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Influence of resistance exercise on human patellar tendon structural and regulatory gene expression

The tendon is mainly composed of collagen surrounded by a matrix of proteoglycans that are regulated by enzymes called matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Studies have shown that acute exercise stimulates collagen turnover, but little is known about the influence exercise has on other components of the tendon. Therefore, we measured the gene expression (mRNA) levels of the tendon's main proteins (collagen type I and collagen type III), proteoglycans (decorin, biglycan, fibromodulin, and versican), and regulatory enzymes (MMP‐2, MMP‐9, MMP‐3, and TIMP‐1) at rest and following resistance exercise (RE). Patellar tendon biopsy samples were taken from six individuals (3M, 3F) before and 4h following a bout of RE (3 sets of 10 repetitions at ~70% of 1RM) and from a separate six individuals (3M, 3F) before and 24h following RE and analyzed using real‐time RT‐PCR. Collagen type I, collagen type III, and MMP‐2 mRNA levels were downregulated (p<0.05) 4h following RE, but were unchanged 24h following RE (p>0.05). The other target mRNAs remained unchanged (p>0.05) following RE. Based on these gene expression results, we speculate that acute resistance exercise stimulates both collagen type I and type III turnover in the human patellar tendon. In addition, the proteoglycans appear to be relatively refractory to a resistance exercise stimulus.