1. Subjects: 53 healthy subjects (28 M, 25 F), between the ages of 18-50 years (mean age = 28.4 ± 8.1 years). All subjects had no history of musculoskeletal, neuromuscular, or cardiovascular disorders, as well as no history of diabetes. Subjects prescribed anti-depressants were not excluded from this study. None of the female subjects were pregnant. Instruments: Strength tests were performed on a Biodex System 3.0 Isokinetic dynamometer (Biodex Medical Systems, New York). Muscle activation was measured using four channels of surface muscle electromography (EMG, Delsys Bagnoli, Boston, MA), Methods: Subjects performed three maximum contractions for plantarflexion (PF) and dorsiflexion (DF) of the right limb at five isometric angles (10° DF, 0°, 10° PF, 20° PF, 30° PF) (Figure 1). Three to ten isokinetic contractions were performed at four to five different velocities (30°/s, 60°/s, 90°/s, 120°/s, 180°/s) for both PF and DF with rest periods between velocities. Post-muscle testing surveys: Subjects completed the International Physical Activity Questionnaire, Reasons for Exercise Inventory, and Positive Affect and Negative Affect Scales. Surface EMG electrodes were placed over four lower leg muscles. Analyses: Peak torques were extracted from a minimum of 20 angle-velocity combinations (e.g. 10 degrees at 60 deg/sec). Mean (SD) were plotted as 2D curves and 3D surfaces. Additional analyses involving EMG and surveys are in progress. Introduction Conclusions Graduate Program in Physical Therapy & Rehabilitation Science Purpose Methods Results Normative 3D Strength Surfaces in Healthy Subjects at the Ankle Joint: Plantarflexion/Dorsiflexion Sara Hussain, Laura Frey Law, PhD, PT The University of Iowa, Iowa City, IA The purposes of this study were to establish a normative strength database for healthy human subjects at the ankle joint, and determine the relationship between torque-angle, and force-velocity properties at the ankle. As industry advances, there is a need to better predict human capability for the purpose of industrial design and injury prevention. Santos™ is one such model that can predict human strength and endurance in a virtual environment. Human capability predictions are useful for military and industrial applications. The ankle joint is an integral part of the kinetic chain of the human body, and is key to locomotion and task performance (static & dynamic). There have been no published studies focusing on the relationship between the length- tension and force-velocity relationships at the ankle joint in healthy human subjects. Figure 1. Dynamometer set up with ankle elevated. Acknowledgements This research was supported in part by an ICRU fellowship. We would like thank Keith Avin, John Gentile, Nick Muhlenbruch, and Allison Stockdale for protocol assistance. We conclude that there is an interaction between the torque and velocity properties of both plantarflexors and dorsiflexors. We found a difference in torque-velocity relationships between plantarflexors and dorsiflexors. Future studies: Co-contraction patterns of plantarflexors and dorsiflexors at the ankle A) B) C) D) Figure 2. Three-dimensional strength surfaces for plantarflexion and dorsiflexion.