Static Cycling Research Articles

Rhythmic arm cycling differentially modulates stretch and H-reflex amplitudes in soleus muscle

During rhythmic arm cycling, soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition. This suppression of reflex amplitude is graded to the frequency of arm cycling with a threshold of 0.8Hz. Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition. Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2Hz. Soleus H-reflexes were evoked using single 1ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus were maintained across conditions. Stretch reflexes were evoked using a single sinusoidal pulse at 100Hz given by a vibratory shaker placed over the triceps surae tendon and controlled by a custom-written LabView program. Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity to Ia presynaptic inhibition.

Bearing capacity of the bucket spudcan foundation for offshore jack-up drilling platforms

Abstract To compare the bearing capacities of the traditional spudcan and the bucket spudcan, the effects of different type spudcans on the rigidity of pile legs and the entire bearing capacity were analyzed in detail. Through the loading method of Swipe and constant displacement, this paper plots the spatial failure envelopes of the vertical-horizontal load, vertical-moment load, vertical-horizontal-moment load of the bucket spudcan and traditional spudcan under the mode of composite loading, as well as the spatial failure envelopes of the vertical static load-vertical cycling limit load, vertical static-load horizontal cycling limit load based on these two spudcans under the mode of cycling loading. Theoretical study showed that the skirt system of bucket spudcan can increase the effective embedded depth, consequently improving the foundation rigidity and entire stiffness of a jack-up drilling platform. It is found that the bearing capacity of the horizontal load and moment load of the new spudcan is increased by at least 10% than that of the traditional spudcan, especially the horizontal load being up to 20% in the dynamic load condition. Under the action of limit storm loading condition including wind, wave and flow loads, the entire bearing capacity of the jackup rig in stiff clay is increased by about 46% with the bucket spudcan foundation compared to the traditional one.

Effect of foot/pedal position on gastrocnemius and tibialis anterior activity during static cycling

Background. The recruitment pattern of lower limb muscles during cycling is known to alter because of changes in workload and seat height. The effect of foot/pedal position is not well understood but may be useful in the prevention and management of injury. Methods. Seven healthy female subjects participated in a study. Three-foot positions on the pedal were tested in a random order: neutral, back and fore. Each subject cycled for 5 minutes at a set cadence and resistance during which 30 seconds of electromyogram data were recorded for gastrocnemius (Gast.) and tibialis anterior (TA). An electrogoniometer was located across the knee to concurrently record pedal revolutions. Analysis. To test the effect of position, an ANOVA and Tukey's post-hoc were used for Gast. However, the data from the TA were not normally distributed; therefore, a Kruskal–Wallis was used for this muscle instead. Results. No statistical significant relationship was found between foot position and TA activity (p = 0.128). However, there was a significantly (p = 0.000) lower level of activity in Gast. when the pedal was placed in the back foot position. Conclusion. Altering the position of the foot on a pedal changes the muscle activity of Gast. This is likely to be caused by the change in moment arm and may be exploited as a strategy to progress resistance during a training programme or as a method of protecting the muscle during a period of recovery. These conclusions should be interpreted with caution because of the small sample size. Copyright © 2010 John Wiley & Sons, Ltd.

Surface Activity of Surfactant Protein SP-B and SP-C in Different Lipid Environments

Pulmonary surfactant is a mixture of lipids and proteins, essential to reduce the surface tension at the air-liquid interface in the alveoli of mammalian lungs and so stabilizing the respiratory surface. Lack of an operative surfactant is associated with severe respiratory pathologies and supplementation with exogenous surfactants has been widely approached as a potential therapeutic intervention. However, the optimal lipid and protein composition of exogenous surfactants has not been properly established, and clinical surfactants currently in use differ substantially in terms of their lipid and protein moieties. In the present study we have compared the surface activity of native SP-B and /or SP-C, purified from porcine lungs, in the Captive Bubble Surfactometer (CBS), once reconstituted into two different synthetic lipid mixtures: DPPC/POPC/POPG/Chol (50:25:15:10) (lipidS), a mixture mimicking lipid composition in natural surfactant, and DPPC/POPG/Palmitic Acid (68:22:9) (lipidTA), a system widely used as a basis for clinical surfactants. We found similar equilibrium surface tensions after 5 min of adsorption of all the samples, regardless the protein and lipid system, although SP-B exhibited somehow slower initial adsorption in lipidTA. Significant differences were found in SP-B activity under quasi static compression-expansion cycling for the two lipid systems tested. In lipidTA, SP-B allowed reaching tensions near 2mN/m, whereas in lipidS surface tension did not fall below 20mN/m. However, SP-B-containing samples produced similarly low tensions, within the two lipid compositions, once cycled dynamically at physiologically relevant compression-expansion rates. Analysis of film stability under mechanical perturbations showed that SP-B introduces a significant resistance of the films to relaxation, which is particularly remarkable in lipidS samples. This stability was maximal in the simultaneous presence of SP-B and SP-C.

The Influence of Elastoplastic Deformation on the Dislocation Structure of 15Kh2MFA Steel

The paper deals with dislocation structure of 15Kh2MFA steel upon static tension and elastoplastic strain cycling is studied. The dislocation density within small-angle boundaries is shown to grow with increasing plastic tensile strain and, in the case of elastoplastic cycling, with increasing strain amplitude and number of cycles. The growth of the dislocation density within small-angle boundaries upon elastoplastic cycling results in a smaller shear stress.

Acute bilateral compartment syndrome of the thigh induced by spinning training

A 49-year-old man, was admitted in the emergency room of our hospital complaining of pain and swelling of the thighs; he had performed a particular exercise for 1h, about 48h before in a fitness centre. This exercise was the so-called “spinning”, a relatively new fitness activity, which consist of group static fast cycling. He was used to training regularly, but had never performed spinning before.

Static analysis of 3D damaged solids and structures by BEM

The boundary element method is employed for the analysis of three-dimensional (3D) brittle solids and structures, such as those composed of concrete, rock, ceramics or masonry, under static (monotonic or cycling) loading. The mechanical behavior of these solids can be successfully described by continuum damage mechanical theories. The integral formulation of the problem contains not only boundary, but also volume integrals as well, accounting for damage effects. Thus, in addition to the boundary one, an interior discretization is necessary, which can be restricted to those parts of the structure expected to behave inelastically. Isoparametric linear quadrilateral elements are used for the surface discretization and isoparametric linear hexahedra for the interior discretization. Advanced numerical integration techniques for singular and nearly singular integrals are employed. Numerical examples involving 3D concrete type structures under static loads are presented to illustrate the method and demonstrate its advantages.

The behaviour of Ni-Mn-Ga martensitic alloys in magnetic field

Some of the Ni-Mn-Ga alloys exhibit a large shape change in magnetic field. This phenomenon occurs in their martensitic state and it is called the magnetic shape memory (MSM), since these materials can change their dimensions when the direction of the magnetic field varies. This kind of behaviour can be utilised in actuators and sensors. In the present work, three different polycrystalline Ni-Mn-Ga alloys are studied. The transformation temperatures together with the ferromagnetic Curie temperatures are determined by the magnetic susceptibility measurement and confirmed by the optical differential scanning calorimetry. The structures of the alloys are investigated with the optical microscopy and the X-ray 8-28-method. The sample behaviour in magnetic field is studied both by the vibrating sample magnetometer and by measuring magnetic-field-induced strain. Also, the effect of thermal, static and dynamic magneto-thermal cycling on the behaviour of the alloys in magnetic field is studied.

Effect of Stress Cycling on Fatigue Behavior of Mica Glass Ceramics and Alumina.

In order to investigate the effect of cyclic stress on fatigue behavior of mica glass ceramics and alumina, the specimens with an indentation induced flaw were tested under static tensile loading and cycling loading at stress ratio R=0 and -1. The frequencies in the cyclic loading tests were 5 and 20 Hz respectively. The main results were as follows ; (1) A significant decrease in fatigue lifetime by cyclic loading was observed on both materials, though there being large scatters on mica glass ceramics. (2) An appreciable decrease in fatigue lifetime due to the increase of frequency was observed on mica glass ceramics, while a little effect of frequency was observed on alumina. (3) The effect of stress ration under cyclic loading was small on both materials, though a somewhat significant decrease in fatigue lifetime being observed in the case of frequency of 20 Hz on alumina. (4) SEM fractography revealed a dominant interglanular fracture on both materials, but in the case of cyclic fatigue fracture of alumina more comminution was observed than in the case of static fatigue fracture. (5) It was considered that the decrease in fatigue lifetime due to cyclic loading in mica glass ceramics results on the degradation of grain briding effect by the pull-out of mica from glass matrix, while the effect of cyclic stress in alumina results on the degradation of grain bridging effect by comminution and fretting in the grain.

Any questions: Physical activity is best for back pain

Several of my patients who suffer with low back pain and stiffness tell me that swimming or static cycling temporarily ease their symptoms. What is the explanation for this? The traditional recommendation for people with back problems is periods of bed rest until they resolve. We now know that advice is wrong, and indeed …

Microstructural Stability of Directionally Solidified Eutectic NiAl-Mo Under Static and Thermal Cycling Conditions

ABSTRACTThe quasi-binary eutectic NiAl-9% Mo with faceted molybdenum fibers was subjected to both thermal annealing conditions and to annealing under thermal cycling conditions to determine the microstructural stability of this alloy. The static temperature tests were run at 0.85TM- 0.97TMin an argon gas atmosphere. The thermal cycling tests were performed between temperatures of 700°C and 1200°C by induction heating disk-shaped specimens in an argon gas atmosphere using time-temperature heating and cooling profiles to approximate potential engine applications. To quantify microstructural changes, the fiber size and size distribution and number of fibers per unit area were measured as a function of time at temperature. The overall results demonstrate that the directionally solidified eutectic NiAl-9Mo subjected to thermal fatigue conditions exhibits cell boundary coarsening and large shape changes, whereas the microstructure under static stress-free annealing is stable.

Plasma‐enhanced deposition of diamond‐like carbon films on high temperature tolerant polymers

AbstractThe feasibility of depositing carbon films with a diamond‐like structure on high temperature polymers, using established plasma‐enhanced chemical vapor deposition techniques, is explored. Potential uses for such a film will depend upon the adhesion of the film to the substrate, the properties of the deposited film, and the effect of the deposition process on the bulk properties of the polymer substrate.Amorphous carbon (diamond‐like carbon) coatings with thicknesses ranging from 2 to 18 μm were deposited on polyimide substrates at temperatures below 420°C. Extended exposure to the plasma processing conditions caused no visible damage but halved the room‐temperature tensile strength of the polymer films. Diamond‐like carbon, graphitic carbon, and a precursor to the diamond‐like carbon structure, attributed to an aromatic carbon ring structure, were observed. The optical transparency of the coated polymer film was attenuated uniformly across the spectral range, 2.5‐22 μm. Static oxidation and limited thermal cycling of the coated polymer produced no widespread delamination of the coating from the substrate: neither the deposited film nor the coated regions of the polymer showed any effect when oxidized at 370°C, for 450 h. © 1994 John Wiley & Sons, Inc.

Effect of multilayer structure and laser pulse width on the reversible cycling of phase change optical storage media

The static cycling behavior of chalcogenide phase change optical recording media was investigated. Thin-film multilayer structure and laser pulse conditions were both varied to determine optimum conditions for good cycling behavior. For all structures, cyclability was always best for short pulses. An aluminum overcoat layer was found to substantially increase the performance. The effect of the temperature excursion experienced during writing on cycling was determined. At the shortest pulses it was demonstrated that the thermal excursions did not depend upon the presence of an aluminum overcoat, suggesting that mechanical strength was important for enhancing cyclability. For longer pulses the aluminum changed the thermal characteristics of the stack. These differences between various samples are compared to try to elucidate modes of failure in optical data storage structures.

Effects of static and dynamic stress on the piezoelectric and dielectric properties of PVF2

The effects of hydrostatic stress on the piezoelectric constants d33, g33, and the dielectric constant K33T of thick film EMI PVF2 are investigated. The results show that the non-voided form of thick film PVF2 suffers little degradation at pressures of 70 MPa. The voided form of PVF2, although suffering considerable degradation at 25 MPa, still exhibits acceptable properties at this pressure. Data are also presented on the effects of static stress cycling on the material constants of voided and nonvoided thick film PVF2. The nonvoided form can withstand repeated cycles to 70 MPa without progressive degradation. On the other hand, the voided sample will only withstand repeated pressure cycles to 25 MPa. The linearity of these materials was also determined to show considerable nonlinearity for the voided samples. The application of PVF2 as a shock sensor was also discussed.