Structural Factors Affecting Ankle Strength
Open Access
- Author:
- Putnam, Hannah Elizabeth
- Area of Honors:
- Biomedical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Stephen Jacob Piazza, Thesis Supervisor
Peter J Butler, Thesis Honors Advisor
Dr. Keefe B Manning, Faculty Reader - Keywords:
- strength
moment arm
muscle size - Abstract:
- Much previous research has been dedicated to analyzing the musculoskeletal structural variables that determine muscle strength. Most of this work has identified muscle volume as the main determinant, with less attention given to joint structure and other muscle architecture values. For this thesis, my primary goal was to identify individuals whose maximal ankle muscle strength could not be explained by the size of their muscles. By specifically seeking “farmer strong” subjects with smaller plantarflexor muscle volumes and comparing their ankle strength to that of average sized subjects, we attempted to show that those who display superior strength with smaller plantarflexor muscles are able to do so because they have longer Achilles tendon moment arms. Based on previous work in our laboratory, we anticipated that a third of the small-calf group would display strength superior to the mean of the control group. After comparing the results from six small calf subjects and 12 controls, one subject from the small calf group showed higher isometric torque values than the control average. This subject also had a longer moment arm than the mean of the control group. There was also a strong correlation in the small calf group between moment arm and isometric torque (R2 = 0.674, p <0.001) showing ankle moment arm has a significant effect on torque production among these subjects. As expected, there were strong correlations between muscle size, as measured by PCSA (R2 = 0.336, p = 0.005) and calf-circumference (R2 = 0.692, p < 0.001), and maximal ankle torque. We did not, however, find significant correlations between size and strength for the control group, possibly because certain artifacts affected dynamometer measurements of strength. We are currently investigating this possibility and making plans to address this limitation with additional testing.