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Background The head, arms and trunk segment constitute a large proportion of the body’s mass. Therefore, small alterations in trunk inclination may affect lower limb joint moments and muscle activation patterns. Although previous research has investigated the effect of changing frontal plane inclination of the trunk, it is not clear how increasing trunk flexion will impact on the activation of the lower limb muscles. Research question What is the effect of independently manipulating trunk flexion angle on lower limb kinematics, moments and muscle function? Methods Gait analysis was carried out on 20 healthy people under four trunk flexion conditions: normal walking (NW), NW-5°, NW+5° and NW+10°. For the latter three conditions, a biofeedback approach was used to tightly control trunk flexion angle. A linear mixed model was used to investigate the effect of changing trunk flexion on joint angles, moments, and knee muscle activation. Results There were clear increases in hip and ankle moments as trunk flexion was increased, but no change in knee moments. The results also showed a linear increase in knee flexor muscle activity and a corresponding increase in co-contraction as trunk flexion increased. Interestingly, there was a dramatic change in the profile of hamstring activity. In the medial hamstrings, this change led to a 100% increase in activation during early stance as flexion was increased by 5° from NW. Significance This is the first study to demonstrate a strong dependence of knee flexor muscle activity on trunk flexion. This is important as people with knee osteoarthritis have been observed to walk with elevated muscle activation and this has been linked to increased joint loads. It is possible that these altered muscle patterns may result from increased trunk flexion during walking.

Background Abdominal draw-in maneuver (ADIM) has been recommended to achieve appropriate trunk muscle response for patients with non-specific chronic low back pain (CLBP). However, it has remained unclear whether the intervention with ADIM could change the trunk muscle response to sudden release from loading, which is considered to contribute mechanical circumstances to low back pain. The purpose of the present study was to investigate the effects of the intervention with ADIM on electromyography (EMG) activities of trunk muscles following sudden release from loading. Methods Seventeen subjects with non-specific CLBP participated. Subjects resisted trunk flexion or extension loading in semi-seated position, and then the loading was suddenly released. EMG recordings of 6 trunk muscles were acquired using a wireless surface EMG system. Onset and offset times were calculated from the EMG data. The intervention with ADIM was provided for 4 weeks. The onset and offset times were compared between pre- and post-intervention with ADIM. Results At the post-intervention, the onset of trunk flexors following release from trunk flexion loading became significantly earlier than pre-intervention (P = 0.028). The offset of flexors following release from trunk extension loading of post-intervention was significantly earlier than that of pre-intervention (P = 0.001). Conclusions We showed that the intervention with ADIM changed the EMG activity of trunk flexors in response to sudden release from loading. These results suggest a possibility that ADIM might be effective to improve the neuromuscular control of trunk flexors for the treatment of young patients with non-specific CLBP.

Background and purpose. Trunk endurance and extensibility are the main physical condition factors related to back pain. The goal was to analyse the effectiveness of a 6-week Pilates programme on trunk endurance and extensibility in adolescents with a history of back pain, determining the influence of sex. Materials and methods Fifty-two students with a history of back pain were randomly assigned to the Pilates group (PG; n = 26) or the control group (CG; n = 26). Trunk flexion (BTC test) and extension (SOR test), and hamstring extensibility (TT test) were measured. Results PG improved significantly BTC, SOR, and TT test. Statistical differences (p = 0.005) were found between the PG and the CG for the SOR test. Conclusion The Pilates programme enhanced trunk endurance and extensibility in adolescents with a history of back pain. Trunk flexor endurance was better in the PG. Results were not influenced by sex.

Objectives To compare patellofemoral joint (PFJ) stress between level, incline, and decline running. Design Experimental study. Setting University laboratory. Participants Twenty recreational runners. Main outcome measures Kinematics and kinetics of the trunk and lower extremity were obtained under 3 treadmill conditions: level, 6° incline, and 6° decline. PFJ stress, PFJ reaction force, and PFJ contact area were determined using a biomechanical model. One-way ANOVAs with repeated measures and post-hoc analyses were used to compare outcome variables across the 3 conditions. Results Peak PFJ stress and PFJ stress-time integral (cumulative PFJ stress over the stance phase) during decline running were significantly higher than during level and incline running. There was no difference in peak PFJ stress and PFJ stress-time integral between level and incline running. The increased peak PFJ stress during decline running was related to increased PFJ reaction force, resulting from a decrease in trunk flexion angle. Conclusions Running on a decline treadmill resulted in higher peak PFJ stress and stress-time integral. Peak PFJ stress and PFJ stress-time integral were similar during level and incline running. Results from this study may be used to prevent excessive PFJ stress during decline running, by targeting a postural strategy utilizing increased trunk flexion.

Background Various diseases of the spine are treated by immobilization via orthoses, although detailed evidence on the efficiency of orthotic bracing remains elusive. The present study sought to investigate the impact of 3 different orthoses on spinal immobilization using 3-dimensional (3D) kinematic measurements. Methods Twelve healthy volunteers performed different motion tasks, including trunk flexion/extension and bilateral trunk bending. Movements were performed under 4 different conditions: 1) without orthosis, 2) while wearing a 3-point hyperextension brace (HB), 3) while wearing a custom-made semirigid orthosis (SO), and 4) while wearing a custom-made rigid orthosis (RO). Spinal motion was analyzed using a 3D optical motion capture system assessing regional, intersegmental, and segmental range of motion (ROM). Results Assessment of spinal motion was successfully accomplished in all subjects. Overall, orthoses significantly reduced spinal motion compared with no bracing. RO caused the greatest restriction of regional, intersegmental, and segmental spinal motion among all orthoses. For flexion/extension, the mean percentage decreases between T3 and L5 in full active ROM with HB, SO, and RO compared with no orthosis were 38%/30%, 48%/47%, and 51%/55%, respectively ( P ≤ 0.05). Lateral bending was impaired by 28%, 44%, and 70%, respectively ( P ≤ 0.05). Assessment of lateral bending revealed greater immobilization by SO and RO compared with HB ( P ≤ 0.05). Conclusions The present 3D kinematic system allows for precise assessment of spinal motion. Custom-made orthoses cause superior restriction on gross spinal motion compared “off-the-shelf” orthoses. If orthotic bracing is indicated, design, comfort, and patient compliance need to be carefully considered to guarantee successful therapy.

Background Fire protective ensembles (FPEs) are essential to safely perform firefighting job tasks; however, they are often burdensome to the workers. The aim of this study was to compare three internationally certified fire protective ensembles from the European Union (EU), South Korea (SK), and United States (US) on physiological responses, mobility, and comfort. Methods Ten male professional firefighters performed a battery of exercises in the laboratory following the ASTM F3031-17 standard to evaluate mobility, occupation-specific performance, and physiological responses (body weight, heart rate (HR), core temperature (Tc), breathing rate (BR), and rating of perceived exertion (RPE)) to 20 min of treadmill walking (3.2 mph, 5% incline). All participants carried out the evaluation wearing each FPE in a random order. Mixed effects models examined time (pre-vs. post-) by ensemble (EU, SK, US) interactions for all physiological variables and compared comfort, performance, and subjective variables across ensembles. Results No interaction effects were observed for body weight, HR, Tc, BR, or RPE (p = 0.890, p = 0.994, p = 0.897, p = 0.435, and p = 0.221; respectively). SK had greater trunk flexion than EU (78.4° vs. 74.6°, p = 0.026) and US had lower standing reach than EU (105.5 cm vs. 115.4 cm, p = 0.004). Agility circuit time was lower in US (9.3 s) compared to EU (9.8 s) or SK (9.9 s) (p = 0.051 and p = 0.019, respectively). Conclusions The findings suggest that physiological burden remained largely unchanged across the international FPEs. However, mobility, performance, and comfort may be significantly influenced across types. International stakeholders and end users should consider design implications when choosing fire protective ensembles.

Recent studies have suggested that ergonomic factors may contribute to risks experienced by overhead crane operators. However, there are few studies that provide a comprehensive overview of the physical demands of overhead crane operation. This study aimed to provide this information by quantifying muscular, postural, and upper limb movement demands of overhead crane operation including examination of muscle activation and trunk posture by task. Trunk posture, upper limb movement demands and muscle activation in the trunk and upper limbs were quantified for seven overhead crane operators. Trunk posture was quantified using trunk angle and joystick motion requirements were determined using camera data. Muscle activation was measured bilaterally using surface EMG for the upper trapezii, anterior deltoids, posterior deltoids, biceps brachii, triceps brachii, flexor carpi radialis and erector spinae. Lastly, joystick force requirements were assessed using a spring scale. High upper limb and trunk muscle loading were observed when compared to joystick use in other heavy machinery, in part due to the forward, trunk-flexed position required to adequately view the workspace, and the increased force requirements of the joysticks. Joystick input force requirements were 9–31 N for the right-hand joystick and 11–40 N for the left-hand joystick. Operators maintained a forward trunk flexion (>20°) for all subtasks which suggests that trunk posture might play a role in sustained trunk muscle activation. Results suggest that the primary issue with overhead crane cab operation is upper limb and trunk muscle loading. Results confirm the need to investigate muscle load reduction strategies such as camera systems to help reduce the need for trunk flexion. Other design modification suggestions include reducing the joystick input force and displacement requirements coupled with potentially distributing the machine functions more evenly across the right and left controllers.

Context Goniometry and posture are commonly used metrics in clinical assessment of the shoulder and spine. When both the shoulder and spine are assessed individually using these techniques, there are structural and functional musculoskeletal relationships between the two anatomical regions that may be overlooked. Objective To determine the relationships between and within the shoulder and spine as measured by active range of motion (ROM) and spine curvature. Design Cross-sectional. Setting Clinical assessment in university setting. Participants 163 asymptomatic, right hand dominant, young adults; Intervention None. Main outcome measures A multivariate canonical correlation was used to identify a shoulder-spine relationship using active ROM assessments. Results A shoulder-spine relationship was determined using planar assessments and multivariate analyses of these two areas. Measures contributing to this relationship included shoulder flexion, internal rotation, external rotation, and trunk flexion and lumbar lordosis. Conclusions The findings of this study suggest that assessment of shoulder ROM should be interpreted with respect to spine region and vice versa, regardless of presenting region of concern, owing to the multivariate shoulder-spine ROM relationship when considering multiple measures of ROM and posture.

Trunk flexion is an understudied biomechanical variable that potentially influences running performance and susceptibility to injury. We present and test a theoretical model relating trunk flexion angle to stride parameters, joint moments and ground reaction forces that have been implicated in repetitive stress injuries. Twenty-three participants (12 male, 11 female) ran at preferred trunk flexion and three more flexed trunk positions (moderate, intermediate and high) on a custom built Bertec™ instrumented treadmill while kinematic and kinetic data were simultaneously captured. Markers adhered to bony landmarks tracked the movement of the trunk and lower limb. Stride parameters, moments of force and ground reaction force were calculated using Visual 3D (C-Motion ©) software. From preferred to high trunk flexion, stride length decreased 6% (P 0.001) and stride frequency increased 7% (P 0.001). Extensor moments at the hip increased 70% (P 0.001), but knee extensor (P 0.001) and ankle plantarflexor moments (P 0.001) decreased 22% and 14%, respectively. Greater trunk flexion increased rate of loading by 29% (P 0.01) and vertical ground reaction force impact transients by 20% (P 0.01). Trunk flexion angle during running has significant effects on stride kinematics, lower extremity joint moments and ground reaction force and should be further investigated in relation to running performance and repetitive stress injuries.

Individuals with knee osteoarthritis (OA) show variability during the sit-to-stand (STS) task, so they may not perform the STS in the same way. This study aimed to determine whether individuals with knee OA have different strategies in performing the STS.Participants with knee OA and able-bodied individuals underwent STS evaluation at a self-selected pace with use of a motion measurement system consisting of 12 cameras and 2 force plates.In total, 101 participants (57 women) with knee OA showed 3 main STS strategies. As compared with the 27 controls (14 women), 24 OA participants, compensated STS, showed greater trunk flexion (47.1° vs. 38.3°; P0.01) and trunk obliquity (4.6° vs. -0.8°; P0.001) when completing the STS task in the same amount of time as controls (2.4 vs. 2.7s; P=0.999). The second group (n=59), inadequately compensated STS, also compensated with trunk flexion (47.7° vs. 38.3°; P0.01) and trunk obliquity (1.6° vs. -0.8°; P0.001) but took longer than controls (3.4 vs. 2.7s; P=0.001). The third group (n=18), severe impaired STS, took an extended amount of time to execute the STS (6s), with marked trunk flexion (59.2°) and obliquity (4.1°), so participants in this group were perhaps severely impaired in completing the STS.This study identified 3 groups STS trunk strategies among participants with STS. Moreover, the data reveal a concise representation of the relations among strategy variables. The findings could be used to simplify the characterization of the STS among patients with knee OA and aid with follow-up.

Repetitive trunk flexion can damage spinal tissues, however its association with low back pain in the workplace may be confounded by factors related to pain sensitivity. Muscle fatigue, exercise-induced hypoalgesia, and creep-induced neuromuscular changes following repetitive trunk flexion may all affect this assumed exposure-pain relationship. This study’s purpose was to determine how mechanical pain sensitivity in the low back is affected by a repetitive trunk flexion exposure and identify factors associated with changes in low back pain sensitivity. Pressure pain thresholds, perceptions of sub-threshold stimuli, and muscle fatigue in the trunk and tibia, as well as lumbar spine creep were tracked in 37 young healthy adults before and up to 40 min after a 10-min repetitive trunk flexion exposure. Pressure pain thresholds (p = 0.033), but not perceptions of sub-threshold stimuli (p > 0.102) were associated with approximately a 12.5% reduction in pain sensitivity 10 min after completing the exposure, while creep and local muscle fatigue effects were only observed immediately following the exposure. Creep and fatigue interactions and the corresponding tibial measure co-varied with individual low back pressure pain thresholds. The net hypoalgesic effects of repetitive trunk flexion have the potential to partially mask possibly injurious loads, which could contribute to the severity or incidence of lower back injuries related to these exposures.

This study examined the influences of schoolbag carrying modes combined with carrying weights on the body posture alterations, muscle activations, and subjective discomfort scores of participants. Twelve male university students were recruited as participants and executed nine test combinations of three carrying methods (2-strap backpack, 1-strap side backpack, and 1-strap crossbody carrying) generally used by Taiwanese young students and three loads (5%, 10%, and 15% of their respective body weights [BWs]). The results revealed that carried load and method significantly affected body posture and trapezius activation. Side backpack carrying should be avoided because of the relatively high lateral shoulder tilt, trunk flexion, right trapezius activation, and low lumbosacral angle observed compared with other two carrying methods. The unbalanced load of side backpack carrying may cause an uneven shoulder posture, thus resulting in extra body strains. Furthermore, carrying loads at 10% of BW was recommended when carrying a 2-strap backpack. Relevance to industry The daily carriage of a schoolbag or backpack on the musculoskeletal health of young students has been a permanent concern. The findings suggest that carrying a load weighing 15% of BW and using the unbalanced side backpack carrying method should be avoided.

Flexion relaxation (FR) is characterized by the lumbar erector spinae (LES) becoming myoelectrically silent near full trunk flexion. This study was designed to: (1) determine if decreasing the lumbar moment during flexion would induce FR to occur earlier; (2) characterize thoracic and abdominal muscle activity during FR. Ten male participants performed four trunk flexion/extension movement conditions; lumbar moment was altered by attaching 0, 5, 10, or 15lb counterweights to the torso. Electromyography (EMG) was recorded from eight trunk muscles. Lumbar moment, lumbar flexion and trunk inclination angles were calculated at the critical point of LES inactivation (CPLES). Results demonstrated that counterweights decreased the lumbar moment and lumbar flexion angle at CPLES (p

The reasons for higher fall risk of people with osteoarthritis (OA) compared to people without OA are not known. It is possible that following a loss of balance OA may negatively affect the recovery stepping response. Stepping responses have not been reported for people with knee OA. Here, we compared recovery step kinematics following laboratory-induced trip and following a large treadmill-delivered perturbation simulating a trip between a group of women with and without self-reported knee OA. We hypothesized that knee OA would significantly impair recovery step kinematics compared to those of a control group. Following the laboratory-induced trip, step length and trunk flexion velocity at recovery step completion of women with OA were significantly impaired and more so for the women who fell. Following the treadmill-delivered perturbation, the recovery step kinematics of women with OA were not significantly impaired. For both perturbations, the women who fell had significantly impaired recovery step kinematics compared to those who did not fall, regardless of OA. The results are consistent with previous work on healthy middle aged and older women and suggest that the same biomechanical risk factors for trip-related falls are shared by middle age and older women regardless of the presence of knee OA. The results support the need to determine whether training protocols which have been shown to improve recovery step kinematics and reduce prospective falls by healthy older women can have similar outcomes for people with knee OA.

The current study examined of the effect of intermittent, short-term periods of full trunk flexion on the development of low back pain (LBP) during two hours of standing. Sixteen participants completed two 2-h standing protocols, separated by one week. On one day, participants stood statically for 2h (control day); on the other day participants bent forward to full spine flexion (termed flexion trials) to elicit the flexion relaxation (FR) phenomenon for 5s every 15min (experimental day). The order of the control and experimental day was randomized. During both protocols, participants reported LBP using a 100mm visual analogue scale every 15min. During the flexion trials, lumbar spine posture, erector spinae and gluteus medius muscle activation was monitored. Ultimately, intermittent trunk flexion reduced LBP by 36% (10mm) at the end of a 2-h period of standing. Further, erector spinae and gluteus medius muscle quietening during FR was observed in 91% and 65% of the flexion trials respectively, indicating that periods of rest did occurred possibly contributing to the reduction in LBP observed. Since flexion periods do not require any aids, they can be performed in most workplaces thereby increasing applicability.

Injury and dropout rates during rodwork training appear to reflect difficulties encountered by apprentices adapting to increased physical demands of tying on slab, one of the rodworking tasks with the highest injury risk. Because experience influences work strategies, and consequently the risk of developing musculoskeletal disorders (MSDs), this study aimed to identify differences in work practices associated with tying rebar on slab, potentially relevant to back MSD development, in experienced and inexperienced rodworkers. Fourteen male rodworkers were recruited from either experienced (>2 years experience post apprenticeship), or inexperienced (

Posture quantification is important for analyzing trunk and upper extremity loading and estimating the risk of work-related musculoskeletal disorders. This study introduced an inertial measurement unit sensor-based posture-matching (ISPM) method. The ISPM method is the concept that involves observers wearing sensors and simulating postures in photos or videos obtained at job sites to assess the postural risks for the trunk and upper extremity. We tested the inter-rater reliability of the method in 4 novice observers. For the trunk, shoulder/elbow, and wrist joint angle category, weighted kappa scores were 0.89, 0.52, and 0.26, respectively. The results of the ISPM method indicated moderate or high inter-rater reliability for trunk flexion, shoulder flexion/extension, shoulder abduction/adduction, and elbow flexion. The ISPM method was more reliable than conventional observation-based posture assessment tools used for trunk posture analyses. However, the assessment of upper extremity angles indicated that the reliability of ISPM was lower than that of conventional observation-based posture assessment tools. This was a proof-of-concept study conducted using a few samples. Therefore, further testing is necessary to support the findings. Relevance to industry The ISPM method requires a minimal level of training. It uses conventional video recording and imposes almost no interruptions to the workers’ performance. The ISPM method showed moderate inter-rater reliability for the trunk, shoulder flexion/extension, shoulder abduction/adduction, and elbow flexion during the joint angle analysis.

Rectus abdominis (RA) and rectus femoris (RF) differently activate in hip and trunk flexion movements. Previous studies using surface electromyography (sEMG) showed heterogenous results in mean and maximum activity of Upper (URA), Middle (MRA), and Lower (LRA) RA. Statistical Parametric Mapping (SPM) and Time-Varying Multi-muscle Co-activation function (TMCf) are emerging methods for whole-time-course continuous comparisons of muscle activity and co-activation. The aim was to analyse RA and RF activity in three core training exercises with continuous approach. Eight subjects performed Curl-up, Sit-up 45° and Sit-up 90° (where 45° is half and 90° is complete trunk flexion). sEMG from URA, MRA, LRA and RF were normalized to the maximum voluntary contraction root-mean-square (RMSMVC), and compared among muscles/exercises with SPM and TMCf. Angular displacement was assessed using stereophotogrammetry. Curl-up, Sit-up 45° and Sit-up 90° did not differently activate URA, MRA or LRA, and in their common range of motion (ROM) RA activity was similar among the three exercises. Conversely, Sit-up exercises elicited higher RF activity than Curl-up (on average 45% vs. 25% RMSMVC) mainly due to the wider ROM. RA-RF co-activation pattern was different in concentric and eccentric phases between Sit-up exercises and Curl-up, leading to significantly higher co-activation in Sit-up exercises.

Parkinson's disease (PD) can present with lateral trunk flexion (LTF). Abnormal posture associated with PD has been treated, but the effectiveness of these treatments is limited, resulting in unsatisfactory outcomes. Unilateral hypertrophy and unilateral hyperactivity may be useful for deciding targets for injection of botulinum toxin or physical rehabilitation. However, such findings may be limited such as the obliquus abdominis muscle or thoracic paraspinal muscles, and several other muscles may have a causative role in LTF. We investigated 8 patients whether other muscles show unilateral hypertrophy by analyzing computed tomographic scans. Cobb's angle was 11° to 34°. The area of the paravertebral muscles was large contralateral to the bending side and this trend intensified from L4 to Th10. The lumbar quadrate muscle and psoas major muscle showed unilateral enlargement. These larger muscles were prominent contralateral to the bending side in five patients and ipsilateral to the bending side in two patients. This unilateral muscle change was mildly seen in the internal and external abdominal oblique muscles. The lumbar quadrate muscle or psoas major muscle showed two hypertrophic patterns, and these muscles might be new therapeutic targets for treatments such as botulinum toxin.

The 1991 NIOSH Lifting Equation (NLE) is widely used to assess the risk of injury to spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses the predictive equations developed based on a detailed trunk musculoskeletal biomechanical model to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in some studies). Fifty lifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the predictive equations. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding the recommended limits. The NIOSH vertical multiplier is the likely cause of this inadequacy; a revised multiplier accounting for the trunk flexion angle is hence needed. The use of a fixed 3400 N compression limit is also questioned. Relevance to industry Ergonomist and occupational health practitioners are advised to use the NLE along with the predictive equations of the spine loads proposed in this study when evaluating the risk of injury to the spine in lifting activities particularly those involving moderate to large trunk flexion.

In this study, we analyzed 100 questionnaire responses to determine consumer conceptions of service personnel bowing as a gesture of politeness. In addition, 12 female participants demonstrate five distinct degrees of bowing by bending their trunk 30°, 45°, 60°, and 90° from an upright position; their spinal curvature and trunk muscle activations were measured. The results showed that most respondents believed that bowing at 30° was the most satisfactory angle, followed by 45°. Bowing at 45° or 60° caused the survey respondents to feel honored, whereas bowing at 90° induced feelings of surprise and novelty; however, this angle produced the lowest proportion level of agreements on the items at ease, necessary, and appropriate among the 100 respondents. When the 12 participants bowed at an angle ≤60°, their spinal posture became increasingly kyphotic, and their muscle activations became more pronounced. Myoelectric silencing of the erector spinae was observed when the participants bowed at 90°, which can increase the risk of low back injury. These findings provide service industries with a reference for the design of service encounters. Relevance to industry Bowing has traditionally signified politeness and respect in many countries. However, whether bowing at a greater trunk flexion actually satisfies customers remains unclear. Findings from this study clarify the customer perceptions and body loads of service personnel when bowing at various trunk positions. The extreme bowing postures (e.g., 90° trunk flexion) should be avoided.

Various kinematic definitions of the thoracic spine have been employed in past work. However, the segments necessary to sufficiently characterize the thoracic spine during trunk movements in all three planes of motion have not yet been identified. This study aimed to determine the minimum number of segments necessary to adequately characterize the kinematics of the thoracic spine. Thirty individuals, asymptomatic for back pain, performed ten trials of maximum trunk flexion, lateral bend, and axial twist; thoracic flexion, lateral bend, and axial twist; and slumped standing. Marker clusters were applied over the C 7 , T 3 , T 6 , T 9 , T 12 , and L 5 vertebrae. Three-dimensional angles of each cluster were calculated, and cross-correlation ( R xy(time) ) and correlation ( R xy(max) ) analyses were employed to assess the relationships in the motion patterns and maximum angles of adjacent clusters, respectively. The motion patterns and maximum angles of adjacent clusters were very strongly ( R xy(time) >0.90 for 26 of 35 pairings) and strongly ( R xy(max) >0.80 for 25 of 35 pairings) correlated, respectively. A four-cluster set (C 7 , T 6 , T 12 , and L 5 ) represented thoracic movement for six of the seven movement tasks tested. These results provide insight into thoracic movement coordination, with implications for predictive spinal modeling and clinical assessment practices.

Our companion paper demonstrated the importance of a systems-level perspective on spine biomechanics by showing the effects of lower extremity constraints during simple, trunk flexion-extension motions. This paper explores the impact of trunk muscle fatigue and stress-relaxation of lumbar passive tissues on this systems-level response. Twelve participants performed experimental protocols to achieve lumbar passive tissue stress-relaxation fatigue and lumbar muscle fatigue. Participants performed full range of sagittal-plane trunk flexion-extension under unconstrained stoop movement and pelvic/lower extremity constrained stoop movement. They performed these motions both before and after the fatigue protocols and trunk kinematics and muscle activities in trunk and lower extremity muscles were monitored. Under the condition of passive tissue fatigue, low back muscles and lower extremity muscles revealed significantly increased activation level (21% and 22%, respectively) in the free stoop condition but under the restricted stoop condition, there was no significant effect of the protocol. Under the lumbar muscle fatigue condition, a significant antagonistic and lower extremity activation effect (34% increase in abdominal muscles, 16% increase in lower extremity muscles) was observed in the free stooping condition while these variables were not affected by the protocol under the restricted stooping condition. Relevance to industry Fatigue of the lumbar musculature and passive tissues is prevalent in jobs requiring full trunk flexion postures. Developing accurate biomechanical models of spinal stress in these full stooping postures can help in the development of appropriate interventions to reduce the prevalence of back injuries in these jobs.

Spine stability demand influences active-passive coordination of the trunk response, especially during sudden perturbations. The objective of this study was to look at the role of passive, stationary active and reflexive subsystems on spinal stability. Spine stability was evaluated here during pre- and post-perturbation phases by computing the minimum (i.e., critical) muscle stiffness coefficient required to maintain stability. The effects of pre-perturbation conditions (preloading, initial posture and abdominal antagonistic coactivation) as well as perturbation magnitude were studied. Results revealed that higher preload, initially flexed trunk posture and abdominal pre-activation enhanced pre-perturbation stiffness and stability. In contrast to the preload, however, larger sudden load, initial flexion and abdominal preactivation significantly increased post-perturbation stability margin. As a result, much lower critical muscle stiffness coefficient was required post-perturbation. Compared to the pre-perturbation phase, the trunk stiffness and stability substantially increased post-perturbation demanding thus a much lower critical muscle stiffness coefficient. Overall, these findings highlight the crucial role of the ligamentous spine and muscles (in both passive and active states) in augmenting the trunk stiffness and hence stability during pre- and post-perturbation phases; a role much evident in the presence of initial trunk flexion.

The purpose of this study was to perform a biomechanics-based assessment of body borne load during the walk-to-run transition and steady-state running because historical research has limited load carriage assessment to prolonged walking. Fifteen male military personnel had trunk and lower limb biomechanics examined during these locomotor tasks with three different load configurations (light, ∼6 kg, medium, ∼20 kg, and heavy, ∼40 kg). Subject-based means of the dependent variables were submitted to repeated measures ANOVA to test the effects of load configuration. During the walk-to-run transition, the hip decreased (P=0.001) and knee increased (P=0.004) their contribution to joint power with the addition of load. Additionally, greater peak trunk (P=0.001), hip (P=0.001), and knee flexion (P0.001) moments and trunk flexion (P0.001) angle, and reduced hip (P=0.001) and knee flexion (P=0.001) posture were evident during the loaded walk-to-run transition. Body borne load had no significant effect (P0.05) on distribution of lower limb joint power during steady-state running, but increased peak trunk (P0.001), hip (P=0.001), and knee (P=0.001) flexion moments, and trunk flexion (P0.001) posture were evident. During the walk-to-run transition the load carrier may move joint power production distally down the kinetic chain and adopt biomechanical profiles to maintain performance of the task. The load carrier, however, may not adopt lower limb kinematic adaptations necessary to shift joint power distribution during steady-state running, despite exhibiting potentially detrimental larger lower limb joint loads. As such, further study appears needed to determine how load carriage impairs maximal locomotor performance.

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h. Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively. In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.

Objective The study was conducted to assess the ergonomic exposures to risk factors that may lead to the reported musculoskeletal injuries (especially back, neck and wrist injuries) of drywall workers. Methods A hierarchical taxonomy for construction of drywall panel hanging (drywall panel fitting and installation) was developed with activities defined within the interior wall systems tasks (drywall panel, studs and insulation). Exposures were characterized for the drywall panel work with the PATH (Posture, Activity, Tools, and Handling) work-sampling observation method. Data on working postures were collected for three main body parts: legs, arms and trunk. Activities performed for each task, tools used, and manually handled loads were also recorded for each observation. Results The study identified several ergonomic exposures in interior systems construction. Several risk factors were especially prevalent in the drywall panel installation task: awkward body postures such as overhead arm posture, trunk flexion, and handling of heavy drywall panels. Some tasks were observed to have combinations of these musculoskeletal risk factors, such as drywall panel installation, where the workers lifted heavy drywall panels in awkward body postures. In addition, a safety hazard frequently resulted when a worker's foot was poorly supported on a ladder while lifting heavy drywall panels to hang them on the ceiling or upper wall. Conclusion The drywall panel installation task poses a severe threat to the safety and musculoskeletal health of the drywall workers. Much of this could be eliminated by reducing the burden of handling heavy and bulky drywall panels. Relevance to industry The construction industry is well-documented to have high rates of injury and musculoskeletal disorders. Design of appropriate interventions requires specific knowledge of which tasks and activities involve the highest levels of exposure to relevant factors. Assessment of such factors in drywall panel hanging has provided data that will be useful to evaluate the ergonomics efficacy of future changes in task processes or tools. Feasible solutions appear to exist; effectiveness trials and worker input are needed in order to evaluate whether they could eliminate the observed exposures.

The purpose of this study was to determine the muscular contributions to the stepping phase of recovery from forward loss of balance in 5 young and 5 older adults that were able to recover balance in a single step, and 5 older adults that required multiple steps. Forward loss of balance was achieved by releasing participants from a static forward lean angle. All participants were instructed to attempt to recover balance by taking a rapid single step. A scalable anatomical model consisting of 36 degrees-of-freedom was used to compute kinematics and joint moments from motion capture and force plate data. Forces for 94 muscle actuators were computed using static optimisation and induced acceleration analysis was used to compute individual muscle contributions to net lumbar spine joint, and stepping side hip joint and knee joint accelerations during recovery. Older adults that required multiple recovery steps used a significantly shorter and faster initial recovery step and adopted significantly more trunk flexion throughout recovery compared to the older single steppers. Older multiple steppers also produced significantly more force in the stance side hamstrings, which resulted in significantly higher hamstring induced flexion accelerations at the lumbar spine and extension accelerations at the hip. However since the net joint lumbar spine and hip accelerations remained similar between older multiple steppers and older single steppers, we suggest that the recovery strategy adopted by older multiple steppers was less efficient as well as less effective than for older single steppers.

1 b abstract The purpose of this study was to investigate the effects of imposing different degrees of forward trunk flexion during sitting pivot transfers on electromyographic activity at the leading and trailing upper limb muscles and on dynamic stability requirements. Thirty-two individuals with a spinal cord injury per- formed three types of sitting pivot transfers: natural technique, exaggerated forward trunk flexion and upright trunk position. Ground reaction forces, trunk kinematics, and bilateral electromyographic activity of eight upper limb muscles were recorded. Electromyographic data were analyzed using the area under the curve of the muscular utilization ratio. Dynamic stability requirements of sitting pivot transfers were assess using a dynamic equilibrium model. Compared to the natural strategy, significantly greater muscle activities were found for the forward trunk flexion condition at the anterior deltoid and both heads of the pectorialis major, whereas the upright trunk strategy yielded greater muscle activity at the latissimus dorsii and the triceps. The forward flexed condition was found to be more dynamically stable, with a lower stabilizing force, increased area of base of support and greater distance traveled. Thus, transferring with a more forward trunk inclination, even though it increases work of few muscles, may be a beneficial trade-off because increased dynamic stability of this technique and versatility in terms of potential dis- tance of the transfer.

Summary Objective To compare sagittal lumbar curvature in several positions between elite cyclists and non-athletic subjects. Methods A total of 60 elite male cyclists and 68 age-matched sedentary controls (mean age: 21.91 ± 2.86 years) participated in the study. Lumbar curvature was measured with a Spinal Mouse ® during relaxed standing, maximal trunk flexion in sitting with knees flexed, during a sit-and-reach test, and while sitting on the bicycle with upper-, middle-, and lower handlebar positions. Results The cyclists exhibited a significantly greater lumbar flexion than non-athletes ( P Conclusions Cycling produces specific adaptations in lumbar curvature when trunk flexion postures are achieved. Cyclists exhibit greater lumbar flexion than non-athletes in maximal trunk flexion and while sitting on the bicycle. However, cycling training does not appear to influence standing lumbar curvature.

Determining the key factors in athletic performance is important for developing the technique and strength of athletes. Many martial arts forms have been studied, but a relatively new form of martial arts competition, San Shou, has not been analyzed. The purpose of this study was to determine key attributes necessary in the development of the San Shou athlete, particularly in female participants. Six elite and six novice competitors performed 30 continuous repetitions of cyclic extension and flexion of the trunk segment, knee joints, and elbows joints at two velocities, 60°/second and 180°/second, using an isokinetic dynamometer. Variables of interest were maximum torque production, normalized torque (Nm/kg), fatigue indexes (average of three maximal forces in the first three cycles/average of maximal forces in the last three cycles), and rate of torque development (Nm/s). Results indicate significant differences between groups only during trunk flexion for maximum torque, normalized torque, and rate of force development, whereas differences between movement velocities were apparent for multiple variables at each anatomic region. These analyses assist in providing further information regarding the possible key factors in developing the San Shou female athlete. Further work is required to identify additional parameters in developing the San Shou athlete.

Clinical assessment of functional disability is an integral part of management in patients with low back pain (LBP). The range of spinal motion is one of LBP disability measure. The aim of this study was to investigate the validity of spinal range of motion as a predictable measure of disability and to analyze the intrarater reliability of back range of motion (BROM) instrument for measurement of active lumber spine range of motion. Forty men patients with chronic low back pain over 6 month’s duration were participated in the study. Their ages ranged from 20 to 40 years. Lumber range of motion was measured with BROM device and disability was evaluated by self reported Roland Morris disability questionnaire (RMDQ). Data were analyzed using Spearman’s correlation, multiple regression analysis models and ICC. Statistical analysis revealed that there was a highly significant moderate to good relation between forward trunk flexion and RMDQ score (rho = −0.59, p 0.05). The main predictors of disability were forward and lateral trunk flexion. Furthermore, intrarater reliability for forward trunk flexion was good (ICC, 0.84), for extension was high (ICC, 0.91), for rotation was good (ICC range, 0.86–0.88), and for lateral flexion was good (ICC range, 0.81–0.82). It was suggested that spinal ROM do not appear to be a valid measure for prediction of the functional disability in patients with chronic low back pain.

Summary Objective To evaluate the effectiveness of Pilates with regard to the degree of scoliosis, flexibility and pain. Method The study included 31 female students divided into two groups: a control group (CG = 11), which had no therapeutic intervention, and an experimental group (EG = 20), which underwent Pilates-based therapy. We used radiological goniometry measurements to assess the degree of scoliosis, standard goniometry measurements to determine the degree of flexibility and the scale of perceived pain using the Borg CR 10 to quantify the level of pain. Results The independent t test of the Cobb angle ( t = - 2.317, p = 0.028), range of motion of trunk flexion ( t = 3.088, p = 0.004) and pain ( t = −2.478, p = 0.019) showed significant differences between the groups, with best values in the Pilates group. The dependent t test detected a significant decrease in the Cobb angle (Δ% = 38%, t = 6.115, p = 0.0001), a significant increase in trunk flexion (Δ% = 80%, t = −7.977, p = 0.0001) and a significant reduction in pain (Δ% = 60%, t = 7.102, p = 0.0001) in the EG. No significant difference in Cobb angle ( t = 0.430, p = 0.676), trunk flexion, ( t = 0.938p = 0.371) or pain ( t = 0.896, p = 0.391) was found for the CG. Conclusion The Pilates group was better than control group. The Pilates method showed a reduction in the degree of non-structural scoliosis, increased flexibility and decreased pain.

We investigated the effect of an alternative welding system designed to reduce exposure to extreme trunk flexion on measures of trunk inclination and muscle activity. Among 10 participants, data were collected while using conventional stud welding equipment and while using the alternate system. Paired t-tests were used to compare results between the two welding systems. Mean trunk inclination angle was reduced with the alternate system (34.4° versus 9.7°, p < 0.01). Percent time with trunk inclination angles greater than 60° was also reduced (40.0% versus 4.7%, p < 0.01). In general, the alternate system resulted in less desirable upper trapezius muscle activity levels. The alternate system appears to be effective in reducing exposure to extreme trunk flexion among stud welders. Continued development of the system should explore features designed to reduce shoulder forces and improve productivity.

Ageing is associated with geometrical changes in muscle fascicles that may lead to deteriorations in physical functions. The purpose of this study was to study the effects of ageing on fibre orientation and strength of the lumbar extensor muscles.Fifty two healthy, 26 younger (10 males and 16 females, aged from 20 to 35) and 26 older (10 males and 16 females, aged from 65 to 90) volunteers participated in this study. Ultrasound images of the lumbar extensor muscles were obtained with the participants in relaxed standing and half flexion (50% of the range of trunk flexion). The fibre angles at the mid-substance of the muscle were recorded. Lumbar extensor muscle strength was measured in the upright posture with a load cell.The mean lumbar extensor fibre angles were found to significantly decrease in the half flexion posture when compared to upright stance (P0.01). Both the fibre angle and the moment generation capability of the muscles decreased with ageing (P0.01). There was a moderate correlation between the fibre angles in the upright posture and the muscle strength measured in this posture (r=0.40, P0.01).Age-related changes in muscle geometry and posture may partly account for the deterioration in muscle function in the elderly.

The purposes of this study were to quantify stability during recovery from forward loss of balance in young and older adults, older single steppers (OSS) and older multiple steppers (OMS), and to identify the biomechanical factors associated with stability during balance recovery. Forward loss of balance was achieved by releasing participants from a static forward lean angle. Participants regained balance by taking one or more rapid steps. Stability was quantified using the margin of stability (MoS), which was computed as the anterio-posterior distance between the forward boundary of the base-of-support and the vertical projection of the velocity adjusted centre of mass. MoS at foot contact and at maximal knee joint flexion angle following foot contact (KJ(MAX)) were smaller in older compared to young adults, and in OMS compared to OSS. Compared to young adults, older adults exhibited a shorter recovery step length, greater trunk flexion angles and exhibited smaller peak knee flexion angles. Trunk flexion angle at foot contact (r=-0.55) and step length (r=0.54) were significantly correlated with MoS at foot contact and together accounted for 51% of the variance in MoS at foot contact. MoS at foot contact was significantly correlated with MoS at KJ(MAX) (r=0.88) and together with peak knee flexion angle during the landing phase (r=0.60) and peak knee extension moment during the landing phase (r=0.47) accounted for 84% of the variance in MoS at KJ(MAX). Overall findings suggest that stability in the first step is lower for older compared to young adults and for multiple compared to single steppers, and that spatial-temporal, kinematic and kinetic factors are associated with stability during recovery from forward loss of balance.

The standing reach movement requires coordinated activation of postural and focal motor responses. For PD patients, both components of this reaching task exhibit evidence of motor deficit. In the present experiment, we examined these motor responses during a standing reaching task in a challenging environmental context. PD patients ( n = 10) and control participants ( n = 8) were asked to reach and drink from a glass while standing on a raised platform (0.6 m) with and without an additional anterior platform. Removal of the anterior platform placed participants in a higher postural threat context. Displacement data were captured from markers on relevant body landmarks to provide reach end-point and whole-body movement kinematics. Our results showed that PD patients delayed trunk flexion and peak end-point velocity during the forward reach phase and peak centre of mass velocity during the transport phase for a challenged standing reach. These behaviours, in combination with the bradykinetic motor control observed in PD patients, could contribute to the frequent falls observed among the PD population.

Cyclic trunk flexion/extension is known to be a risk factor for low back pain or disorders. Changes in the in vivo low back musculature associated with cyclic flexion/extension have not been adequately examined. The purpose of this study was to investigate the effects of cyclic flexion/extension on muscle activity of the low back extensors by quantifying changes in activation timing and mean amplitude of electromyography (EMG). Trunk flexion angle and EMG were recorded during 30 cyclic flexion/extension movements over a 5 min period, and during isometric extension performed before and after the 5 min period. Mean EMG in isometric extension increased (30% increase in average) significantly after cyclic flexion/extension, confirming a transfer of extension moment from viscoelastic passive tissues to the extensor muscles in isometric extension. However, in the extension phase of cyclic flexion/extension, a significant delay in the re-activation and a decrease in the mean amplitude of EMG were observed. The results of this study, together with findings in previous research, suggest that the biomechanical effects and potential risk associated with cyclic flexion/extension may be sensitive to the task demands. Further research is needed to investigate how different moment generating components function together to compensate for the loss of tissue stiffness under varying task conditions.

Introduction/Background Performing sitting transfers figures among the most demanding activities in manual wheelchair users living with spinal cord injury (MWUSCI). Surprisingly, little is known about how the built environment may change movement strategies and upper extremity (UE) muscle demands during transfers. This study aims to determine to what extent the use of an armrest changes UE muscle demands during lateral sitting transfers in MWUSCI. Material and method Twenty MWUSCI performed lateral transfers toward the left under three experimental conditions: 1. without armrest, 2. with a left armrest at 9 cm, 3. with a left armrest at 18 cm above seat surface. Bilateral recorded EMG signals of the anterior deltoid, pectoralis major, biceps, and triceps were selected for analysis. Muscular utilization ratio (MUR) was obtained through amplitude-normalization using maximum voluntary contractions. Peak MUR and area under the MUR curve (AUC) of each muscle were compared across conditions using a non-parametric ANOVA. Results When transferring using the 9-cm armrest, the peak MUR increased in both triceps and decreased in left anterior deltoid, while the AUC decreased in right biceps compared to transfers without armrest. When transferring using the 18-cm armrest, the peak MUR increased in both triceps and decreased in left anterior deltoid and biceps, while AUC decreased in both biceps compared to transfers without armrest. Furthermore, the peak MUR increased in left pectoralis major compared to transfers using the 9-cm armrest. Conclusion The use of an armrest during sitting transfers shifts part of the UE muscle demands from the shoulder flexors to the elbow extensors in MWUSCI. This adaptation may be linked to a reduced forward trunk flexion during transfer, although a confirmatory kinematic analysis is needed. Nonetheless, the availability of an armrest during transfers provides additional opportunities to vary UE muscle demands and to minimize UE musculoskeletal risk exposure.

Aims: This study has aimed to analyze whether the application of Kinesio taping increases trunk flexion compared with the application of placebo bandages and conventional adhesive bandages and to study in which segments this possible increase occurs.

Background In the third trimester, trunk flexion movements become difficult due to abdominal enlargement. Moreover, muscle load increases when rising from a seated position (sit-to-stand) due to the increased abdominal weight. Sit-to-stand is frequently performed by working women; this activity becomes more difficult in the third trimester. The purpose of this study was to investigate the effect of decreasing the amount of muscle load during the third trimester with the use of a handrail and to analyze the amount of muscle load during sit-to-stand. Methods Eight pregnant women in their third trimester and eight non-pregnant women performed sit-to-stand from 450-mm high seats using different types of handrails (i.e., distal bar, proximal bar, one-handed handrail, and armrest). Body load measurements were based on the leg joint moment, combined floor reaction force, the angle of trunk flexion and extension, handrail reaction force, and subjective perceived strength using a 3D motion analysis system and a force plate. Findings With the armrest, the maximal handrail reaction force increased, and the combined floor reaction force and subjective perceived strength decreased. The bilateral leg joint moments were symmetrical, and the knee extension moment did not exceed the hip extension moment. Interpretation With the armrest, the forward and upward movements of the center of gravity were ensured by the reaction force on the armrest, and a symmetrical dispersion of the muscle's load on the legs was noted. Relevance to industry This study evaluates the effect of handrail for pregnant woman. As for the handrail of the restroom of the obstetrics and gynecology department, the armrest is more desirable.

INTRODUCTION The momentum of the upper body (UB) during transfer sit-to-stand (STS) could be sensitive to the deterioration of dynamic postural control, and also the risk of falls. The aim of this study is to quantify the differences in the momentum development on UB during the STS in a sample of fall and no-fall elderly subjects. MATERIAL AND MEHODS: The sample consisted of twenty three voluntary elderly subjects (n=23), six elderly adults with antecedents of frequent falls (more than two within a year period) and seventeen without histories of frequent falls. Through a motion analysis system we registered the kinematics of UB during STS, from which we calculated the momentum of UB. The determined analysis variables were: the maximum values of the vertical (P(V)M) and horizontal (P(H)M) lineal momenta, the minimum (L(Max)) and maximum (L(Min)) values of the angular momentum and maximum trunk flexion (thetaM(UB)). RESULTS No difference was observed in P(H)M, L(Max) and L(Min) (P>0.05) between both groups. However, a significant difference was found for the variable P(V)M (P=0.03) and thetaM(UB) (P=0.03) between both groups. CONCLUSIONS We can conclude that, for the sample studied, the frequent fall condition relates to a smaller capacity to develop vertical momentum and increase flexion of the upper body.

We investigated the effects of stance width on postural movement pattern and activation timing of postural muscles during unilateral arm abduction. Thirty-two healthy subjects abducted the right arm at their own timing. Stance width was 0, 9, 18 or 27 cm. Movement angles of leg lateral inclination and trunk lateral flexion to the leg in the frontal plane were analyzed. Based on movement angles at 0 cm width, subjects were classified into three groups: contralateral whole body leaning (CWBLg); ipsilateral trunk flexion (ITFg); and contralateral trunk flexion (CTFg). A high correlation between the movement angles was obtained at 0 cm width (r = 0.82). With increasing stance width, postural movement pattern in the ITFg shifted to patterns characterized by lateral flexion of the trunk toward the side opposite to arm movement, and movement angle of leg-inclination in ITFg and CWBLg decreased. At 0 cm width, left gluteus medius and tensor fascia latae were activated significantly about 40 ms ahead of the right middle deltoid in CWBLg and CTFg, but not in ITFg. However, preceding activation became prominent (about 20 ms) in ITFg for wide stances. Moreover, bilateral activation of the tensor fascia latae was observed in CTFg for all widths.

The objectives of this research were to explore the changes in the low back biomechanical responses during a harvesting task as a function of different harvesting techniques/postures and to explore the effects of an ergonomic intervention designed to reduce the low back stress during this work activity. Nine participants performed a series of simulated harvesting activities in a laboratory setting using four different harvesting techniques: full kneeling posture, squatting posture, stooping posture and kneeling on a knee support device (the intervention). As they performed these tasks the activity of muscles of the torso and thighs was captured using electromyography and trunk kinematics were captured using the lumbar motion monitor and a magnetic field-based motion tracking system. The results showed that (1) three postures – knee support, squatting, and stooping – required high flexion of low back (more than 60°) and (2) squatting and stooping postures showed significantly higher passive tissue moment compared with two kneeling postures. The results also indicate that the beneficial aspects of the knee support intervention appear to be outweighed by reduced productivity and the high degree of trunk flexion and that the current strategy used by these workers of alternating between the various harvesting postures may be the best strategy available. Relevance to industry Understanding how changes in harvesting technique affect lumbar biomechanics can help ergonomists design effective interventions for the prevention of back injury in farm workers.