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[Purpose] The purpose of this study was to develop a simpler method to estimate the intervertebral disc compressive force in healthy older adults. We also examined the validity of a simpler estimation formula for patients with spinal diseases. [Participants and Methods] Fifty-two older adults participated in the study. The standing posture was measured using a three-dimensional motion capture system. The intervertebral disc compressive force was calculated using a previously reported method. Correlation analysis was used to detect the relationship between the measured parameters and the intervertebral disc compressive force. Multiple regression analysis was performed to obtain an equation for the intervertebral disc compressive force. Correlation analysis was used to determine the regression equation for the patients with spinal diseases. [Results] Multiple regression analysis showed that trunk flexion/extension angle and body mass were significantly associated with intervertebral disc compressive force. A correlation was found between the measured and predicted values in the healthy older adults, whereas both values were inconsistent in patients with spinal diseases. [Conclusion] The results of our study demonstrated that the trunk flexion/extension angle and body mass are indicators of intervertebral disc compressive force and can be used to assess low back mechanical stress in healthy older adults.

[Purpose] To compare flexion and extension peak torque of patients with nonspecific-chronic low back pain who were classified as directional preference subgroups, and their matched healthy controls. [Participants and Methods] Fifty male volunteers (25 with non-specific chronic low back pain and 25 healthy-matched controls) consented to participate. The investigator collected all demographic data, hips, knees and spinal mobility in addition to the peak torque using the Biodex isokinetic dynamometer. The measurement protocol consisted of 2 sets of 10 consecutive flexion-extension efforts performed at 120°/sec and 60°/sec angular velocity. A two minutes rest period was given between sets. The preset 50° range of motion included 20°(+20°) of trunk extension and 30°(-30°) of trunk flexion. [Results] A 2 × 2 mixed-design ANOVA showed a significant group X isokinetic velocity interaction. The main effect of isokinetic velocity was also significant. In reference to the peak torque of the flexors of the trunk, the main effect of group was significant. [Conclusion] The extension peak torque significantly depends on the velocity of the isokinetic dynamometer; however the flexion peak torque significantly depends on the participants' group attribution.

[Purpose] To clarify the relationship between asymmetric trunk flexion movement and erector spinae (ES) muscle activity using a three-dimensional motion analysis system and surface electromyography. [Subjects and Methods] The subjects comprised 14 healthy individuals. Angles of trunk flexion, rotation, and side bending were measured using a three-dimensional motion analysis system attached to the trunk and pelvic segment. Activities of the ES muscle on both sides at the L1 and L4 levels were measured using surface electromyography. [Results] In healthy individuals, the ES was more markedly activated in the trunk extension phase than in the trunk flexion phase. There was no significant difference in terms of the extent of trunk rotation and trunk side bending during these tasks. [Conclusion] This study did not clarify the relationship between asymmetric movement during trunk flexion and ES activity.

[Purpose] The aim of this study was to compare immediate effects between new medical stretching (NMS) and conventional medical stretching (CMS) techniques on Hamstrings flexibility. [Subjects and Methods] Thirteen healthy adult males, with finger floor distance (FFD) less than zero centimeter, without known musculoskeletal and neurological impairment in spine or lower extremities, were included. The subjects were randomly allocated to two groups. The subjects were instructed to perform NMS and CMS (hold for 30 seconds once, twice for each side of lower extremity) for both sides (total two minutes, only one session for one day). The interval between the two techniques was one week. FFD was measured with digital standing trunk flexion meter at the pre-intervention and post-intervention of both techniques. [Results] The mean values of FFD improved at the post-interventions of both techniques. The tests of within subject effects indicated that the main effect of treatment was not significant but the main effect of time was significant and the interaction of treatment and time was also significant. [Conclusion] The results of this study indicated that both medical stretching techniques were effective on Hamstrings flexibility immediately after the intervention and NMS technique was more effective on improving flexibility.

[Purpose] This study investigated the flexion-relaxation phenomenon of the erector spinae in elderly women with chronic knee osteoarthritis and determined whether the flexion-relaxation phenomenon can be used as a pain evaluation tool in such cases. [Subjects and Methods] Seventeen elderly females with chronic knee osteoarthritis and 13 healthy young females voluntarily participated in this study. They performed three postural positions in 15 s: trunk flexion, complete trunk flexion, and trunk extension, each for 5 s. While these positions were held, muscle activation of the thoracic and lumbar erector spinae were measured using surface electromyography. The flexion-relaxation rate was determined by dividing the values for trunk extension by those of complete trunk flexion and by dividing the values for trunk flexion by those of complete trunk flexion. [Results] According to our results, the flexion-relaxation phenomenon was different between healthy young and elderly females with chronic knee osteoarthritis. Specifically, there was a difference in the left thoracic erector spinae muscle, but not in the left and right lumbar erector spinae or right thoracic spinae muscle. [Conclusion] Our study demonstrated that the erector spinae muscle flexion-relaxation phenomenon can be used as a pain evaluation tool in elderly females with chronic knee osteoarthritis.

[Purpose] The time-series waveforms of mechanical energy generation, absorption, and transfer through the joints indicate how movements are produced and controlled. Previous studies have used these waveforms to evaluate and describe the efficiency of human movements. The purpose of this study was to examine the influence of trunk flexion on mechanical energy flow in the lower extremities during gait. [Subjects and Methods] The subjects were 8 healthy young males (mean age, 21.8 ± 1.3 years, mean height, 170.5 ± 6.8 cm, and mean weight, 60.2 ± 6.8 kg). Subjects walked at a self-selected gait speed under 2 conditions: normal gait (condition N), and gait with trunk flexion formed with a brace to simulate spinal curvature (condition TF). The data collected from initial contact to the mid-stance of gait was analyzed. [Results] There were no significant differences between the 2 conditions in the mechanical energy flow in the knee joint and negative mechanical work in the knee joint. However, the positive mechanical work of the knee joint under condition TF was significantly less than that under condition N. [Conclusion] Trunk flexion led to knee flexion in a standing posture. Thus, a strategy of moving of center of mass upward by knee extension using less mechanical energy was selected during gait in the trunk flexed posture.

[Purpose] To explore the differences in bilateral trunk muscle activation between chronic stroke patients and healthy controls, this study investigated the symmetry index and cross-correlation of trunk muscles during trunk flexion and extension movements. This study also assessed the differences in trunk reposition error between groups and the association between trunk reposition error and bilateral trunk muscle activation. [Subjects and Methods] Fifteen stroke patients and 15 age- and gender-matched healthy subjects participated. Bilateral trunk muscle activations were collected by electromyography during trunk flexion and extension. Trunk reposition errors in trunk flexion and extension directions were recorded by a Qualisys motion capture system. [Results] Compared with the healthy controls, the stroke patients presented lower symmetrical muscle activation of the bilateral internal oblique and lower cross-correlation of abdominal muscles during trunk flexion, and lower symmetry index and cross-correlation of erector spinae in trunk extension. They also showed a larger trunk extension reposition error. A smaller trunk reposition error was associated with higher cross-correlation of bilateral trunk muscles during trunk movements in all subjects. [Conclusion] Trunk muscle function during symmetrical trunk movements and trunk reposition sense were impaired in the chronic stroke patients, and trunk position sense was associated with trunk muscle functions. Future studies should pay attention to symmetrical trunk movements as well as trunk extension position sense for patients with chronic stroke.

[Purpose] The purposes of this study were to investigate differences between patients with chronic stroke and age matched healthy controls in trunk stability, by assessing the kinematics of the center of mass and moving body segments during voluntary limb and trunk movement, and the relationship between trunk stability and clinical measurements. [Subjects and Methods] Fifteen stroke patients and 15 age- and gender-matched healthy subjects participated. Each subject performed flexion of the hip and shoulder of the non-paretic or matched side as fast as possible, as well as trunk flexion and extension at a self-selected speed. A Qualisys motion system was employed to track the kinematics of the trunk and limbs. [Results] Patients presented larger mediolateral displacement of the center of mass during all limb and trunk movements, and larger velocity of center of mass during hip flexion movement. Healthy subjects showed greater movement velocity during shoulder flexion, trunk flexion and extension. Patients' clinical measurements only correlated with movement characteristics during voluntary trunk motions. [Conclusion] Trunk stability in patients with chronic stroke was compromised during voluntary trunk as well as non-paretic limb movements, and the voluntary trunk movements reflected the trunk deficits measured using clinical measurements. Rehabilitation of patients with chronic stroke should include programs to improve trunk stability.

[Purpose] The purpose of this study was to investigate the effect of the difficulty level of a biofeedback device for postural correction on the orbicularis oculi and upper trapezius muscle activity and trunk flexion angle during computer work. [Subjects] Ten computer workers were included in this study. [Methods] The biofeedback tool used in this study provided visual and auditory feedback with regard to changes in trunk flexion angle under two different conditions during computer work: The first condition was when there was an increase of more than 10 degrees in a standard sitting posture. The second condition was when there was an increase of more than 20 degrees in the same posture. [Results] The trunk flexion angle showed no significant difference between conditions. The muscle activities of the orbicularis oculi and upper trapezius under condition 1 (high difficulty level) was significantly increased compared with those under condition 2 (low difficulty level). [Conclusion] This result showed that frequent feedback with greater sensitivity can trigger stress and lead to the outbreak of other illnesses.

[Purpose] The purpose of this study was to evaluate the effect of wearing the tight pants on the trunk flexion and pelvic tilting angles in the stand-to-sit movement and a seated posture. [Subjects] Nine male subjects were recruited. [Methods] The trunk flexion angle and pelvic posterior tilting angle were measured using a motion-capture system during the stand-to-sit movement and in a seated posture. [Results] The trunk flexion and the posterior pelvic tilting angles during the stand-to-sit movement and in the seated posture when wearing tight pants significantly increased compared with those when wearing of general pants. [Conclusion] Therefore, wearing tight pants could produce musculoskeletal disorders via abnormal movement and posture in the lumbar spine and pelvis. So the effects of wearing tight pants need to be investigated in further studies to reveal their direct relationship to musculoskeletal problems.

[Purpose] This study examined the effects of band exercise types on the physical ability and muscular topography for elderly females. [Subjects and Methods] Twenty-six females older than 65 years were divided into the dynamic band exercise (DBE; n=13) group and the Static band exercise (SBE; n=13) group. Each participant performed 12 weeks of elastic band exercises. Physical abilities were measured by leg extension power, sitting trunk flexion, closed eyes foot balance, and time to get up. Changes in muscle topography were evaluated with Moire measurement equipment for the chest, abdomen, and lumbar region. All results were compared before and after 12 weeks of exercise. [Results] Changes in physical ability were significantly increased in both groups. The scores for the muscular topography of the chest, abdomen, lumbar region, and all body parts was significantly improved in both groups for closed eyes foot balance. There were more improvements in the DBE group. [Conclusion] Two types of static and dynamic elastic band exercises effectively changed the physical fitness and muscle topography of elderly females. Therefore, to increase the effects of exercise, dynamic band exercises are considered useful. Because band exercises are simple, they can be used to maintain the health of elderly people.

[Purpose] Age-related mediolateral (ML) instability of static postural control in the elderly has been well studied. Recent studies have provided evidence that ML center of pressure (CoP) parameters during dynamic postural control are more sensitive for differentiation of the fallers in the elderly. However, very limited studies have been done in which ML stability differences between fallers and non-fallers were investigated. The purpose of this study was to investigate the differences in ML CoP parameters between elderly fallers and elderly non-fallers during dynamic postural control. [Subjects and Methods] Twenty-nine community-dwelling older adults were divided into either fallers or non-fallers according to a self-report related to falling history within a year. Every participant performed 4 different tasks (static postural control tasks comprising quiet stance with eyes open and eyes closed and dynamic postural control tasks comprising stance with arm lifting and with trunk flexion) on force plates. [Results] The fallers demonstrated decreased AP and ML CoP parameters, and ML CoP distance was significantly smaller than in the non-fallers during both dynamic postural control tasks. [Conclusions] ML CoP parameters were able to differentiate the fallers from the non-fallers in a community-dwelling elderly population.

[Purpose] This study developed a reciprocal hip exercise using Thera-Band for those with flat lumbar spines and observed changes in standing and movement angles during sit-to-stand. [Participants and Methods] Eleven females participated in this study. The participants performed the reciprocal hip exercise using Thera-Band. [Results] The trunk flexion angle increased significantly after reciprocal hip exercise. The sit-to-stand time after reciprocal hip exercise was significantly faster than that before exercise. [Conclusion] The reciprocal hip exercise would useful for patients with flat back who can then sit and work for long periods.

[Purpose] The purpose of this study was to investigate the linear relationship between the thoracolumbar flexion angle and hip posterior displacement. [Subjects and Methods] This study was performed on 15 subjects. The subjects performed three trials of a lumbar flexion–extension task. To quantify the statistical linear relationship between the thoracolumbar flexion angle and hip posterior displacement, Spearman’s rank correlation coefficient was used. [Results] The thoracolumbar flexion angle was significantly correlated with the degree of hip posterior displacement. [Conclusion] According to the results of this study, movement of the thoracolumbar joint and posterior movement of the pelvis must be considered for accurate analysis of the lumbopelvic rhythm.

[Purpose] The purpose of this study was to investigate the activation of back and lower limb muscles in subjects who were performing a squat exercise at different angles of trunk flexion. [Subjects and Methods] Twenty healthy subjects (age 21.1± 1.8 years, height 168.7 ± 8.2 cm, weight 66.1 ± 12.3 kg) volunteered. The activation of the erector spinae muscle, rectus femoris muscle, gluteus maximus muscle and biceps femoris muscle was observed while the subjects performed squat exercises with a trunk flexion of 0°, 15°, and 30°. [Results] The erector spinae muscle, gluteus maximus muscle, and biceps femoris muscle were activated more during the squat exercise with the trunk flexion at 30° than the exercise with the trunk flexion at 0°. The rectus femoris muscle showed a tendency to decrease as the truck flexion increased. [Conclusion] Squat exercise be executed while maintaining an erect trunk posture if one wishes to strengthen the quadriceps muscle while reducing the load on the lower back.

[Purpose] The purpose of this study was to demonstrate the effects of expiration on abdominal muscle activity during maximum trunk flexion. [Subjects] Twenty-one healthy university students (10 men, 11 women) participated in this study. [Methods] Electromyography (EMG) was used to quantify the activity of the right rectus abdominis, external oblique, and internal oblique muscles. The paired t-test was used to examine the significance of differences in the abdominal muscles between maximum trunk flexion with breath holding and slow expiration. [Results] There was a significantly lower EMG activity in the external oblique muscle during maximum trunk flexion with slow expiration. [Conclusion] The results of this study indicate that slow expiration reduces external oblique muscle activity during maximum trunk flexion performed by healthy young subjects.

[Purpose] The aim of the present study was to measure the interrater and intrarater reliabilities of spinal motions using a skin-surface device (SpinalMouse; Idiag, Voletswil, Switzerland). [Methods] Spinal motion was measured in upright standing, trunk flexion, and trunk extension in 38 healthy adults. Intraclass correlation coefficients (ICCs) and Pearson's correlation coefficient were used to examine between-day and interrater reliabilities for spinal motion. [Results] For intrarater reliability of Raters 1 and 2, Pearson's correlation coefficient was 0.76-0.98, and ICC was 0.73-0.98, indicating high reliability in all cases except for extension of the sacral/hip. For interrater reliability on days 1 and 2, Pearson's correlation coefficient was 0.75-0.97 and ICC was 0.77-0.97 for all cases except for extension of the sacral/hip. [Conclusion] The reliability of SpinalMouse was demonstrated to be fair or higher but the measurement for extension of the sacral/hip needs further investigation.

[Purpose] The purpose of this study was to validate the characteristic of an exercise program consisting of simple exercise methods under the instruction of physiotherapists for general elderly people living in a community (general elderly group) and a frail elderly group. [Subjects] The general elderly group consisted of 44 persons (74.2 ± 4.38 years old: 6 men, 38 women) and the frail elderly group, 30 persons (80.6 ± 6.12 years old: 10 men, 20 women). [Methods] The measurement items were weight, body fat percentage, grip strength, knee extensor strength, sitting trunk flexion, one leg standing, functional reach test, timed "up and go" test, 10-m walking time, TMIG Index of Competence, MOS Short-Form 36-Item Health Survey, and the Life-Space Assessment. In each group, group and individual exercises were provided by physiotherapists. All the exercises were easy to perform. [Results] Knee extensor strength of the frail elderly group improved to almost the same level of the general elderly group. There were significant improvements in balance, gait ability, social and psychological attitudes in both groups. [Conclusion] We think that muscle strengthening exercises without exercise tools as resistance under the instruction of physiotherapists would be effective for improving the muscle strength of frail elderly persons.

[Purpose] This study developed a push-up plus guide and resistance device and investigated the effectiveness of the device. [Subject and Methods] A 39-year-old man presented with moderate pain with left scapular dyskinesis. A newly designed assistance device was used as a push-up plus guide and resistance device (PPGRD). The subject performed the push-up plus exercise without and then with the PPGRD for 2 weeks each. [Results] After performing the push-up plus exercise with the PPGRD for 2 weeks, the serratus anterior muscle power was increased, the pain score was decreased, and the absence of scapular dyskinesis was confirmed. [Conclusion] The PPGRD provided appropriate guidance and prevented excessive trunk flexion during the push-up plus exercise.

We studied the influence of posture on maximal mouth pressure in Part I. The study of Part II was aimed at determining the influence of trunk flexion on maximal mouth pressure. Nineteen healthy, young adult students from WCMAS comprised a STANDING study group, and 27 healthy, young adult students from IUHW comprised a LYING study group (same subjects of Part I). Maximal expiratory mouth pressure (PEmax) and maximal inspiratory mouth pressure (PImax) were measured at 0, 30, and 60 degrees of trunk flexion. Posture changes were significantly related to maximal mouth pressure values, and trunk flexion from the standing posture statistically influenced maximal mouth pressure. PEmax and PImax in standing were enhanced with trunk flexion. Respiratory muscle strength changes with trunk flexion, because respiratory muscle tension occurs with the change in interabdominal pressure and the muscle length-tension relationship.

[Purpose] We assessed the effects of a suspension seat support chair on the trunk flexion angle and gluteal pressure during computer work. [Subjects] Ten males were recruited. [Methods] The suspension seat support was developed to prevent abnormal gluteal pressure and a slumped sitting posture during computer work. The gluteal pressure was measured with a TekScan system and the trunk flexion angle was measured with a video camera, to compare the differences between a general chair and the suspension seat support. [Results] The gluteal peak pressures were decreased significantly in the suspension seat support versus the general chair. The trunk flexion angle was also decreased significantly in the suspension seat support compared with the general chair. [Conclusions] This study suggests that the suspension seat support chair contributes to preventing abnormal gluteal pressure and a slumped sitting posture.

Healthy 30 persons, 15 males and 15 females, were subjected to study the movement of the hip-joint, pelvis and trunk during standing trunk flexion using a digital camera. The movement of the hip joint linearly increased in correlation with the scale of standing trunk flexion. The trunk movement was exponentially inclined and then remained stable with the trunk flexion of the finger-floor distance less than 10 cm. Thus, while the anterior trunk flexion was much more involved at the initial stage of standing trunk flexion, the movement of the hip joint played more important role at a later half of flexion. In females the range of motion of the hip joint played a greater role than in males. Standing trunk flexion was considered to be highly influenced by the anterior inclination of hip joints or pelvis.

[Purpose] The purpose of this study was to compare the hamstring muscle (HAM) activities and flexion-relaxation ratios of an asymptomatic group and a computer work-related low back pain (LBP) group. [Subjects] For this study, we recruited 10 asymptomatic computer workers and 10 computer workers with work-related LBP. [Methods] We measured the RMS activity of each phase (flexion, full-flexion, and re-extension phase) of trunk flexion and calculated the flexion-relaxation (FR) ratio of the muscle activities of the flexion and full-flexion phases. [Results] In the computer work-related LBP group, the HAM muscle activity increased during the full-flexion phase compared to the asymptomatic group, and the FR ration was also significantly higher. [Conclusion] We thought that prolonged sitting of computer workers might cause the change in their HAM muscle activity pattern.