The biomechanical assessment of pelvic kinematics during a single leg squat (SLS) commonly relies on expensive equipment, which precludes its wider implementation in ecological settings. Smartphone ...sensors could represent an effective solution to objectively quantify pelvic kinematics remotely, but their measure properties need to be evaluated before advocating their use in practice. This study aimed to assess whether measures of pelvic kinematics collected remotely using smartphones during SLS are repeatable between days, and if changes in pelvic kinematics can be identified during an endurance task. Thirty-three healthy young adults were tested remotely on two different days using their own smartphones placed on the lumbosacral region. Pelvic orientation and acceleration were collected during three sets of seven SLS and an endurance task of twenty consecutive SLS. The intersession reliability was assessed using Intraclass Correlation Coefficient (ICC.sub.2,k ), Standard Error of Measurement, and Minimal Detectable Change. T-tests were used to identify pelvic kinematics changes during the endurance task and to assess between-day bias. Measures of pelvic orientation and frequency features of the acceleration signals showed good to excellent reliability (multiple ICC.sub.2,k greater than or equal to 0.79), and a shift of the power spectrum to lower frequencies on the second day (multiple p<0.05). The endurance task resulted in larger contralateral pelvic drop and rotation (multiple p<0.05) and increased spectral entropy (multiple p<0.05). Our findings demonstrate that reliable measures of pelvic kinematics can be obtained remotely using participants' smartphones during SLS. Smartphone sensors can also identify changes in motor control, such as contralateral pelvic drop during an endurance task.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A plethora of evidence supports the existence of neuromuscular changes in people with chronic spinal pain (neck and low back pain), yet it is unclear whether neuromuscular adaptations persist for ...people with recurrent spinal pain when in a period of remission. This systematic review aimed to synthesise the evidence on neuromuscular adaptations in people with recurrent spinal pain during a period of remission. Electronic databases, grey literature, and key journals were searched from inception up to the 4th of September 2020. Eligibility criteria included observational studies investigating muscle activity, spine kinematics, muscle properties, sensorimotor control, and neuromuscular performance in adults (≥ 18 years) with recurrent spinal pain during a period of remission. Screening, data extraction, and quality assessment (Newcastle-Ottawa Scale) were conducted independently by two reviewers. Data synthesis was conducted per outcome domain. A meta-analysis with a random-effects model was performed where possible. The overall strength of evidence was rated using the Grading of Recommendations, Assessment, Development and Evaluation guidelines (GRADE). From 8292 records, 27 and five studies were included in a qualitative and quantitative synthesis, respectively. Very low level of evidence supports muscle activity changes in people with recurrent low back pain, especially greater co-contraction, redistribution of muscle activity, and delayed postural control of deeper trunk muscles. Reduced range of motion of the lumbar spine was also found. Meaningful conclusions regarding other outcome domains or people with recurrent neck pain could not be drawn. In conclusion, people with recurrent low back pain during a period of remission show muscle activity and spine kinematics adaptations. Future research should investigate the long-term impact of these changes, as well as adaptations in people with recurrent neck pain.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Altered regional activation of the lumbar extensors has been previously observed in individuals with low back pain (LBP) performing high-effort and fatiguing tasks. It is currently unknown whether ...similar alterations can be observed during low-effort functional tasks. Similarly, previous studies did not investigate whether side differences in regional activation are present in individuals with LBP. Finally, there is limited evidence of whether the extent of the alteration of regional activation is associated with clinical factors. Therefore, the aim of this study was to investigate whether individuals with LBP exhibit asymmetric regional activation of the thoraco-lumbar extensor muscles during functional tasks, and if the extent of neuromuscular control alteration is associated with clinical and psychosocial outcome domains.
21 participants with and 21 without LBP performed five functional tasks (gait, sit-to-stand, forward trunk flexion, shoulder flexion and anterior pelvic tilt). The spatial distribution of activation of the thoraco-lumbar extensor muscles was assessed bilaterally using high-density electromyography. For each side, the distribution of electromyographic (EMG) amplitude was characterized in terms of intensity, location and size. Indices of asymmetry were calculated from these features and comparisons between groups and tasks were performed using ANOVA. The features that significantly differed between groups were correlated with self-reported measures of pain intensity and other outcome domains.
Indices of asymmetry did not differ between participants with and without LBP (p > 0.11). The cranio-caudal location of the activation differed between tasks (p < 0.05), but not between groups (p = 0.64). Participants with LBP showed reduced EMG amplitude during anterior pelvic tilt and loading response phase during gait (both p < 0.05). Pearson correlation revealed that greater pain intensity was associated with lower EMG amplitude for both tasks (R<-0.5, p < 0.05).
Despite clear differences between tasks, individuals with and without LBP exhibited similar distributions of EMG amplitude during low-effort functional activities, both within and between sides. However, individuals with LBP demonstrated lower activation of the thoraco-lumbar muscles during gait and anterior pelvic tilt, especially those reporting higher pain intensity. These results have implications in the development or refinement of assessment and intervention strategies focusing on motor control in patients with chronic LBP.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this study we investigated whether the spatial distribution of surface electromyographic (EMG) amplitude can be used to describe the activation of muscle portions with different biomechanical ...actions. Ten healthy subjects performed isometric contractions aimed to selectively activate a number of forearm muscles or muscle subportions. Monopolar electromyographic signals were collected with an electrode grid of 128 electrodes placed on the proximal, dorsal portion of the forearm. The monopolar EMG amplitude root mean square (RMS) value distribution was calculated for each contraction, and high-amplitude channels were identified through an automatic procedure; the position of the EMG source was estimated with the barycenter of these channels. Each of the contractions tested was associated to a specific EMG amplitude distribution, whose location in space was consistent with the expected anatomical position of the main agonist muscle (or subportion). The position of each source was significantly different from the others in at least one direction (ANOVA; transversally to the forearm: P < 0.01, F = 125.92; longitudinally: P < 0.01, F = 35.83). With such an approach, we could distinguish the spatial position of EMG distributions related to the activation of contiguous muscles e.g., extensor carpi ulnaris (ECU) and extensor digitorum communis (EDC), different heads of the same muscle (i.e., extensor carpi radialis (ECR) brevis and longus) and different functional compartments (i.e., EDC, middle, and ring fingers). These findings are discussed in terms of how forces along a given direction can be produced by recruiting population of motor units clustered not only in specific muscles, but also in muscle sub-portions. In addition, this study supports the use of high-density EMG systems to characterize the activation of muscle subportions with different biomechanical actions.
High-density surface electromyography (HDEMG) is an electrophysiological technique that can be used to quantify the spatial distribution of activity within muscles. When pain-free individuals perform ...sustained or repetitive tasks, different regions within a muscle become progressively more active; this is thought to reflect a strategy to redistribute the load to different regions, thus limiting localised muscle fatigue. The use of HDEMG has revealed that when people with musculoskeletal pain perform the same tasks, the distribution of activity within the same muscle is usually different, and the same muscle region tends to be active throughout the whole task without progressive activation of different muscle regions. This potentially results in a focal overload of a muscle region, and may contribute to fatigue, localised muscle pain and potentially pain persistence and/or recurrence over time. Interestingly, not all patients with musculoskeletal pain present with this regional alteration in muscle activation, reflecting the heterogeneity of patient presentations. This article will briefly review the technique of HDEMG followed by a review of studies demonstrating spatial redistribution of muscle activity in asymptomatic people during both isometric and dynamic conditions, including functional tasks. Lastly, the article will provide a review of HDEMG studies with a focus on changes in the behaviour of the lumbar erector spine and upper trapezius in people with spinal pain. These studies have revealed subtle changes in the distribution of muscle activity in people with spinal pain, which may have relevance for onset, persistence or recurrence of symptoms and could become a target of novel therapeutic approaches.
The aim of this study was to examine for the presence of differences in neuromuscular and psychological function in individuals with recurrent neck pain (RNP) or chronic neck pain (CNP) following a ...whiplash trauma compared to healthy controls. A secondary aim was to examine whether neuromuscular characteristics together with psychological features in people with RNP were predictive of future painful episodes. Multiple features were assessed including neck disability, kinesiophobia, quality of life, cervical kinematics, proprioception, activity of superficial neck flexor muscles, maximum neck flexion and extension strength, and perceived exertion during submaximal contractions. Overall, those with RNP (
= 22) and CNP (
= 8) presented with higher neck disability, greater kinesiophobia, lower quality of life, slower and irregular neck movements, and less neck strength compared to controls (
= 15). Prediction analysis in the RNP group revealed that a higher number of previous pain episodes within the last 12 months along with lower neck flexion strength were predictors of higher neck disability at a 6-month follow-up. This preliminary study shows that participants with RNP presented with some degree of altered neuromuscular features and poorer psychological function with respect to healthy controls and these features were similar to those with CNP. Neck flexor weakness was predictive of future neck disability.
ABSTRACT
Introduction: The aim of this study was to determine whether muscle fibers innervated by single motor neurons are confined in small subvolumes of the vastus medialis (VM) and if motor unit ...fiber orientation depends on their position within the muscle. Methods: Single motor units were identified from a grid of surface electrodes. The size of their surface representation and fiber orientation were extracted using an algorithm validated on simulated signals. Results: The action potentials of 77 motor units were represented locally on the skin (10th–90th percentiles: 14–25 mm). According to simulations, this indicates territories smaller than 11.8–64.8 mm. Motor units in distal regions of VM had fibers at a greater angle than those in proximal regions (R = –0.54, P < 0.001). Conclusion: Motor units with small territories and varying fiber orientations may be an anatomical predisposition to regulate how regions within VM apply forces to the patella. This could help to redistribute loads within the joint in painful conditions. Muscle Nerve 52: 1057–1065, 2015
The purpose of this study was to examine scalene (SA) and sternocleidomastoid (SM) activation during normoxic (norm‐ITL; FIO2 = 21%) and hypoxic (hyp‐ITL; FIO2 = 15%) incremental inspiratory ...threshold loading (ITL). Thirteen healthy participants (33 ± 4 years, 9 female) performed two ITL tests breathing randomly assigned gas mixtures through an inspiratory loading device where the load was increased every two minutes until task failure. SA and SM root mean square (RMS) electromyography (EMG) were calculated and expressed as a percentage of maximum (RMS%max) to reflect muscle activation intensity. Myoelectric manifestations of fatigue were characterized as decreased SA or SM EMG median frequency during maximum inspiratory pressure maneuvers before and after ITL. Dyspnea was recorded at baseline and task failure. Ventilatory parameters and mouth pressure (Pm) were recorded throughout the ITL. SA,RMS%max and SM,RMS%max increased in association with ITL load (p ≤ .01 for both). SA,RMS%max was similar between norm‐ITL and hyp‐ITL (p = .17), whereas SM,RMS%max was greater during the latter (p = .001). Neither SA nor SM had a decrease in EMG median frequency after ITL (p = .75 and 0.69 respectively). Pm increased in association with ITL load (p < .001) and tended to be higher during hyp‐ITL compared to norm‐ITL (p = .05). Dyspnea was similar during both conditions (p > .05). There was a trend for higher tidal volumes during hyp‐ITL compared to norm‐ITL (p = .10). Minute ventilation was similar between both conditions (p = .23). RMS,%max of the SA and SM increased linearly with increasing ITL. The presence of hypoxia only increased SM activation. Neither SA nor SM presented myoelectric manifestations of fatigue during both conditions.
Sternocleidomastoid activation was greater during hypoxic than mildly normoxic incremental inspiratory loading. Scalene activation was similar during both conditions. Both sternocleidomastoid and scalene demonstrated significant increases in activation that were linearly related to respiratory loading during both hypoxic and normoxic ITL. Neither scalene nor sternocleidomastoid exhibited changes in EMG median frequency or absolute voluntary respiratory strength.
Purpose: To investigate the effect of trunk positions and experimental lumbar pain location on lumbar extensor muscles recruitment strategies. Methods: 19 healthy participants (10 men: 9 women), aged ...25.3 ± 4.7 years, performed isometric back extension contractions in three positions: neutral, 45° and 90° trunk flexion and under three conditions: no pain, caudal pain and cranial pain. Lumbar muscle activation strategies were recorded using high-density surface electromyography. The effect of position and pain conditions on muscle activity amplitude and spatial redistributions was assessed. Results: Muscle activity amplitude was 43% higher in 45° trunk flexion than in neutral position on both sides (p < 0.05). In the 90° trunk flexion, participants showed a more lateral spatial distribution than in the 45° trunk flexion on the left side p < 0.01, 5.4 mm difference) and the neutral position on both sides (p < 0.05, 8.2 mm difference). In the 45° trunk flexion, participants exhibited a more lateral spatial distribution compared with the neutral position on the right side (p < 0.05, 3.7 mm difference). A lateral spatial redistribution of muscle activity was observed in the caudal pain condition compared with no pain on the right side (p < 0.05, 3.0 mm difference). Individual responses to pain varied across all variables. Conclusions: Different trunk positions result in different distributions of activation within the lumbar extensor muscles, possibly based on regional mechanical advantage. No clear indication of location-specific pain adaptation, and no effect of task-dependent pain adaptation were found, whereas individual-specific adaptations were observed.
PDF
