Table 2.

Equilibrium and individual rate constants derived from the simulation of force-[P_i] curve in fast and slow myofibrils by the model illustrated in Scheme 3

	Psoas		Soleus
	5°C	15°C	15°C
K2	0.05	0.09	0.92
K3 (mM)	110	64	10
k+1	5	20	6
k−1	1	5	1
k+2	8	20	3
k-2	180	250	3.3
k+3	500	1000	40
k-3 (M−1 s−1)	0.5 ± 104	1.5 ± 104	0.4 ± 104
k+4	1	3	1

Equilibrium constants for Steps 2 and 3 of Scheme 3 (abbreviated as K₂, K₃) as derived from hyperbolic fitting of experimental force-[P_i] curves of fast and slow myofibrils at the different temperatures (see Methods, eqns (4–5)). Forward and backward rate constants for all the transitions assumed by the cross-bridge model of Scheme 3 (abbreviated as k_+x and k_-x and expressed s⁻¹, when not otherwise stated) were assigned based on k_TR and k_Pi(+) measurements in myofibrils (this study and Tesi et al. 2000) or in skinned fibres from psoas (Millar & Homsher, 1990; Dantzig et al. 1992; Zhao & Kawai, 1994; Regnier et al. 1995) and soleus muscle (Millar & Homsher, 1992; Wahr et al. 1997; Wang & Kawai, 1997), in similar experimental conditions. Simulation of soleus myofibrils at 20°C not shown.