Abstract
Previously (17), we reported the formation of microtears in an in vivo loaded FDP rabbit tendon with a repetition rate of 60 repetitions per minute and a peak force of 15% of maximum (Po). Pathophysiological changes were observed. The tear area as a percent of tendon area, tear density (tears/mm2) and mean tear size (μm2) were higher in tendons from the loaded limb compared to the unloaded limb. The purpose of the present study was to compare those results to results obtained with a lower repetition rate of 10 (per minute) while maintaining the same peak force and work (equal force-time integral) (n=8). Due to regional properties of the tendon, a strain gradient between the inner and outer sides of the FDP tendon exists. Therefore, microtears were quantified in four regions, two regions each along the inner and outer sides of the tendon. The tear area as a percent of total tendon area and the mean tear size were significantly greater in the loaded limb compared to the unloaded limb (p < 0.03). However, the effects were less than those observed at 60 repetitions/min. The high repetition rate loading pattern resulted in an increase in tear measures in all four regions, while the lower rate produced changes only in the outer regions of the tendon. This finding may establish where the initial sites of damage occur in tendons that insert into bone in a similar arrangement as the FDP. The results also suggest that repetition rate is associated with tendon damage in a dose-response pattern.
Get full access to this article
View all access options for this article.