Reproducibility of Standing Posture for X-Ray Radiography: A Feasibility Study of the <Emphasis Type="Italic">BalancAid</Emphasis> with Healthy Young Subjects

Unreliable spinal X-ray radiography measurement due to standing postural variability can be minimized by using positional supports. In this study, we introduce a balancing device, named BalancAid, to position the patients in a reproducible position during spinal X-ray radiography. This study aimed to investigate the performance of healthy young subjects’ standing posture on the BalancAid compared to standing on the ground mimicking the standard X-rays posture in producing a reproducible posture for the spinal X-ray radiography. A study on the posture reproducibility measurement was performed by taking photographs of 20 healthy young subjects with good balance control standing on the BalancAid and the ground repeatedly within two consecutive days. We analyzed nine posterior–anterior (PA) and three lateral (LA) angles between lines through body marks placed in the positions of T3, T7, T12, L4 of the spine to confirm any translocations and movements between the first and second day measurements. No body marks repositioning was performed to avoid any error. Lin’s CCC test on all angles comparing both standing postures demonstrated that seven out of nine angles in PA view, and two out of three angles in LA view gave better reproducibility for standing on the BalancAid compared to standing on the ground. The PA angles concordance is on average better than that of the LA angles.     

后半规管非平面性对夹角测量的影响

目的 测量后半规管夹角,观察后半规管非平面性对夹角测量的影响。 方法 对20例磁共振三维稳态构成干预序列内耳检查影像进行分析,通过使用3D Slicer 4.4软件直接测量左、右后半规管的夹角来推算后半规管和矢状面的夹角。 结果 左、右后半规管夹角为90.5°±8.9°,最小夹角73°,最大夹角108°。可推算后半规管和矢状面夹角为45.3°±4.4°,最小36.5°,最大54°。 结论 后半规管切面经过或不经过共脚,由此导致夹角测量差异约为9°,故此次测量数据和既往研究相符,但本方法更加直观方便。     

人体运动过程中侧切落地模式和角度对下肢运动生物力学的影响

背景:在体育运动中,侧切动作是最常见的进攻技术,受落地模式和角度的影响。侧切落地模式和角度的不同会增加下肢膝关节损伤的风险。目的:阐述侧切动作中不同的落地模式和角度对下肢运动生物力学的影响。方法:在PubMed、WOS、CNKI数据库检索2020年8月之前收录的相关研究。中文搜索词为“侧切动作;侧切角度;侧切落地模式;侧切生物力学”“变向动作”;英文检索词为“cutting maneuver;cutting maneuver angle;cutting foot strike;cutting biomechanics”“changeof-direction”。结果与结论:采用后足落地模式和较大的角度进行侧切时所表现出的生物力学指标特点,预示着前交叉韧带损伤风险的加大。但是目前的研究只集中于单一因素的分析,很少把落地模式和侧切的角度结合起来进行讨论,这两者在侧切动作中的交互作用,缺少明确的结论,尚无足够证据支持侧切角度增大时改变落地模式会降低下肢损伤的风险,这仍需要大量的研究进行深入论证。     

Automatic beam angle selection in IMRT planning using genetic algorithm

The selection of suitable beam angles in external beam radiotherapy is at present generally based upon the experience of the human planner. The requirement to automatically select beam angles is particularly highlighted in intensity-modulated radiation therapy (IMRT), in which a smaller number of modulated beams is hoped to be used, in comparison with conformal radiotherapy. It has been proved by many researchers that the selection of suitable beam angles is most valuable for a plan with a small number of beams (< or = 5). In this paper an efficient method is presented to investigate how to improve the dose distributions by selecting suitable coplanar beam angles. In our automatic beam angle selection (ABAS) algorithm, the optimal coplanar beam angles correspond to the lowest objective function value of the dose distributions calculated using the intensity-modulated maps of this group of candidate beams. Due to the complexity of the problem and the large search space involved, the selection of beam angles and the optimization of intensity maps are treated as two separate processes and implemented iteratively. A genetic algorithm (GA) incorporated with an immunity operation is used to select suitable beam angles, and a conjugate gradient (CG) method is used to quickly optimize intensity maps for each selected beam combination based on a dose-based objective function. A pencil-beam-based three-dimensional (3D) full scatter convolution (FSC) algorithm is employed for the dose calculation. Two simulated cases with obvious optimal beam angles are used to verify the validity of the presented technique, and a more complicated case simulating a prostate tumour and two clinical cases are employed to test the efficiency of ABAS. The results show that ABAS is valid and efficient and can improve the dose distributions within a clinically acceptable computation time.     

Assessment of four midcarpal radiologic determinations

Several radiologic measurement methods have been described for determining static carpal alignment of the wrist. These include the scapholunate, radiolunate, and capitolunate angles. The triangulation method is an alternative radiologic measurement which we believe is easier to use and more reproducible and reliable than the above mentioned methods. The purpose of this study is to assess the intraobserver reproducibility and interobserver reliability of the triangulation method, scapholunate, radiolunate, and capitolunate angles. Twenty orthopaedic residents and staff at varying levels of training made four radiologic measurements including the scapholunate, radiolunate and capitolunate angles as well as the triangulation method on five different lateral, digitized radiographs of the wrist and forearm in neutral radioulnar deviation. Thirty days after the initial measurements, the participants repeated the four radiologic measurements using the same radiographs. The triangulation method had the best intra-and-interobserver agreement of the four methods tested. This agreement was significantly better than the capitolunate and radiolunate angles. The scapholunate angle had the next best intraobserver reproducibility and interobserver reliability. The triangulation method has the best overall observer agreement when compared to the scapholunate, radiolunate, and capitolunate angles in determining static midcarpal alignment. No comment can be made on the validity of the measurements since there is no radiographic gold standard in determining static carpal alignment.The authors have not received anything of value from any individual(s) or institution for this work. The views of the authors do not necessarily represent those of the Department of Defense or the United States Army     

Haptic two-dimensional angle categorization and discrimination

This study examined the extent to which haptic perception of two-dimensional (2-D) shape is modified by the design of the perceptual task (single-interval categorization vs. two-interval discrimination), the orientation of the angles in space (oblique vs. horizontal), and the exploration strategy (one or two passes over the angle). Subjects (n = 12) explored 2-D angles using the index finger of the outstretched arm. In the categorization task, subjects scanned individual angles, categorizing each as “large” or “small” (2 angles presented in each block of trials; range 80° vs. 100° to 89° vs. 91°; implicit standard 90°). In the discrimination task, a pair of angles was scanned (standard 90°; comparison 91–103°) and subjects identified the larger angle. The threshold for 2-D angle categorization was significantly lower than for 2-D angle discrimination, 4° versus 7.2°. Performance in the categorization task did not vary with either the orientation of the angles (horizontal vs. oblique, 3.9° vs. 4°) or the number of passes over the angle (1 vs. 2 passes, 3.9° vs. 4°). We suggest that the lower threshold with angle categorization likely reflects the reduced cognitive demands of this task. We found no evidence for a haptic oblique effect (higher threshold with oblique angles), likely reflecting the presence of an explicit external frame of reference formed by the intersection of the two bars forming the 2-D angles. Although one-interval haptic categorization is a more sensitive method for assessing 2-D haptic angle perception, perceptual invariances for exploratory strategy and angle orientation were, nevertheless, task-independent.     

Do Mid‐Crown Enamel Formation Front Angles Reflect Factors Linked to the Pace of Primate Growth and Development?

Enamel formation front (EFF) angles represent the leading edge of enamel matrix secretion at particular points in time. These angles are influenced by rates of enamel extension (the rates at which tooth crowns grow in height), rates of enamel matrix secretion and the angles that prisms make with the enamel‐dentine junction. Previous research suggests, but has not yet established, that these angles reflect aspects of primate biology related to their pace of growth and development, most notably brain and body size. The present study tested this possibility on histological sections using phylogenetically‐controlled and Bonferroni‐corrected analyses spanning a broad taxonomic range. Ten species were represented in the analysis of anterior teeth; 17 in the analysis of posterior (postcanine) teeth (with varying sample sizes). Also, tested was the relationship of EFF angles to striae of Retzius periodicity (long period growth rhythms in enamel) and degree of folivory, as both factors are related to primate developmental rates. Finally, several analyses were conducted to investigate whether tooth size (operationalized as EDJ length) might mediate these relationships. Central results are as follows: (1) Relationships between EFF angles and brain weight (anterior teeth) and between EFF angles and body mass (anterior and posterior teeth) are statistically significant and (2) Mid‐crown EFF angles are not statistically significantly related to EDJ lengths. These results suggest that tooth size does not mediate relationships between EFF angles and brain weight/body mass and are discussed with respect to underlying enamel growth variables (especially rates of enamel extension and secretion). Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:125–139, 2018. © 2017 Wiley Periodicals, Inc.     

胫骨平台后外侧髁“边缘曲线”的影像学研究及临床意义

研究胫骨平台后外侧髁弧形轮廓的角度及长度,为临床钢板塑形和设计新型水平带状钢板提供理论依据。 方法　收集50例成人膝关节CT数据[男31 例,女19例,平均（37.68±12.76）岁]。在横断面平扫图像下,以腓骨头尖初次显露为标准图片,在胫骨平台外侧髁边缘标记A、B、C、D、E五点。分段测量并记录其连线的长度与夹角,计算后外侧髁曲线长度和曲线的转折角。 结果　胫骨平台后外侧髁曲线长度平均（44.04±11.33）mm (19.50~75.50 mm), 由前向后的三点折弯角平均为（163.36±7.67）°、（127.95±20.85）°和（160.50±11.99）°。手术中按照该测量参数进行钢板折弯与塑形,5例患者术后CT显示,钢板形状与胫骨平台后外侧髁贴服紧密,对皮质轮廓包绕良好。 结论　按照骨骼测量的边缘曲线参数进行术中钢板折弯和设计新型解剖钢板,能够提高钢板与后外侧髁的贴合程度。     

Elbow flexor evoked twitch contractile properties in untrained men and women and male bodybuilders

Summary The influence of elbow joint angle on elbow flexor isometric evoked twitch contractile properties was assessed in 15 young women (F), 18 young men (M) and 11 male bodybuilders (BB). Measurements were made at elbow joint angles of 1.31, 1.57, 1.83, 2.09, 2.36, 2.62 and 2.88 rad (3.14 rad =180° =full extension). The largest peak twitch torque values [mean (SE) N · m] in F [3.77 (0.20)], M [10.38 (0.68)] and BB [11.38 (1.05)] occurred at 2.88 rad. Peak torque was progressively smaller at smaller joint angles, but the decline from 2.88 to 1.31 rad was greater in M (68%) and BB (76%) than F (59%). Thus, the magnitude of intergroup differences in peak twitch torque (PT) was joint angle dependent. Twitch time to peak torque (TPT) was influenced in a complex way by joint angle in the three groups; BB had the lowest values at small joint angles but the highest values at the largest angles. Half-relaxation time (HRT) generally increased from the smallest to largest joint angles in a pattern that did not differ significantly among the three groups. Maximum rates of twitch torque development and relaxation showed the same pattern of results as PT; indicating that these time-related measures were more sensitive to joint angle effects on PT than on TPT or HRT. The results of this study indicate that careful consideration should be given to the selection of joint angles in the measurement of evoked twitch contractile properties for the purpose of making group comparisons or investigating the effects of interventions such as training.     

Pythagoras and Cosines: The skin–dural sac distance and optimal angles in paramedian spinal anesthesia

The classical recommendation for paramedian approaches is needle insertion 1–2 cm paramedian and an angle of 10°–15° medial–cephalad to the plane of the back, but contact with vertebrae is frequent. A mathematical approach to individualizing punctures is proposed on the basis of skin–dural sac distance (d): Optimal angle ～ inverse cosine [d/ and the distance covered by the needle ～ for 1 cm paramedian punctures. The inferred angles were compared to optimal angles leading to the central dorsal part of the dural sac from 1 to 2 cm paramedian, measured by Magnetic Resonance Imaging (MRI) in seven cases and in a short stature volunteer (1.58 m, Body Mass Index (BMI) 23.2), to study supine and fetal positions using both closed MR and ultrasound. The average (d) decreased rostrally [6.8 cm (L4–L5)?4.3 cm (T11–T12)] while the mean optimal incidence angles increased [8.3°–16.5° (L4–L5) to 12.7°–24.1° (T11–T12) at 1–2 cm paramedian, respectively] and coincided with the estimated angles with a correlation coefficient = 0.98. In the volunteer, the optimal lateromedial angles increased from 14.4° to 26.7° (L3–L4) to 17.1°–30.3° (T11–T12) for a (d) = 3.7 cm (L3–L4)?3.1 cm (T11–T12) and increased ≤3.7° and ≤5.1° at 1 and 2 cm paramedian, respectively, in fetal positions in MR. Ultrasound yielded comparable figures. The range of possible angles for dural punctures is wider at 1 cm paramedian in lower approaches in lateral decubitus [from 3.6° at T12L1 (12.2°–15.8°) to 9° at L3L4 (8.8°–18.7°)]. The classically recommended angles of 10°–15° differ from the optimal angles, particularly in small patients, suggesting the need for ultrasound guidance or for inferring angles prior to spinal anesthesia. Clin. Anat. 29:1046–1052, 2016. © 2016 Wiley Periodicals, Inc.     

Bend Sweep Angle and Reynolds Number Effects on Hemodynamics of S-Shaped Arteries

The purpose of this study is to investigate the effects of the Reynolds number and the bend sweep angle on the blood flow patterns of S-shaped bends. The numerical simulations of steady flows in S-shaped bends with sweep angles of 45°, 90°, and 135° are performed at Reynolds numbers of 125, 500, and 960. Hemodynamic characteristics such as secondary flows, vorticity, and axial velocity profiles are analyzed in detail. Flow patterns in S-shaped bends are strongly dependent on both Reynolds number and bend sweep angle, which can be categorized into three groups based on the first bend secondary flow effects on the transverse flow of the second bend. For low Reynolds numbers and any sweep angles, secondary flows in the second bend eliminate the first bend effects in the early sections of the second bend and therefore the axial velocity profile is consistent with the bend curvature, while for high Reynolds numbers depending on the bend sweep angles the secondary vortex pattern of the first bend may persist partially or totally throughout the second bend leading to a four-vortex secondary structure. Moreover, an interesting flow feature observed at the Reynolds number of 960 is that the secondary flow asymmetrical behavior occurred around the second bend exit and along the outflow straight section. This symmetry-breaking phenomenon which has not been reported in the previous studies is shown to be more pronounced in the 90° S-shaped bend as compared to other models considered here. The probability of flow separation as one of the important flow features contributing to the onset and development of arterial wall diseases is also studied. It is observed that the second bend outer wall of gentle bends with sweep angles from 20° to 30° at high enough Reynolds numbers are prone to flow separation.     

Non-linear flexion relationships of the knee with the hip and ankle, and their relative postures during landing

The knee joint, together with the hip and ankle, contributes to overall shock absorption through their respective flexion motions during landing. This study sought to investigate the presence of a lower extremity coordination pattern by determining mathematical relationships that associate knee flexion angles with hip flexion and ankle dorsiflexion angles during landing phase, and to determine relative postures of the hip and ankle, with reference to the knee, and examine how these relative postures change during key events of the landing phase. Eight healthy male subjects were recruited to perform double-leg landing from 0.6-m height. Motion capture system and force-plates were used to obtain kinematics and ground reaction forces (GRF) respectively. Non-linear regression analysis was employed to determine appropriate mathematical relationships of the hip flexion and ankle dorsiflexion angles with knee flexion angles during the landing phase. Relative lower extremity postures were compared between events of initial contact, peak GRF and maximum knee flexion, using ANOVA on ranks. Our results demonstrated a lower extremity coordination pattern, whereby the knee flexion angles had strong exponential (R² = 0.92–0.99, p < 0.001) and natural logarithmic (R² = 0.85–0.97, p < 0.001) relationships with hip flexion and ankle dorsiflexion angles respectively during the landing phase. Furthermore, we found that the subjects adopted distinctly different relative lower extremity postures (p < 0.05) during peak GRF as compared to initial contact. These relative postures were further maintained till the end of the landing phase. The occurrence of these relative postures may be a reflexive mechanism for the subjects to efficiently absorb the impact imposed by the peak GRF.     

多层螺旋CT三维重建技术在辅助微螺钉种植支抗植入中的选择应用

背景：提高正畸支抗系统微螺钉种植体稳定性的关键在于种植前对局部骨质、骨量进行精确评估,但常规二维影像学检查,如根尖片、曲面断层摄影片、侧位头影测量片等均存在不同程度的局限性。 目的：分析总结多层螺旋CT多种图像重建技术在辅助微螺钉种植支抗植入中的不同特点及优势,以便精确指导微螺钉的种植,提高其稳定性。 方法：种植前以多层螺旋CT对猪颅骨进行定位扫描及多种图像重建,通过多种图像联合应用初步观测种植区骨质骨量及解剖情况,然后利用计算机在影像上精确设计三维种植角度,根据影像信息制作隧道式手术模板指导种植32枚微螺钉支抗,种植后多层螺旋CT再次扫描重建,将种植前后多层螺旋CT设计及测量角度与术后解剖组织块实物测量角度作对比分析。 结果与结论：32枚微螺钉种植情况满意,无伤及邻近牙根及周围重要组织结构的情况。种植前设计与种植后多层螺旋CT测量角度比较,以及种植后多层螺旋CT测量与实物测量角度比较,在轴位面及侧断面上其差异均无显著性意义(P > 0.05),且一致性极好。说明多层螺旋CT能够提供精确而丰富的影像信息,恰当选择合理应用能充分实现微螺钉种植影像学检查目的,从而为提高种植的成功率提供可靠保障。     

Measurement of fibre pennation using ultrasound in the human quadriceps in vivo

Summary Real-time ultrasound scanning was used to measure the angles of fibre pennation of vastus lateralis (VL) and vastus intermedius (VI) of the human quadriceps (n = 12) in vivo. The maximum isometric force and cross-sectional area of the quadriceps were also measured. With the knee at right-angles the mean fibre angles for VL and VI respectively were 0.133 (0.021) rad [7.6° (1.2°)] and 0.143 (0.028) rad [8.2° (1.6°)] [mean (SD)], which is within the range of angles measured on cadavers. The mean angle decreased in going from the contracted [VL, 0.244 rad (14°); VI, 0.279 rad (16°)] to the stretched [VL, 0.105 rad (6°); VI, 0.122 rad (7°)] position. There was a significant positive correlation between fibre angle and muscle cross-sectional area but no relationship between fibre angle and force per cross-sectional area. No increase in fibre angle was detected after 3 months strength training. We conclude that ultrasound can be used to measure pennation angles of superficial muscle groups but we could not demonstrate a relationship between pennation and force-generating capacity.     

Influence of angle between the nozzle and skin surface on the heat flux and overall heat extraction during cryogen spray cooling

High speed video imaging and an inverse heat conduction problem algorithm were used to observe and measure the effect of the angle between the nozzle and surface of a skin phantom on: (a) surface temperature; (b) heat flux q; and (c) overall heat extraction Q during cryogen spray cooling (CSC). A skin phantom containing a fast-response temperature sensor was sprayed with 50 ms cryogen spurts from a commercial nozzle placed 30 mm from the surface. The nozzle was systematically positioned at angles ranging from 5 to 90 degrees (perpendicular) with respect to the phantom surface. It is shown that angles as low as 15 have an insignificant impact on the surface temperature, q and Q. Only exaggerated angles of 5 show up to 10% lower q and 30% lower Q with respect to the maximal values measured when nozzles are aimed perpendicularly. This study proves that the slight angle that many commercial nozzles have does not affect significantly the CSC efficiency.     

An analytical formulation of the law of intersegmental coordination during human locomotion

The law of intersegmental coordination is a kinematic law that describes the coordination patterns among the elevation angles of the lower limb segments during locomotion (Borghese et al. in J Physiol 494:863–879, 1996). This coordination pattern reduces the number of degrees of freedom of the lower limb to two, i.e. the elevation angles covary along a plane in angular space. The properties of the plane that constrains the time course of the elevation angles have been extensively studied, and its orientation was found to be correlated with gait velocity and energy expenditure (Bianchi et al. in J Neurophysiol 79:2155–2170, 1998). Here, we present a mathematical model that represents the rotations of the elevation angles in terms of simple oscillators with appropriate phase shifts between them. The model explains what requirements the time courses of the elevation angles must fulfill in order for the angular covariation relationship to be planar. Moreover, an analytical formulation is proposed for both the orientation of the plane and for the eccentricity of the nearly elliptical shape that is generated within this plane, in terms of the amplitudes and relative phases of the first harmonics of the segments elevation angles. The model presented here sheds some new light on the possible interactions among the Central Pattern Generators possibly underlying the control of biped locomotion. The model precisely specifies how any two segments in the limb interact, and how a change in gait velocity affects the orientation of the intersegmental coordination plane mainly through a change in phase shifts between the segments. Implications of this study with respect to neural control of locomotion and other motor activities are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

膝关节后交叉韧带损伤对侧副韧带生物力学的影响

背景：目前对膝关节后交叉韧带损伤后的研究多集中于软骨、后外侧结构及关节的松弛度等方面。 目的：观察后交叉韧带断裂对膝关节内、外侧副韧带生物力学的影响。 方法：取12具正常成人新鲜尸体膝关节标本,在200 N载荷下,测试膝关节屈曲0°,30°,60°,90°位时,内、外侧副韧带中点的应变,后将12具标本的后交叉韧带全部切断再进行相同的测试。 结果与结论：膝屈曲0°和30°位时,后交叉韧带断裂前后内、外侧副韧带中点的应变均为压应变,且差异无显著性意义 (P > 0.05);膝屈曲30°~90°位时,内侧副韧带中点的应变随着角度增加而逐渐增大;膝屈曲60°和90°位时,后交叉韧带断裂后拉应变较断裂前明显增大(P < 0.05),其中内侧副韧带中点的应变均为拉应变,而外侧副韧带中点的应变在后交叉韧带完整情况下膝屈曲60°时为压应变。说明后交叉韧带完全断裂对30°内的膝关节运动无明显影响,但是随着屈曲角度的增加,内、外侧副韧带受到的影响逐渐增大。     

Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity

The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methy) methacrylate) (PMMA), poly(hydroxyethy) methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-CI). Bacterial and polymer surfaces were characterized by means of water contact angles and zeta potentials. Both the sessile drop contact angles and the zeta potentials of the bacterial surfaces were significantly different. No significant differences in the sessile drop contact angles of the polymer surfaces were observed. Using the Wilhelmy plate technique large contact angle hysteresis was observed for the different polymer surfaces. Surfaces of copolymers with MAA had more negative zeta potentials than those of the corresponding homopolymers. Surfaces of copolymers with TMAEMA-CI had positive zeta potentials. The highest numbers of adherent bacteria were found on materials with positive zeta potentials, irrespective of the bacterial strain used. Bacterial adhesion on to copolymers with MAA was less than on to the corresponding homopolymers. Bacterial equilibrium adhesion values correlate with the zeta potentials of the polymer surfaces (r > 0.85). On substrates with less negative zeta potentials high numbers of adhered bacteria were observed. Additionally, the equilibrium bacterial adhesion values could be related with receding contact angles of polymer surfaces with negative zeta potentials (r > 0.86). High equilibrium adhesion values were obtained for polymers with high contact angles. No correlation between the zeta potentials and contact angles of the bacteria with the adhesion values was found.     

Is there a preferred coordinate system for perception of hand orientation in three-dimensional space?

Summary The purpose of this experiment was to determine the preferred coordinate system for representation of hand orientation in 3-dimensional space. The ability of human subjects to perceive angles of the hand in 3-dimensional space (elevation, yaw, roll angles extrinsic coordinate system) was compared to their ability to perceive hand angles relative to the proximal upper limb segments (wrist joint angles, forearm pronation intrinsic coordinate system). With eyes closed, subjects performed a matching task in which the experimenter positioned the left arm, forearm and hand and the right arm and forearm. Subjects were then told to match an angle in one of the two coordinate systems by moving only the right hand at the wrist or the forearm as in pronation or roll matching. Absolute constant error (ACE), variable error (VE) and normalized variable error (NVE-normalized to tested range of motion) of matching were quantified for each subject for each of the six angles matched. It was hypothesized that matching angles in a preferred coordinate system would be associated with lower ACE, VE and NVE. Overall, ACE and VE were lower for matching hand angles in the intrinsic coordinate system. This suggests that the preferred coordinate system involved specification of hand angles relative to forearm and arm angles (joint angles) rather than the hand angles relative to axes external to the upper limb. However, matching of pronation angles was associated with larger VE and NVE than roll angle matching. There were no significant differences in ACE between pronation and roll matching. In a second experiment subjects with their forearms constrained at different elevations matched hand elevation and wrist flexion angles. Thus, errors in matching the angles in the non preferred coordinate system were predictable if the subjects were biased toward matching angles in the preferred coordinate system. Trends in the data suggested that subjects preferred matching hand elevation angles but these trends were not consistent within or between subjects. Thus a preferred intrinsic coordinate system for wrist flexion matching was not observed in this experiment. We suggest that matching angles when proximal limb segments are constrained is a simpler task for the subjects (VE lower than in the first experiment) and may bias the matching toward the extrinsic coordinate system. Thus, hand orientation in 3-dimensional space may be perceived as follows: wrist flexion and abduction angles together with forearm elevation and yaw are used to specify hand elevation and yaw; these together with hand roll angle, completely specify the hand angle in 3-dimensional space.     

不同关节角度肌肉等长最大自主收缩抗阻力训练的神经适应分析

目的 研究不同关节角度下肌肉等长最大自主收缩(maximum voluntary contraction,MVC)抗阻力训练神经适应特点.方法 将30名健康男性大学生随机分成3组,每组分别做肘关节角度在45°、90°、135° MVC等长收缩抗阻力训练,测量训练前后肱二头肌的表面肌电(surface electromy...