@article {548401,
	title = {Accuracy of gastrocnemius muscles forces in walking and running goats predicted by one-element and two-element Hill-type models},
	journal = {J BiomechJ BiomechJ Biomech},
	volume = {46},
	number = {13},
	year = {2013},
	note = {Lee, Sabrina S MArnold, Allison SMiara, Maria de BoefBiewener, Andrew AWakeling, James MengR01 AR055648/AR/NIAMS NIH HHS/R01AR055648/AR/NIAMS NIH HHS/Research Support, N.I.H., Extramural2013/07/23 06:00J Biomech. 2013 Sep 3;46(13):2288-95. doi: 10.1016/j.jbiomech.2013.06.001. Epub 2013 Jul 18.},
	month = {Sep 3},
	pages = {2288-95},
	abstract = {Hill-type models are commonly used to estimate muscle forces during human and animal movement-yet the accuracy of the forces estimated during walking, running, and other tasks remains largely unknown. Further, most Hill-type models assume a single contractile element, despite evidence that faster and slower motor units, which have different activation-deactivation dynamics, may be independently or collectively excited. This study evaluated a novel, two-element Hill-type model with "differential" activation of fast and slow contractile elements. Model performance was assessed using a comprehensive data set (including measures of EMG intensity, fascicle length, and tendon force) collected from the gastrocnemius muscles of goats during locomotor experiments. Muscle forces predicted by the new two-element model were compared to the forces estimated using traditional one-element models and to the forces measured in vivo using tendon buckle transducers. Overall, the two-element model resulted in the best predictions of in vivo gastrocnemius force. The coefficient of determination, r(2), was up to 26.9\% higher and the root mean square error, RMSE, was up to 37.4\% lower for the two-element model than for the one-element models tested. All models captured salient features of the measured muscle force during walking, trotting, and galloping (r(2)=0.26-0.51), and all exhibited some errors (RMSE=9.63-32.2\% of the maximum in vivo force). These comparisons provide important insight into the accuracy of Hill-type models. The results also show that incorporation of fast and slow contractile elements within muscle models can improve estimates of time-varying, whole muscle force during locomotor tasks.},
	keywords = {*Models, Biological, Animals, Electromyography, Female, Goats, Male, Muscle Contraction/physiology, Muscle, Skeletal/*physiology, Reproducibility of Results, Running/*physiology, Walking/*physiology},
	isbn = {1873-2380 (Electronic)0021-9290 (Linking)},
	author = {Lee, S. S. and Arnold, A. S. and Miara Mde, B. and Biewener, A. A. and Wakeling, J. M.}
}
