The Study On Flexion Relaxation Phenomenon In The Condition Of Asymmetric Support And Loading

Objective: Injuries of lumbar muscles and low back pain happen frequently in thegeneral population today. Many researchers have found that erector spinae having aflexion relaxation phenomenon when they try to work out the pathogenesis andpreventive measures. The phenomenon changes when the muscle has a differentworking condition. In daily life, the movements of human action are mostlyasymmetric and with load. Therefore, we can observe the variation of flexionrelaxation phenomenon of erector spinae being in different working environment bysetting different double feet support and asymmetric load conditions, which will helpus to understand the muscle working principle better and conclude possibleapproaches that injuries occur. This is good for us to keep our waist from injury.Methods:15students who meet the requirement from Shandong NormalUniversity are selected to participate in the experiment voluntarily. With GermanBiovision multi-channel surface EMG analysis and Sony digital camera, the EMGsignals of bilateral erector spinaes, rectus abdominis, biceps femoris and track imagesof the markers on the skin surface are collected synchronously in different gesture andloading conditions, from which are muscular work conditions of different joint anglesobtained, thereby the difference of muscle working among different gesture andloading conditions can be analysed.Results:1) In5different conditions, in addition to left lifting, no significantdifferences in MAV peak value between the left and the right erector spinae.2) Theleft erector spinae is slightly different from the right erector spinae when using thetrunk angle α to mark the opening and closing of the EMG signal. The right erectorspinae closes in almost the same trunk angle between right foot support condition andboth feet support condition, while the left erector spinae is opposite.3) When marking with lumbar angle β, both sides of erector spinae have the same changes. When theEMG signal closes, there is difference only between left foot support condition andboth feet support condition, no difference in other conditions. When the EMG signalopens, the other four conditions are all different from both feet support condition.4)Comparing the two sides of erector spinae under5different conditions, when EMGsignal closes, there is significant difference in the trunk angle α under theconditions of left foot support, left lifting, right lifting and in the lumbar angle βunder both feet support condition; when the EMG signal opens, there is no differenceboth in the trunk angle α and lumbar angle β under5conditions.5) In addition tothe EMG closing angle under right foot support condition, the antagonism betweenerector spinae and rectus abdominis shows that there are significant differences bothbetween erector spinae closing angle and rectus abdominis opening angle andbetween erector spinae opening angle and rectus abdominis closing angle in otherconditions.6) biceps femoris has a similar flexion relaxation phenomenon, generally,under the both feet support condition, both sides of biceps femoris have thephenomenon; under the left foot support condition, the left biceps femoris loses thephenomenon, while the right biceps femoris has a longer relaxation period and lowerEMG value; under the right foot support condition, the right biceps femoris loses thephenomenon, while the left biceps femoris has a longer relaxation period and lowerEMG value; under the left lifting and right lifting conditions, both sides of bicepsfemoris show a shorter relaxation period and higher EMG value.Suggestion: When marking the opening and closing of EMG signal with thetrunk angle α, there is difference between two erector spinae muscles whencomparing the other four conditions to the both feet support condition. But whenmarking with the lumbar angle β, two erector spinae muscles show the samechanges. So maybe it’s better to choose the lumbar angle βas marking angle.