Effect of Different Upper Limb Preload on Voluntary Contraction of Lumbar Muscle
Objective:This study explores the effects of different upper limb preload methods and intensities on the maximum voluntary contraction force of lumbar muscles.Methods:20 subjects were recruited in this study,and each subject participated in 4 groups of experiments in random order.During the experiment,the subjects maintained in a neutral and upright sitting position,and were subjected to full force co-activation of the lumbar and abdominal muscles under no preload,arm lift preload,hand pull preload and hand grip preload,respectively.The preload intensity of each preload method was set at 20％and 40％of the maximum load force.At the same time,the electromyographic signals of the bilateral lumbar multifidus and erector spinalis muscles were recorded.Results:In bilateral multifidus muscles,the root mean square(RMS)and integrated electromyography(IEMG)values of the arm lift and hand pull preload methods were higher than those of the no preload group(P＜0.05).There was no statistical difference in RMS and IEMG values between the hand grip preload method and the no preload group(P＞0.05);There was no statistically significant difference in RMS and IEMG val-ues between the three preload methods and the no preload group in the bilateral vertical spine muscles(P＞0.05).In the comparison of dif-ferent preload methods,the RMS and IEMG values of the arm lift and hand pull preload methods were higher than those of the hand grip preload method(P＜0.05),and the RMS and IEMG values of arm lift preload method were higher than those of hand pull preload method(P＜0.05).Conclusion:The muscle pre-activation brought about by arm lift and hand pull preload methods can effectively improve the voluntary contraction strength of the lumbar multifidus muscle.The greater the preload intensity,the greater the muscle contraction strength may also be,and the arm lift preload method has a better promoting effect.
NETL
NSTL
万方数据
