| Purpose:Skeletal muscle is a highly adaptable tissue,exercise training can cause adaptive changes of skeletal muscles,increase the skeletal muscle dimension and strength.These years,the goal of sports science has always been to achieve maximum training by the best possible way,however,the fatigue damage of skeletal muscles restricts the improvement of athletes’ performance.Therefore,more and more attention has been paid to find ways to promote fatigue recovery and improve exercise ability.Physical therapy was as an emerging therapy in the field of rehabilitation,with a good therapeutic effect on bone and muscle fatigue recovery.Thereinto,ultrasound as a kind of acoustic therapy,has a large number of literature report its therapeutical effect on bone,ligament and muscle damage.Howere,there is little research on the application of ultrasound on exercise system to promote the exercise-induced skeletal muscle hypertrophy.Therefore,this paper will preliminary discussion the low intensity pulsed ultrasound(LIPUS)target sports system improved skeletal muscle hypertrophy of synergistic effect,and the influence of skeletal muscle specific secrete factors secreted Myostatin(MSTN)to regulate the molecular mechanisms of skeletal muscle reconstruction.In order to expore ultrasound targeted sports system to improve sports ability and be providing a theoretical basis about being applied better in the field of sports science.Methods:Thirty SD rats were randomly divided into three groups:normal control group(NC),treadmill exercise group(TE),treadmill exercise and low-intensity pulsed ultrasound group(TE + LIPUS),10 rats in each group.NC without any operation,TE was carried out slope treadmill training,slope is 5 °,speed is 28 m/min,60 min/d,experimental period for eight weeks,training 6 d a week,only one day rest.LIPUS group training methods were similarly to TE,but every time after training to exert treatment for 20 min and TE group was treated similarly to the TE+LIPUS group,expect that the power was not turn on.During the experiment,weight was measured once every 3 d and grip test was measured once a week.After the last training,empty stomach for 12 h,weighing the rat body weight,draw materials,accurate weighing on both sides of gastrocnemius on rats.The activity of Succinate dehydrogenase(SDH)and Malate dehydrogenase(MDH)level of gastrocnemius was analyzed by standard colorimetric using commercial kits;morphometric analysis gastrocnemius that HE stains analyze the change of the average areas of the myofibers in different groups;extract gastrocnemius of protein and RNA in different group test the molecular pathways.Western Blotting was used to detect skeletal muscle the expression of protein and phosphorylation using MSTN、ActRIIB、Akt、mTOR、FoxO1,and RT-qPCR was used to detect the expression of gene using MSTN ActRIIB、Akt、mTOR、FoxO1.On the basis of animal experiments,to further explore the effect of LIPUS,we also conducted cell experiments.Successful culture myoblast C2C12 cell line,cells were randomly divided into two groups:normal control group(NC),low-intensity pulsed ultrasound group(LIPUS).And LIPUS groups were accepted different intensity stimulate with 13 mW/cm2、30 mW/cm2、45 mW/cm2,20 min/d,NC group was treated similarly to the LIPUS group,expect that the power was not turn on.LIPUS stimulated three days,every day the microscopic observation and take photos,CCK-8 was used to test cell proliferation,H&E staining analysis cell differentiation.Results:1.Through 8 weeks of animal experiments,each group(NC、TE、TE+LIPUS)of weight and grip both have significantly different(P<0.05).The result of weight showed,compared with before,three groups of rat weight had increased and among them the largest rise was NC group.Compare with NC group,TE group had increased but no significantly different,TE+LIPUS showed a significant decrease(P<0.05).The result of grip strength showed,both TE and TE+LIPUS group significantly enhanced the grip strength of rats compared with the NC group(P<0.01,P<0.01).Especially,the grip strength in the TE+LIPUS group was significantly higher than the TE group(P<0.05).2.The results of the gastrocnemius wet weight showed,the gastrocnemius wet weight in both TE group(P<0.05)and TE+LIPUS group(P<0.01)were significantly increase compared with the NC group,and there was a significant difference between TE group and TE+LIPUS group(P<0.05).3.The results of the biochemical analysis showed,the SDH activity in both the TE and TE+LIPUS group were significantly higher than that in the NC group(P<0.01,P<0.01);but there was no significant difference between the TE and TE+LIPUS group.Compared with the NC group,both the TE and TE+LIPUS treatment correlated with an increase in the activity of MDH(P<0.05,P<0.01),and the activity of MDH in the TE+LIPUS group was significantly higher compared with the TE group(P<0.05).4.The results of the morphometric analysis showed,compared with the NC group,both TE and TE+LIPUS group presented increased average surface of muscle fibers(P<0.01,P<0.01).Furthermore,compared with the TE group,TE+LIPUS further significantly increased the cross-sectional area of muscle fibers(P<0.01).5.The results of the expression of protein and gene showed,LIPUS treatment significantly up regulated the expression of Akt,mTOR,p-Akt,p-mTOR,and significantly down regulated the expression of MSTN,ActRIIB,FoxO1 and its phosphorylation;genetic testing results with the protein had consistency.6.The result of the cell experiment showed,CCK-8 was used to detect cell proliferation,compared with the NC group,LIPUS stimulate different group but all no significant difference;among them,Lhe intensity was 30mw/cm2 showed a higher trend than others but also no significant difference.Through HE stains to analysis the cell differentiation,when the intensity was 30mw/cm2 that LIPUS group of nucleus fusion index had increased(P<0.05).Conclusion:1.The result of animal experiment showed that LIPUS can promote exercise-induced muscle hypertrophy,through increasing muscle strength,mass,muscle fiber cross-sectional area,regulating the activity of key enzymes in the Krebs cycle,improving aerobic metabolism rate,to make the skeletal muscle energy metabolism ability enhancement,inhibiting gastrocnemius the expression of MSTN protein and gene and its receptors to inhibit muscle atrophy,balancing Akt and its main downstream signaling molecules which is closely related to metabolism of skeletal muscle,making the expression of mTOR increased,accelerating protein synthesis,reduce the expression of FoxO1,leading to protein degradation,further promotng exercise-induced skeletal muscle hypertrophy.2.The result of myoblast experiment showed that LIPUS stimulation cell proliferation was not obvious,but playing an important role in cell differentiation.It is showed that in the absence basis of training.LIPUS also played a beneficial effect on skeletal muscle hypertrophy.3.LIPUS as a new kind of physical therapy method,was expected to become promotion of the fitness fanatics,athletes and some patients of muscle atrophy to increase skeletal muscle mass of adjuvant therapy,but for the widespread application in sports science and health science remained to be further explored. |
