A standing posture support device that reduces laparoscopic surgeons’ occupational lower limb stress

Background: We developed a surgical knee rest (SKR) that can be used to decrease the stress placed on the lower half of the body when surgeons work in the standing position. We tested the effectiveness of this device in the context of laparoscopic surgery.

Material and methods: Five healthy, right-handed male surgeons participated, and we recorded surface electromyography (sEMG) signals from the two heads of the left and right gastrocnemius (Gc) muscles during laparoscopic resections of colorectal cancer. The outcome variable was the percentage of maximum Gc muscle effort generated, reported as percent maximal isometric voluntary contraction (%MVC), and this variable was compared between surgeries performed with and without use of the SKR. Assessment covered the first 100?min of surgery, subdivided into two 50-min periods.

Results: Mean %MVC of the left Gc muscle for the full 100-min test period was significantly decreased when the SKR was used (p?=?.027, vs. SKR not used). Notably, mean %MVC of both Gc muscles was significantly decreased during the first 50?min of surgery (p?=?.008 and p?=?.0046).

Conclusion: The SKR is useful for decreasing physical stress incurred by laparoscopic surgeons when working in the standing position.     

Biomechanical Analysis of Reducing Sacroiliac Joint Shear Load by Optimization of Pelvic Muscle and Ligament Forces

Effective stabilization of the sacroiliac joints (SIJ) is essential, since spinal loading is transferred via the SIJ to the coxal bones, and further to the legs. We performed a biomechanical analysis of SIJ stability in terms of reduced SIJ shear force in standing posture using a validated static 3-D simulation model. This model contained 100 muscle elements, 8 ligaments, and 8 joints in trunk, pelvis, and upper legs. Initially, the model was set up to minimize the maximum muscle stress. In this situation, the trunk load was mainly balanced between the coxal bones by vertical SIJ shear force. An imposed reduction of the vertical SIJ shear by 20% resulted in 70% increase of SIJ compression force due to activation of hip flexors and counteracting hip extensors. Another 20% reduction of the vertical SIJ shear force resulted in further increase of SIJ compression force by 400%, due to activation of the transversely oriented M. transversus abdominis and pelvic floor muscles. The M. transversus abdominis crosses the SIJ and clamps the sacrum between the coxal bones. Moreover, the pelvic floor muscles oppose lateral movement of the coxal bones, which stabilizes the position of the sacrum between the coxal bones (the pelvic arc). Our results suggest that training of the M. transversus abdominis and the pelvic floor muscles could help to relieve SI-joint related pelvic pain.     

Palmar arch dynamics during reach-to-grasp tasks

The relationship between arm transport and grip aperture scaling has traditionally been used to study the control of reaching and grasping. Since the palmar concavity forms a postural base of the hand, intuitively it should play an essential role in hand shape modulation during grasping. This role however has not yet been investigated. This study investigated whether hand shape modulation was initiated at the palmar level or at the level of the finger joints during two types of power grasps (spherical, cylindrical). Hand shape modulation was studied in eight healthy adults and was characterized by the change in palmar arch movement during three phases of the reach-to-grasp tasks, traditionally defined as arm transport, hand preshaping and object contact. Palmar arch kinematics changed significantly during arm transport for both types of grasp (spherical 47.4%, cylindrical 63.7%). Approximately 16% more modulation was observed when grasping the cylindrical as compared to the spherical object. This was counterbalanced by relatively less modulation during the preshaping and object contact phases compared to the spherical grasp. These results showed that the three grasping phases occurred concurrently in a common time window. Furthermore, an increase in the duration of either one of the components impacted the execution of the others. A secondary finding was that hand shape modulation began at the same time or within 125 ms of the initiation of arm transport for both grasp types. In most cases (60%), movement in the palmar arch occurred prior to movement at the metacarpophalangeal joint (MCP) of the index and middle fingers. The same was observed when palmar arch modulation was compared with the time of movement initiation in the proximal interphalangeal (PIP) joints of the index and middle fingers (60–75%). Thus palmar and finger joint movement were initiated almost simultaneously and hand shape modulation began early in the reach-to-grasp task. The findings show that hand shape and arm transport were modulated together and suggest that prehensile movement, including both palmar arch and finger configuration, is planned as early as the intent to grasp.     

The intrinsic shape of the human lumbar spine in the supine, standing and sitting postures: characterization using an active shape model

The shape of the lumbar spine in the sagittal plane varies between individuals and as a result of postural changes but it is not known how the shape in different postures is related. Sagittal images of the lumbar spines of 24 male volunteers were acquired using a positional magnetic resonance scanner. The subjects were imaged lying supine, standing and sitting. An active shape model was used to characterize shape in terms of independent modes of variation. Two modes were identified that described the total (mode 1) and distribution (mode 2) of the curvature. The spinal shape was found to be intercorrelated between the three postures for both modes, suggesting that the lumbar spine has an element of shape that is partially maintained despite postural alterations. Mode 1 values indicated that the spine was straightest when standing and curviest when sitting. Mode 2 values indicated that the distribution in the curvature was most even when sitting and least even when lying supine. Systematic differences in the behaviour of the spine, when changing posture, were found that suggest that the shape of the spine may affect its biomechanics.     

Thermal asymmetry of the human scrotum

BACKGROUND: Scrotal temperatures in men have been reported to be either similar on both sides or higher on the left than the right scrotum. We aimed to clarify this discrepancy from new data. METHODS: Retrospective analyses of scrotal temperatures in men aged 20-52 years measured every 2 min with probes connected to a data collector in three experiments. In Experiment I, eight men have been submitted to four successive body positions for 15 min each, first naked then clothed. Experiment II involved 11 postal employees working in a standing position for 90 min continuously. Experiment III involved 11 bus drivers and a 90 min period of continuous driving. Outcome parameters were left and right scrotal temperatures. RESULTS: In Experiment I, mean values and kinetics of scrotal temperature differed significantly in the naked and clothed state. In all three experiments, left scrotal temperature in the clothed state was higher than right scrotal temperature in terms of mean values and temperature kinetics. CONCLUSIONS: Lack of thermal symmetry was seen in the right and left scrotum, whether naked or clothed, and this applied regardless of position or activity when clothed. This thermal difference between right and left scrotum could contribute to the asymmetry in the male external genital organs.     

Age-related complexity and coupling of children's sitting posture

This study tested the hypothesis that postural complexity increases as the coupling across the axes of motion decreases as children get older. Children aged 6 and 10 years and young adults (18-23 years) were seated on a wooden box placed atop a force platform that recorded their mediolateral and anteroposterior center of pressure (COP) motion with their feet supported and unsupported. The COP path length and complexity decreased with age, and this was paralleled by an increase in relative phase entropy across the axes of sway motion. The postural sway of the younger children was dominated by slower fluctuations that were more tightly coupled across the axes of motion than the adults. The findings support the postulation that the development of children's sitting posture is characterized by increased freedom in postural coordination that realizes a more loosely coupled but adaptive postural motion with a reduced amount of sway.     

Development of dynamic stability in children's rhythmic movement

This study examined the hypothesis that the stability of rhythmic motor patterns increases with developmental age in children. Children aged 6 and 10 years and adults (18‐ to 23‐year‐olds) rocked back and forth at their preferred amplitude and frequency while seated on a wooden box placed atop a force platform. Participants performed the seated rocking task with their feet supported and unsupported. There was an age‐related decrease in rocking frequency and variability of the rocking cycle period, while the stability of the rocking dynamics increased, as indexed by the standard deviation of the phase angle of center of pressure motion. The presence of foot support decreased the stability of the rocking dynamics and reduced cycle period variability in the children, but not the adults. The results revealed that increments of age are associated with an increase in the stability of rhythmic motor patterns even when environmental conditions are altered. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 465–473, 2009     

直立性T波改变与血管迷走性晕厥的相关研究

目的探讨无晕厥病史患者出现的直立性T波改变的发生机理及其与血管迷走性晕厥的相关性;方法利用活动平板运动试验初筛出直立性T波改变预检患者,经基础倾斜试验进一步确证,再行硝酸甘油倾斜试验。第2天,阳性患者经随机分组,双盲对照服用安慰剂(=22)或30mg普荼各尔(=21)60min后重复基础倾斜试验、硝酸甘油倾斜试验。结果100例直立性T波改变患者在基础倾斜试验中无1例阳性反应,在随后的NTTT中有43例出现阳性结果。第2天,安慰剂组直立性T波改变及NTTT阳性有比率明显高于普荼各尔组(依次为86.4%∶23.8%,P<0.01,72.7%∶28.6%,P<0.01)。结论直立性T波改变是人体由卧位到立位引起神经-体液变化所致的心室肌复极异常,它是血管迷走性晕厥形成过程中某一阶段出现的一种伴随现象,与血管迷走性晕厥有一定的相关性,心得安等β-受体阻滞剂作为首选药物来治疗直立性T波改变和伴随有直立性T波改变的血管迷走性晕厥患者,收到肯定的临床疗效。     

Cells in monkey STS responsive to articulated body motions and consequent static posture: a case of implied motion?

We show that populations of visually responsive cells in the anterior part of the superior temporal sulcus (STSa) of the macaque monkey code for the sight of both specific articulated body actions and the consequent articulated static body postures. We define articulated actions as actions where one body part (e.g. a limb or head) moves with respect to the remainder of the body which remains static; conversely non-articulated actions are actions where the equivalent body parts do not move with respect to each other but move as one. Similarly, articulated static body postures contain a torsion or rotation between parts, while non-articulated postures do not. Cells were tested with the sight of articulated and non-articulated actions followed by the resultant articulated or non-articulated static body postures. In addition, the static body postures that formed the start and end of the actions were tested in isolation. The cells studied did not respond to the sight of non-articulated static posture, which formed the starting-point of the action, but responded vigorously to the articulated static posture that formed the end-point of the action. Other static postures resembling the articulated end-point posture, but which were in a more relaxed muscular state (i.e. non-articulated), did not evoke responses. The cells did not respond to body actions that were less often associated with the effective static articulated postures. Our results suggest that the cells' responses were related to the implied action rather than the static posture per se. We propose that the neural representations in STSa for actual biological motion may also extend to biological motion implied from static postures. These representations could play a role in producing the activity in the medial temporal/medial superior temporal (V5(MT)/MST) areas reported in fMRI studies when subjects view still photographs of people in action.