Muscle recruitment during plyometric exercises in overhead athletes with and without shoulder pain

ObjectivesTo investigate if there is a difference in muscle activity patterns during high load plyometric shoulder exercises between overhead athletes with and without shoulder pain.DesignControlled laboratory EMG study.SettingUniversity EMG Laboratory.ParticipantsSixty overhead athletes, 30 with shoulder pain and 30 healthy controls were included.Main outcome measuresThe EMG activity of Upper Trapezius (UT), Middle Trapezius (MT), Lower Trapezius (LT), Serratus Anterior (SA), Latissimus Dorsi (LD) and Pectoralis Major (PM) on the tested side and bilateral on Abdominal Obliques Externus (OE) muscles was registered with wireless surface EMG during 3 rotational plyometric shoulder exercises in 3 positions, prone, sidelying and standing.ResultsA significant higher muscle activity was found in the shoulder pain group for MT together with an overall significant higher activity in the thoraco-humeral and abdominal muscles compared to healthy controls.ConclusionsWhen rehabilitating the overhead athlete with shoulder pain, shoulder muscles together with both thoraco-humeral and abdominal muscles need to be engaged.     

The effect of age on elbow range of motion in pitchers

BackgroundAlteration of elbow range of motion (ROM) has been observed in baseball pitchers. This study aims to compare dominant elbow ROM between early-puberty, late-puberty, and young–adult pitchers.MethodsWe recruited 62 pitchers, consisting of 17 early-puberty (mean age 13.1 years old), 22 late-puberty (mean age 17.7 years old), and 23 young–adult players (mean age 19.4 years old). Dominant elbow ROMs was measured. One-way ANOVA was used to compare the differences in elbow ROM variables between 3 groups.ResultsLate-puberty pitchers exhibited a significantly lower elbow hyperextension and flexion than early-puberty or young–adult pitchers (P < .05). Valgus angle was significantly lower in young–adult (7.7°±5.5°) versus early-puberty (12.1°±2.3°) and late-puberty pitchers (13.0°±4.1°; P < .05). Young–adult pitchers had the largest forearm supination range (101.2°±18.1°), followed by early-puberty (82.5°±6.5°; P < .05) and late-puberty pitchers (70.6°±15.8°). Elbow flexion-hyperextension total range was smallest in late-puberty pitchers (130.3°±7.4°), followed by young–adult (142.6°±9.3°) and early-puberty pitchers (144.6°±8.3°; P < .05). Forearm pronation–supination total range was also smallest in late-puberty pitchers (142.0°±20.3°), followed by early-puberty (159.8°±9.5°) and young–adult pitchers (177.2°±20.8°; P < .05).ConclusionsThese results indicate that careful monitoring of the elbow and forearm range of motion should be undertaken in adolescent baseball pitchers to prevent and or minimize injury risk.     

A Compact Band-Pass Filter with High Selectivity and Second Harmonic Suppression

The design of a novel band-pass filter with narrow-band features based on an electromagnetic resonator at 6.4 GHz is presented. A prototype is manufactured and characterized in terms of transmission and reflection coefficient. The selective passband and suppression of the second harmonic make the filter suitable to be used in a C band frequency range for radar systems and satellite/terrestrial applications. To avoid substantial interference for this kind of applications, passive components with narrow band features and small dimensions are required. Between 3.6 GHz and 4.2 GHz the band-pass filter with harmonic suppression should have an attenuation of at least 35 dB, whereas for a passband, less than 10% is sufficient.     

Films of Carbon Nanomaterials for Transparent Conductors

The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Doped metal oxides, especially indium tin oxide, are the commonly used materials for transparent conductors. As there are some drawbacks to this class of materials, exploration of alternative materials has been conducted. There is an interest in films of carbon nanomaterials such as, carbon nanotubes and graphene as they exhibit outstanding properties. This article reviews the synthesis and assembly of these films and their post-treatment. These processes determine the film performance and understanding of this platform will be useful for future work to improve the film performance.     

Superiority of the limb leads over the precordial leads on the 12-lead ECG in monitoring fluctuating fluid overload in a patient with congestive heart failure

A 78-year old woman with congestive heart failure had fluctuating peripheral edema and weights while hospitalized and was subsequently followed in the cardiac clinic. Sums of the amplitudes of the QRS complexes for the leads I + II (∑QRS_{I + II}), the 6 limb leads (∑QRS_6L), the 6 precordial leads (∑QRS_V1-V6), and all 12 leads (∑QRS_12L) were calculated. Analysis showed that ∑QRS_{I + II} and ∑QRS_6L correlated very well with corresponding weights (r = 0.78, P .01 and r = 0.75, P = .02, respectively), whereas ∑QRS_V1-V6 and ∑QRS_12L did not (r = 0.20, P = .60 and r = 0.47, P = .20, respectively). The reason for the poor correlation of the latter two was the erratic values of ∑QRS_V1-V6 in serial electrocardiogram recordings. ∑QRS_{I + II} and ∑QRS_6L are useful for serially following patients with congestive heart failure and peripheral edema.     

Ultrahigh electrical conductivity in solution-sheared polymeric transparent films

With consumer electronics transitioning toward flexible products, there is a growing need for high-performance, mechanically robust, and inexpensive transparent conductors (TCs) for optoelectronic device integration. Herein, we report the scalable fabrication of highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films via solution shearing. Specific control over deposition conditions allows for tunable phase separation and preferential PEDOT backbone alignment, resulting in record-high electrical conductivities of 4,600 ± 100 S/cm while maintaining high optical transparency. High-performance solution-sheared TC PEDOT:PSS films were used as patterned electrodes in capacitive touch sensors and organic photovoltaics to demonstrate practical viability in optoelectronic applications.Conductive films of high optical transparency are required in a myriad of applications, including electromagnetic shielding, antistatic layers, lighting displays, touch sensors, and as electrodes for photovoltaics (1, 2). As flexible, lightweight displays for televisions and portable consumer electronics become closer to reality, emerging transparent conductors (TCs) need to be mechanically robust (3). An ideal TC, therefore, should have a sheet resistance <100 Ω/□, transmissivity greater than 0.90, and be inherently flexible, all while remaining inexpensive to process on a mass scale (4).Indium tin oxide (ITO) is the most widely used TC material due to the combination of low sheet resistance and high transparency when grown on a variety of substrates. Although common to use, ITO is an expensive material due to the requirement for vacuum deposition and a number of postprocessing steps (5). For example, in organic photovoltaic (OPV) modules ITO was estimated to represent 24% of the module cost (6). However, alternative transparent conductor materials, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are estimated to comprise only ∼1% of an OPV module cost. Additionally, ITO is not compatible with flexible applications, because small applied strains of as little as 4.5% lead to an order of magnitude increase in the resistance (7).In recent years there have been a number of emerging TC materials studied in the literature ranging from metal nanowires (Au, Ag, Cu) (8–11), conducting carbon allotropes (graphene, carbon nanotubes) (12–15), conducting polymers (16, 17), and other hybrid approaches (18). Recent attempts using metal nanotroughs by Wu et al. have resulted in superior optoelectronic properties with a sheet resistance of 2 Ω/□ at 90% transmission (19). The use of metal mesoscale grids further enhanced the properties of metal nanowires electrodes to a sheet resistance of 0.36 Ω/□ at 92% transmission (20). Although metal nanowires combine low resistance and high transparency, they have inferior flexibility and stretchability compared with polymer-based TCs (3).PEDOT:PSS consists of insoluble PEDOT that is charge stabilized by PSS (Fig. 1A), which affords good solubility in aqueous formulations. Within these solutions, PEDOT:PSS forms micelles where hydrophilic PSS is in contact with water and hydrophobic PEDOT is located in the micelle core (21). Upon spin-coating from solution, the micelles are deposited as a film and can have conductivities on the order of ∼1 S/cm (22). Subsequent annealing, treatment with cosolvents, and postprocessing steps can increase the conductivity of films to over 3,000 S/cm (23, 24). High-performing spin-cast PEDOT:PSS TCs have reached a sheet resistance of 46 Ω/□ at 90% transmission (25, 26). Furthermore, it is compatible with flexible electronics as films can withstand over 90% applied strain without electrical breakdown (7).Open in a separate windowFig. 1.Schematic of solution shearing process. (A) Chemical structure of PEDOT:PSS. (B) Schematic of the solution shearing design and (C) patterning PEDOT:PSS via selective patterning of solvent wetting and dewetting regions.There is a wide variety of solution processing techniques used to deposit uniform, low-roughness films (27). Spin-casting is a popular laboratory-scale deposition technique due to its simplicity and ability to deposit high-quality films with a variety of materials. However, it is a batch process that is difficult to implement on a continuous mass production scale. Furthermore, it is difficult to use elevated substrate temperatures during spin-coating, a parameter that may play a role in the final film characteristics. Contrarily, scalable fabrication through solution shearing allows for tunable deposition conditions which enable enhanced kinetic control resulting in large impacts on the electrical performance of organic electronics (28–30).In this work we use solution shearing to fabricate high-performance TC PEDOT:PSS films (Fig. 1B). Tunable control of PEDOT backbone orientation, local ordering, and phase separation is demonstrated via precise control of the deposition parameters. Record-high PEDOT:PSS conductivities of 4,600 ± 100 S/cm are obtained and reach a sheet resistance of 17 ± 1 Ω/□ at 97.2 ± 0.4% transmission. A patterning method (Fig. 1C) is also developed which enables the use of high-conductivity transparent conductive films in capacitive pressure sensors and OPV devices.     

Arterial Compression during Overhead Throwing: A Risk for Arterial Injury?

Case studies reporting aneurysm formation in the axillary artery have been described in overhead throwing athletes, possibly due to repetitive arterial compression by the humeral head that has been transiently observed during sonographic diagnostic arm manoeuvres. Whether compression negatively alters arterial health has not been investigated and was the focus of this study. The throwing arm of elite overhead athletes was screened for inducible axillary artery compression. Compressors (COMP, n = 11, mean age: 20 (SD: 2) year, 7 male, 4 female) were age and sex matched with noncompressing (NONCOMP) athlete controls. Four indices of arterial health (flow mediated dilation [FMD], conduit artery vasodilatory capacity [CADC], glyceryl-trinitrate [GTN]-induced vasodilation and intima-media thickness [IMT]) were assessed with high-resolution ultrasound at the brachial and the axillary, artery. No significant between-group differences were observed at the brachial, or axillary, artery for FMD (brachial: COMP: mean (SD) 6.2 (3.1)%, NONCOMP: 6.1 (3.5)%, p = 0.967, axillary: COMP: 8.0 (5.5)%, NONCOMP: 9.0 (3.6)%, p = 0.602), CADC (brachial: COMP: 10.4 (3.4)%, NONCOMP: 10.4 (5.4)%, p = 0.999, axillary: COMP: 9.6 (4.2)%, NONCOMP: 8.5 (3.2)%, p = 0.492), GTN-induced vasodilation (brachial: COMP: 17.9 (5.1)%, NONCOMP:14.1 (7.2)%, p = 0.173, axillary: COMP: 9.5 (4.3)%, NONCOMP: 7.7 (3.1)%, p = 0.302) or IMT (brachial: p = 0.084, axillary: p = 0.581). These results suggest that transient arterial compression, observed during diagnostic arm manoeuvres in overhead throwing athletes, is not associated with abnormal indices of artery function or structure and that other mechanisms must be responsible for the published cases of aneurysm formation in elite athletes performing overhead throwing actions. (E-mail: c.stapleton@ljmu.ac.uk)     

电力电缆导体压接型连接金具相关标准的讨论

我国电缆导体及导体压接型连接金具产品标准相对滞后于电力电缆产品及连接金具产品的发展,高于35kV的电缆导体连接金具尚无参考试验标准。不利于保证电力电缆安全稳定运行、不利于电缆线路的动态增容等工作的开展。