The Effects Of Enforced Training On The Remodeling Of Achilles Tendons: Animal Experiments And Human Intervened Studies

There is no doubt that long-term training is benefit to the mechanics of tendons. But as the main component of extracellular matrix and being considered as the main bearing of loads, collagen and proteoglycan have not been proved to change their components or contents with training, neither as the cross-sectional areas (CSA) of tendons and diameter of collagen fibrils. From which can we conclude the mechanics of tendon is not justly determined by the component of extracellular matrix and the diameter of collagen fibril. Whether the ultrastructure of collagen fibril- proteoglycan is related with training, and whether training might affect this ultrastructure is unclear. In a conclusion, the mechanism and material properties of tendons' remodeling towards training remain to be completely understood.Military training related injuries, which are the main causes of non-combat depletion, still have high incidence, and the incidence could be cut down by adequate training plans. Enforced cyclic training has been proved to advance the remodeling of bone, so we presume that enforced training be benefit to the remodeling of tendons.Based on such ideas and as one part of series of prevention and treatment of military training related injuries, animal experiments andhuman intervened studies are carried out to explore the effects of enforced training on the remodeling of Achilles tendons. PART I The effect of enforced training on the mechanics, collagen fibril-proteoglycan ultrastructure, the component and content of collagen and proteoglycan of Guinea pig's Achilles tendon.To explore the effect of enforced training on the remodeling of Guinea pig's Achilles tendon. Thirty five five-month healthy male Guinea pigs were divided randomly into five groups, seven per group, namely the control group, the middle-intensity group (A lasting for four weeks and B for eight weeks) and the high-intensity group(C for four weeks and D for eight weeks). The control group lived freely and the enforced groups undertook run-training at the speed of 40 meter per minute. When the experiments were over, the two sides of Achilles tendons were harvested under anaesthesia, one for mechanics test and the orthers were stained by picrosirius and toluidine blue respectively to observe and semiquantify collagen I -. III and proteoglycan with polarization microscopy, the interaction of collagen fibril-proteoglycan was observed with atomic force microscopy (AFM).After four-week training, the ultimate stress and stiffness of group A and C increased. Eight weeks later, the ultimate stress and stiffness of group B and D increased more (vs control, P<0.05 and 0.01 respectively). But the strain showed no difference between each group. Observed through AFM shows that the fibrils of control group arrange regularly, and the effect of middle-intensity on the structure of tendon is small. But the effect of high-intensity is marked, the fibrils of groupC and D are irregular, some fibrils dissolved at the forth weekend, and the arrangement of fibril became regular gradually at the eighth weekend. What should be mentioned is that some distinct chains could be seen running orthogonal or parallel to the fibrils, some in gap-zones and some among the fibrils, weaving with fibrils multi-dimensionally. The chains have been proved to be the proteoglycans side-chains. In the control group, collagen I is the main collagen and collagen III is less. When suffered enforced training, the relative content of collagen III increased markedly, especially in the high-intensity group C and D (vs control, P<0.01). With time prolonged, the content of collagen III decreased gradually. So did the fibrablasts and glycosaminoglycans.The data showed that after training the ultimate stress of Achilles tendon increased, which help tendon support much more tensile. The stiffer tendon is benefit to transmitting load and muscular movement, and at the same time to help resist tendon damage due to fatigue. Multi-dimensional interweaving exists between collagen fibrils and proteoglycans, and the interweaving is strengthened through training, which may be the structural base of tendon's adaptive ability to stress. High-intensity training could speedup the converts of collagen and proteoglycan of tendon, abundant collagen III are produced firstly, and converted into collagen I gradually. Training may result mainly in the change of the component and content of collagen and proteoglycan or glycosaminoglycan rather than the gross of collagen and proteoglycan. PART II Effect of immobilization on extracellular matrix and mechanics of Guinea pig's Achilles tendonTo investigate the effect of immobilization on collagen and proteoglycan and mechanics of Guinea pig's Achilles tendon. Twenty one five-month Guinea pigs were divided randomly into control group, two-week immobilized group (A) and four-week immobilized group (B), seven in each group. The immobilization models were made by hindlimbs suspension. The Achilles tendons were harvested after experiments, dyed by picrosirius and toluidine blue respectively, collagen I and III are observed and analyzed semiquantitatively with polarization microscopy, proteoglycans with microscopy. The stress, strain and so on mechanical properties were tested. After immobilization, the relative content of collagen III increases markedly(especially in group B, P<0.01), and together with the increase of fibrablasts and glycosaminoglycans. Compared with the control group, the stress and stiffness decreased, especially in group B(P<0.05), but the strain showed no difference between each group.The paper shows that immobilization can speedup the breakdown of the extracellular matrix of tendon, and more immature collagen III are produced. Immobilization can reduce the mechanics of tendon, especially the stress and stiffness, which lows down the ability of transmitting load and adds the chance of injuries. Physical load is needed to keep the metabolizing balance and function of tendon, not to say the importance of exercise and training.PART HI The effect of enforced training on muscular strength of light infantry soldier's ankle joint and the cross-sectional area of Achilles tendon...