Thoracic Erector Spinae Muscles Research Articles

Effects of unstable load and unstable surface ontrunk muscles activation and postural control in healthy subjects

Exercise with an unstable load is considered a new training method to activate the core muscles. Research has shown consistency regarding an unstable surface but has not provided comprehensive findings about the effect of an unstable load. The study aimed to examine the impact of an unstable load and unstable surfaces on core muscle activation and postural control during lifting. Thirty-eight participants lifted a load equivalent to 10 % of their body weight under three conditions: a stable load on an unstable surface, a stable load on a stable surface, and an unstable load on a stable surface. The center of pressure (COP) displacement and electromyography activity of abdominal and back extensor muscles were measured during lifting. The results indicated that lifting on an unstable surface activated the lumbar erector spinae and multifidus muscles more than in a stable condition (P<0.05). However, there was no significant difference in the level of thoracic erector spinae muscle activity between the unstable load and unstable surface conditions. The stable condition increased activity in the internal oblique muscle (1.37 times) compared to the unstable conditions. The analysis of postural control revealed that lifting the load on an unstable surface significantly decreased COP displacement in the anteroposterior direction (P<0.05), while holding the load on the unstable surface significantly increased COP displacement in the anteroposterior direction compared to the other conditions. These findings could be valuable for future rehabilitation research, learning appropriate lifting techniques, and setting specific training goals in sports.

Effects of a posture correction feedback system on neck and trunk posture and muscle activity during computer work

BackgroundComputer work often involves prolonged periods of static sitting, which can result in incorrect posture and increase the risk of developing musculoskeletal disorders and associated pain. The incidence of neck pain among computer workers is increasing due to the association with incorrect posture. To solve the problem accurately, it is necessary to correct the incorrect posture. ObjectiveThis study investigated how the angle and muscle activity of the upper body changed when a posture correction feedback (PCF) system was applied during computer work. MethodsFifteen healthy, young adults participated in this study that was conducted in two sessions of 16 min each: the first without feedback and the second with feedback. Neck and trunk angle changes of the participants, as well as cervical erector spinae, upper trapezius, and thoracic erector spinae muscle activation, were measured during computer work. Kinematic and kinetic data were analyzed using a two-way repeated analysis of variance. ResultsNeck and trunk flexion were reduced with the feedback system. Muscle activation of the cervical erector spinae significantly increased over time with computer use and decreased with feedback system use (p < 0.05). ConclusionOur study demonstrates the PCF system may be an effective tool for alleviating postural stress in the neck and trunk in an office setting. Relevance to industryThe PCF system can assist computer workers in improving posture. This demonstrates ergonomic benefits and does not interfere with computer work, making it suitable for use in a real work environment. This can help prevent musculoskeletal disorders and associated pain resulting from prolonged computer work.

The Effects of Posture and Dynamic Stretching on the Electromechanical Delay of the Paraspinal Muscles

Electromechanical delay (EMD) of muscle is influenced in part by its in-series arrangement with connective tissue. Therefore, studying EMD might provide a better understanding of the muscle-connective tissue interaction. Here, EMD of the thoracic and lumbar erector spinae muscles were investigated under conditions that could influence muscle-connective tissue interaction. A total of 19 participants performed isometric back extension contractions in 3 different postures that influence lumbar spine angle: sitting, standing, and kneeling. They then performed a 15-minute dynamic stretching routine and repeated the standing contractions. Mean lumbar flexion angles of 0.5°, 9.9°, and 19.8° were adopted for standing, kneeling, and sitting, respectively. No statistically significant differences in the thoracic erector spinae EMD were found between the different postures. Lumbar erector spinae EMD was significantly longer in the sitting (94.1ms) compared to the standing (69.9ms) condition, with no differences compared to kneeling (79.7ms). There were no statistically significant differences of the thoracic or lumbar erector spinae EMDs before and after dynamic stretching. These results suggest that dynamic stretching does not affect the mechanical behavior of the muscle-tendon-aponeurosis units in a way that alters force generation and transmission, but a sitting posture can alter how force is transmitted through the musculotendinous complex of the lumbar erector spinae.

Association of gross motor function and activities of daily living with muscle mass of the trunk and lower extremity muscles, range of motion, and spasticity in children and adults with cerebral palsy

ABSTRACT Purpose We examined the association of gross motor function and activities of daily living (ADL) with muscle mass of the trunk and lower extremity muscles in children and adults with cerebral palsy (CP). Methods The subjects were 32 children and adults with CP. Muscle thickness of the trunk and lower extremity muscles was measured using an ultrasound imaging device. Results Stepwise regression analysis revealed that the thoracic erector spinae muscle thickness was a significant and independent factor of gross motor function. Stepwise regression analysis also showed that the thickness of the rectus abdominis and vastus lateralis muscles were significant and independent factors of ADL. Conclusions Our findings suggest that declined gross motor function is associated with decreased thoracic erector spinae muscle mass in children and adults with CP. The results also indicate that declined ADL is associated with decreased muscle mass of the rectus abdominis and vastus lateralis muscles.

Effects of Ground Slopes on Erector Spinae Muscle Activities and Characteristics of Golf Swing.

(1) Background: 'Slope' refers to the position faced by golfers on the course. Research on the recruitment strategies of thoracolumbar erector spinae during golf swings on different slopes may help us to understand some underlying mechanisms of lower back pain. (2) Purpose: The purpose of the present study is to assess electromyography (EMG) patterns of the erector spinae muscles (ES) and the kinematics of the trunk and swing parameters while performing golf swings on three different ground slopes: (1) no slope where the ball is level with the feet (BLF), (2) a slope where the ball is above the feet (BAF), and (3) a slope where the ball is below the feet (BBF). Furthermore, the present study evaluates the effect of slope on the kinematics of the trunk, the X-factor angle, and the hitting parameters. (3) Methods: Eight right-handed recreational male golfers completed five swings using a seven-iron for each ground slope. Surface electromyograms from the left and right sides of the ES thoracolumbar region (T8 and L3 on the spinous process side) were evaluated. Each golf swing was divided into five phases. Kinematics of the shoulder, trunk, and spine were evaluated, and the ball speed, swing speed, carry, smash factor, launch angle, and apex were measured using Caddie SC300. (3) Results: The muscle activity of the BAF and BBF slopes was significantly lower than that of the BLF slope during the early follow-through phase of the thoracic ES on the lead side (i.e., left side) and during the acceleration and early follow-through phases of the lumbar ES on the lead side. The lead and trail side (i.e., right side) lumbar ES were more active during acceleration than the thoracic ES. Additionally, the trends of the lead and trail sides of the thoracolumbar regions on the three slopes were found to be the same across the five phases. Trunk angle and X-factor angles had no significant differences in address, top of backswing, or ball impact. The maximum separation angles of the X-factor appeared in the early phase of the downswing for all the three slopes. Regarding smash factor and launch angle, there were no significant differences between the three slopes. The ball speed, swing speed, carry, and apex were higher on BLF than on BAF and BBF slopes. (4) Conclusion: The findings suggest that amateur golfers face different slopes with altered muscle recruitment strategies. Specifically, during the acceleration phase of the golf swing, the BAF and the BBF slopes, compared with the BLF slope, significantly underactivated the lead side thoracolumbar erector spinae muscles, thereby increasing the risk of back injury. Changes in muscle activity during critical periods may affect neuromuscular deficits in high-handicap players and may have implications for the understanding and development of golf-related lower back pain. In addition, the X-factor angle was not affected by the slope, however, it can be found that the hitting parameters on the BLF slope are more dominant than on the other slopes.

Biomechanical assessment of a passive back-support exoskeleton during repetitive lifting and carrying: Muscle activity, kinematics, and physical capacity

Introduction: Most people have experienced low back pain (LBP) more or less in their lifetime. Heavier load weight could increase the risk of LBP, especially in repetitive lifting and carrying tasks. The risk could also increase with the frequency of lifting. This study aims to investigate the effects of a passive back-support exoskeleton (PBSE) on trunk muscle activation, kinematics, and physical capacity in a repetitive lifting task and a carrying task in consideration of load weights in a laboratory setting. Results: Results showed that using the PBSE, the activities of the thoracic erector spinae and lumbar erector spinae muscles were reduced significantly by nearly 7% MVC and 3% MVC in the repetitive lifting task and the carrying task, respectively. There was no significant effect of the PBSE on the spine kinematics and physical capacity. Practical Applications: This study supports the use of the PBSE to reduce trunk muscle activity in repetitive lifting and carrying tasks.

Effect of non-contact boxing training on the frequency and timing of anticipatory postural adjustments in healthy adults.

The experiment tested the effect of non-contact boxing training on the frequency and timing of anticipatory postural adjustments (APAs) resulting from self-induced postural perturbations in healthy adults. The 8-week non-contact boxing intervention study involved 33 healthy adults between 18 and 27 years of age who had no boxing experience (control group = 17 participants, boxing group = 16 participants). Pretests and post-tests utilized rapid bilateral arm raising as a focal movement to elicit APAs. EMG in the anterior deltoid, thoracic and lumbar erector spinae, semitendinosus, and soleus muscles was recorded. The boxing group completed twenty 90-min non-contact boxing training sessions over 8 weeks, whereas the control group kept physical activity consistent during the intervention period. Non-contact boxing training caused APAs to become more frequent during the focal movement, in comparison to the control group, in the soleus and in the semitendinosus after an outlier was removed. Non-contact boxing training caused earlier APA onset during the focal movement, in comparison to the control group, in the lumbar erector spinae after an outlier was removed. Non-contact boxing training had a modest positive effect on the frequency and timing of APAs resulting from self-induced postural perturbations in healthy adults.

Evaluation of a Chair-Mounted Passive Trunk Orthosis: A Pilot Study on Able-Bodied Subjects

Trunk stability is important for adequate arm function due to their kinematic linkage. People with Duchenne muscular dystrophy (DMD) can benefit from trunk-assistive devices for seated daily activities, but existing devices limit trunk movement to forward bending. We developed a new trunk orthosis that has spring and pulley design. This study evaluated orthosis performance with 40 able-bodied subjects under with and without orthosis condition in 20 seated tasks for trunk rotation, forward bending, and side bending movements. Subjects adopted static posture in specific trunk orientation while their muscle activity was recorded. They also rated the subjective scales of perceived exertion and usability. A percent change in muscle activity for each task, due to orthosis use, is reported. Significant muscle activity reductions up to 31% and 65% were observed in lumbar and thoracic erector spinae muscles, respectively. Using three-way ANOVA, we found these reductions to be specific to the task direction and the choice of upper limb that is used to perform the asymmetric tasks. A total of 70% participants reported acceptable usability and ~1-point increase in exertion was found for maximum voluntary reaching with the orthosis. The outcomes of this study are promising, though tested on able-bodied subjects. Hence, orthosis mounted on wheelchairs should be further evaluated on DMD patients.

Association of mobility capacity with the masses and amounts of intramuscular non-contractile tissue of the trunk and lower extremity muscles in community-dwelling older adults.

We examined the association of mobility capacity with muscle thicknesses and echo intensities of the trunk and lower extremity muscles measured using an ultrasound imaging device in community-dwelling older adults. The participants were 57 community-dwelling older adults. Mobility capacity was assessed based on the measurement of usual and maximal walking speeds and timed up-and-go (TUG) time. Muscle thickness and echo intensity of the trunk and lower extremity muscles were measured using an ultrasound imaging device. Finally, sagittal spinal alignment was assessed based on the measurement of thoracic kyphosis, lumbar lordosis, and sacral anterior inclination angles in the standing position using a Spinal Mouse. Stepwise regression analysis showed that the tibialis anterior muscle thickness, tibialis posterior muscle echo intensity, and body weight were significant and independent factors of usual walking speed, with a coefficient of determination (R2) of 0.25. The thicknesses of the thoracic erector spinae and obliquus externus abdominis muscles were significant and independent factors of maximal walking speed (R2=0.26). Moreover, only age was a significant and independent factor for TUG time (R2=0.10). The results of this study suggested associations 1) between slow usual walking speed and low tibialis anterior muscle thicknesses and high echo intensity of the tibialis posterior muscle and 2) between slow maximal walking speed and low thoracic erector spinae and obliquus externus abdominis thicknesses in community-dwelling older adults.

The Effects of Head Support on Muscle Activity and Pain in a Forward-leaning Posture

Background: Because a forward-leaning posture can cause increased back muscle activity and pain. Therefore, an innovative method to reduce back muscle activity and pain is required. Objects: This study aimed to investigate the effects of a head support on muscle activity and pain in a forward-leaning posture. Methods: A total of 14 male and 16 female students (average age, 21.65 ± 2.37 years; height, 166.15 ± 7.90 cm; and weight, 60.65 ± 9.00 kg) were recruited for the experiment. Two of them were excluded due to musculoskeletal disorders. The muscle activity and pain in the forward-leaning posture were assessed while participants washed dishes for 7 minutes with and without a head support. The condition of using a head support was randomly performed with a 5-minutes break. To confirm a lumbar flexion angle of 30° during the experiment, myoVIDEO was used, and surface electromyography was used to measure muscle activity. Pain was assessed using a 10-point visual analog scale (VAS). The Wilcoxon signed-rank test was used to analyze the data, with p < 0.05 indicating statistical significance. Results: The cervical, thoracic, and lumbar erector spinae muscle activities significantly decreased with the use of the head support, but there was no significant change in the gluteus maximus. There was a significant decrease in the VAS score for the lumbar erector spinae (p < 0.05), but there was no significant change in the VAS score for the cervical region. Conclusion: The use of a head support in a forward-leaning posture reduced cervical, thoracic, and lumbar erector muscle activity and pain. Therefore, it could be recommended during working in a forward-leaning posture, such as during dishwashing, cooking, and working as a factory employee.

Neuromechanical response of the upper body to unexpected perturbations during gait initiation in young and older adults.

Control of upper body motion deteriorates with ageing leading to impaired ability to preserve balance during gait, but little is known on the contribution of the upper body to preserve balance in response to unexpected perturbations during locomotor transitions, such as gait initiation. To investigate differences between young and older adults in the ability to modify the trunk kinematics and muscle activity following unexpected waist lateral perturbations during gait initiation. Ten young (25 ± 2years) and ten older adults (73 ± 5years) initiated locomotion from stance while a lateral pull was randomly applied to the pelvis. Two force plates were used to define the feet centre-of-pressure displacement. Angular displacement of the trunk in the frontal plane was obtained through motion analysis. Surface electromyography of cervical and thoracic erector spinae muscles was recorded bilaterally. A lower trunk lateral bending towards the stance leg side in the preparatory phase of gait initiation was observed in older participants following perturbation. Right thoracic muscle activity was increased in response to the perturbation during the initial phase of gait initiation in young (+ 68%) but not in older participants (+ 7%). The age-related reduction in trunk movement could indicate a more rigid behaviour of the upper body employed by older compared to young individuals in response to unexpected perturbations preceding the initiation of stepping. Older adults' delayed activation of thoracic muscles could suggest impaired reactive mechanisms that may potentially lead to a fall in the early stages of the gait initiation.

Design, Implementation and Preliminary Testing of a Novel Orthosis for Reducing Erector Spinae Muscle Activity, and Improving Balance Control for Hyperkyphotic Elderly Subjects

Background: Aging often results in thoracic kyphosis and adverse postural changes. This may interfere with physiologic activity of paraspinal muscles. Few styles of spinal orthosis have been already used to reduce thoracic kyphosis. This paper describes the development of a novel orthosis, which is designed based on the anatomy of the back muscles. This novel orthosis may potentiate muscle activity and balance control among older hyper kyphotic subjects.Objectives: The object of this study was to design and preliminary testing of a new orthosis to potentiate muscle activity and balance control among older hyper kyphotic subjectsMaterial and Methods: In this quasi-experimental study, a new postural control orthosis with a textile band structure was designed to provide an additional support for spine and muscles of the back. The functional impact of this orthosis was evaluated in six older hyper-kyphotic subjects. According to the results, the paraspinal muscles activity and balance control were significantly improved.Results: The RMS sEMG of the lumbar and thoracic erector spinae muscles reduced significantly (p<0.05), and a significant improvement (p<0.05) was observed in the balance test when patients put on the novel orthosis (p<0.05).Conclusion: The new orthosis can considerably improve the paraspinal muscles activity at both the upper and lower lumbar levels. It can also recover balance control among elderly subjects

Evaluation of Trunk-Supporting Exoskeleton

Trunk Supporting Exoskeletons are increasingly being evaluated in workplaces as viable ergonomic interventions for reducing the risk of back injuries. A series of trunk-supporting exoskeletons have been designed and built at the University of California at Berkeley and suitX. These exoskeletons decrease the forces on the wearer’s back at L5/S1 location. This article describes one of these exoskeletons, referred to as backX, and its evaluation method. backX is designed not only to reduce the forces and torques on the wearer’s back at L5/S1 location, but also to allow the wearer to perform all kinds of maneuvers such as walking, squatting, ascending and descending stairs, slopes and ladders, riding bicycles and driving trucks. This study finds that average muscle activities of the thoracic and lumbar erector spinae muscles among equal populations of male and female subjects, wearing backX while maintaining forward bending postures, are reduced by 75% and 56% respectively. The results of this study and extended field evaluations indicate that wearing backX minimizes the risk of back injuries among workers who repeatedly go through stooping, squatting, and bending postures for various tasks, such as lifting objects.

Chronic low back pain influences trunk neuromuscular control during unstable sitting among persons with lower-limb loss

BackgroundPersons with unilateral lower-limb loss are at increased risk for developing chronic low back pain. Aberrant trunk and pelvis motor behavior secondary to lower-limb loss potentially alters trunk postural control and increases demands on the trunk musculature for stability. However, it is unclear whether trunk postural control is associated with the presence or chronicity of low back pain within this population. Research questionIs there a potential role of impaired trunk postural control among persons with lower limb loss and chronic low back pain? MethodsTwo groups of males with unilateral lower-limb loss (n = 18 with chronic low back pain; n = 13 without pain) performed an unstable sitting task. Trunk postural control was characterized using traditional and non-linear measures derived from center-of-pressure time series, as well as trunk kinematics and the ratio of lumbar to thoracic erector spinae muscle activations. ResultsTraditional and non-linear center-of-pressure measures and trunk muscle activation ratios were similar between groups, while participants with chronic low back pain demonstrated greater trunk motion and reduced local dynamic stability. SignificanceOur results suggest that persons with both lower-limb loss and chronic low back pain exhibit impaired trunk postural control compared to those with limb loss but without pain. Aberrant trunk motor behavior may be a response to altered functional requirements of walking with a prosthesis. An inability to adequately control the trunk could lead to spinal instability and pain in the presence of repetitive exposure to aberrant motor behavior of these proximal structures during everyday activities.

The characteristics of trunk muscle activity in patients with Parkinson′s disease

Objective To explore the characteristics of trunk muscle activity in persons with Parkinson′s disease (PD) in search of better treatments for abnormal posture. Methods Ninety persons with PD of different severity and 8 normal controls were studied using surface electromyography (sEMG). A sixteen-lead sEMG instrument was used to collect sEMG amplitudes from the bilateral thoracic erector spinae, lumbar erector spinae, external oblique and rectus abdominis muscles when the subjects were lying, standing and walking. Results Compared with the control group, a significant increase was observed in the sEMG amplitude of the lumbar erector spinal muscle [(18.56±14.57)μV] and rectus abdominis muscles [(24.00±18.80)μV] of the PD group when lying. Significant relative increases in (P<0.05), of the external oblique muscles were observed [(27.87±11.49)μV] when standing (P<0.05), and in the thoracic erector spinae muscle [(58.74±29.69)μV] and external oblique muscles [(59.01±25.20)μV] increased when walking (P<0.05). Compared with the control group, the sEMG activity of the external oblique muscles was significantly elevated in PD patients at Hoehn and Yahr stage 1 to 1.5 when walking. One or more of the trunk muscle groups showed significantly greater activity in the PD patients in Hoehn and Yahr stage 2 or 3 in all three positions. Conclusions The sEMG activities of the extensor and flexor muscles increase simultaneously in PD patients. More trunk muscles are involved in PD patients with higher H-Y grades. These findings provide a neurophysiological basis for the customizaton of rehabilitation therapy for patients with Parkinson′s disease and for the precise selection of muscles for botulinum toxin injection. Key words: Parkinson′s disease; Trunk muscles; Surface electromyography

Back muscle activity and sagittal spinal alignment during quadruped upper and lower extremity lift in young men with low back pain history

BackgroundQuadruped upper and lower extremity lift (QULEL) is performed for selective training of the lumbar multifidus muscle in patients with low back pain (LBP) or individuals with LBP history (LBPH). However, the activities of the back muscles and sagittal spinal alignment during QULEL are not clarified in individuals with LBPH. Research questionThis study aimed to analyze the activities of the back muscles and sagittal spinal alignment during QULEL in young male with LBPH. MethodsThe study comprised 9 asymptomatic young men and 8 young men with LBPH. The activities of the lumbar multifidus, latissimus dorsi and thoracic erector spinae, and lumbar erector spinae muscles were measured using surface electromyography. The flexion angles of the upper and lower thoracic spine, and extension angle of the lumbar spine were measured using a 6-DF electromagnetic motion tracking system. The association with LBPH was investigated using multiple logistic regression analysis with a forward selection method, with the activities of the back muscles, sagittal spinal alignment, age, body height, and body weight as independent variables. ResultsMultiple logistic regression analysis (p = 0.0002) showed that the activity of the latissimus dorsi and thoracic erector spinae muscles in the side on which the lower extremity was lifted and body height were significant and independent determinants of LBPH, but other factors were not. SignificanceThe results of this study suggest that the activity of the latissimus dorsi and thoracic erector spinae muscles increases while there are no decrease in activity of the lumbar multifidus muscle and excessive extension of the lumbar spine during QULEL in young men with LBPH.

A Cadaveric Study Investigating the Mechanism of Action of Erector Spinae Blockade.

Erector spinae block is an ultrasound-guided interfascial plane block first described in 2016. The objectives of this cadaveric dye injection and dissection study were to simulate an erector spinae block to determine if dye would spread anteriorly to the involve origins of the ventral and dorsal branches of the spinal nerves. In 10 unembalmed human cadavers, 20 mL of 0.25% methylene blue dye was injected bilaterally into the plane between the fifth thoracic transverse process and erector spinae muscle. An in-plane ultrasound-guided technique with the transducer orientated longitudinally was used. During dissection, superficial and deep muscles were identified, and extent of dye spread was documented in cephalocaudal and lateral directions. The ventral and dorsal rami of spinal nerves and dorsal root ganglion at each level were examined to determine if they were stained by dye. There was extensive cephalocaudad and lateral spread of dye deep and superficial to the erector spinae muscles. Except for 1 injection (from 20), the ventral rami were not stained by the dye. In only 2 injections did the dye track posteriorly through the costotransverse foramen to the dorsal root ganglion. In all other cases, the dorsal root ganglia were not involved in the dye injection. The dye stained the dorsal rami posterior to the costotransverse foramen. There was no spread of dye anteriorly to the paravertebral space to involve origins of the ventral and dorsal branches of the thoracic spinal nerves. Dorsal ramus involvement was posterior to the costotransverse foramen.

Muscle Strength and Neuromuscular Control in Low-Back Pain: Elite Athletes Versus General Population.

The purpose of the study was to investigate the athletic-based specificity of muscle strength and neuromuscular control of spine stability in chronic non-specific low-back pain (LBP). Thirty elite athletes and 29 age-matched non-athletes with (15 athletes and 15 non-athletes) and without LBP (15 athletes and 14 non-athletes) participated in the study. Muscle strength was measured during maximal isometric trunk flexion and trunk extension contractions. The neuromuscular control of spine stability was analyzed by determining trunk stiffness, trunk damping, and onset times of the lumbar and thoracic erector spinae muscles after sudden perturbations (quick release experiments) as well as maximum Lyapunov exponents (local dynamic stability) using non-linear time series analysis of repetitive lifting movements. LBP was assessed using the visual analog scale. We found lower maximal trunk extension moments (p = 0.03), higher trunk damping (p = 0.018) and shorter onset times (p = 0.03) of the investigated trunk muscles in LBP patients in both athletes and non-athletes. Trunk stiffness and the local dynamic stability did not show any differences (p = 0.136 and p = 0.375, respectively) between LBP patients and healthy controls in both groups. It can be concluded that, despite the high-level of training in athletes, both athletes and non-athletes with LBP showed the same deconditioning of the lumbar extensor muscles and developed similar strategies to ensure spine stability after sudden perturbations to protect the spine from pain and damage. The findings highlight that specific training interventions for the trunk muscles are not only crucial for individuals of the general population, but also for well-trained athletes.

Effect of Tactile Feedback on Trunk Posture and EMG Activity in People With Postural Kyphosis During VDT Work

Background: Recently, there has been an emphasis on the use of interventions with biofeedback information for the maintenance or correction of posture. Objects: This study assessed the change of trunk posture and trunk muscle activation when people exhibiting postural kyphosis performed visual display terminal work with or without a contact feedback device (CFD). Methods: Eighteen right-handed individuals were recruited. Thoracic angle and right thoracic erector spinae (TES) muscle amplitude were analyzed. There were two sessions in these experiments. The control session involved 16 minutes of typing without a CFD, and the CFD session involved 16 minutes of typing with a CFD. The visual analog scale score was analyzed with a paired t-test, and the kinematic and electromyography data were analyzed through two-way repeated analysis of variance. Results: The paired t-tests revealed that subjects had significantly less pain after the CFD sessions than after the control sessions (p<.05). Significant main effects by session and by time were observed in the thoracic kyphosis angle (p<.05). There was a significant session×time interaction for TES amplitude (p<.05), along with significant main effects by session and by time (p<.05). Conclusion: The CFD caused people with postural kyphosis to straighten and to activate their TES continuously, even though they were habituated to bend their bodies forward. Therefore, the CFD was a beneficial treatment tool.

Comparison of the thoracic flexion relaxation ratio and pressure pain threshold after overhead assembly work and below knee assembly work.

[Purpose] The purpose of this study was to compare the thoracic flexion relaxation ratio following overhead work and below-knee work. [Subjects and Methods] Ten men (20–30 years) were recruited to this study. The thoracic flexion relaxation ratio and pressure pain threshold was measured after both overhead work and below-knee work. [Results] The pressure-pain thresholds of the thoracic erector spinae muscle decreased significantly from initial, to overhead, to below-knee work. Similarly, the thoracic flexion relaxation ratio decreased significantly from initial, to overhead, to below-knee work. [Conclusion] Below-knee work results in greater thoracic pain than overhead work. Future studies should investigate below-knee work in detail. This study confirmed the thoracic relaxation phenomenon in the mid-position of the thoracic erector spinae.