Matrix metalloproteinase (MMP)-1 and -3 protein levels increase in flexor digitorum tendons with high repetition negligible force (HRNF) task. a Representative Western blot of tendon homogenates probed with anti-MMP-1. Bands are at the expected molecular weight of 54 kDa. β-actin used as a loading control (at 42 kDa). b Densitometric analysis of three replicate Western blots shows the ratio of the MMP1 band after normalization to β-actin levels. c A representative Western blot of muscle homogenates probed with MMP-3. Bands are at the expected molecular weights of latent and active forms of MMP-3 (approximately 57–59 and 45). β-actin used as a loading control. d, e Densitometric analysis of latent (57–59 kDa) and active (45 kDa) forms of MMP-3 from three replicate Western blots after normalization to β-actin levels. *p < 0.05, **p < 0.01, compared to FRC and 3 week rats. n.s. = not significant.