Head and shoulder posture affect scapular mechanics and muscle activity in overhead tasks

Forward head and rounded shoulder posture (FHRSP) is theorized to contribute to alterations in scapular kinematics and muscle activity leading to the development of shoulder pain. However, reported differences in scapular kinematics and muscle activity in those with forward head and rounded shoulder posture are confounded by the presence of shoulder pain. Therefore, the purpose of this study was to compare scapular kinematics and muscle activity in individuals free from shoulder pain, with and without FHRSP. Eighty volunteers were classified as having FHRSP or ideal posture. Scapular kinematics were collected concurrently with muscle activity from the upper and lower trapezius as well as the serratus anterior muscles during a loaded flexion and overhead reaching task using an electromagnetic tracking system and surface electromyography. Separate mixed model analyses of variance were used to compare three-dimensional scapular kinematics and muscle activity during the ascending phases of both tasks. Individuals with FHRSP displayed significantly greater scapular internal rotation with less serratus anterior activity, during both tasks as well as greater scapular upward rotation, anterior tilting during the flexion task when compared with the ideal posture group. These results provide support for the clinical hypothesis that FHRSP impacts shoulder mechanics independent of shoulder pain.     

Torsion and Bending in the Neck and Tail of Sauropod Dinosaurs and the Function of Cervical Ribs: Insights from Functional Morphology and Biomechanics

The long necks of sauropods have been subject to many studies regarding their posture and flexibility. Length of the neck varies among groups. Here, we investigate neck posture and morphology in several clades from a mechanical viewpoint. Emphasis is put on comparing sauropod necks and tails with structures in living archosaurs and mammals. Differences in the use made of necks and tails lead to clear-cut differences in the mechanical loads occurring in the same models. Ways of sustaining loads are identified by theoretical considerations. If the observed skeletal structures are suited to resist the estimated loading in a particular posture, this concordance is taken as an argument that this posture or movement was of importance during the life of the individual. Apart from the often-discussed bending in side view, we analyze the often overlooked torsion. Because torsional stresses in a homogenous element concentrate near the periphery, a cylindrical cross section gives greatest strength, and the direction of forces is oblique. In a vertebrate neck, during e.g. shaking the head and twisting the neck, oblique muscles, like the mm. scaleni, if activated unilaterally initiate movement, counterbalance the torsional moments and keep the joints between neck vertebrae in equilibrium. If activated bilaterally, these muscles keep the neck balanced in an energy-saving upright posture. The tendons of the mm. scaleni may have ossified as cervical ribs The long cervical ribs in brachiosaurids and mamenchisaurids seem to have limited flexibility, whereas the shorter cervical ribs in Diplodocidae allowed free movement. The tails of sauropods do not show pronounced adaptation to torsion, and seem to have been carried more or less in a horizontal, extended posture. In this respect, sauropod tails resemble the necks of herbivorous cursorial mammals. These analyses provide an improved understanding of neck use that will be extended to other sauropods in subsequent studies.     

Surface EMG and torsion measurements during snow skiing: laboratory and field tests

The relationship between mean rectified EMG (MREMG) measured with surface electrodes and the longitudinal torsion of the lower extremity was investigated in laboratory and snow skiing experiments. Linear regression of the MREMG from the gluteus medius and the peroneus longus with the torsion measured at the foot in the laboratory tests showed that torsion can be predicted with correlation coefficients greater than 0.95 and with a standard deviation less than 5 Nm over all knee flexions and weight bearing. A similar correspondence between MREMG and torsion during skiing does not exist. MREMG is dominantly correlated to posture and body position control functions in skiing. During falling, during ski binding release, and during possible injury sustaining situations, the MREMG was always relatively large, but it was not distinguishable from that associated with smaller torsion of the lower extremity.     

Working memory in attention deficit/hyperactivity disorder is characterized by a lack of specialization of brain function

Working memory impairments are frequent in Attention Deficit/Hyperactivity Disorder (ADHD) and create problems along numerous functional dimensions. The present study utilized the Visual Serial Addition Task (VSAT) and functional magnetic resonance imaging (fMRI) to explore working memory processes in thirteen typically developing (TD) control and thirteen children with ADHD, Combined type. Analysis of Variance (ANOVA) was used to examine both main effects and interactions. Working memory-specific activity was found in TD children in the bilateral prefrontal cortex. In contrast the within-group map in ADHD did not reveal any working-memory specific regions. Main effects of condition suggested that the right middle frontal gyrus (BA6) and the right precuneus were engaged by both groups during working memory processing. Group differences were driven by significantly greater, non-working memory-specific, activation in the ADHD relative to TD group in the bilateral insula extending into basal ganglia and the medial prefrontal cortex. A region of interest analysis revealed a region in left middle frontal gyrus that was more active during working memory in TD controls. Thus, only the TD group appeared to display working memory-modulated brain activation. In conclusion, children with ADHD demonstrated reduced working memory task specific brain activation in comparison to their peers. These data suggest inefficiency in functional recruitment by individuals with ADHD represented by a poor match between task demands and appropriate levels of brain activity.     

Effects of a posture-sensing air seat device (PSASD) on kinematics and trunk muscle activity during continuous computer work

The prevalence and incidence of musculoskeletal disorders is high with computer workers, and poor sitting posture can be considered a factor contributing to low back discomfort. In the clinical literature, maintaining a neutral spinal curvature has been considered an optimal sitting posture. This study investigated the flexion and lateral flexion of trunk movements and trunk muscle activity during computer work with and without a posture-sensing air seat device (PSASD). By sensing a certain amount of increased pressure over the baseline, posture-related visual feedback was given to participants through the PSASD. Eleven regular computer workers participated in this study. PSASD had the function of alerting the subject to their poor posture by using visual feedback. Subjects performed 20 min of computer work with and without a PSASD. Surface electromyography was used to measure the activity of the erector spine and internal abdominal oblique. Kinematic data were obtained using an electrogoniometer. The results showed that the mean of trunk flexion and lateral flexion was significantly reduced with PSASD. The activity of the erector spine and internal oblique was significantly higher with the PSASD than without. Our findings indicated that the PSASD helps to prevent habitual poor posture by maintaining an erect sitting posture during prolonged computer work.     

Working Memory-Related Functional Brain Patterns in Never Medicated Children with ADHD

Attention Deficit/Hyperactivity Disorder (ADHD) is a pervasive neurodevelopmental disorder characterized by 3 clusters of age-inappropriate cardinal symptoms: inattention, hyperactivity and impulsivity. These clinical/behavioural symptoms are assumed to result from disturbances within brain systems supporting executive functions including working memory (WM), which refers to the ability to transiently store and flexibly manipulate task-relevant information. Ongoing or past medications, co-morbidity and differences in task performance are potential, independent confounds in assessing the integrity of cerebral patterns in ADHD. In the present study, we recorded WM-related cerebral activity during a memory updating N-back task using functional Magnetic Resonance Imaging (fMRI) in control children and never medicated, prepubescent children with ADHD but without comorbid symptoms. Despite similar updating performance than controls, children with ADHD exhibited decreased, below baseline WM-related activation levels in a widespread cortico-subcortical network encompassing bilateral occipital and inferior parietal areas, caudate nucleus, cerebellum and functionally connected brainstem nuclei. Distinctive functional connectivity patterns were also found in the ADHD in these regions, with a tighter coupling in the updating than in the control condition with a distributed WM-related cerebral network. Especially, cerebellum showed tighter coupling with activity in an area compatible with the brainstem red nucleus. These results in children with clinical core symptoms of ADHD but without comorbid affections and never treated with medication yield evidence for a core functional neuroanatomical network subtending WM-related processes in ADHD, which may participate to the pathophysiology and expression of clinical symptoms.     

Posture effects on timing of abdominal muscle activity during stimulated ventilation.

In humans during stimulated ventilation, substantial abdominal muscle activity extends into the following inspiration as postexpiratory expiratory activity (PEEA) and commences again during late inspiration as preexpiratory expiratory activity (PREA). We hypothesized that the timing of PEEA and PREA would be changed systematically by posture. Fine-wire electrodes were inserted into the rectus abdominis, external oblique, internal oblique, and transversus abdominis in nine awake subjects. Airflow, end-tidal CO2, and moving average electromyogram (EMG) signals were recorded during resting and CO2-stimulated ventilation in both supine and standing postures. Phasic expiratory EMG activity (tidal EMG) of the four abdominal muscles at any level of CO2 stimulation was greater while standing. Abdominal muscle activities during inspiration, PEEA, and PREA, were observed with CO2 stimulation, both supine and standing. Change in posture had a significant effect on intrabreath timing of expiratory muscle activation at any level of CO2 stimulation. The transversus abdominis showed a significant increase in PEEA and a significant decrease in PREA while subjects were standing; similar changes were seen in the internal oblique. We conclude that changes in posture are associated with significant changes in phasic expiratory activity of the four abdominal muscles, with systematic changes in the timing of abdominal muscle activity during early and late inspiration.     

Steroid sulfatase is a potential modifier of cognition in attention deficit hyperactivity disorder

Deletions encompassing the X-linked STS gene (encoding steroid sulfatase) have been observed in subjects with neurodevelopmental disorders, including attention deficit hyperactivity disorder (ADHD). Recently, two single nucleotide polymorphisms (SNPs) within STS (rs12861247 and rs17268988) have been reported to be associated with ADHD risk and inattentive symptoms in ADHD, respectively. Using a UK sample of ADHD subjects (aged 5-18 years), we tested the hypothesis that rs12861247 is associated with ADHD risk using a case-control approach (comparing 327 ADHD cases with 358 male controls from the Wellcome Trust Case Control Consortium). Using a subset of males from the ADHD sample, we also examined whether variation within STS is associated with symptomatology/cognitive function in ADHD. We then tested whether SNPs associated with cognitive function in ADHD were also associated with cognitive function in healthy male subjects using a German sample (n = 143, aged 18-30 years), and whether STS was expressed in brain regions pertinent to ADHD pathology during development. We did not replicate the previously identified association with rs12861247. However, in ADHD males, variation at rs17268988 was associated with inattentive symptoms, while variation within STS was significantly associated with performance on three cognitive measures. Three SNPs associated with cognitive function in ADHD males were not associated with cognitive function in healthy males. STS was highly expressed in the developing cerebellar neuroepithelium, basal ganglia, thalamus, pituitary gland, hypothalamus and choroid plexus. These data suggest that genetic variants affecting STS expression and/or activity could influence the function of brain regions perturbed in ADHD.     

Differential costal and crural diaphragm compensation for posture changes

The electromyographic (EMG) activities of the costal and crural diaphragm were recorded from bipolar fine-wire electrodes placed in the costal fibers adjacent to the central tendon and in the anterior portions of the crural fibers in 12 anesthetized cats. The EMG activities of costal and crural recordings were compared during posture changes from supine to head up and during progressive hyperoxic hypercapnia in both positions. The activity of both portions of the diaphragm was greater in the head up compared with supine posture at all levels of CO2; and increases in crural activity were greater than those in costal activity both as a result of changes in posture and with increasing CO2 stimuli. These results are consistent with the concept that diaphragm activation is modulated in response to changes in resting muscle length, and further, that neural control mechanisms allow separate regulation of costal and crural diaphragm activation.     

Interaction between the vertical posture and movement control systems during a quick voluntary arm raise

The study was aimed at a deeper understanding of the interaction between the system of vertical posture control and the system of voluntary movement control based on the analysis of postural muscle activity components resulting from the action of the former or the latter system. For this purpose, a quick arm raise was performed in the standing and sitting positions with body fixation at different levels, when the task of maintaining a vertical posture was simplified or completely eliminated. Under these conditions, the muscle activity associated with posture control was supposed to change, while the activity of muscles raising the arm was supposed to remain invariable. The results showed that the simplification of the posture control resulted in a decrease or elimination of anticipatory changes in the activity of some muscles. However, most of the muscle activity variations were retained even in the sitting position, and these variations appeared simultaneously with the activity of muscles raising the arm. The so-called “anticipatory postural activity” during an arm raise in a normal standing position is supposed to consist of two components: an initial component reflecting the work of the posture control system and a later component reflecting the work of the movement control system. It is suggested that the planning of muscle activity and exchange of information between these two systems take place only before the beginning of the movement; after that, they act independently and in parallel.     

Quantitative study of activity patterns and postures of formosan monkeys by the radio-telemetrical technique

Twenty-four hours locomotive activity and posture of four formosan monkeys were recorded continuously by radio-telemetrical technique. (1) The movement activity were drawn; during day time the activity peak and valley come alternatively. They have three-five activity peak per day. (2) Average of time spent in movement is only 1 hour and 8 minutes however frequencies of movement are very high, average is 557.0 per day. (3) Measured the time spent in and the frequency of orthograde and pronograde posture; orthograde posture occupies 20 hours and 10 minutes. These results signify monkeys are sitting for 84% of the day. The frequency of change posture (moving, sitting, and lying) shows 1477.8 times a day on the average. (4) Observing the social interactions and self-directed responses, behavior pattern were analyzed.The fact that monkeys take the orthograde posture for 84% has a very important evolutionary meaning. Sitting posture (orthograde) is an adaptive behavior derived from arboreal life. The orthograde posture that put on a social basis of fundamental physical condition for bipedalism has already prepared in the forest life.Grant in aid for special project research No. 92031.     

Activity of respiratory muscles in upright and recumbent humans

It is established that during tidal breathing the rib cage expands more than the abdomen in the upright posture, whereas the reverse is usually true in the supine posture. To explore the reasons for this, we studied nine normal subjects in the supine, standing, and sitting postures, measuring thoracoabdominal movement with magnetometers and respiratory muscle activity via integrated electromyograms. In eight of the subjects, gastric and esophageal pressures and diaphragmatic electromyograms via esophageal electrodes were also measured. In the upright postures, there was generally more phasic and tonic activity in the scalene, sternocleidomastoid, and parasternal intercostal muscles. The diaphragm showed more phasic (but not more tonic) activity in the upright postures, and the abdominal oblique muscle showed more tonic (but not phasic) activity in the standing posture. Relative to the esophageal pressure change with inspiration, the inspiratory gastric pressure change was greater in the upright than in the supine posture. We conclude that the increased rib cage motion characteristic of the upright posture owes to a combination of increased activation of rib cage inspiratory muscles plus greater activation of the diaphragm that, together with a stiffened abdomen, acts to move the rib cage more effectively.     

Gap Effect Abnormalities during a Visually Guided Pro-Saccade Task in Children with Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that starts in early childhood and has a comprehensive impact on psychosocial activity and education as well as general health across the lifespan. Despite its prevalence, the current diagnostic criteria for ADHD are debated. Saccadic eye movements are easy to quantify and may be a quantitative biomarker for a wide variety of neurological and psychiatric disorders, including ADHD. The goal of this study was to examine whether children with ADHD exhibit abnormalities during a visually guided pro-saccadic eye-movement and to clarify the neurophysiological mechanisms associated with their behavioral impairments. Thirty-seven children with ADHD (aged 5–11 years) and 88 typically developing (TD) children (aged 5–11 years) were asked to perform a simple saccadic eye-movement task in which step and gap conditions were randomly interleaved. We evaluated the gap effect, which is the difference in the reaction time between the two conditions. Children with ADHD had a significantly longer reaction time than TD children (p < 0.01) and the gap effect was markedly attenuated (p < 0.01). These results suggest that the measurement of saccadic eye movements may provide a novel method for evaluating the behavioral symptoms and clinical features of ADHD, and that the gap effect is a potential biomarker for the diagnosis of ADHD in early childhood.     

Enhancing Proper Sitting Position Using a New sEMG Protocol, The “Minimax” Procedure, With Boolean Logic

The modification of posture in children using sEMG is a new area that offers much potential to aid disabled children regain function. This article describes a new protocol, the minimax procedure, to aid children regain motor function in sitting. The protocol uses selective reinforcement to encourage recruiting/relaxing target sites (gluteus medius/maximus) in a predetermined way so as to encourage good form in sitting. Children often are unaware how to make changes in posture, and when they do succeed the progress is so slow that sustaining motivation is a challenge. This paper describes a procedure that helps the child recognize when they have achieved the correct posture, immediately rewards them for doing so, and generates data using Boolean operations to numerically substantiate the clinically observed changes in posture.     

Effect of head-down tilt on respiratory responses and human inspiratory muscles activity

The effect of head-down tilt on respiration and diaphragmal and parasternal muscles activity was investigated in 11 healthy subjects. The short-time (30 min) head-down tilt posture (-30 degrees relatively horizont) increased the inspiratory time (P < 0.05), decreased breathing frequency (P < 0.05), inspiratory and expiratory flow rate (P < 0.05) and increased the airway resistance (P < 0.05) compared with values in vertical posture. There were no significant changes in tidal volume and minute ventilation. Constant values of tidal volume and minute ventilation during head-down tilt were provided by increasing in EMG activity of parasternal muscles more then twice. It was established that the contribution of chest wall inspiratory muscles increased while the diaphragm's contribution decreased during head-down spontaneous breathing. Maximal inspiratory effort (Muller's maneuver) during head-down tilt evoked the opposite EMG-activity pattern: the contribution of inspiratory thoracic muscles was decreased and diaphragm's EMG-activity was increased compared with vertical posture. These results suggest that coordinate modulations in inspiratory muscles activity allows to preserve the functional possibility of human inspiratory muscles during short-time head-down tilt.     

Associations between cervical and scapular posture and the spatial distribution of trapezius muscle activity

The first aim of this investigation was to quantify the distribution of trapezius muscle activity with different scapular postures while seated. The second aim of this investigation was to examine the association between changes in cervical and scapular posture when attempting to recruit different subdivisions of the trapezius muscle. Cervical posture, scapular posture, and trapezius muscle activity were recorded from 20 healthy participants during three directed shoulder postures. Planar angles formed by reflective markers placed on the acromion process, C7, and tragus were used to quantify cervical and scapular posture. Distribution of trapezius muscle activity was recorded using two high-density surface electromyography (HDsEMG) electrodes positioned over the upper, middle, and lower trapezius. Results validated the assumption that directed scapular postures preferentially activate different subdivisions of the trapezius muscle. In particular, scapular depression was associated with a more inferior location of trapezius muscle activity (r = 0.53). Scapular elevation was coupled with scapular abduction (r = 0.52). Scapular adduction was coupled with cervical extension (r = 0.35); all other changes in cervical posture were independent of changes in scapular posture. This investigation provides empirical support for reductions in static loading of the upper trapezius and improvements in neck posture through verbal cueing of scapular posture.     

Compensation effect of visual biofeedback in upright posture control

The effectivity of the compensatory role of visual biofeedback in cases of decreased stability of upright posture has been analysed. The deterioration of stance was modelled by a subject standing on a soft surface and with additional weight load on the body. The influence of visual biofeedback was positive only for the compensation of decreased stability of upright posture caused by artificially increased body weight of the subject. The compensatory effectivity of visual biofeedback in stabilization of upright posture during stance on a soft surface was practically negligible. The results have shown that effective compensation of the destabilizing effect by visual biofeedback in human upright posture was possible only when the activity and efficiency of efferent-action part of the postural system remained unchanged.     

Measurement of the Effect of Physical Exercise on the Concentration of Individuals with ADHD

Attention Deficit Hyperactivity Disorder (ADHD) mainly affects the academic performance of children and adolescents. In addition to bringing physical and mental health benefits, physical activity has been used to prevent and improve ADHD comorbidities; however, its effectiveness has not been quantified. In this study, the effect of physical activity on children''s attention was measured using a computer game. Intense physical activity was promoted by a relay race, which requires a 5-min run without a rest interval. The proposed physical stimulus was performed with 28 volunteers: 14 with ADHD (GE-EF) and 14 without ADHD symptoms (GC-EF). After 5 min of rest, these volunteers accessed the computer game to accomplish the tasks in the shortest time possible. The computer game was also accessed by another 28 volunteers: 14 with ADHD (GE) and 14 without these symptoms (GC). The response time to solve the tasks that require attention was recorded. The results of the four groups were analyzed using D''Agostino statistical tests of normality, Kruskal-Wallis analyses of variance and post-hoc Dunn tests. The groups of volunteers with ADHD who performed exercise (GE-EF) showed improved performance for the tasks that require attention with a difference of 30.52% compared with the volunteers with ADHD who did not perform the exercise (GE). The (GE-EF) group showed similar performance (2.5% difference) with the volunteers in the (GC) group who have no ADHD symptoms and did not exercise. This study shows that intense exercise can improve the attention of children with ADHD and may help their school performance.     

Lumbar back muscle activity of helicopter pilots and whole-body vibration

Several studies have attributed the prevalence of low back pain (LBP) in helicopter pilots mainly to poor posture in-flight and whole-body vibration, with the latter hypothesis particularly related to a cyclic response of the erector spine (ES) muscle to vibration. This work aims to determine if helicopter vibration and the pilot's normal posture during flight have significant effects on the electromyogram (EMG) of the ES muscle. The bilateral surface EMG of the ES muscle at the L3 level was collected in 10 young pilots before and during a short flight in UH-50 helicopters. The vibration was monitored by a triaxial accelerometer fixed to the pilots' seat. Prior to the flight, the EMG was recorded for relaxed seated and standing postures with 0 degrees (P0) and 35 degrees (P35) of trunk flexion. The effect of the posture during the flight was tested by comparing left and right EMG (normalized with respect to P35). The in-flight muscle stress was evaluated by histograms of EMG activity, and compared to P0 values. Only one pilot in ten showed significant (p<0.05) correlation between the vibration and the EMG over cycles of vibration, and no consistent causal effect was found. The pilots' posture did not show significant asymmetric muscular activity, and low EMG levels were observed during most of the duration of the flight. The results do not provide evidence that LBP in helicopter pilots is caused by ES muscle stress in the conditions studied.     

Influence of posture and breathing route on neural drive to upper airway dilator muscles during exercise.

Our purpose was to determine the influence of posture and breathing route on electromyographic (EMG) activities of nasal dilator (NDM) and genioglossus (GG) muscles during exercise. Nasal and oral airflow rates and EMG activities of the NDM and GG were recorded in 10 subjects at rest and during upright and supine incremental cycling exercise to exhaustion. EMG activities immediately before and after the switch from nasal to oronasal breathing were also determined for those subjects who demonstrated a clear switch point (n = 7). NDM and GG EMG activities were significantly correlated with increases in nasal, oral, and total ventilatory rates during exercise, and these relationships were not altered by posture. In both upright and supine exercise, NDM activity rose more sharply as a function of nasal inspired ventilation compared with total or oral inspired ventilation (P < 0.01), but GG activity showed no significant breathing-route dependence. Peak NDM integrated EMG activity decreased (P = 0.008), and peak GG integrated EMG activity increased (P = 0.032) coincident with the switch from nasal to oronasal breathing. In conclusion, 1) neural drive to NDM and GG increases as a function of exercise intensity, but the increase is unaltered by posture; 2) NDM activity is breathing-route dependent in steady-state exercise, but GG activity is not; and 3) drive to both muscles changes significantly at the switch point, but the change in GG activity is more variable and is often transient. This suggests that factors other than the breathing route dominate drive to the GG soon after the initial changes in the configuration of the oronasal airway are made.