Quantitative Study On Paraspinal Muscle Of Amateur Marathon Runners Based On MR Chemical Shift Imaging

Objective: Aim to study the effect of marathon on the fat content,cross sectional area(CSA)and effective muscle content of paraspinal muscle(PM)of amateur marathon runners and healthy volunteers by MR chemical shift imaging technique to quantitatively analyze the fat content and CSA of PM of amateur marathon runners and healthy volunteers in order to explore the effect of marathon exercise on the fat content,CSA and effective muscle content of human PM.Methods: 28 amateur marathon runners were recruited as the experimental group and 25 healthy volunteers as the control group.The baseline information of all the subjects were collected,and the body mass index(BMI)was calculated.All subjects were examined by Siemens Magnetom Aera 1.5T MRI.The bilateral psoas major and erector spinae were divided into L2,L3,L4 and L5 segments with vertebral body as the symbol.Tools-Freehand tool was used to avoid subcutaneous fat and muscle-fat boundary,and the region of interest(ROI)of psoas major and erector spinae on both sides was manually delineated.PDFF and CSA of corresponding muscles were obtained and recorded,and the average value of both sides was taken,and the CMI value of this muscle was calculated.The calculation formula of CMI value was CMI=CSA ×(1-PDFF).The data were measured by two radiologists who were engaged in imaging diagnosis of musculoskeletal system.Results: The CSA,PDFF,CMI of L2,L3,L4,L5 segments of psoas major and PDFF of each segment of erector spinae were significantly different from those of the control group(P<0.05).The CSA,CMI of L5 segment of erector spinae were significantly higher than those of the control group(P<0.05),while the CSA,CMI of L2,L3,L4 segments of erector spinae were not significantly different from those of the control group(P>0.05);After standardization of CSA/BMI,the CSA/BMI of L2,L3,L4 and L5 segments of psoas in the experimental group was still significantly higher than that of the control group(P<0.05),the CSA/BMI of L5 segment of erector spinae was significantly higher than that of the control group(P=0.005),the CSA/BMI of L3 and L4 segments of erector spinae had no significant difference with the control group(P>0.05),and the CSA/BMI of L2 segment of erector spinae had marginal difference with the control group(P=0.048).Conclusion: This study explores the regional differences of PM composition and the differences between amateur marathon runners and healthy volunteers.The results show that each segment of psoas major and L5 erector spinae has higher CSA and muscle contraction index,and each segment of psoas major and erector spinae has less fat infiltration,which reveals that these muscles play an important role in marathon endurance running.