Sarcomere Stiffness during Stretching and Shortening of Rigor Skeletal Myofibrils

Figure 1. Scanning electron microscope image of the top view of the cantilever. The cantilever profile changes from rectangular to triangular at the tip of the cantilever. The inset shows a side view of the cantilever thickness and the cantilever tip where a myofibril is glued.

Figure 2. (i) Example of a psoas myofibril suspended between a cantilever and microneedle in rigor solution with a resting SL of 2.38 μm. (ii) Box-and-whisker plots summarize the number of myofibrils (M) and sarcomeres (S) within all the tested myofibril samples.

Figure 3. Box-and-whisker plots summarizing the resting SL, SL after the prestretch, and the SLs after the main stretch. Note that eight psoas myofibril samples were used in nine experimental sets.

Figure 4. Representative plots (i–vi) of the force per myofibril and SL as a function of time for experiments on the same myofibril. The SL plot in (i) is annotated with letters (a) to (f) to show the experimental steps. To see this figure in color, go online.

Figure 5. Mean ± SE of the absolute value for the change in force per myofibril and change in sarcomere length of the main stretch and main shortening. Three parenthesized values are shown above each group—sequentially: number of observations, difference in mean values (a symbol (—) is used when no statistically significant difference is present), and p value arising from the one-way ANOVA for repeated measures. Some parentheses have an R symbol to indicate the use of a one-way ANOVA for repeated measures on ranks. To see this figure in color, go online.

Figure 6. Representative plots (i–vi) of the change in force per myofibril as a function of the change in sarcomere length during the main stretch (c to d) and main shortening (e to f) stages. All the experiments in these plots used the same myofibril.

Figure 7. Stiffness during the main stretch and main shortening for the different experimental conditions. Plots summarize the effect of the microneedle input speed and displacement on the main stretch and main shortening. To see this figure in color, go online.

Figure 8. Representative plots (i and ii) showing the start and end tests of a given experimental set with the same myofibril. Both cases used the same condition (0.1 μm (0.4 μm/s)).

Figure 9. Mean ± SE of the absolute value for the change in force per myofibril and change in sarcomere length for the 0.1 μm (0.4 μm/s) condition at the start and the end of each experimental set. The main stretch from the start experiments is compared to the main stretch and the main shortening from the end experiments. Similarly, the main shortening from the start experiment is compared to the main stretch and the main shortening from the end experiments. Three parenthesized values are shown above each group—sequentially: number of observations, difference in mean values (a symbol (—) is used when no statistically significant difference is present), and p value arising from the one-way ANOVA for repeated measures. Some parentheses have an R symbol to indicate the use of a one-way ANOVA for repeated measures on ranks. To see this figure in color, go online.