Lower Limb Kinematics And Its Measurement Accuracy During Running In Runners With Different Foot Strike Patterns Using Inertial Measurement Units

Background and Objective: As a portable kinematic measurement tool,inertial measurement units(IMUs)have been widely used in the field of sports science and can evaluate and monitor motion in a variety of sports environments.IMUs’ measurements can not only provide real-time feedback on athletic performance during running,but also facilitate the monitoring of runner’s running biomechanics to prevent the occurrence of running-related sports injuries.However,the quantitative summaries of the validity and reliability of three-dimensional kinematics measurements of the lower extremity joints derived from IMUs during running are still lacking.In addition,foot strike pattern(FSP)is one of the important potential risk factors affecting running gait,it is essential to investigate whether FSP has an impact on the validity and reliability of IMUs-based three-dimensional kinematic measurements of the lower extremity joints during running,which will be beneficial to provide evidence and practical support for the application of IMUs in runners with different FSPs.Based on this,Study 1 was conducted to summarize and quantify the validity and reliability of gait spatiotemporal parameters and lower extremity joint kinematic measurements during running obtained from IMUs through an evidence-based study;then,Study 2 was conducted to discuss the effect of FSP on three-dimensional kinematic measurements of the lower extremity joint.Study 1: Validity and reliability of IMUs on gait spatiotemporal outcomes and lower extremity joint kinematics during running: a systematic review and Meta-analysisObjective: Through systematic review and Meta-analysis,to investigate the development of the research on the validity and reliability of IMUs for measuring gait spatiotemporal outcomes and lower extremity joint kinematics in health adults during running,providing theoretical and evidence-based support for subsequent studies.Methods: Pub Med,CINAHL,Embase,Scopus and Web of Science electronic databases were searched from inception until September 2021.The inclusion criteria were as follows: 1)evaluated the validity and/or reliability of measurements obtained from IMUs,2)measured specific gait spatiotemporal or lower extremity joint kinematic outcomes,3)compared measurements using IMUs with those obtained using reference systems,4)collected data during running,5)assessed human beings and 6)were published in English.Eligible articles were reviewed using a modified quality assessment.Results: Twenty-five articles were included in the systematic review,and data from 12 were pooled for Meta-analysis.The methodological quality of studies ranged from low to moderate.Concurrent validity was excellent for stride length [intraclass correlation coefficient(ICC)(95% confidence interval(CI))=0.937(0.859,0.972),p<0.001],step frequency [ICC(95% CI)=0.926(0.896,0.948),Pearson correlation coefficient(r)(95% CI)=0.989(0.957,0.997),p<0.001] and ankle angle in the sagittal plane(r(95% CI)=0.939(0.544,0.993),p=0.002),moderate to excellent for stance time(ICC(95% CI)=0.664(0.354,0.845),r(95% CI)=0.811(0.701,0.881),p<0.001)and good for running speed(ICC(95% CI)=0.848(0.523,0.958),p<0.001).The summary Fisher’s Z value of fight time was not statistically significant(p=0.13).Similarly,the stance time showed excellent test–retest reliability(ICC(95% CI)=0.954(0.903,0.978),p<0.001)and step frequency showed good test–retest reliability(ICC(95% CI)=0.896(0.837,0.933),p<0.001).Conclusions:(1)Findings in the current Meta-analysis support the use of IMUs for monitoring running gait spatiotemporal parameters in healthy adults,but the validity and reliability of IMUs-based measurements of lower extremity joint kinematics during running lacks sufficient evidence.(2)Running speed,IMUs’ mounting position and running surface can affect the validity and reliability of IMUs’ measurements.(3)There is a lack of high-quality literature on the kinematics of running gait based on IMUs.Study 2: Validity and reliability of three-dimensional lower limb joint kinematics measured by the IMUs of runners with different FSPsObjective: To determine the effect of FSP on the validity and reliability of the IMUs’ measurements,the validity and reliability of the three-dimensional lower limb joint kinematic outcomes obtained by the IMUs for runners with rearfoot strike pattern(RFS)and non-rearfoot strike pattern(NRFS)were assessed.Methods: Fifteen habitual recreational male RFS runners and 15 habitual recreational male NRFS runners participated in the study.An IMUs and an optical motion capture system were used to simultaneous collect 3D kinematic of lower extremity joint data from participants running at 12km/h.Ten consecutive gait strides were used to calculate hip,knee and ankle kinematics.Validity was evaluated using the coefficient of multiple correlation(CMC),Systematic error(SE),Spearman’s correlation coefficient(r)and root mean square error(RMSE).Reliability was evaluated using the CMC,SE,ICC with 95% CI and RMSE.Results: The joint angle waveforms showed a high correlation between the two systems after the offset correction in the sagittal plane(NRFS: CMC=0.924–0.968,SE=4.6°–13.7°;RFS: CMC=0.930–0.965,SE=3.1°–7.7°),but revealed high variability in the frontal and transverse planes.The reliability of the hip,knee and ankle joint angle waveforms measured by the IMUs were shown to be very good to excellent in the sagittal plane(between-rater: NRFS: CMC=0.967–0.975,SE=1.9°–2.9°;RFS:CMC=0.922–0.989,SE=1.0°–2.5°;intra-rater: NRFS: CMC=0.950–0.978,SE=1.6°–2.7°;RFS: CMC=0.920–0.989,SE=1.7°–2.2°),whereas the reliability was weak to very good(between-rater: NRFS: CMC=0.480–0.947,SE=1.1°–2.7°;RFS:CMC=0.646–0.873,SE=0.7°–2.4°;intra-rater: NRFS: CMC=0.666–0.867,SE=0.7°–2.8°;RFS: CMC=0.321–0.805,SE=0.9°–5.0°)in the frontal and transverse planes across all joints in both types of runners.Conclusions:(1)FSPs can affect the accuracy of the kinematic measurements measured by the IMUs.(2)The IMUs system is a feasible tool for measuring lower extremity joint kinematics in the sagittal plane during running,especially for RFS runners.(3)Lower extremity running kinematic measurements in the frontal and transverse planes measured by the IMUs system showed low validity and reliability,and therefore need to be used with caution.