TABLE II.
Musculotendon Parameters
| Muscle | Abbreviation | Optimal force (N) | Optimal fiber length (cm) | Tendon slack length (cm)a | Pennation angle (°) |
|---|---|---|---|---|---|
| Adductor brevis | addbrev | 626 | 10.3 | 3.5* | 6.6 |
| Adductor longus | addlong | 917 | 10.8 | 13.2 | 7.9 |
| Adductor magnusb | |||||
| Adductor magnus (distal) | addmagDist | 597 | 17.7 | 8.7* | 11.2 |
| Adductor magnus (ischial) | addmagIsch | 597 | 15.6 | 21.6 | 9.6 |
| Adductor magnus (middle) | addmagMid | 597 | 13.8 | 4.7* | 11.9 |
| Adductor magnus (proximal) | addmagProx | 597 | 10.6 | 4.0* | 17.8 |
| Biceps femoris long head | bflh | 1313 | 9.8 | 32.5 | 10.1 |
| Biceps femoris short head | bfsh | 557 | 11.0 | 10.6* | 15.1 |
| Extensor digitorum longusc | edl | 603 | 6.9 | 36.9 | 12.5 |
| Extensor hallucis longusc | ehl | 286 | 7.5 | 32.7 | 11.3 |
| Flexor digitorum longus | fdl | 423 | 4.5 | 37.9 | 12.9 |
| Flexor hallucis longus | fhl | 908 | 5.3 | 35.4 | 14.8 |
| Gastrocnemius lateral head | gaslat | 1575 | 5.9 | 37.6 | 12.0 |
| Gastrocnemius medial head | gasmed | 3116 | 5.1 | 39.9 | 9.5 |
| Gluteus maximusb | |||||
| Gluteus maximus (superior) | glmaxl | 984 | 14.7 | 4.9* | 20.3 |
| Gluteus maximus (middle) | glmax2 | 1406 | 15.7 | 6.8* | 21.0 |
| Gluteus maximus (inferior) | glmax3 | 948 | 16.7 | 7.0* | 21.9 |
| Gluteus mediusb | |||||
| Gluteus medius (anterior) | glmedl | 1093 | 7.3 | 5.6* | 18.1 |
| Gluteus medius (middle) | glmed2 | 765 | 7.3 | 6.5* | 18.1 |
| Gluteus medius (posterior) | glmed3 | 871 | 7.3 | 4.5* | 18.1 |
| Gluteus minimusb | |||||
| Gluteus minimus (anterior) | glminl | 374 | 6.8 | 1.6* | 10.0 |
| Gluteus minimus (middle) | glmin2 | 395 | 5.6 | 2.6* | 0.0 |
| Gluteus minimus (posterior) | glmin3 | 447 | 3.8 | 5.1 | 1.0 |
| Gracilis | grac | 281 | 22.8 | 17.2* | 9.9 |
| Iliacus | iliacus | 1021 | 10.7 | 9.6* | 16.0 |
| Peroneus brevisd | perbrev | 521 | 4.5 | 14.8 | 11.8 |
| Peroneus longusd | perlong | 1115 | 5.1 | 33.2 | 14.2 |
| Piriformis | piri | 1030 | 2.6 | 11.5 | 10.0 |
| Psoas | psoas | 1427 | 11.7 | 10.0* | 12.3 |
| Rectus femoris | recfem | 2192 | 7.6 | 44.9 | 12.4 |
| Sartorius | sart | 249 | 40.3 | 12.4* | 1.5 |
| Semimembranosus | semimem | 2201 | 6.9 | 34.8 | 14.6 |
| Semitendinosus | semiten | 591 | 19.3 | 24.7 | 13.8 |
| Soleus | soleus | 6195 | 4.4 | 27.7 | 21.9 |
| Tensor fascia latae | tfl | 411 | 9.5 | 45.0 | 3.0 |
| Tibialis anterior | tibant | 1227 | 6.8 | 24.1 | 11.2 |
| Tibialis posterior | tibpost | 1730 | 3.8 | 28.1 | 13.0 |
| Vastus intermedius | vasint | 1697 | 9.9 | 20.2 | 3.6 |
| Vastus lateralis | vaslat | 5149 | 9.9 | 22.1 | 14.5 |
| Vastus medialis | vasmed | 2748 | 9.7 | 20.0 | 24.2 |
Musculotendon parameters. Muscle physiological cross sectional areas (PCSAs) were calculated from muscle volumes measured by Handsfield et al. [26] in healthy, young subjects. Optimal fiber lengths were measured by Ward et al. [20] in cadaver subjects. Pennation angle at optimal fiber length was calculated using pennation angle measurements in cadavers by Ward et al. and adjusted for fiber length using the constant-volume assumption made by Millard et al. Tendon slack length was set in the model to match normalized fiber length measurements reported by Ward et al.
Tendons were modeled as rigid when the tendon slack length was less than the muscle optimal fiber length. Rigid tendons are indicated with a (*).
Muscle volume was only available for the whole muscle. Total muscle volume for each muscle was divided equally between the muscle-tendon units using the same volume distribution as in the model by Arnold et al. [15].
Muscle volume was only available for extensor digitorum longus, extensor hallucis longus, and peroneus tertius combined. Peroneus tertius was not included in our model. The total muscle volume was divided between extensor digitorum longus and extensor hallucis longus using the volume proportions used by Arnold et al. [15].
Muscle volume was only available for peroneus brevis and peroneus longus combined. The total muscle volume was divided between the two using the volume proportions used by Arnold et al. [15].