, repeat the compression test. she will feel the compression in her feet if her thorax is actually aligned over her base of support. next issue: identifying adaptive muscle patterns. A 108 massage & bodywork may/june 2013 B A poorly aligned, off-center posture. A well-aligned, joint-neutral posture.