The Study Of PJPs Domain Changes As The Causative Factor Of Skeletal Muscle Overuse Injury Caused By Eccentric Exercise

1.Objective:Overuse injury is a common skeletal-muscle system disease with strong sports and work relevance,which has a serious impact on the life of competitive athletes and ordinary working people.Overuse injury is extremely common,but its mechanism is not yet clear.Based on the research of domestic and foreign scholars,it is found that the overuse of skeletal muscle may be closely related to the changes of the perimysial junction plates?perimysial junctional plate,PJPs?domain.Therefore,this study used eccentric training to cause overuse damage,and explore the mechanism of skeletal muscle overuse injury based on changes in PJPs domain.2.Methods:Thirty healthy male Wistar rats were randomly divided into 5 groups after one week of adaptive training:control group?CON?,4-week continuous training group?4E?,4 weeks next day training group?4N?,4 weeks of continuous training one week natural recovery group?1RG?,4 weeks next day training one week natural recovery group group?1RNG?.The normal diet of each group,the CON group is free to move.The 4E group was trained for 4 weeks(running platform slope-16°,speed16²0m·min^-1,60⁹0min·d^-1,5days/week).The 4N group was trained for 4 weeks(running platform slope-16°,speed 16²0m·min^-1,60⁹0min·d^-1,3days/week).The1RG and 1RNG groups naturally recovered for one week after the end of training.The CON group was removed immediately after the end of the four weeks?extensor digitorum longus?,4E and 4N groups removed 36 hours later after the last training;1RG and 1RNG group were removed immediately after the end of the 5th week.Transmission electron microscopy was used to observe the changes of PJPs domain.Scanning electron microscopy was used to observe the branching changes of the perimysium collagen network?1.5 mol/L NaOH digestion and non-digestion technique?.3.Results:3.1 Changes in PJPs domain in 4E group:?1?In the external sarcolemma PJPs structural,the skeletal muscle perimysial collagen network plexi and its small plexi increased,and the number of PJPs showed an excessive decrease?P<0.001?.?2?In the sarcolemmal PJPs structural,the number of caveolae in the sarcolemmal PJPs structure increased?P<0.001?,and the sarcolemma was severely degraded?P<0.001?.?3?In the subsacrolemmal PJPs structural,mitochondrial swelling occurred in the intermyofibrial and subsarcolemmal mitochondria;sarcomere severely shortened?P<0.001?,and sarcomere structure disorder.3.2 Changes in PJPs domain in 1RG group:?1?In the external sarcolemma PJPs structural,the skeletal muscle perimysial collagen network plexi and its small plexi increased,and the number of PJPs showed an excessive increase?P<0.001?.?2?In the sarcolemmal PJPs structural the number of caveolae increased?P<0.001?,slightly less than the 4E group,and the degree of sarcolemmal degradation was still severe but decreased compared with the 4E group?P<0.001?;?3?In the subsacrolemmal PJPs structural,the intermyofibrial and subsarcolemmal mitochondria were clearly mitochondrial fusion,the severity of sarcomere damage was reduced,and the length of sarcomere was still significantly shortened?P<0.001?.3.3 Changes in PJPs domain in 4N group:?1?In the external sarcolemma PJPs structural,the skeletal muscle perimysial collagen network plexi and its small plexi increased,the number of PJPs showed an increased state?P<0.001?,but the magnitude was small;?2?In the sarcolemmal PJPs structural,the number of caveolae increased?the first in the 5 groups??P<0.001?,the size varied,and the sarcolemma was moderately degraded;?3?In the subsacrolemmal PJPs structural,there were mitochondrial fusion in the intermyofibrial and subsarcolemmal mitochondria,and the sarcomere was severely shortened?after the 4E group??P<0.001?,and the sarcomere structure was disordered.3.4 Changes in PJPs domain in 1RNG group:?1?In the external sarcolemma PJPs structural,the skeletal muscle perimysial collagen network branch cable and its small branches decrease,the number of PJPs has basically recovered;?2?In the sarcolemmal PJPs structural,the number of caveolae recovered,and the sarcolemma was slightly degraded.?3?In the subsacrolemmal PJPs structural,the intermyofibrial and subsarcolemmal mitochondrial structure was basically normal,and the length and structure of the sarcomere were basically restored.3.5 The changes of blood indexes in the rats of each group:the levels of serum H₂O₂,MDA and LDH in the 4E,4N,1RG,and 1RNG groups were higher than those in the CON group,and the H₂O₂ content,MDA content,and LDH content in the 4N group were higher than those in the 4E group;H₂O₂ content and MDH content were higher than 1RNG group,and there was no significant difference in LDH content between1RG group and 1RNG group.4.Conclusion:4.1 By observing the changes in the skeletal muscle PJPs domain,it was found that the effect of the next day training group was better than that the continuous training group.4.2 Excessive eccentric training reduces the small branches of the fascia collagen fiber network branch cable,deviates from the endometrium and sarcolemma,affects the PJPs homeostasis of the domai,and causes the occurrence of overuse injury.4.3 After 1 week of excessive eccentric training and natural recovery,the number of PJPs increased,affecting the steady state recovery of PJPs domain,and the repair of skeletal muscle injury was slow.4.4 The steady-state changes in the PJPs domain caused by excessive eccentric training are related to the inhibition of inflammatory response during exercise,leading to prolonged repair time of skeletal muscle injury.