Supplementary Information 
Inferring muscle functional roles of the ostrich pelvic limb during walking and running using 
computer optimization 
Jeffery W. Rankin, Jonas Rubenson, John R. Hutchinson 
Supplementary Information – Tables 
 
 
Table S1 – Root mean square (RMS) and peak differences between the experimental and simulated joint angles (degrees) 
obtained with computed muscle control in walking and running over the entire movement. 
 
RMS Error Peak Error RMS Error Peak Error RMS Error Peak Error RMS Error Peak Error
Hip Flexion-Extension
0.002
0.061
0.001
0.039
0.007
0.148
0.002
0.044
Hip Ad-Abduction
0.002
0.106
0.001
0.034
0.005
0.164
0.002
0.065
Hip Medial-Lateral Rotation
0.005
0.139
0.003
0.076
0.012
0.347
0.003
0.054
Knee Flexion-Extension
0.006
0.201
0.002
0.047
0.024
0.497
0.002
0.069
Knee Ad-Abduction
0.005
0.130
0.002
0.103
0.014
0.361
0.004
0.071
Knee Medial-Lateral Rotation
0.005
0.236
0.003
0.071
0.010
0.264
0.005
0.122
Ankle Flexion-Extension
0.009
0.325
0.001
0.053
0.051
1.304
0.004
0.093
MTP Flexion-Extension
0.010
0.292
0.007
0.313
0.051
1.543
0.008
0.193
RCMCR
RCMCC
WCMCR
WCMCC
Joint Angle (Degrees)
 
 
Table S2 –Percent of muscle activity (as predicted by the simulations) that occurs during the swing phase. Predictions were 
calculated by normalizing the entire gait cycle to 100% and then integrating the entire cycle and swing-phase-only portions 
of the simulated muscle activation patterns. 
Simulation Percent of Muscle 
Activity in Swing
WSO
13.9
WCMCR
15.6
WCMCC
29.8
RSO
24.4
RCMCR
31.8
RCMCC
38.6
 
 
Supplementary Information 
Inferring muscle functional roles of the ostrich pelvic limb during walking and running using 
computer optimization 
Jeffery W. Rankin, Jonas Rubenson, John R. Hutchinson 
Supplementary Information – Figures 
Figure S1 – Example fibre excursions of the digital flexor muscles during ostrich running. Due to having short muscle fibres, 
these muscles undergo extensive fibre lengthening relative to their optimal fibre length during swing. As a result, passive 
muscle forces generate a large ankle extension moment that cannot be counteracted by the ankle flexors (TCf,TCt, EDL) 
alone and a reserve torque is required. Shaded area represents stance and the arrow indicates the point of peak ankle 
reserve actuator torque. 
 
 
 

Inferring muscle functional roles of the ostrich pelvic limb during walking and running using computer optimization.
Rankin, Jeffery W,Rubenson, Jonas,Hutchinson, John R