ORCID Profile
0000-0001-7616-9003
Current Organisations
University of Tasmania
,
The University of Queenslad
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Publisher: American Physiological Society
Date: 04-2020
DOI: 10.1152/JAPPLPHYSIOL.00756.2019
Abstract: This study presents for the first time novel insights into the adaptations to hypogravity of spinal curvatures, trunk stiffness, and paraspinal muscle activity. We showed that exposure to hypogravity reduces the displacement of the trunk by an applied perturbation, partially compensated by weaker stabilizing contributions of the paraspinal muscles and concomitant increase in abdominal muscle responses. These findings may have relevance for future recommendations for planetary surface explorations.
Publisher: American Physiological Society
Date: 07-2021
DOI: 10.1152/JAPPLPHYSIOL.00990.2020
Abstract: This study presents novel insights into the morphological adaptations occurring in the lumbar spine after 60-day head-down bed rest and the potential role of artificial gravity (AG) to mitigate them. Results demonstrated no protective effect of AG protocols used in this study. In atrophied paraspinal muscles, the ratio of lipids versus intramuscular water increased in the postural lumbar muscles, which could impair muscle function during upright standing. These findings have relevance for future space explorations.
Publisher: Public Library of Science (PLoS)
Date: 25-08-2016
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 24-01-2022
DOI: 10.1097/J.PAIN.0000000000002585
Abstract: Risk factors for low back pain (LBP) flares have been considered about self-reported measures. This case–crossover study aimed to investigate whether (1) objective measures of physical activity and sleep were associated with the risk of experiencing LBP flares and (2) these associations differed for flares defined as pain 2 or more points greater than average pain over the period using an 11-point Numerical rating scale (0-no pain and 10-worst pain imaginable) (pain-defined flare: PDF) and flares identified by participants according to a broader definition that considered emotions or coping (self-reported flare [SRF]). We included 126 participants who had experienced LBP for months. Physical activity and sleep were monitored for 28 days using wearable sensors. Occurrence of flares (PDF or SRF) was assessed daily using a smartphone application. Data on exposure to risk factors 1, 2, and 3 days preceding PDF or SRF were compared with nonflare control periods. Conditional logistic regression determined association between each factor and flares. Data show that day-to-day variation in physical activity and in-bed time are associated with the risk of LBP flares, but associations differ depending on how flare is defined. Longer in-bed time increased the risk of PDF but not SRF. Although physical activity was not associated with the risk of PDF, greater sedentary behaviour increased the risk of SRF and being more physically active decreased the risk for SRF. These results highlight the potential role of targeting sleep and physical activity in interventions to prevent LBP flares and indicate that risk factors differ depending on how LBP flares are defined.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 23-02-2021
DOI: 10.1097/AJP.0000000000000926
Abstract: The term flare is commonly used to describe low back pain (LBP) fluctuations, but in iduals with LBP consider that it does not always correspond to increased pain. This case cross-over study aimed to: (1) determine the extent to which days with a flare identified according to a multidimensional definition (self-reported flare, SRF) corresponded to days with greater than average pain (pain-defined flare, PDF) and (2) to investigate whether physical and psychosocial features differ between PDF and SRF. In iduals with LBP for ≥3 months (N=126) provided data on flares, physical, and psychosocial features daily for 28 days using a smartphone application. Most days with SRF (68%) did not have greater than average pain (ie, PDF), but most days with greater than average pain (64%) were reported as an SRF. On days with SRF-only all physical and psychosocial features were worse than nonflare days. SRF+PDF had lower sleep quality and higher pain intensity, fatigue, disability, pain catastrophizing, and fear avoidance than SRF-only. SRF+PDF had higher pain in the afternoon and evening, disability and pain catastrophizing than PDF-only. Self-efficacy at work and during leisure activities was worse on SRF+PDF days than SRF-only and PDF-only days. These findings highlight that when in iduals with LBP consider they have a flare, they do not always have greater than average pain, but have worse psychosocial features. This emphasizes that flare has broader dimensions than pain alone. Consideration of flare according to broad dimensions is important when investigating symptom fluctuations across different LBP trajectories.
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.GAITPOST.2018.08.033
Abstract: This study investigated the effects of a single exercise session using a device developed for postural muscle training on the function of postural muscles in healthy, pain free in iduals. During standardised rapid arm movements, timing of onset of electromyography (EMG) was measured using intramuscular and surface recordings of the transversus abdominis (TrA), obliquus internus abdominis (OI), obliquus externus abdominis (OE), lumbar multifidus (LM) and lumbar erector spinae (LES) muscles. A single exercise session with the device led to significantly (main effect of time: P = 0.03) earlier LES EMG onset in advance of the postural perturbation induced by rapid forward arm movements from -1 ms (SD: 32 ms) at baseline to -11 ms (SD: 27 ms) post-exercise and -16 ms (SD: 22 ms) at 10-min Wash-Out after the FRED exercise bout. The timing of EMG onset of the other trunk muscles was not affected by the single bout of exercise. A significant correlation was found between background activity and the EMG onset times of of TrA (r = 0.6 P < 0.001), OI (r = 0.59 P < 0.001), LES (r = 0.32 P = 0.046) and LM
Publisher: Springer Science and Business Media LLC
Date: 11-02-2014
DOI: 10.1007/S00421-014-2840-Y
Abstract: Although it appears obvious that we change movement behaviors to unload the painful region, non-systematic motor adaptations observed in simple experimental tasks with pain question this theory. We investigated the effect of unilateral pain on performance of a bilateral plantarflexion task. This experimental task clearly allowed for stress on painful tissue to be reduced by modification of load sharing between legs. Fourteen participants performed a bilateral plantarflexion at 10, 30, 50 and 70 % of their MVC during 5 conditions (Baseline, Saline-1, Washout-1, Saline-2, Washout-2). For Saline-1 and -2, either isotonic saline (Iso) or hypertonic saline (Pain) was injected into the left soleus. The force produced by the painful leg was less during Pain than Baseline (range -52.6 % at 10 % of MVC to -20.1 % at 70 % of MVC P < 0.003). This was compensated by more force produced by the non-painful leg (range 18.4 % at 70 % of MVC to 70.2 % at 10 % of MVC P < 0.001). The reduction in plantarflexion force was not accompanied by a significant decrease in soleus electromyographic activity at 10 and 30 % of MVC. Further, no significant linear relationship was found between changes in soleus electromyographic activity and change in plantarflexion force for the painful leg (with the exception of a weak relationship at 10 % of MVC, i.e., R (2) = 0.31). These results show that when the nervous system is presented with an obvious solution to decrease stress on irritated tissue, this option is selected. However, this was not strongly related to a decrease in soleus (painful muscle) activity level.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 21-06-2018
DOI: 10.1097/J.PAIN.0000000000001317
Abstract: Movement is changed in pain, but the mechanisms remain unclear. Key questions are unresolved such as whether activation can be inhomogeneously distributed within a muscle in a manner that is specific to the location of noxious input. This study addressed this question using high-density electromyography (EMG) to study regional redistribution of muscle activation within the vasti muscles and changes in knee extension force direction in response to noxious stimulation applied to muscular and nonmuscular tissues around the knee. Fourteen participants performed a low-force knee extension contraction at baseline, during, and after pain induced in 4 locations (infrapatellar fat pad, vastus lateralis, distal vastus medialis, or proximal vastus medialis). The knee extension force direction was estimated from a 3-dimensional load cell positioned just above the ankle. Regional muscle activation was estimated from litude of high-density surface EMG signals from vastus medialis and lateralis. Pain-induced spatial variations of activation were identified as the position of the 5 channels that showed the largest decrease (or smallest increase) in litude from baseline to pain or after pain. Knee extension force was produced more medially during pain after infrapatellar pad injection only ( P = 0.01). Preferential reduction of activation of the distal region of vastus medialis was observed when distal vastus medialis ( P 0.001) or vastus lateralis ( P 0.05) was injected. Both adaptations persisted after pain resolution. These results support the hypothesis that specific adaptation depends on the location of a noxious stimulus and imply that recovery of pain is not necessarily concomitant with return of the EMG to prepain patterns.
Publisher: Wiley
Date: 18-09-2017
DOI: 10.1111/SMS.12942
Abstract: The external hip adduction moment during walking is greater in in iduals with gluteal tendinopathy (GT) than pain-free controls. Although this likely represents a greater demand on the hip abductor muscles implicated in GT, no study has investigated activation of these muscles in GT. For this purpose, fine wire electrodes were inserted into the segments of the gluteus minimus and medius muscles, and surface electrodes placed on the tensor fascia lata, upper gluteus maximus, and vastus lateralis muscles of eight in iduals with, and eight without, GT. Participants underwent six walking trials. In idual muscle patterns were compared between groups using a wavelet-based linear effects model and muscle synergy analysis performed using non-negative matrix factorization to evaluate muscle activation patterns, within- and between-participant variability. Compared to controls, in iduals with GT exhibited a more sustained initial burst of the posterior gluteus minimus and middle gluteus medius muscle segments. Two muscle synergies were identified Synergy-1 activated in early-mid stance and Synergy-2 in early stance. In GT participants, posterior gluteus minimus and posterior gluteus medius and tensor fascia lata contributed more to Synergy-1 active during the period of single leg support. Participants with GT exhibited reduced within-participant variability of posterior gluteus medius and reduced between-participant variability of anterior gluteus minimus and medius and upper gluteus maximus. In conclusion, in iduals with GT exhibit modified muscle activation patterns of the hip abductor muscles during walking, with potential relevance for gluteal tendon loading.
Publisher: Elsevier BV
Date: 07-2021
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2019
DOI: 10.1249/MSS.0000000000002059
Abstract: Pain affects movement planning and execution, and may interfere with the ability to learn new motor skills. Variations among previous studies suggest task-specific effects of pain on the initial acquisition and subsequent retention of motor strategies. The present study assessed how acute pain in the anterior deltoid muscle affects movement accuracy of fast arm-reaching movements during force field perturbations and upon immediate pain-free repetition of the same task. Despite having slower initial rate of improvement, in iduals who experienced pain during training achieved the same final performance as pain-free controls. However, pain altered the strategy of muscle activation adopted to perform the task, which involved less activity of the shoulder and arm muscles. Strikingly, motor strategies developed during the first exposure to the force field were retained upon reexposure to the same perturbation after resolution of pain. Although reduced muscle activation may be interpreted as metabolically efficient, it reduces joint stability and can have negative consequences for joint integrity. These results demonstrate that alternative motor strategies developed in the presence of pain can be maintained when training is resumed after resolution of pain. This effect could have deleterious consequences if it applies when learning motor skills in sports training and rehabilitation.
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.SPINEE.2021.11.007
Abstract: Prolonged bedrest induces accumulation of intramuscular lipid concentration (ILC) in the lumbar musculature however, spatial distribution of ILC has not been determined. Artificial gravity (AG) mitigates some adaptations induced by 60 day bedrest by creating a head-to-feet force while participants are in a supine position. To quantify the spatial distribution of accumulation of ILC in the lumbar musculature after 60 day bedrest, and whether this can be mitigated by AG exposure. Prospective longitudinal study. Twenty-four healthy in iduals (8 females) participated in the study: Eight received 30 min continuous AG (cAG) Eight received 6 × 5 min AG (iAG), interspersed with rests Eight were not exposed to AG (CRTL). From 3T magnetic resonance imaging (MRI), axial images were selected to assess lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles from L1/L2 to L5/S1 intervertebral disc levels. Chemical shift-based 2-echo lipid and/or water Dixon sequence was used to measure tissue composition. Each lumbar muscle was segmented into four equal quartiles (from medial to lateral). Participants arrived at the facility for the baseline data collection before undergoing a 60 day strict 6° head-down tilt (HDT) bedrest period. MRI of the lumbopelvic region was conducted at baseline and Day-59 of bedrest. Participants performed all activities, including hygiene, in 6° HDT and were discouraged from moving excessively or unnecessarily. At the L4/L5 and L5/S1 intervertebral disc levels, 60-day bedrest induced a greater increase in ILC in medial and lateral regions (∼+4%) of the LM than central regions (∼+2% p<.05). A smaller increase in ILC was induced in the lateral region of LES (∼+1%) at L1/L2 and L2/L3 than at the centro-medial region (∼+2% p<.05). There was no difference between CRTL and intervention groups. Inhomogeneous spatial distribution of accumulation of ILC was found in the lumbar musculature after 60 day bedrest. These findings might reflect pathophysiological mechanisms related to muscle disuse and contribute to localized lumbar spine dysfunction. Altered spatial distribution of ILC may impair lumbar spine function after prolonged body unloading, which could increase injury risk to vulnerable soft tissues, such as the lumbar intervertebral discs. These novel results may represent a new biomarker of lumbar deconditioning for astronauts, bedridden, sedentary in iduals, or those with chronic back pain. Changes are potentially modifiable but not by the AG protocols tested here.
Publisher: IEEE
Date: 08-2008
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: American Physiological Society
Date: 08-2021
DOI: 10.1152/JAPPLPHYSIOL.00180.2021
Abstract: This study presents novel insights into the effect of artificial gravity (AG) on the deterioration of standing balance and anticipatory postural adjustments (APAs) of trunk muscles induced by 60-day strict head-down bed rest. The results indicated severe balance dysfunction and delayed APAs during rapid arm movement. AG partially mitigated the deterioration in standing balance and may thus be considered as a potential countermeasure for future planetary surface explorations. Optimization of AG protocols might enhance effects.
Publisher: Elsevier BV
Date: 11-2015
Publisher: IEEE
Date: 08-2008
Publisher: IEEE
Date: 08-2008
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 20-04-2023
DOI: 10.1007/S00421-023-05193-5
Abstract: Redundancy of the musculoskeletal system implies multiple strategies are theoretically available to coordinate back extensor muscles. This study investigated whether coordination between back muscles during a tightly constrained isometric trunk extension task varies within and between in iduals, and whether this changes following brief exposure to activation feedback of a muscle. Nine healthy participants performed three blocks of two repetitions of r ed isometric trunk extension in side-lying against resistance from 0–30% of maximum voluntary contraction over 30 s (force feedback). Between blocks, participants repeated contractions with visual feedback of electromyography (EMG) from either superficial (SM) or deep multifidus (DM), in two conditions ‘After SM’ and ‘After DM’. Intramuscular EMG was recorded from SM, DM, and longissimus (LG) simultaneously with shear wave elastography (SWE) from SM or DM. In the ‘Natural’ condition (force feedback only), group data showed incremental increases in EMG with force, with minor changes in distribution of activation between muscles as force increased. SM was the most active muscle during the ‘Natural’ condition, but with DM most active in some participants. In idual data showed that coordination between muscles differed substantially between repetitions and in iduals. Brief exposure to EMG feedback altered coordination. SWE showed in idual variation, but findings differed from EMG. This study revealed substantial variation in coordination between back extensor muscles within and between participants, and after exposure to feedback, in a tightly constrained task. Shear modulus revealed similar variation, but with an inconsistent relationship to EMG. These data highlight highly flexible control of back muscles.
Publisher: IOP Publishing
Date: 28-03-2011
DOI: 10.1088/0967-3334/32/5/004
Abstract: The goal of this work is to study the behavior of electromyographic variables during the menstrual cycle. Ten female volunteers (24.0 ± 2.8 years of age) performed fatiguing isometric contractions, and electromyographic signals were measured on the biceps brachii in four phases of the menstrual cycle. Adaptations of classical algorithms were used for the estimation of the root mean square (RMS) value, absolute rectified value (ARV), mean frequency (MNF), median frequency (MDF), and conduction velocity (CV). The CV estimator had a higher (p = 0.002) rate of decrease at the end of the follicular phase and at the end of the luteal phase. The MDF (p = 0.002) and MNF (p = 0.004) estimators had a higher rate of decrease at the beginning of the follicular phase and at the end of the luteal phase. No significant differences between phases of the menstrual cycle were detected with the ARV and RMS estimators (p > 0.05). These results suggest that the behavior of the muscles in women presents different characteristics during different phases of the menstrual cycle. In particular, women were more susceptible to fatigue at the end of the luteal phase.
Publisher: Cold Spring Harbor Laboratory
Date: 12-07-2023
DOI: 10.1101/2023.07.11.548624
Abstract: The ability to stop simple ongoing actions has been extensively studied using the stop signal task, but less is known about inhibition in more complex scenarios. Here we used a task requiring bimanual responses to go stimuli, but selective inhibition of only one of those responses following a stop signal. We assessed how proactive cues affect the nature of both the responding and stopping processes, and the well-documented “stopping delay” in the continuing action following successful stopping. In this task, estimates of the speed of inhibition based on a simple-stopping model are inappropriate, and have produced inconsistent findings about the effects of proactive control on motor inhibition. We instead used a multi-modal approach, based on improved methods of detecting and interpreting partial electromyographical (EMG) responses and the recently proposed SIS ( simultaneously inhibit and start ) model of selective stopping behaviour. Our results provide clear and converging evidence that proactive cues reduce the stopping delay effect by slowing bimanual responses and speeding unimanual responses, with a negligible effect on the speed of the stopping process.
Publisher: Cold Spring Harbor Laboratory
Date: 23-10-2023
Publisher: Wiley
Date: 06-03-2019
DOI: 10.1111/EJN.14369
Abstract: Noxious stimuli induce a nociceptive withdrawal reflex (NWR) to protect the tissue from injury. Although the NWR was once considered as a stereotyped response, previous studies report distinct responses depending on the stimulation site and context for limbs. We aimed to determine whether noxious stimuli over the trunk produced adaptable complex NWR. We hypothesized that organization of the NWR of the trunk muscle would vary with the site of noxious input and would differ between body and spine postures, which modify the potential for specific muscles to remove threat. Fourteen participants were tested in sitting and three lumbar spine postures in side lying (neutral, flexion and extension). Noxious electrical stimuli were applied over the sacrum, spinous process of L3 and T12, lateral side of the 8th rib and anterior midline. NWR latency and litude were recorded with surface electromyography (EMG) electrodes over different trunk muscles. Distinct patterns of muscle activation depended on the stimulation site and were consistent with motor strategies needed to withdraw from the noxious stimuli. The NWR pattern differed between body positions, with less modulation observed in sitting than side lying. Spine posture did not affect the NWR organisation. Our results suggest the circuits controlling trunk muscle NWR presents with adaptability as a function of stimulation site and body position by utilizing the great complexity of the trunk muscle system to produce an efficient protective response. This suggests that the central nervous system (CNS) uses multiple adaptable strategies that are unique depending on which context the noxious stimuli are applied.
Publisher: Springer Science and Business Media LLC
Date: 03-02-2021
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.HUMOV.2015.04.001
Abstract: This study assessed how the low back motor control strategies were affected by experimental pain. In twelve volunteers the right m. longissimus was injected by hypertonic and isotonic (control) saline. The pain intensity was assessed on a visual analog scale (VAS). Subjects were seated on a custom-designed chair including a 3-dimensional force sensor adjusted to the segmental height of T1. Electromyography (EMG) was recorded bilaterally from longissimus, multifidus, rectus abdominis, and external oblique muscles. Isometric trunk extensions were performed before, during, and after the saline injections at 5%, 10%, and 20% of maximum voluntary contraction force. Visual feedback of the extension force was provided whereas the tangential force components were recorded. Compared with isotonic saline, VAS scores were higher following hypertonic saline injections (P<.01). Experimental low back pain reduced the EMG activity bilaterally of the rectus abdominis muscles during contractions at 10% and 20% MVC (P<.01) although force accuracy and tangential force variability was not affected. Increased variability in the tangential force composition was found during pain compared with the non-painful condition (P<.05). The immediate adaptation to pain was sufficient to maintain the quality of the task performance however the long-term consequence of such adaptation is unknown and may overload other structures.
Publisher: Wiley
Date: 26-10-2022
DOI: 10.1111/JOA.13575
Abstract: Motion of the fascial layers of the iliotibial band (ITB), as a reinforcement of the deep fascia lata, is likely to be relevant for its function and mechanical behaviour. This exploratory study aimed to evaluate the ITB fascial layers displacement during a weight shift task. Thirteen pain‐free runners performed a 6‐second standing weight shift task. B‐mode ultrasound imaging using an automated fascicle tracking algorithm was used to measure proximal and distal displacement of superficial and deep ITB layers at the middle region. To study the potential contributors to in idual variation of fascial motion, we recorded the activity of five hip/thigh muscles with electromyography (EMG), thigh elvis/trunk position with accelerometers, and centre of pressure with a force plate. Linear regressions estimated the relationship between displacement of fascial layers and hip/trunk angles. Independent t‐tests or Fisher's exact tests compared EMG and movement‐related parameters between participants who demonstrated motion of the fascia in the proximal and distal directions. Thickness of the ITB and the loose connective tissue between its layers were calculated. Proximal displacement was observed in six (−4.1 ± 1.9 mm [superficial]) and two (−6.2 ± 2.0 mm [deep]) participants. Distal displacement was observed for seven participants for each layer (3.1 ± 1.1 mm [superficial] 3.6 ± 1.3 mm [deep]). Four participants did not show displacement of the deep layer. Trunk lateral flexion and gluteus medius muscle activity were determinants of proximal motion of the superficial layer. Loose connective tissue was thinner in participants without displacement of the deep layer. Displacement of the ITB fascial layers varies between in iduals. Variation related to differences in joint movements and muscle activity. This study highlights the complex interaction between fascia and movement.
Publisher: Public Library of Science (PLoS)
Date: 14-06-2023
DOI: 10.1371/JOURNAL.PONE.0286786
Abstract: In iduals with chronic low back pain (CLBP) move their spine differently. Changes in brain motor areas have been observed and suggested as a mechanism underlying spine movement alteration. Nociceptive withdrawal reflex (NWR) might be used to test spinal networks involved in trunk protection and to highlight reorganization. This study aimed to determine whether the organization and excitability of the trunk NWR are modified in CLBP. We hypothesized that in iduals with CLBP would have modified NWR patterns and lower NWR thresholds. Noxious electrical stimuli were delivered over S1, L3 and T12, and the 8 th Rib to elicit NWR in 12 in iduals with and 13 in iduals without CLBP. EMG litude and occurrence of lumbar multifidus (LM), thoracic erector spinae , rectus abdominus , obliquus internus and obliquus externus motor responses were recorded using surface electrodes. Two different patterns of responses to noxious stimuli were identified in CLBP compared to controls: (i) abdominal muscle NWR responses were generally more frequent following 8 th rib stimulation and (ii) occurrence of erector spinae NWR was less frequent. In addition, we observed a subgroup of participants with very high NWR threshold in conjunction with the larger abdominal muscle responses. These results suggest sensitization of NWR is not present in all in iduals with CLBP, and a modified organization in the spinal networks controlling the trunk muscles that might explain some changes in spine motor control observed in CLBP.
Publisher: Springer Science and Business Media LLC
Date: 24-07-2424
DOI: 10.1007/S00421-012-2461-2
Abstract: Knee pain is a common symptom of different knee pathologies, affecting muscle strength and force generation. Although the control of precise three-dimensional forces is essential for the performance of functional tasks, current evidence of pain effects in force variability is limited to single-directional assessments of contractions at moderate force levels. This study assessed the effects of experimental knee joint pain in the three-dimensional force variability during isometric knee extensions at a wide range of target forces (2.5-80 % of maximal voluntary contraction, MVC). Fifteen healthy subjects performed contractions before, immediately following, and after injections of hypertonic (painful) or isotonic (control) saline into the infrapatellar fat pad. Pain intensity was measured on a 10-cm visual analogue scale. Force magnitude, direction, and variability were assessed using a six-axis force sensor while activity of quadriceps and hamstring muscles was recorded by surface electromyography. Significant correlation was found between tangential force displacements and variability of quadriceps muscle activity. Experimental knee pain increased the variability of the task-related force component at all force levels, while variability of tangential force components increased at low forces (≤5 % of MVC). The mean quadriceps activity decreased during painful contractions only at 80 % of MVC. Pain adaptations underlying increased force variability at low contraction levels probably involve heterogeneous reorganization of muscle activity, which could not be detected by surface electrodes. These findings indicate a less efficient motor strategy during knee joint pain, suggesting that pain relief may enhance training for the control of smooth forces by knee pain patients.
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.HUMOV.2011.08.012
Abstract: The orientation of the resultant force during a given contraction depends on the architecture of the muscles involved, and cooperation among muscles may induce force fluctuations in multiple directions. A novel setup for recording three-dimensional forces was developed to assess the effects of muscle fatigue on submaximal contractions. Fifteen subjects performed isometric dorsiflexions, elbow flexions, knee extensions, plantarflexions, and trunk extensions (12 s, 2.5-80% of maximal voluntary force) before and after a fatigue protocol. Electromyography (EMG) was recorded from relevant muscles. The standard deviation of force in the three directions and the agonist EMG litude increased with target force (p<.045), while the coefficient of variation of force and total excursions of the center of pressure showed maximal values at low target forces, reaching a plateau at moderate forces. Fatigue induced higher force fluctuations in task-related and tangential directions and increased agonist EMG litude for all muscle groups (p<.04). Fluctuations of tangential forces were greater during knee extensions compared with other muscle groups (p<.007). The present data demonstrate that fatigue increases the litude of force fluctuations in task-related and tangential forces. Moreover, alternation of activity between multiple synergist muscles is associated with increased fluctuations of tangential forces, especially during fatigue.
Publisher: Springer Berlin Heidelberg
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 14-02-2012
DOI: 10.1007/S00421-012-2343-7
Abstract: Pain elicits complex adaptations of motor strategy, leading to impairments in the generation and control of steady forces, which depend on muscle architecture. The present study used a cross-over design to assess the effects of muscle pain on the stability of multidirectional (task-related and tangential) forces during sustained dorsiflexions, elbow flexions, knee extensions, and plantarflexions. Fifteen healthy subjects performed series of isometric contractions (13-s duration, 2.5, 20, 50, 70% of maximal voluntary force) before, during, and after experimental muscle pain. Three-dimensional force magnitude, angle and variability were measured while the task-related force was provided as feedback to the subjects. Surface electromyography was recorded from agonist and antagonist muscles. Pain was induced in agonist muscles by intramuscular injections of hypertonic (6%) saline with isotonic (0.9%) saline injections as control. The pain intensity was assessed on an electronic visual analogue scale. Experimental muscle pain elicited larger ranges of force angle during knee extensions and plantarflexions (P < 0.03) and higher normalized fluctuations of task-related (P < 0.02) and tangential forces (P < 0.03) compared with control assessments across force levels, while the mean force magnitudes, mean force angle and the level of muscle activity were non-significantly affected by pain. Increased multidirectional force fluctuations probably resulted from multiple mechanisms that, acting together, balanced the mean surface electromyography. Although pain adaptations are believed to aim at the protection of the painful site, the current results show that they result in impairments in steadiness of force.
Publisher: American Physiological Society
Date: 05-2018
Abstract: As in iduals with musculoskeletal disorders often experience motor impairments, contemporary rehabilitation relies heavily on the use of motor learning principles. However, motor impairments are often associated with pain. Although there is substantial evidence that muscle pain interferes with motor control, much less is known on its impact on motor learning. The objective of the present study was to assess the effects of muscle pain on locomotor learning. Two groups (Pain and Control) of healthy participants performed a locomotor adaptation task (robotized ankle-foot orthosis perturbing ankle movements during swing) on two consecutive days. On day 1 (acquisition), hypertonic saline was injected in the tibialis anterior (TA) muscle of the Pain group participants, while Control group participants were pain free. All participants were pain free on day 2 (retention). Changes in movement errors caused by the perturbation were assessed as an indicator of motor performance. Detailed analysis of kinematic and electromyographic data provided information about motor strategies. No between-group differences were observed on motor performance measured during the acquisition and retention phases. However, Pain group participants had a residual movement error later in the swing phase and smaller early TA activation than Control group participants, thereby suggesting a reduction in the use of anticipatory motor strategies to overcome the perturbation. Muscle pain did not interfere with global motor performance during locomotor adaptation. The different motor strategies used in the presence of muscle pain may reflect a diminished ability to anticipate the consequences of a perturbation. NEW & NOTEWORTHY This study shows that experimental muscle pain does not influence global motor performance during the acquisition or next-day retention phases of locomotor learning. This contrasts with previous results obtained with cutaneous pain, emphasizing the risk of directly extrapolating from one pain modality to another. Muscle pain affected motor strategies used when performing the task, however: it reduced the ability to use increased feedforward control to overcome the force field.
Publisher: Elsevier BV
Date: 10-2020
Publisher: Wiley
Date: 03-2017
DOI: 10.14814/PHY2.13188
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.JELEKIN.2013.10.014
Abstract: The aim of this study was to quantify the effects of spatial reorganisation of muscle activity on task-related and tangential components of force variability during sustained contractions. Three-dimensional forces were measured from isometric elbow flexion during submaximal contractions (50s, 5-50% of maximal voluntary contraction (MVC)) and total excursion of the centre of pressure was extracted. Spatial electromyographic (EMG) activity was recorded from the biceps brachii muscle. The centroids of the root mean square (RMS) EMG and normalised mutual information (NMI) maps were computed to assess spatial muscle activity and spatial relationship between EMG and task-related force variability, respectively. Result showed that difference between the position of the centroids at the beginning and at the end of the contraction of the RMS EMG and the NMI maps were different in the medial-lateral direction (P 30% MVC, R(2)>0.30, P<0.05), suggesting that changes in spatial muscle activity could impact on the modulation of tangential forces. Therefore, within-muscle adaptations do not necessarily increase force variability, and this interaction can be quantified by analysing the RMS EMG and the NMI map centroids.
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: IEEE
Date: 08-2008
Publisher: Wiley
Date: 27-06-2023
DOI: 10.1111/PSYP.14372
Abstract: Inhibiting ongoing responses when environmental demands change is a critical component of motor control. Experimentally, the stop signal task (SST) represents the gold standard response inhibition paradigm. However, an emerging body of evidence suggests that the SST conflates two dissociable sources of inhibition, namely an involuntarily pause associated with attentional capture and the (subsequent) voluntary cancellation of action. The extent to which these processes also occur in other response tasks is unknown. Younger n = 24 (20–35 years) and older n = 23 (60–85 years) adults completed tasks involving rapid unimanual or bimanual responses to visual stimuli. A subset of trials required cancellation of one component of an initial bimanual response (i.e., selective stop task stop left response, continue right response) or enacting an additional response (e.g., press left button as well as right button). Critically, both tasks involved some infrequent stimuli baring no behavioral imperative (i.e., they had to be ignored). EMG recordings of voluntary responses during stopping tasks revealed bimanual covert responses (muscle activation, which was suppressed before a button press ensued), consistent with a pause process, following both stop and ignore stimuli, before the required response was subsequently enacted. Critically , we also observed the behavioral consequences of a similar involuntary pause in trials where action cancellation was not part of the response set. Notably, the period over which movements were susceptible to response delays from additional stimuli was longer for older adults than younger adults. The findings demonstrate that an involuntary attentional component of inhibition significantly contributes to action cancellation processes.
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