Figure 5.

Associations of baseline collagen measures and change in immune cell abundance with progressive resistance training (PRT). Pearson correlations for univariant comparisons and multiple linear regression adjusting for sex (standardized betas) and variable by sex to identify sex interactions are shown. Scatterplots show baseline fibrous collagen content, quantified by area stained with Sirius Red (SR+) was negatively associated with change in CD11b+/CD206− (A, n = 31), but not CD11b+/CD206+ (B, n = 31) cell abundance. Polarized light imaging of Sirius Red-stained sections showed that baseline collagen density does not associate with either CD11b+/CD206− (C, n = 32), or CD11b+/CD206+ (D, n = 32) cell abundance. Collagen interactions with CD11b+/CD206+ cells in females only may contribute to sex differential response in whole muscle hypertrophy. Males are designated as blue circles and females are designated as orange triangles. CO, collagen organization.