Figure 1.
Muscle geometries with uniform-size fibers.
A) An example of the 3D structure of skeletal muscle with uniform-size fibers and microvasculature. B) 3D structure of the microvasculature. C) 2D cross section of skeletal muscle with uniform-size fibers and uniform capillary distribution (G1). D) 2D cross section of skeletal muscle with uniform size fiber and fiber type dependent capillary distribution (G2). Fiber type I is shown in blue, type IIa in green and type IIb in yellow. Microvessels are shown in red.
Figure 2.
Muscle geometries with non-uniform-size fibers.
A) An example of the 3D structure of skeletal muscle including non-uniform-size fibers and microvasculature. B) 3D structure of the microvasculature. C) 2D cross section of skeletal muscle with non-uniform size fibers and uniform capillary distribution (G3). D) 2D cross section of skeletal muscle with non-uniform size fibers and fiber-type-dependent capillary distribution (G4). Fiber type I is shown in blue, type IIa in green and type IIb in yellow. Microvessels are shown in red.
Table 1.
Fiber-type-specific parameters of the model.
Table 2.
Non-fiber-type-specific parameters of the model.
Table 3.
List of simulation annotations.
Figure 3.
PO2 histograms for muscle geometries with uniform-size fibers under exercising conditions.
Fiber PO2 probability distribution profiles in muscle tissue under A) light intensity exercise conditions, volume-averaged Mc = 3.34×10−4 mlO2 ml−1 s−1; B) moderate intensity exercise conditions, volume-averaged Mc = 6.68×10−4 mlO2 ml−1 s−1 ; and C) high intensity exercise conditions, volume-averaged Mc = 1.02×10−3 mlO2 ml−1 s−1, for simulation cases G1S1, G1S2, G2S1, G2S2. Dotted lines are simulation results for G1 geometry, while solid lines are results for G2 geometry. Black lines are the simulation scenarios S1 with uniform fiber-type properties (Mc, DO2, CMb) and red lines are the simulation scenarios (S2 using fiber-type-specific parameters (except size) for different fiber types.
Table 4.
Effects of fiber type properties on oxygen (PO2) distribution.
Figure 4.
PO2 histograms for muscle geometries with non-uniform-size fibers under exercise conditions.
PO2 probability distribution profiles for all points within fibers in muscle tissues under A) light intensity exercise. B) moderate intensity exercise. C) high intensity exercise, for simulation cases G3S1, G3S2, G4S1, G4S2. Dotted lines are simulation results for G3 geometry, while solid lines are results for G4 geometry. Black lines are the simulation scenarios S1 and red lines are the simulation scenarios S2.
Figure 5.
3D PO2 distribution in skeletal muscle.
3D tissue PO2 profiles in muscle tissues at light intensity exercise conditions for geometries A) G1S1; B) G3S1; C) G3S2.
Table 5.
Effects of fiber type properties and fiber size on oxygen (PO2) distribution.
Figure 6.
Distribution of average PO2 levels of individual fibers in skeletal muscle under exercise conditions.
Average (across all fibers of each type) of the mean PO2 levels of individual fibers under A) light intensity exercise; B) moderate intensity exercise; and C) high intensity exercise, for simulation cases G3S1, G3S2, G4S1 and G4S2. Type I is shown in blue, type IIa in green, type IIb in yellow.
Figure 7.
Effects of variation of oxygen consumption rate in different fiber types on PO2 histograms.
Fiber PO2 probability distribution profiles in muscle tissues under A) light intensity exercise; B) moderate intensity exercise; and C) high intensity exercise, for simulation cases G3S1, G3S3, G4S1 and G4S3. Dotted lines are simulation results from G3 geometry, solid lines are results from G4 geometry. Black lines are the simulation scenarios S1 and red lines are the simulation scenarios (S3) when Mc is fiber-type-dependent while others use uniform values for different fiber types.
Figure 8.
Effects of variation of oxygen diffusivity in different fiber types on PO2 histograms.
Fiber PO2 probability distribution profiles in muscle tissues under A) light intensity exercise; B) moderate intensity exercise; and C) high intensity exercise, for simulation cases G3S1, G3S4, G4S1 and G4S4. Dotted lines are simulation results for G3 geometry, solid lines are results for G4 geometry. Black lines are the simulation scenarios S1 and red lines are simulations scenarios S4 when DO2 is fiber-type-dependent while others use uniform values for different fiber types.
Figure 9.
Effects of variation of myoglobin concentration in different fiber types on PO2 histograms.
Fiber PO2 probability distribution profiles in muscle tissues under A) light intensity exercise; B) moderate intensity exercise; and C) high intensity exercise, for simulation cases of G3S1, G3S5, G4S1 and G4S5. Dotted lines are simulation results for G3 geometry with uniform capillary distribution, solid lines are results for G4 geometry with fiber type-dependent distribution. Black lines are simulation scenarios S1 and red lines are simulations scenarios S5 when CMb is fiber-type-dependent while others use uniform values for different fiber types.
Table 6.
Effects of heterogeneities of Mc, DO2, and CMb on oxygen (PO2) distribution.