By Ron Scott PT, EdD, MA
An educational and highly interesting mixed science and math investigation – most suitable for students in grades 5-8 – is measuring elbow carrying angle in each member of the class, and computing averages (means) and ranges for the class as a whole, and by gender. This simple-to-calculate anthropological measurement is useful to teach students about human anatomic variability and adaptation, and as an introduction to biostatistics.
Elbow carrying angle is important on an everyday basis to select bioscience professionals – forensic scientists, occupational therapists, orthopedic surgeons, physical anthropologists and physical therapists, among others. For students, measuring and analyzing elbow carrying angle is a unique way to advance their knowledge of science and math; to compare and contrast subtle gender differences in the human species; and to advance respect for one another as classmates and research subjects.
Elbow carrying angle typically ranges from 5-15 degrees, and is designed to allow one’s forearms to clear the hips during arm-swing while walking or running. Different within-range variants of elbow carrying angle also afford relative greater or lesser mechanical advantage during lifting tasks. Students can be tasked to analyze why women typically have greater elbow carrying angles than men (a wider pelvis to accommodate a developing fetus or fetuses), and whether narrower or wider elbow carrying angle facilitates better mechanical advantage during lifting (narrower more advantageous, due to a more linear force vector).
To measure elbow carrying angle, subjects stand erect, with arms at sides, palms facing forward, feet shoulder-width apart (“anatomical position”). Using an inexpensive plastic goniometer [Greek origin: gonia (angle), metron (measurement)], place the axis at the center of the anterior elbow crease, and place the long arms of the goniometer along the center of the anterior upper arm and forearm, and measure and record the angulation. Analyze and report results.
Extension question: What kinds of conditions might render a subject atypical in terms of elbow carrying angle? (Elbow fracture, e.g. from a skateboard mishap)
Extension activities: Aggregate, analyze and create a poster depicting results from multiple class sections, exercising the ethical responsibility to shield individual student identities. Present processes and findings at a school, district or regional science fair – maybe even at CAST.
Reference: Rajesh B, Reshma V, Jaene R, Somasekhar I, Vaithilingam A. An evaluation of the carrying angle of the elbow joint in adolescents. Int J Med Biomed Res, 2013;2(3):221-225 (60 subjects, ages 17-20, average elbow carrying angles: 13.6 for females, 6.7 for males).
Ron Scott, PT, EdD, MA, is a retired Associate Professor of Physical Therapy, UTHSCSA. Ron served under Troops-to-Teachers as the 5th-grade bilingual science teacher at Comal Elementary School, New Braunfels, Texas, from 2006-8.