Table 1.

Influence of mitochondrial distribution and subdivision of dark fibers on η, average nondimensional O₂ and ATP concentrations, k₁, and k₂ for small and large fibers

Length, μm	SS fraction, %	k1, s−1	k2, mM−1 ·s−1	Avg Nondimensional O2 Concn	Avg Nondimensional ATP Concn	η	ATP Turnover Rate, mM/min
Light fiber
40	48	0.0009	0.86	0.94	0.86	0.99	0.47
40	0	0.0009	0.86	0.90	0.86	0.99	0.46
300	88	0.005	0.186	0.55	0.16	0.77	0.47
300	0	0.005	0.186	0.20	0.05	0.26	0.16
Dark fiber
17.5	75	0.005	1.10	0.96	0.61	0.99	1.84
17.5	0	0.005	1.10	0.92	0.59	0.98	1.80
300	75	0.012	14.9	0.065	0.25	0.32	1.84
300	0	0.012	14.9	0.027	0.13	0.17	0.98

SS, subsarcolemma; k₁, ATPase rate constant; k₂, oxidative phosphorylation rate constant. Data are based on experimentally determined diffusion path lengths and phosphagen recovery rates (6, 24, 30, 38). Output was obtained at the lowest values of k₁ that would satisfy the observed rate, which maximized η. ATP turnover rate is fixed in the observed case (SS mitochondrial fraction =48, 88, or 75%), and k₁ and k₂ values from these observed cases are used in the hypothetical cases with only intermyofibrillar mitochondria (SS mitochondrial fraction = 0).