Posture related to myoelectric silence of erectores spinae during trunk flexion

Electromyographic activity of erectores spinae exhibits points of abrupt change during trunk flexion from the erect position and return extension. This study examined the positions at which the myoelectric activity suddenly disappeared and later reappeared. Forty adults were investigated to define accurately the inclinations of the trunk, pelvis, and vertebral column at these positions. The positions at the commencement and cessation of the period of electrical silence both occurred at two-thirds of maximum trunk flexion (mean = 80 degrees +/- 13 degrees SD). At these positions, all flexion measurements were significantly less than their maxima (P less than 0.001). Hip flexion at the commencement of electrical silence was slightly above one-half its maximum range, and similar to the position at the recommencement of electrical activity (mean = 40 degrees +/- 12 degrees SD). The most reproducible measurement (r = 0.88) in both positions was vertebral flexion (89% Max.; mean = 48 degrees +/- 6 degrees SD). Eleven of the male subjects repeated the experimental task holding 10.1 kg in their hands. The effect of this was to produce inhibition and reactivation of erectores spinae at a greater degree of vertebral flexion.     

The influence of lordosis on axial trunk torque and trunk muscle myoelectric activity.

Force contributions from the facet complex and posterior ligaments during the generation of axial torque are a function of lordosis, and it has been speculated that these forces together with muscular contributions play a role in axial trunk twisting. This study investigated the electromyographic activity of the trunk musculature and torque-generating capacity of the lumbar spine under the conditions of normal lordosis, hyperlordosis, and hypolordosis. Eleven male subjects volunteered for this study. The subjects performed isometric twisting efforts and maximum dynamic twisting efforts at 30 degrees/sec. The myoelectric activity levels (normalized to maximal amplitude obtained from nontwist activities) were quite low despite maximal efforts to generate axial torque (for example: approximately 60% maximum voluntary contraction for latissimus dorsi and even lower for the abdominals). Furthermore, changes in lordosis did not produce any consistent changes in muscle activity, although a hyperlordotic spine produced significantly smaller axial torques, and a hypolordotic spine smaller still. Larger torques were measured during all three conditions of lordosis, as the subjects rotated toward an untwisted position, and lower torques as the subjects rotated away. The opposite trend was observed, however, in myoelectric activity of the agonistic side of latissimus dorsi, the thoracic level of erector spine, and the lumbar level of erector spinae, i.e., larger amplitudes were observed as the trunk was twisted away from the untwisted position. These data suggest that tissues other than muscle (i.e., passive tissue) contribute significantly to axial torque production and that the flexed and twisted spine is less able to resist applied axial torques, possibly increasing the risk of torsional injury.     

Myoelectric activity and sequencing of selected trunk muscles during isokinetic lifting.

Trained weight lifters lift heavy loads without a concomitant degree of acute low-back injuries. To study the process by which large loads are lifted with minimal injury, integrated electromyographic signals were recorded from four large muscle groups: gluteus maximus, quadriceps, latissimus dorsi, and erector spinae in 4 weight lifters and 11 asymptomatic control subjects. These signals were recorded during a floor-to-knuckle-height isokinetic lift (dead lift) at 30.5 and 45.7 cm/sec. The signals were normalized for the height of the lift and the maximal isokinetic integrated electromyographic activity. The weight lifters achieved maximal force at 50% of maximal lift height, whereas the control subjects achieved it at 67%. Although not statistically significant, the weight lifters used the gluteus maximus more during the early stages of the lift, perhaps contributing to earlier development of force. This process would stabilize the pelvis and permit the erector spinae to extend the trunk more efficiently. The weight lifter then completed the lift with prolonged and increasing activity in the quadriceps. This technique may minimize the required force in the erector spinae and the forces on the low-back structures. Clinical implications include more effective strength training of lifting muscle groups other than spinal extensors and the teaching of lifting strategies employed by weight lifters in low-back rehabilitation and work-hardening programs.     

脊柱侧方运动时躯干肌肌电图期相变化和活动规律

目的 研究脊柱侧方运动时躯干肌肌电图期相变化和活动规律。方法在6个站立的受试者，单手不同负重（0～40kg）进行侧提和侧放时，应用肌内电极检测8块躯干肌的活动；测量摄像中对侧躯干角运动。分析所记录的对侧和同侧（负重侧）肌运动期相EMG。结果本实验观察到躯干肌活动的三个期，两个来自对侧肌在运动开始和结束，一个来自同侧肌在运动的中期。随负重增加，对侧肌活动增加，同侧肌活动减低。腹部肌的双侧协同活动大于背部肌，并且侧放时大于侧提，无负重和轻负重大于重负重。结论侧对侧躯干运动时，躯干肌的共济协调活动取决于躯干的位置和负重。腹部肌，特别是腹壁斜肌和腹横肌，比其他躯干肌参与更多的躯干稳定功能，尤其见于轻负重侧放时。     

The activity of individual trunk muscles during heavy physical loading

The myoelectric activity of ten trunk muscles were recorded, using intramuscular electrodes, when ten subjects made maximal and 50% of maximal static exertions in standing postures. Exertions were made in flexion, extension, and left and right lateral bending. Three heavy-lifting tasks also were studied. A biomechanical model was used to predict the forces in the trunk muscles, and the predictions then were compared to the measurements. The abdominal muscles were all active in attempted flexion, while the erector spinae muscles were inactive. In attempted extension, the erectors were maximally active, but considerable activity was present in the abdominal muscles as well. The highest activity levels recorded in the oblique abdominal muscles were in lateral bending. There were high degrees of correlation between the measured muscle activities and predicted muscle tensions for the erector spinae and rectus abdominus muscles, while the correlation coefficients for the oblique abdominal muscles were lower (0.4-0.7). The study indicates that inclusion of antagonistic activity is an important consideration to improve model predictions. The oblique abdominal muscles appear to be more active, in general, than predicted. For the longitudinal trunk muscles, the predictions are excellent throughout.     

Lumbar spine orthosis wearing. II. Effect on trunk muscle myoelectric activity

The effects of wearing commonly prescribed low-back braces and corsets on myoelectric signal levels in the erector spinae and oblique abdominal muscles were investigated. A lumbosacral corset, a chairback brace, and a molded thoracolumbosacral orthosis (TLSO) were studied. Nineteen tasks involving sitting and standing were performed by five healthy adult men. Myoelectric signal levels measured when wearing each orthosis were compared with those measured when performing the same task while wearing no orthosis. The changes in mean myoelectric signal levels ranged from a 9% reduction to a 44% increase when the lumbosacral corset was worn, from a 27% reduction to a 25% increase when the chairback brace was worn, and from a 38% reduction to a 19% increase when the TLSO was worn.     

Intramuscular pressures during exercise. Comparison of measurements with and without infusion

Our objective was to compare two techniques for measuring intramuscular pressures during dynamic exercise. In 20 volunteers muscle contraction and relaxation pressures were recorded with a noninfusion method (slit catheter) and with a microcapillary infusion method (Myopress catheter). Relaxation pressures measured by noninfusion were higher than those measured by infusion. The dynamic properties of the infusion method were higher as compared with the noninfusion method. The dynamic properties of the noninfusion method increased when microcapillary infusion was connected. This resulted in a lower recording of the muscle-relaxation pressure than without infusion. We concluded that the microcapillary infusion technique and the design of the tip of the Myopress catheter are better suited for pressure recordings during exercise.     

Intramuscular pressures during exercise Comparison of measurements with and without infusion

Our objective was to compare two techniques for measuring intramuscular pressures during dynamic exercise. In 20 volunteers muscle contraction and relaxation pressures were recorded with a noninfusion method (slit catheter) and with a microcapillary infusion method (Myopress catheter). Relaxation pressures measured by noninfusion were higher than those measured by infusion. The dynamic properties of the infusion method were higher as compared with the noninfusion method. The dynamic properties of the noninfusion method increased when microcapillary infusion was connected. This resulted in a lower recording of the muscle-relaxation pressure than without infusion. We concluded that the microcapiliary infusion technique and the design of the lip of the Myopress catheter are better suited for pressure recordings during exercise.     

Electromyographic activity of trunk and hip muscles during stabilization exercises in four-point kneeling in healthy volunteers

Stabilization exercises are intended to optimize function of the muscles that are believed to govern trunk stability. Debate exists whether certain muscles are more important than others in optimally performing these exercises. Thirty healthy volunteers were asked to perform three frequently prescribed stabilization exercises in four-point kneeling. The electromyographic activity of different trunk and hip muscles was evaluated. Average amplitudes obtained during the exercises were normalized to the amplitude in maximal voluntary contraction (% MVIC). During all three exercises, the highest relative muscle activity levels (> 20% MVIC) were consistently found in the ipsilateral lumbar multifidus and gluteus maximus. During both the single leg extension (exercise 1) and the leg and arm extension exercise (exercise 2) the contralateral internal oblique and ipsilateral external oblique reached high levels (> 20%MVIC). During exercise 2 there were also high relative activity levels of the ipsilateral lumbar part and the contralateral thoracic part of the iliocostalis lumborum and the contralateral lumbar multifidus. During the leg and arm extension exercise with contralateral hip flexion (exercise 3) there were high relative muscle activity levels of all back muscles, except for the latissimus dorsi muscle. The lowest relative muscle activity levels (< 10% MVIC) were found in the rectus abdominis and the ipsilateral internal oblique during all exercises, and in the contralateral gluteus maximus during exercises 1 and 2. The results of this study show that in exercises in four-point kneeling performed by healthy subjects, hip and trunk muscles seem to work together in a harmonious way. This shows that when relative activity of muscles is measured, both “global and local” muscles function together in order to stabilize the spine.     

In vivo medial and lateral tibial loads during dynamic and high flexion activities.

Though asymmetric loading between the medial and lateral compartments of total knee replacements may contribute to implant loosening and failure, the in vivo contact force distribution during dynamic daily activities remains unknown. This study reports in vivo medial and lateral contact forces experienced by a well-aligned knee implant for a variety of activities. In vivo implant motion and total axial load data were collected from a single knee replacement patient performing treadmill gait (hands resting on handlebars), step up/down, lunge, and kneel activities. In vivo motion was measured using video fluoroscopy, while in vivo axial loads were collected simultaneously using an instrumented tibial component. An elastic foundation contact model employing linear and nonlinear polyethylene material properties was constructed to calculate medial and lateral contact forces based on the measured kinematics, total axial loads, and centers of pressure. For all activities, the predicted medial and lateral contact forces were insensitive to the selected material model. The percentage of medial to total contact force ranged from 18 to 60 for gait, 47 to 65 for step up/down, and 55 to 60 for kneel and lunge. At maximum load during the motion cycle, medial force was 1.2 BW for gait and 2.0 BW for step up/down, while the corresponding lateral forces were 1.0 and 1.5 BW, respectively. At mean load in the final static pose, medial force was 0.2 BW for kneel and 0.9 BW for lunge, with corresponding lateral forces of 0.1 and 0.7 BW, respectively. For this patient, a constant load split of 55% medial-45% lateral during loaded activity would be a reasonable approximation for these test conditions.     

Geometric measurements of the lumbar spine in Chinese men during trunk flexion

STUDY DESIGN: An analysis of the geometric data of the lumbar spine in Chinese men. Lateral radiographs were obtained of 16 men in the upright position to a trunk flexion of 90 degrees in 30 degrees increments. OBJECTIVES: To establish reference data concerning the geometry of the lumbar spine for various degrees of trunk flexion. SUMMARY OF BACKGROUND DATA: In previous studies, the morphometry and alignment of the lumbar spine have been investigated. Reports of systematic analyses of the lumbar spine in trunk flexion have lacked adequate radiographic data. Moreover, few studies have focused on measuring lumbar spine geometric data in Chinese individuals. METHODS: A total of 67 landmarks on each radiograph were identified. They were marked by investigators and digitized using a HyperSpace digitizing system (V.17: Mira Imaging Inc., Salt Lake City, UT). The geometric configuration of the vertebrae and discs then was derived from the digitized points. RESULTS: The dimensions of the vertebrae and disc on the lumbar spine obtained in this study were similar to those of previous studies. The motion of the lumbosacral spine had the greatest contribution in trunk flexion, approximately 90% (i.e., rotating at the rate of 9 degrees for each 10 degrees of trunk flexion) when the trunk was flexed from 30 degrees to 60 degrees. After that, the hips were dominant in accomplishing the trunk flexion from 60 degrees to horizontal. This motion patterns may be useful for making clinical diagnoses of lumbar function in Chinese men. CONCLUSIONS: No obvious interracial differences were found in the geometric data found in this study, which suggests that morphometric data obtained from Caucasian individuals may be applied to Chinese patients for clinical purposes.     

Functional roles of abdominal and back muscles during isometric axial rotation of the trunk.

Electromyographic (EMG) studies have shown that a large number of trunk muscles are recruited during axial rotation. The functional roles of these trunk muscles in axial rotation are multiple and have not been well investigated. In addition, there is no information on the coupling torque at different exertion levels during axial rotation. The aim of the study was to investigate the functional roles of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus during isometric right and left axial rotation at 100%, 70%, 50% and 30% maximum voluntary contractions (MVC) in a standing position. The coupling torques in sagittal and coronal planes were measured during axial rotation to examine the coupling nature of torque at different levels of exertions. Results showed that the coupled sagittal torque switches from nil to flexion at maximum exertion of axial rotation. Generally, higher EMG activities were shown at higher exertion levels for all the trunk muscles. Significant differences in activity between the right and left axial rotation exertions were demonstrated in external oblique, internal oblique, latissimus dorsi and iliocostalis lumborum while no difference was shown in rectus abdominis and multifidus. These results demonstrated the different functional roles of trunk muscles during axial rotation. This is important considering that the abdominal and back muscles not only produce torque but also maintain the spinal posture and stability during axial rotation exertions. The changing coupling torque direction in the sagittal plane when submaximal to maximal exertions were compared may indicate the complex nature of the kinetic coupling of trunk muscles.     

Abdominal plasty with and without plication-effects on trunk muscles,lung function,and self-rated physical function

Background: Weight loss after obesity and pregnancy is associated with excess abdominal skin and weakness of the abdominal wall, which is assumed to cause low back pain and reduce lung function. Today, abdominoplasty is the only known method to treat excess skin, and plication is used to improve aesthetics and function alone or in addition to surgery. There is lack of evidence concerning the surgery’s effect on trunk muscles, lung function, and physical function. The aim was to evaluate the effect on trunk muscle endurance, lung function and self-rated physical function after abdominoplasty with and without muscle plication.

Aim: To evaluate the effect on trunk muscle endurance, lung function, and self-rated physical function after abdominoplasty with and without muscle plication.

Methods: A series of 125 people were randomised to abdominoplasty with or without rectus abdominis muscle plication. Trunk muscle endurance, lung function, and self-rated physical function (disability rating index) were measured before and 1 year after surgery.

Results: There were no significant differences in any of the measured variables between the groups either before or after surgery. A significant decrease (p?=?.02) in back muscle endurance was seen after abdominoplasty without muscle plication. A significant positive effect (p?=?.04) in one of the activities (running) assessed by DRI was reported after abdominoplasty with muscle plication.

Conclusions: No significant differences in trunk muscle endurance, lung function, or self-rated physical function were found after abdominoplasty with vs without plication. As the primary indication for surgery was excess skin and not diastasis of the rectus abdominis muscles, there is a need for future trials before conclusions can be drawn of effect of abdominoplasty and plication.     

The onset of deep abdominal muscles activity during tasks with different trunk rotational torques in subjects with non-specific chronic low back pain

BackgroundAlthough delayed onset of the deep abdominal muscles activity in subjects with non-specific chronic low back pain (CLBP) has been suggested to be related to trunk rotational torque, no study has examined the onsets associated with non-specific CLBP during a variety of tasks with different trunk rotational torque. The aim of this study is to compare the onsets of deep abdominal muscles activity among tasks with different trunk rotational torques in subjects with and without non-specific CLBP.MethodsTwelve subjects with non-specific CLBP and 13 control subjects were included. They performed 8 types of upper limb movements. The onsets of muscular activity of bilateral internal oblique-transversus abdominis (IO-TrA) and trunk rotational torque due to the upper limb movements were measured using a surface electromyography and a three-dimensional motion analysis system.ResultsIn non-specific CLBP group, right IO-TrA activities were significantly delayed during tasks with left trunk rotational torque compared with the control (P < 0.05), while onsets of the left IO-TrA activities were significantly later than those of the control during tasks with right rotational torque of the trunk (P < 0.05). There were no significant differences in onsets of both sides IO-TrA during tasks without trunk rotational torque between non-specific CLBP and control groups (P > 0.05).ConclusionsThe onsets of IO-TrA activities in subjects with non-specific CLBP were delayed during tasks with rotational torque of the trunk in the opposite direction, suggesting a possibility that delayed onset of the deep abdominal muscles during rotational torque of the trunk might be etiology of chronic low back pain.