Impact of sex and chronic resistance training on human patellar tendon dry mass, collagen content, and collagen cross-linking

Abstract

Collagen content and cross-linking are believed to be major determinants of tendon structural integrity and function. Sex and chronic resistance training have been shown to alter tendon function and may also alter the key structural features of tendon. Patellar tendon biopsies were taken from untrained men [n = 8, 1 repetition maximum (RM) = 53 +/- 3 kg], untrained women (n = 8, 1 RM = 29 +/- 2 kg), and resistance-trained (10 +/- 1 yr of training) men (n = 8, 1 RM = 71 +/- 6 kg). Biopsies were analyzed for dry mass, collagen content, and collagen cross-linking (hydroxylysylpyridinoline). We hypothesized that these elements of tendon structure would be lower in women than men, whereas chronic resistance training would increase these parameters in men. Tendon dry mass was significantly lower in women than men (343 +/- 5 vs. 376 +/- 8 microg dry mass/mg tendon wet wt, P < 0.01) and was not influenced by chronic resistance training (P > 0.05). The lower tendon dry mass in women tended to reduce (P = 0.08) collagen content per tendon wet weight. Collagen content of the tendon dry mass was not influenced by sex or resistance training (P > 0.05). Similarly, cross-linking of collagen was unaltered (P > 0.05) by sex or training. Although sex alters the water content of patellar tendon tissue, any changes in tendon function with sex or chronic resistance training in men do not appear to be explained by alterations in collagen content or cross-linking of collagen within the dry mass component of the tendon.

Fig. 1.

In vivo tendon dry mass and collagen content in men and women. Expression of dry mass and collagen content per tendon wet weight demonstrates the functional amounts of these elements in whole tendon. *P < 0.01; **P = 0.08 vs. men.

Fig. 2.

Dry tendon collagen content and collagen cross-linking in men and women. Normalization of collagen to dry mass demonstrates amount of collagen in nonwater material of tendon tissue. Hydroxylysylpyridinoline (HP) cross-links relative to collagen reveal number of cross-links per collagen in tendon tissue. Taken together, these 2 variables indicate quality of biosynthesized tendon tissue, independent of tissue water content. No differences (P > 0.05) were observed between men and women.

Fig. 3.

In vivo tendon dry mass and collagen content in men and chronically resistance-trained (RT) men. Expression of dry mass and collagen content per tendon wet weight demonstrates functional amounts of these elements in whole tendon tissue. No differences (P > 0.05) were seen in these variables between men and RT men.

Fig. 4.

Dry tendon collagen content and collagen cross-linking in men and chronically resistance-trained (RT) men. Normalization of collagen to dry mass demonstrates amount of collagen in nonwater material of the tendon tissue. HP cross-links relative to collagen reveal number of cross-links per collagen in tendon tissue. Taken together, these 2 variables indicate quality of biosynthesized tendon tissue, independent of tissue water content. No differences (P > 0.05) were observed between men and RT men.