The effect of running, strength, and vibration strength training on the mechanical, morphological, and biochemical properties of the Achilles tendon in rats.

Compared with muscle or bone, there is a lack of information about the relationship between tendon adaptation and the applied loading characteristic. The purpose of the present study was to analyze the effect of different exercise modes characterized by very distinct loading patterns on the mechanical, morphological, and biochemical properties of the Achilles tendon. Sixty-four female Sprague-Dawley rats were divided into five groups: nonactive age-matched control (AMC; n = 20), voluntary wheel running (RT; n = 20), vibration strength-trained (LVST; n = 12), high-vibration strength-trained (HVST; n = 6), and high strength-trained (HST; n = 6) group. After a 12-wk-long experimental period, the Achilles tendon was tested mechanically and the cross-sectional area, the soleus and gastrocnemius muscle mass, and mRNA concentration of collagen I, collagen III, tissue inhibitor of metalloproteinase-1 (TIMP-1), transforming growth factor-beta, connective tissue growth factor, and matrix metalloproteinase-2 was determined. Neither in the LVST nor in the HVST group could any adaptation of the Achilles tendon be detected, although the training had an effect on the gastrocnemius muscle mass in the LVST group (P < 0.05). In the HST group, the highest creep was found, but the effect was more pronounced compared with the LVST group (P < 0.05) than with the AMC group. That indicates that this was rather induced by the low muscle mass rather than by training. However, the RT group had a higher TIMP-1 mRNA concentration in the Achilles tendon in contrast to AMC group (P < 0.05), which suggests that this exercise mode may have an influence on tendon adaptation.