Page 79 - Development of Functional Scaffolds for Bone Tissue Engineering Using 3D-Bioprinting of Cells and Biomaterials - Yasaman Zamani

muscle. The force length factor (FL) was estimated by the following third degree equation fitting experimental data from cadavers:
FL = 0.41SL3 – 4.40SL2 + 14.80SL – 15.05 (4)
The relative velocity (v) of the sarcomeres in interval i was determined from SL in the previous
and following interval:
𝑣𝑣𝑣𝑣= 1 .𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑖𝑖𝑖𝑖−1−𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑖𝑖𝑖𝑖+1 (5)
𝑖𝑖𝑖𝑖 2.73 2.𝑡𝑡𝑡𝑡
where t is the duration of an interval. The FV is calculated separately for shortening and lengthening contractions. In the first case the following equation was used [23]:
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = 𝑣𝑣𝑣𝑣𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 − 𝑣𝑣𝑣𝑣𝑖𝑖𝑖𝑖 (𝑣𝑣𝑣𝑣 > 0) (6) 𝑖𝑖𝑖𝑖𝑣𝑣𝑣𝑣+𝑃𝑃𝑃𝑃.𝑣𝑣𝑣𝑣𝑖𝑖𝑖𝑖
𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 0𝑎𝑎𝑎𝑎 𝑖𝑖𝑖𝑖
For negative contraction velocities, the increase in FV was approached by: 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 =1.5−0.5. 𝑣𝑣𝑣𝑣𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 + 𝑣𝑣𝑣𝑣𝑖𝑖𝑖𝑖 (𝑣𝑣𝑣𝑣 <0) (7)
𝑖𝑖𝑖𝑖 𝑣𝑣𝑣𝑣−2𝑃𝑃𝑃𝑃𝑎𝑎𝑎𝑎.𝑣𝑣𝑣𝑣𝑖𝑖𝑖𝑖 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 0𝑖𝑖𝑖𝑖
This curve fitted experimental data [24]. The FP was estimated, using previous data [25] as: 𝐹𝐹𝐹𝐹𝑃𝑃𝑃𝑃 = 0.0014. exp (6. 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑖𝑖𝑖𝑖 − 2.73) (8)
𝑖𝑖𝑖𝑖 2.73
The activation factor FQ depended on the time course of the EMG.
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