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Inspite of common lifting advice to maintain a lordotic posture, there is debate regarding optimal lumbar spine posture during lifting. To date, the influence of lumbar posture on trunk muscle recruitment, strength and efficiency during high intensity lifting has not been fully explored.How do differences in lumbar posture influence trunk extensor strength (moment), trunk muscle activity, and neuromuscular efficiency during maximal lifting?Twenty-six healthy participants adopted three lumbar postures (maximal extension (lordotic), mid-range (flat-back), and fully flexed) in a free lifting position. Motion analysis and force measurements were used to determine the back extensor, hip and knee moments. Surface electromyography (EMG) of three trunk extensors and the internal obliques were recorded. Neuromuscular efficiency (NME) was expressed as a ratio of normalised extensor moment to normalised EMG.Significantly higher back extensor moments were exerted when moving from an extended to mid-range, and from a mid-range to fully flexed lumbar posture. This was accompanied by a decrease in activity across all three back extensor muscles (P 0.001) resulting in a higher NME of these muscles in more flexed postures. Change in lumbar posture did not influence hip or knee moments or internal oblique activation.A flexed-back posture is associated with increased strength and efficiency of the back muscles compared to a lordotic posture. These findings further question the manual handling advice to lift with a lordotic lumbar spine.

Background Reaction time task performance using electromyography (EMG) has been widely studied in the evaluation of motor responses. However, specific testing conditions with tray usage and the reliability of the bilateral trunk muscle reactions have not been proven. Research Questions Are there internal consistencies of the reaction times for a particular condition, such as a handheld task, among the examiners? Is there a delayed reaction time on the dominant abdominal muscle in response to a treadmill-induced slip perturbation while holding or not holding a tray? Methods One hundred and nineteen right upper and lower limb dominant individuals (71 female and 48 male subjects) were exposed to a treadmill-induced slip perturbation (0.24 m/s velocity for 1.2 cm) for 0.10 s in standing. The EMG electrodes were placed on both sides of the rectus abdominis (RA) and erector spinae (ES) muscles. The reliability of the test was established by using Cronbach’s alpha, intra-class correlation coefficients (ICC2, k), and the standard error of measurements. Results The results for holding a tray indicated a high degree of consistency based on Cronbach’s alpha for the left RA (0.79), right RA (0.86), left ES (0.82), and right ES (0.73) muscles. However, there was a significant reaction time difference among trunk muscles (F = 10.58, p = 0.002) while not holding a tray. The post-hoc results indicated that the right RA muscle was delayed more than the bilateral ES muscles, although there was no significant difference with the left RA muscle. Significance Overall, the EMG analyses for the reaction times were highly consistent with and without tray usage. The reaction times of the dominant abdominal muscles were delayed while not holding a tray. Given the high reliability, compensatory strategies by trunk dominance might be considered with a tray usage task.

Background Fatigability and postural control deficits are both serious concerns in a variety of chronic musculoskeletal conditions. Research has shown that muscle fatigue may adversely affect postural control. This is while the evidence on the relevance of fatigue to postural control has never been summarized nor critically appraised. Research question Is there sufficient and strong enough evidence to accept trunk muscle fatigue as a contributing factor to postural control alterations during upright standing posture?. Methods EMBASE, Scopus, ELSEVIER, PubMed, ProQuest, Google scholar and reference lists of the relevant articles were searched through April 2018. Studies having investigated the trunk muscle fatigue effect on postural control in asymptomatic individuals were included in the study. Only those studies having assessed postural control in terms of center of pressure driven variables were included. Results Twelve studies (218 asymptomatic participants) matched the inclusion criteria of this systematic review. Their results supported the hypothesis that fatigue has a significant effect on postural control in terms of the time domain variables. Sway velocity was consistently found to be affected by fatigue. The results were inconsistent in the frequency domain. The only study on the structural dynamics of center of pressure displacements also confirmed such a relationship. Significance The present review indicates that postural control is altered in asymptomatic individuals following trunk muscle fatigue. This may suggest that trunk muscle endurance training is crucial to address postural impairment in chronic spine musculoskeletal conditions.

Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography-EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations. Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p

Prolonged standing has been associated with development and aggravation of low back pain (LBP). However, the underlying mechanisms are not well known. The aim of the present study was to investigate postural control and muscle activation during and as a result of prolonged standing in chronic LBP (cLBP) patients compared to healthy controls (HCs). Body weight shifts and trunk and hip muscle activity was measured during 15 min standing. Prior and after the standing trial, strength, postural sway, reposition error (RE), flexion relaxation ratio (FRR), and pain were assessed and after the prolonged standing, ratings of perceived exertion. During prolonged standing, the cLBP patients performed significantly more body weight shifts (p

Postural adjustments are used by the central nervous system to pre-empt and correct perturbations in balance during voluntary body movements. Alteration in these responses is associated with a number of neuromuscular/musculoskeletal conditions. Attention has been identified as important in this system; performing a concurrent cognitive task has been suggested to reduce the efficacy of this postural control. The aim of this study was to examine the effect of concurrent cognitive tasking on anticipatory postural adjustments while sitting on an exercise ball with a view to help inform future rehabilitation programmes. Bilateral EMG activity was recorded from the external and internal obliques, rectus abdominis, erector spinae and the right rectus femoris of 20 healthy subjects (9 males) with mean (SD) age of 21.88 (0.86) years (range 21–24 years). A rapid hip flexion protocol was carried out under three conditions: no concurrent task, counting out loud up from one and completing a serial sevens task. The addition of the cognitive task delayed and reduced the EMG in the prime mover muscle but had little impact on the responses of the trunk muscles within the time frame of the anticipatory responses; suggestive of a decoupling of voluntary and postural control mechanisms. The results of this study suggest that perhaps the clinical effects of dual task may not be largely due to changes in anticipatory postural adjustments. However, it would be important to compare these results to those seen in older and functionally impaired individuals as this would be more representative of the typical population undertaking such rehabilitation programmes.

Before altering the travel direction in normal gait, anticipatory activation in trunk muscles is observed, followed by a top-down sequence of rotation of body segments. Turning while pushing a cart is a more challenging task for the trunk because of its low stiffness in pushing while walking and the interaction with the high inertia of the cart. 12 healthy subjects pushed a 200. kg cart at shoulder and hip height while making turns (gradual, sharp and unexpected sharp). The normalized electromyogram amplitudes of left (right) lateral and anterior external oblique muscle, and right (left) internal oblique muscle were averaged to represent left (right) trunk rotator muscle activity. The baseline values of trunk rotator muscle activity before the turn and the peak values after the turn were determined. Additionally, peak values of hand forces, twisting moments and twisting motions were assessed. Before turning, higher trunk rotator muscle activity than in straight pushing without turning was only observed before making a turn in the gradual or sharp turn conditions. After the turn, clockwise twisting motion was associated with a clockwise twisting moment induced by the reaction forces at the left hand. Anticipatory activation was initially absent in the unexpected sharp turn, while bilateral trunk rotator muscle activity increased after the turn, indicating co-contraction. In the unexpected turn condition the combination of an uncontrolled twisting motion with delayed muscle activation may increase the potential risk of low-back injury. © 2012 Elsevier B.V.

This study investigated if asymmetry exists in the responses of trunk muscles to a perturbation of the trunk induced by loading of an outstretched arm. Nineteen healthy right-handed subjects were recruited into the study. Electromyographic recordings were made from trunk muscles (erector spinae and rectus abdominus) and upper limb muscles (deltoid). A weight was dropped into a receptacle held out laterally by the subjects. The perturbation induced a rise in EMG activity in the deltoid at a latency which was not different between the dominant and non-dominant arms. It also induced a rise in EMG activity in the contralateral trunk muscles. Although not significantly different, there was a trend for the responses from the right trunk to be longer than those from the left trunk. Furthermore, there were higher levels of EMG activity in the trunk muscles opposite the dominant arm than those in the trunk muscles opposite the non-dominant arm. This study reveals a pattern of trunk muscle activation following movement in the arm induced by loading of an outstretched hand that is different on the side of the back opposite the dominant arm than on the side of the back opposite the non-dominant arm. These results may have implications in terms of mechanisms contributing to low back pain and further work is warranted to examine these responses in left-handed individuals.

modulate tight and trunk muscle activity to fit task conditions. However, the degree of modulation in the SDCP group was not as much as in the control group, and the peak CoPy displacement was larger in the SDCP group. These results suggest that an increase in tight and trunk muscle activity is insufficient to compensate for a delayedonset latencyof lower legmuscleactivityanda lackofmodulationof lower legmuscle activity, resulting in a largerdisturbance of postural equilibrium.