Differential control of abdominal muscles during multi-directional support-surface translations in man

The current study aimed to understand how deep and superficial abdominal muscles are coordinated with respect to activation onset times and amplitudes in response to unpredictable support-surface translations delivered in multiple directions. Electromyographic (EMG) data were recorded intra-muscularly using fine-wire electrodes inserted into the right rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI) and transversus abdominis (TrA) muscles. Twelve young healthy male subjects were instructed to maintain their standing balance during 40 support surface translations (peak acceleration 1.3 m s⁻²; total displacement 0.6 m) that were counter-balanced between four different directions (forward, backward, leftward, rightward). Differences between abdominal muscles in EMG onset times were found for specific translation directions. The more superficial RA (backward translations) and OE (forward and leftward translations) muscles had significantly earlier EMG onsets compared to TrA. EMG onset latencies were dependent on translation direction in RA, OE and OI, but independent of direction in TrA. EMG amplitudes in RA and OE were dependent on translation direction within the first 100 ms of activity, whereas responses from the two deeper muscles (TrA and OI) were independent of translation direction during this interval. The current results provide new insights into how abdominal muscles contribute to postural reactions during human stance. Response patterns of deep and superficial abdominal muscles during support surface translations are unlike those previously described during upper-body perturbations or voluntary arm movements, indicating that the neural mechanisms controlling individual abdominal muscles are task-specific to different postural demands.     

The influence of sudden perturbations on trunk muscle activity and intra-abdominal pressure while standing

Unexpected ventral and dorsal perturbations and expected, self-induced ventral perturbations were delivered to the trunk by suddenly loading a vest strapped to the torso. Six male subjects were measured for intra-abdominal pressure (IAP) and intra-muscular electromyography of the transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abominis (OE) and rectus abdominis (RA) muscles. Erector spinae (ES) activity was recorded using surface electromyography. Displacements of the trunk and head were registered using a video-based system. Unexpected ventral loading produced activity in TrA, OI, OE and RA, and an IAP increase well in advance of activity from ES. Expected ventral loading produced pre-activation of all muscles and an increased IAP prior to the perturbation. The TrA was always the first muscle active in both the unexpected and self-loading conditions. Of the two ventral loading conditions, forward displacement of the trunk was significantly reduced during the self-loading. Unexpected dorsal loading produced coincident activation of TrA, OI, OE, RA and ES. These results indicate a response of the trunk muscles to sudden expected and unexpected ventral loadings other than the anticipated immediate extensor torque production through ES activation. It is suggested that the increase in IAP is a mechanism designed to improve the stability of the trunk through a stiffening of the whole segment.     

Task specificity in the control of intrinsic trunk muscles in man

The human trunk is a complex mechanical system comprised of large and small segments interconnected with several layers of muscles. An accurate control of this system is important during a variety of everyday tasks such as voluntary movements of the trunk, walking and running. This study was designed to investigate the interaction between muscles controlling the pelvis and the trunk during a variety of movements requiring a finely tuned coordination. Four subjects carried out seven different forms of fast oscillatory movements of the pelvis and trunk in the sagittal and transverse planes. Electromyographical activity (EMG) was recorded with surface electrodes from the abdominal muscles rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI), and erector spinae (ES), from the hip flexor muscle rectus femoris (RF), the hip extensor muscle gluteus maximus (GM) and from the hip extensor/knee flexor muscles of the hamstrings group (HAM). Movements were recorded with an optoelectronic system (Selspot). The results indicate that during spontaneous flexion-extension movements of the trunk there was a basic alternating activation between a pure flexor (RF-RA-OE-OI) and an extensor synergy (ES-GM-HAM). Different mixed synergies appeared when more specific patterns of coordination of the pelvis and spine were performed. For example, during pelvic tilts in the sagittal plane, RA-OE-OI-GM formed a synergy which was activated reciprocally with ES. The neural circuitry controlling muscles of the pelvis and trunk is apparently adaptable to a variety of different tasks. Individual muscles were shown to either cause, brake or prevent a movement and to be integrated in several different task-specific motor synergies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feedforward contraction of transversus abdominis is not influenced by the direction of arm movement

 Because the structure of the spine is inherently unstable, muscle activation is essential for the maintenance of trunk posture and intervertebral control when the limbs are moved. To investigate how the central nervous system deals with this situation the temporal components of the response of the muscles of the trunk were evaluated during rapid limb movement performed in response to a visual stimulus. Fine-wire electromyography (EMG) electrodes were inserted into transversus abdominis (TrA), obliquus internus abdominis (OI) and obliquus externus abdominis (OE) of 15 subjects under the guidance of real-time ultrasound imaging. Surface electrodes were placed over rectus abdominis (RA), lumbar multifidus (MF) and the three parts of deltoid. In a standing position, ten repetitions of shoulder flexion, abduction and extension were performed by the subjects as fast as possible in response to a visual stimulus. The onset of TrA EMG occurred in advance of deltoid irrespective of the movement direction. The time to onset of EMG activity of OI, OE, RA and MF varied with the movement direction, being activated earliest when the prime action of the muscle opposed the reactive forces associated with the specific limb movement. It is postulated that the non-direction-specific contraction of TrA may be related to the control of trunk stability independent of the requirement for direction-specific control of the centre of gravity in relation to the base of support. Received: 29 September 1995 / Accepted: 30 September 1996     

Fibre types in human abdominal muscles

Histochemical muscle fibre composition was studied in biopsies from the four different muscles of the abdominal wall (rectus abdominis, RA, obliquus externus, OE, obliquus internus, OI, and transversus abdominis, Tr) in 13 normal human subjects (9 females and 4 males, age 24–55 years) undergoing gall-bladder surgery. Muscle fibres were classified as Type I, II A, II B or II C on the basis of their myofibrillar ATPases' pH lability. There were large inter-individual variations in fibre composition, whereas, in general, the differences between the different muscles were minor or non-existent. Mean fibre distribution ranges were 55–58% I, 15–23% II A, 21–28% II B, and 0–1% II C fibres. The least fibre diameters were similar for all types and muscles (range of means 50–54 μm) except for Tr in which the Type II fibres were smaller (mean 45 μm). There was a high correlation in the size of Type I vs. II fibres and Type II A vs. II B fibres in all layers. The oxidative potential (NADH-diaphorase staining intensity) appeared high in Type I fibres and low in Type II fibres, irrespective of subgroups. Thus, based on histochemical fibre composition, the different abdominal muscles appear to have a similar functional capacity. However, functional differences between individuals were indicated by the large inter-individual variation in muscle fibre distribution.     

Fibre types in human abdominal muscles.

Histochemical muscle fibre composition was studied in biopsied from the four different muscles of the abdominal wall (rectus abdominis, RA, obliquus externus, OE, obliquus internus, OI, and transversus abdominis, Tr) in 13 normal human subjects (9 females and 4 males, age 24-55 years) undergoing gall-bladder surgery. Muscle fibres were classified as Type I, IIA, IIB or IIC on the basis of their myofibrillar ATPases' pH lability. There were large inter-individual variations in fibre composition, whereas, in general, the differences between the different muscles were minor or non-existent. Mean fibre distribution ranges were 55-58% I, 15-23% 22A, 21-28% IIB, and 0-1% II C fibres. The least fibre diameters were similar for all types and muscles (range of means 50-54 micrometer) except for Tr in which the Type II fibres were smaller (mean 45 micrometer). There was a high correlation in the size of Type I vs. II fibres and Type IIA vs. IIB fibres in all layers. The oxidative potential (NADH-diaphorase staining intensity) appeared high in Type I fibres and low in Type II fibres, irrespective of subgroups. Thus, based on histochemical fibre composition, the different abdominal muscles appear to have a similar functional capacity. However, functional differences between individuals were indicated by the large inter-individual variation in muscle fibre distribution.     

Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man.

The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion--extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the co-ordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus abdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.     

Electromyographic activity of selected trunk muscles during stabilization exercises using a gym ball

Trunk stabilization is very important for the injured lower back. The use of a gym ball, the surface of which is labile, is becoming more popular for strengthening the trunk muscles and challenging the motor control system in trunk stabilization exercises. However, little is known about the activity of the trunk muscles during such exercises. The purpose of this study was to compare the electromyographic (EMG) activity of the trunk muscles during seven stabilization exercises using a gym ball. Eleven healthy men (19.9 +/- 1.8 years old) without low back pain volunteered to participate in the study. Bipolar surface electrodes were attached to the right side of the upper and lower rectus abdominis, the obliquus externus abdominis and the upper and lower back extensor muscles. EMG signals were recorded during seven types of stabilization exercises using a gym ball and normalized to maximal voluntary contraction (% MVC). A two-way analysis of variance (ANOVA) was performed on % MVC from each task for each of the five trunk muscle sites (p < 0.05). Push-up exercise, supporting with both hands on the gym ball and toes on the floor in prone position, resulted in the highest activity of all abdominal muscles, and an exercise of the lifting the gym ball up, holding it actively between both legs with both knees flexed in supine position resulted in the lowest. Lifting up of the pelvis in a bridged position exercise, supporting the head with the gym ball and with the feet on the floor in supine position, resulted in higher muscle activity of the back extensor muscles than another exercise. It is very important for physical therapists to make clear the purpose of the trunk stabilization exercises, because different kinds of exercises with the gym ball demand various levels of muscular activity and use of various parts of the trunk muscles.     

Trunk muscle coordination in reaction to load-release in a position without vertical postural demand

The aim of this study was to investigate the coordination between the innermost muscle layer of the ventro-lateral abdominal wall, the transversus abdominis (TrA), and other trunk muscles, in reaction to a load-release without the postural demand of keeping the trunk upright. Eleven healthy male volunteers participated. Intramuscular fine-wire electromyography (EMG) was obtained bilaterally from the TrA, rectus abdominis (RA), obliquus externus (OE) and erector spinae (ES) muscles. The subjects lay on their right side on a horizontal swivel-table with immobilized pelvis and lower limbs and with the trunk strapped to a movable platform allowing for trunk flexion and extension. Subjects maintained trunk flexion or extension at different force levels against a static resistance, which was suddenly released. They were instructed to resume the start position as fast as possible. EMG signals were analysed with respect to amplitude and timing of muscle activation. Following released static flexion, TrA increased its activity in synergy with ES. Also in released static extension, TrA increased its activity, but now in synergy with RA and OE. The direction-independent activation of TrA indicates a role of this muscle in controlling inter-segmental movements of the lumbar spine. This function was not accompanied by an early activation of TrA as has been shown previously for trunk perturbations in standing, i.e. a situation with an additional demand of maintaining the trunk posture upright against gravity.     

Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man

Cresswell , A. G., Grundström , H. & Thorstensson , A. 1992. Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man. Actri Physiol Scand 144 , 409418. Received 16 July 1 991 , accepted 11 October 1991. ISSN 0001–6772. Department of Physiology III, Karolinska Institute, and Department of Radiology, Danderyd Hospital, Stockholm, Sweden. The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion-extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the coordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus ahdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.     

Abdominal muscle size and symmetry at rest and during abdominal hollowing exercises in healthy control subjects

The symmetry of, and physical characteristics influencing, the thickness of the lateral abdominal muscles at rest and during abdominal exercises were examined in 57 healthy subjects (20 men, 37 women; aged 22–62 years). M-mode ultrasound images were recorded from the abdominal muscles at rest and during abdominal hollowing exercises in hook-lying. The fascial lines bordering the transvs. abdominis, obliquus internus and obliquus externus were digitized and the absolute thickness, relative thickness (% of total lateral thickness) and contraction ratio (thickness during hollowing/thickness at rest), as well as the asymmetry (difference between sides expressed as a percent of the smallest value for the two sides) for each of these parameters were determined for each muscle. Both at rest and during hollowing, obliquus internus was the thickest and transvs. abdominis the thinnest muscle. There were no significant differences between left and right sides for group mean thicknesses of any muscle; however, individual asymmetries were evident, with mean values for the different muscles ranging from 11% to 26%; asymmetry was much less for the contraction ratios (mean % side differences, 5–14% depending on muscle). Body mass was the most significant positive predictor of absolute muscle thickness, for all muscles at rest and during hollowing, accounting for 30–44% variance. Body mass index explained 20–30% variance in transvs. abdominis contraction ratio (negative relationship). The influence of these confounders must be considered in comparative studies of healthy controls and back pain patients, unless groups are very carefully matched. Asymmetries observed in patients should be interpreted with caution, as they are also common in healthy subjects.     

Electromyographic activity of selected trunk muscles during bicycle ergometer exercise and walking

Recently, active treatment such as exercise has been increasingly advocated for CLBP (chronic low back pain). Specially, exercise to improve fitness has been recommended for the prevention of back injuries. The bicycle ergometer or walking have often been used to improve the fitness of CLBP patients. However, little is known about the activity levels of the trunk muscles during such exercise. In this study, the electromyographic (EMG) activities of the trunk muscles during bicycle ergometer exercises and walking were compared and the load level on these muscles during such exercises was investigated. The present study provides basic information concerning fitness exercise in CLBP patients. Eleven healthy male volunteers (21.7 +/- 2.5 years old) without low back pain participated in the study. Bipolar surface electrodes were attached to the right side of the rectus abdominis, the obliquus externus abdominis and lower back extensor muscles (L3). EMG signals were continuously recorded while walking and during gradual loading exercises and normalized to maximal voluntary contractions (% MVC). One way analysis of variance (ANOVA) was performed on the % MVC from each exercise and walking for each of the three trunk muscle sites (p < 0.05). The rectus abdominis muscle showed activity of about 6% MVC during any grade of exercise and walking and no significant differences were found between these forms of exercise. The obliquus externus abdominis muscle showed about 30% MVC during any grade of exercise and walking, but no significant difference was found between them. The low back muscles showed activity of about 12% MVC while walking, whereas activity level increased as the exercise load using the bicycle ergometer increased. More significant low back muscles activity was observed while walking than during exercises of 25 w and 50 w. The results of this study indicated that exercise using the bicycle ergometer should be useful for maintaining or improving fitness in CLBP patients, because it results in less load on the trunk muscles and relatively more oxygen uptake than walking.     

Electromyographic analysis of the rectus abdominis muscle in pelvic retroversion and the decrease of the lower limbs

We often face patients searching for rehabilitation for lower back disorders during the physiotherapeutic routine, and it is known that the abdominal muscle, specially the rectus abdominis muscle, aid the stabilization of the pelvis. Therefore, this paper analyzes the electrical activity of the rectus abdominis muscle in the pelvic retroversion in dorsal decubitus and in orthostatic position and in the lowering of the lower limbs. 30 healthy students, male and female, 17 - 40 yr, divided into two groups--Group 1 : 15 volunteers (pelvic balance); Group 2 (pelvic unbalance) took part in this study. The electrical activity of the right and left supra-umbilical and infra-umbilical portions of the rectus abdominis muscle was detected. The mean RMS values from three attempts from the electromyographic traces were used for the analysis of the electrical activity. The RMS value was submitted to the normalization process. The data were submitted to statistic treatment by the Friedman test, and the analyses of the means and standard deviation towards a level of significance of 95%. The results demonstrated that the portions of the rectus abdominis muscle presented low electrical activity for the groups studied for pelvic retroversion either in dorsal decubitus or and orthostatic position. However, the decreasing movement of the lower limbs towards the portions of the rectus abdominis muscle presented more significant electrical activity whereas the lower portions presented higher activity than the higher ones for Group 2.     

Maximal oxygen uptake,maximal voluntary isometric contraction and physical activity in young Danish adults

Summary The purpose of this study was to determine and compare interactions between the abdominal musculature and intea-abdominal pressure (IAP) during controlled dynamic and static trunk muscle loading. Myoelectric activity was recorded in six subjects from the rectus abdominis, obliquus externus, obliquus internus, transversus abdominis and erector spinae muscles using surface and intea-muscular fine-wire electrodes. The IAP was recorded intea-gastrically. Trunk flexions and extensions were performed lying on one side on a swivel table. An adjustable brake provided different friction loading conditions, while adding weights to an unbraked swivel table afforded various levels of inertial loading. During trunk extensions at all friction loads, IAP was elevated (1.8–7.2 kPa) with concomitant activity in transversus abdominis and obliquus internus muscles — little or no activity was seen from rectus abdomin is and obliquus externus muscles. For inertia loading during trunk extension, IAP levels were somewhat lower (1.8–5.6 kPa) and displayed a second peak when abdominal muscle activity occurred in the course of decelerating the movement. For single trunk flexions with friction loading, IAP was higher than that seen in extension conditions and increased with added resistance. For inertial loading during trunk flexion, IAP showed two peaks, the larger first peak matched peak forward acceleration and general abdominal muscle activation, while the second corresponded to peak deceleration and was accompanied by activity in transversus abdominis and erector spinae muscles. It was apparent that different loading strategies produced markedly different patterns of response in both trunk musculature and intea-abdominal pressure.     

腹前外侧群肌的肌内神经分布模式

目的 揭示腹前外侧群肌的肌内神经分布模式,探讨其临床意义。 方法 取经甲醛固定的12具24侧中国成年尸体的腹前外侧群肌,行改良的Sihler染色。 结果 腹前外侧群肌的神经绝大多数源于节段性分布的胸神经。腹外斜肌各肌齿有独立的神经支配,在髂前上棘和髂结节之间的髂嵴上方有一纵向神经密集带。腹内斜肌腹股沟韧带中点上方有一纵向神经密集带,髂嵴上方有一横向神经密集带。腹横肌髂前上棘与第8、9肋软骨连结处之间有一弧形的神经密集带。腹直肌各肌腹中部有一横向神经密集带,上3个肌腹有独立神经支配。 结论 腹外斜肌和腹直肌可分出神经肌肉亚部;各肌内的神经密集带应被考虑为肉毒毒素A注射和局部麻醉的最佳靶点部位,不宜设为腹壁手术的切口部位。     

Trunk muscle reactions to sudden unexpected and expected perturbations in the absence of upright postural demand

The aim was to increase the understanding of the multifunctional role of the trunk muscles in spine control, particularly transversus abdominis (TrA). In 11 healthy males, intramuscular fine-wire electromyography (EMG) was obtained bilaterally from TrA, obliquus externus (OE), rectus abdominis (RA) and erector spinae (ES). The subjects lay on their right side on a horizontal swivel-table with immobilized pelvis and lower limbs and the trunk strapped to a movable platform. Unexpected or expected release of loads attached to the table by steel cables produced a perturbation inducing either trunk flexion or extension. The timing and the amplitude of activation of TrA were independent of direction of induced trunk movement. Furthermore, timing of TrA activation was simultaneous to or later than that of the more superficial abdominal muscles. Expectation of the perturbation caused a general shortening of onset latencies. The results indicate a direction independent function of TrA in lumbar spine control. Balancing the trunk vertically appears to add specific demands, since the recruitment of TrA in relation to the other abdominal muscles differed from earlier experiments in standing.     

静态姿势下均匀负重和非负重时躯干和表面肌电活动

目的观察躯干均匀负重和非负重状态下静态前屈和后伸时腰背部、腹部及臀中肌的肌电活动规律和运动学特征。方法 6位正常健康的男性受试者直腿站立于特殊设计的试验框架和平台内做静态前屈和后伸的负重和非负重动作,每次试验持续4 s,重复3次。动作时,记录双侧腰臀部的10块肌肉:腹直肌、腹外斜肌、竖脊肌、多裂肌、臀中肌的肌电活动,以及三维角度运动轨迹和足底力系。计算标准化肌电、腰部躯干角和足底中心压力的位移。将所得数据作常规的统计分析。结果负重和非负重前屈时,都是背侧肌活动较大(10.47～16.94)。非负重后伸时,腹侧肌活动也较大;负重后,背侧肌(3.70～17.95)和臀中肌(6.64～11.52)活动增加,腹肌活动减少(10.66～4.18)。后伸时,躯干的闪动次数随负重增加而增多,在3D角上增加1.55次;负重后,足底中心压力向前后的移动多于侧方移动,前屈的前后方移动(14.60)多于后伸的移动(7.65)。结论后伸状态增加了背侧肌的活动,而且多裂肌更明显;同时,腰部角位移度和闪动次数增加,特别在后伸提重时更为显著。     

Influence of trunk muscle co-contraction on spinal curvature during sitting for desk work

Nowadays, a lot of office workers are forced to sit at a desk for many hours while doing their jobs. While sitting, the pelvis rotates backwardly, and lumbar lordosis is flattened. At the same time, the load on the intervertebral discs and spine increases. Sitting in a slumped position is known to increase disc pressure even more, and to aggravate chronic low back pain (CLBP). Therefore, it is very important to teach workers about the correct sitting posture. In addition, it has been recognized that co-contraction of the deep spine-stabilizing muscles enhances lumbar segmental stability and the sacro-iliac joint. However, little is known about the influence of co-contraction of the trunk deep muscles on spinal curvature during sitting for while doing desk work. The purpose of this study was to compare EMG (electromyographic) activity of the trunk muscles during slump sitting with that during co-contraction of the trunk muscles and to investigate how this co-contraction influences spinal curvature. Ten healthy male volunteers (21.7 +/- 2.5 years old) without CLBP participated in the study. Bipolar surface electrodes were attached to the rectus abdominis, the obliquus externus abdominis, the obliquus internus abdominis, the lower back extensor muscles (L3) and the multifidus on the right side. EMG signals were continuously recorded during slump sitting and co-contraction of the trunk muscles, simulating a desk work sitting posture; i.e., slightly inclined forward. They were amplified, band-pass filtered, digitized and stored by a data acquisition system. The average muscle activity values over the five-second sample for each sitting posture were normalized to maximal voluntary contractions (%MVC). While the subjects performed both sitting postures, the curvature of the spine was measured using a new skin-surface and hand-held device, the "Spinal Mouse". More significant activities of the trunk muscles, with the exception of the rectus abdominis, were observed during co-contraction of the trunk muscles than during slump sitting The co-contraction of the trunk muscles resulted in significantly less lumbar curvature and more sacral angle than during slump sitting. The thoracic curvature showed no significant change during either sitting posture. The results of this study indicated that co-contraction of the trunk muscles during sitting while doing desk work could bring about the correct lumbar curvature, and effectively stabilize the lumbopelvic region, and decrease focal stress on passive structures.     

Segmental stabilization and muscular strengthening in chronic low back pain: a comparative study

OBJECTIVE:

To contrast the efficacy of two exercise programs, segmental stabilization and strengthening of abdominal and trunk muscles, on pain, functional disability, and activation of the transversus abdominis muscle (TrA), in individuals with chronic low back pain.

DESIGN:

Our sample consisted of 30 individuals, randomly assigned to one of two treatment groups: segmental stabilization, where exercises focused on the TrA and lumbar multifidus muscles, and superficial strengthening, where exercises focused on the rectus abdominis, abdominus obliquus internus, abdominus obliquus externus, and erector spinae. Groups were examined to discovere whether the exercises created contrasts regarding pain (visual analogical scale and McGill pain questionnaire), functional disability (Oswestry disability questionnaire), and TrA muscle activation capacity (Pressure Biofeedback Unit  =  PBU). The program lasted 6 weeks, and 30‐minute sessions occurred twice a week. Analysis of variance was used for inter‐ and intra‐group comparisons. The significance level was established at 5%.

RESULTS:

As compared to baseline, both treatments were effective in relieving pain and improving disability (p<0.001). Those in the segmental stabilization group had significant gains for all variables when compared to the ST group (p<0.001), including TrA activation, where relative gains were 48.3% and ‐5.1%, respectively.

CONCLUSION:

Both techniques lessened pain and reduced disability. Segmental stabilization is superior to superficial strengthening for all variables. Superficial strengthening does not improve TrA activation capacity.     

Spinal cord location of the motoneurons innervating the abdominal,cutaneous maximus,latissimus dorsi and longissimus dorsi muscles in the cat

Summary Horseradish peroxidase (HRP) injections were made in the rectus abdominis, obliquus externus, obliquus internus, transversus abdominis, cutaneous maximus, latissimus dorsi and the longissimus dorsi muscles in the cat. The results showed that motoneurons innervating the obliquus externus, obliquus internus and transversus abdominis muscles were located in greatly overlapping areas of midthoracic, caudal thoracic and upper lumbar spinal segments. These motoneuronal cell groups were present laterally in the ventral horn and at caudal thoracic and upper lumbar levels they bordered on the white matter. The location of the rectus motoneurons differed somewhat from the location of the other motoneuronal cell groups because they were also present at low cervical and upper thoracic levels and in the segments T12 to L3 they were found in the ventral horn medial to the other abdominal muscle motoneuronal cell group. At mid-thoracic levels rectus motoneurons were located in the same area as the other abdominal muscle motoneurons. Latissimus dorsi motoneurons were observed in a large cell group in the ventrolateral part of the ventral horn at the levels caudal C6 to rostral C8. Furthermore they were found in the segments T9 to L3 laterally in the ventral horn which is the same area in which the other abdominal muscle motoneurons except the rectus ones are located. Longissimus dorsi motoneurons were located in the most ventral portion of the ventral horn in all thoracic and upper 4 lumbar segments. The cutaneous maximus motoneurons were found in a cell group, located ventrolaterally in the ventral horn at the edge of the gray and white matter at the level caudal C8-rostral T1. This cell group corresponds to the caudal part of the ventral motor nucleus (VMN) of Matsushita and Ueyama (1973). Interestingly, labeled motoneurons were also present in the VMN after injecting HRP in the abdominal muscles as well as in the caudal (but not in the rostral) parts of the latissimus dorsi muscle but not in the longissimus dorsi injected cases. The possibility whether these motoneurons are labeled because of leakage of HRP to abdominal and caudal latissimus dorsi muscles is discussed. If leakage would not be the case, motoneurons in the VMN may be involved in specific functions of the abdominal muscles, such as the so-called steady state contractions.