Effect of training and sudden detraining on the patellar tendon and its enthesis in rats.
BACKGROUND
Different conditions may alter tendon characteristics. Clinical evidence suggests that tendon injuries are more frequent in athletes that change type, intensity and duration of training. Aim of the study was the assessment of training and especially detraining on the patellar tendon (PT) and its enthesis.


METHODS
27 male adult Sprague-Dawley rats were divided into 3 groups: 20 rats were trained on a treadmill for 10 weeks. Of these, 10 rats were euthanized immediately after training (trained group), and 10 were caged without exercise for 4 weeks before being euthanized (de-trained group). The remaining 7 rats were used as controls (untrained rats). PT insertion, structure (collagen fiber organization and proteoglycan, PG, content), PT thickness, enthesis area, and subchondral bone volume at the enthesis were measured by histomorphometry and microtomography.


RESULTS
Both PG content and collagen fiber organization were significantly lower in untrained and detrained animals than in trained ones (p < 0.05 and p < 0.0001). In the detrained group, fiber organization and PG content were worse than that of the untrained groups and the untrained group showed a significantly higher score than the detrained group (p < 0.05). In the trained group, the PT was significantly thicker than in untrained group (p < 0.05). No significant differences in the enthesis area and subchondral bone volume among the three groups were seen.


CONCLUSIONS
Moderate exercise exerts a protective effect on the PT structure while sudden discontinuation of physical activity has a negative effect on tendons. The present results suggest that after a period of sudden de-training (such as after an injury) physical activity should be restarted with caution and with appropriate rehabilitation programs.
Department of Histology, Embryology and Applied Biology, University of Bologna, Italy.
Antonio
A
Frizziero
Milena
M
Fini
Francesca
F
Salamanna
Arsenio
A
Veicsteinas
Nicola
N
Maffulli
Marina
M
Marini
D000818:Animals; D004195:Disease Models, Animal; D008297:Male; D017847:Patellar Ligament / Q000473:pathology / Q000503:physiopathology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013708:Tendon Injuries / Q000209:etiology / Q000503:physiopathology* / Q000534:rehabilitation; D013710:Tendons / Q000473:pathology / Q000503:physiopathology*; D055114:X-Ray Microtomography / Q000379:methods
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