Abstract: BACKGROUND: Post-exercise gastrocnemius tension increase is the main cause of degeneration, and overweight people are more susceptible. The gastrocnemius needling treatment has been considered as an effective way to reduce post-exercise muscle tension. 
OBJECTIVE: To study the effect of post-exercise gastrocnemius needling treatment on the risk of Achilles tendon degeneration by observing the changes in the expression of mechanical growth factors and tissue proteins after needling.
METHODS: Thirty-two 12-week-old male Sprague-Dawley rats were fed with high fat diet for 4 weeks to establish obese rats with a body weight of (500.27±29.11) g. All rat models were randomly divided into blank control group, exercise group, needling group and post-exercise needling group. Eccentric running at -16° was performed, and the exercise intensity was set at 60% of the maximum oxygen uptake (15.6 m/min) for 60 minutes. The exercise was performed 6 days per week for 4 continuous weeks. Needling treatment was performed in the needling group and the post-exercise needling group at the end of each exercise. The needle position was in the middle of the gastrocnemius muscle, and the needling time was 5 minutes. Achilles tendon and gastrocnemius of rats were harvested followed by histological analysis in the 5th week. Hematoxylin-eosin staining was used to observe the structural changes of Achilles tendon; immunofluorescence staining was used to detect the expression of collagen and related cytokines in the Achilles tendon; western blot assay was used to detect transforming growth factor β1 expression in the gastrocnemius. The study protocol was approved by the Experimental Animal Ethics Committee of Beijing Sport University.
RESULTS AND CONCLUSION: The collagen fibers of the Achilles tendon were disordered in the exercise and post-exercise needling groups. The expression of transforming growth factor β1 in the gastrocnemius was significantly higher in the exercise group than the other three groups (P < 0.05), and was significantly higher in the post-exercise needling group than the blank control and needling groups (P < 0.05). The expression of type I collagen in the Achilles tendon was significantly lower in the exercise group than in the other three groups (P < 0.05). The expression of type III collagen was significantly higher in the exercise group than in the other three groups (P < 0.05), and significantly higher in the post-exercise needling group than the needling and blank control groups (P < 0.05). The expression of matrix metalloproteinase 1 in the Achilles tendon was significantly lower in the exercise group than the other three groups (P < 0.05), whereas the expression of matrix metalloproteinase 13 in the Achilles tendon was significantly higher in the exercise group than the other three groups (P < 0.05). The expression of transforming growth factor β1 in the Achilles tendon was significantly higher in the exercise group than the other three groups (P < 0.05), and was significantly higher in the post-exercise needling group than the needling and control groups (P < 0.05). There was no significant difference in insulin-like growth factor 1 expression among the four groups. To conclude, post-exercise gastrocnemius needling can reduce the risk of Achilles tendon degeneration in obese rats.

Key words: needling, gastrocnemius, Achilles tendon degeneration, mechanical growth factor, tension, collagen, matrix metalloproteinase