Download Normative 3D Strength Surfaces in Healthy

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
Introduction
Results
Purpose
Male DF Torque
Male PF Torque
A)
PF Torque (Nm)
• 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 lengthtension and force-velocity relationships at the ankle joint in healthy human subjects.
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.
B)
80
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10
0
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velocity (deg/s)
175
200
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-5
0
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125
10
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velocity (deg/s)
15
175
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angle (deg)
25
200
30
DF Torque (Nm)
Graduate Program in Physical Therapy
& Rehabilitation Science
Female PF Torque
30
25
20
15
10
5
0
-5
angle (deg)
Female DF Torque
Methods
D)
C)
• 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),
• 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.
30
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0
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velocity (deg/s)
175
200
• 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).
60
DF Torque (Nm)
PF Torque (Nm)
• 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.
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.
20
15
10
5
25
50
75
-5
100
0
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125
10
velocity (deg/s)
150
15
20
175
angle (deg)
25
200
30
-5
0
5
10
15
20
25
angle (deg)
30
Figure 2. Three-dimensional strength surfaces for plantarflexion and dorsiflexion.
Conclusions
• 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