Front crawl stroke in swimming: Phase durations and self-similarity.

Human movements, such as walking and running, are able to generate rhythmic motor patterns, with the consequent appearance of hidden time-harmonic structures. Such harmonic structures are represented (at comfortable speed) by the occurrence of the golden ratio as ratio of durations of specific walking and running gait sub-phases. Preliminary experimental evidences suggest that front crawl swimming may behave, under this point of view, like walking and running. This paper aims to demonstrate that a mathematical connection between the golden ratio and the front crawl swimming stroke actually exists, at a pace that plays the role of the comfortable speed in walking and running. Generalized Fibonacci sequences are used to this purpose. They rely on the durations of aggregate phases of the front crawl swimming stroke with a clear physical meaning, while characterizing self-similarity of front crawl strokes in its simple nature and enhanced (stronger) variant. Experimental data on front crawl swimmers illustrate the theoretical derivations, suggesting that the pace playing the role of the comfortable speed in walking and running is the middle/long-distance one, while showing that the self-similarity level increases with the swimming technique and the enhanced self-similarity is associated with the performance of top-level swimmers.

Sarcopenic obesity: etiology and lifestyle therapy.

OBJECTIVE: Sarcopenic obesity (OS) is a multifactorial condition characterized by the simultaneous presences of sarcopenia and obesity. The prevalence of OS is increasing in adults over 65 years of age; people with OS present greater health risks than people who are only sarcopenic or obese. Therefore, the study of OS and the search for effective treatment are important due to the constant increase of the elderly population. MATERIALS AND METHODS: This review discusses the etiology and evolutionary mechanisms of OS while exploring its molecular, metabolic, oxidative, inflammatory, hormonal, and nutritional stresses. Studies have tried to unravel the causes related to the onset of sarcopenia, which is responsible for the decrease of muscle mass and strength in elderly subjects. The diagnostic criteria and the methods of evaluation of OS are described in these research studies, although there is no univocal definition for these parameters. The most studied treatments in OS are illustrated and highlight how the physical activity performed through both aerobic and resistance exercises, as well as a correct nutritional treatment, prove to be the most effective interventions in the regression of the pathology and in the improvement of physical function. RESULTS: New therapies for OS are hypothesized that will open the way to other possible types of intervention in the future. CONCLUSIONS: The deficiency of muscle mass in obese elderly subjects will be one of the health challenges of the future to reduce the risk of chronic diseases.

Footstep manipulation during uphill running.

The present study investigated the effects of step frequency manipulation during training on slopes (2%) on biomechanical parameters at Iso-Efficiency Speed (without increasing the metabolic demand). 24 male marathon runners were randomly allocated to one of 2 training groups for 3 weeks: step frequency manipulation group (SFM, n=12) and free step frequency group (SFF, n=12). Lower limb kinematic parameters were measured before and after the 3 weeks training. The SFM group increased step length 4.30% (p<0.001), flight time 29.48% (p<0.001) and decreased contact time 14% (p<0.01). These findings coincide with characteristics of better running performances. The SFF group did not elicit such results. The results from the study could help coaches to devise training methods which could improve an athlete's performance through increasing step length. The method provided may aid faster race times for athletes.

Uphill running at iso-efficiency speed.

The purpose of this study was to investigate the effects of slopes (0%, 2% and 7%) on temporal gait kinematics during running at iso-efficiency speed (IES). 65 male marathon runners were selected for this study. A single digital camera (210 Hz) was used to record motion; Dartfish5.5Pro was used to perform 2-dimensional (2D) video analysis and heart rate was recorded during the test. The parameters considered in this study were: step length (SL), flight time (FT), step frequency (SF), contact time (CT) and heart rate (HR). The results showed SL, FT and SF decreased as a result of the increasing treadmill gradient; SL=[(0-2%=8.38%, p<0.0001), (0-7%=23.61%, p<0.0001)]; FT=[(0-2%=8.92%, p<0.02), (0-7%=23.40%, p<0.0001)]; SF=[(0-2%=1.18%), (0-7%=4.02%, p<0.001)]. The CT and HR however increased with the increasing gradient CT=[(0-2%=9.06% p<0.0001), (0-7%=25.64%, p<0.0001)]; HR=[(0-2%=1.65%), (0-7%=3.58%)]. These results show a different trend of the footstep's kinematic parameters when running on a slope at IES. Moreover, we can calculate the optimal run speed on a slope without increasing the metabolic demand.

Kinematic analysis of soccer players in shuttle running.

The intermittent shuttle running test is mainly used within soccer to assess aerobic power. For this reason we studied kinematic parameters and heart rate at both an increasing speed, [Yo-Yo Endurance Lv 1 (Y1)] and at constant velocity [95% maximal aerobic velocity (MAV(95%))]. 12 soccer players were selected for this study. A high-speed digital camera (210 Hz) was used to record motion; Dartfish5.5Pro was used to perform 2D video analysis and heart rate was also recorded and computed during the test. The parameters considered (baseline measures with respect to the end of each test) in this study were: step length (SL), contact time (CT) and heart rate (HR). SL: 40% in Y1 and -22% in MAV(95%). CT: -31% in Y1 and 29% in MAV(95%). HR: increased 96% in Y1 and 17% in MAV(95%). These results highlight 2 different neuromechanical strategies adopted under fatigued conditions. In light of the clear changes of the CT in MAV(95%) (29%) and with respect to the moderate changes in HR (17%) it is clear that the CT is the most important parameter, as it experiences greater adaptations associated with neuromuscular patterns, under a fatigued condition as opposed to HR.

THz-waves channeling in a monolithic saddle-coil for Dynamic Nuclear Polarization enhanced NMR.

A saddle coil manufactured by electric discharge machining (EDM) from a solid piece of copper has recently been realized at EPFL for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance experiments (DNP-NMR) at 9.4 T. The corresponding electromagnetic behavior of radio-frequency (400 MHz) and THz (263 GHz) waves were studied by numerical simulation in various measurement configurations. Moreover, we present an experimental method by which the results of the THz-wave numerical modeling are validated. On the basis of the good agreement between numerical and experimental results, we conducted by numerical simulation a systematic analysis on the influence of the coil geometry and of the sample properties on the THz-wave field, which is crucial in view of the optimization of DNP-NMR in solids.

Pushing the limit of liquid-state dynamic nuclear polarization at high field.

Dynamic nuclear polarization in the liquid state was predicted more than 50 years ago by Overhauser. Its application for NMR sensitivity enhancement has been limited because of intrinsic and experimental problems to apply this method at high magnetic fields. Here we report on 95 GHz DNP experiments using the common TEMPO radical dissolved in water. In an efficient non-radiative microwave resonator, we observe average experimental enhancement factors up to -65. The local enhancement in the center of the resonator is calculated to reach a level of -94 at the highest microwave power. At high microwave power, the DNP enhancement shows a linear increase with no tendency to saturation. The results indicate that a substantial sensitivity enhancement is possible for liquid state NMR in nL sample volumes.

High-frequency EPR applications of open nonradiative resonators.

A new class of open single-mode cavities, the nonradiative (NR) resonators, has recently been proposed in order to overcome the limitations of standard cylindrical cavities and Fabry-Perot resonators at millimeter wavelengths. This paper presents the first applications of a NR resonator in W-band pulsed electron paramagnetic resonance spectroscopy. It consists of a cylindrical cavity having a lateral aperture that represents about 35% of its total height. Electron-spin-echo measurements performed on different samples show that the signal-to-noise ratio and the optimal pulse length obtained with the proposed device are comparable to those obtained with the closed cavity used in the commercial W-band spectrometer, at both cryogenic and room temperature. Similar results have been obtained for paramagnetic species optically activated by means of an optical fiber inserted in the aperture of the resonator. The insertion losses estimated for the probe employed with the NR resonator are higher than those of the commercial probe, hence, demonstrating that the proposed cavity holds the promise of improved resonator performance.

High frequency single-mode resonators for EPR spectroscopy enabling rotations of the sample about two orthogonal axes.

A novel single-mode resonant structure which enables the rotation of the sample about two orthogonal axes is investigated in view of electron paramagnetic resonance applications. The proposed solution is based on cylindrical non-radiative resonators laterally loaded by the sample holder. The resulting structure can still operate in non-radiative regime, although no longer rotationally invariant. These theoretical predictions, based on symmetry considerations, are confirmed by means of a finite element numerical modelling. Theoretical and computational results are then substantiated by experimental investigations at millimeter wavelengths. As a result, a single-mode resonator which enables all the relevant rotations of the sample is demonstrated at millimeter wavelengths for the first time. In this resonator the intensity of the microwave field on the sample and its orientation with respect to the static magnetic field can be kept constant during the rotations. Therefore, a complete characterization of anisotropic systems is possible at the highest sensitivity, without the need of split-coil magnets. Possible applications at very high frequencies are discussed.

Effects of whole-body vibration exercise on the endocrine system of healthy men.

Whole-body vibration is reported to increase muscle performance, bone mineral density and stimulate the secretion of lipolytic and protein anabolic hormones, such as GH and testosterone, that might be used for the treatment of obesity. To date, as no controlled trial has examined the effects of vibration exercise on the human endocrine system, we performed a randomized controlled study, to establish whether the circulating concentrations of glucose and hormones (insulin, glucagon, cortisol, epinephrine, norepinephrine, GH, IGF-1, free and total testosterone) are affected by vibration in 10 healthy men [age 39 +/- 3, body mass index (BMI) of 23.5 +/- 0.5 kg/m2, mean +/- SEM]. Volunteers were studied on two occasions before and after standing for 25 min on a ground plate in the absence (control) or in the presence (vibration) of 30 Hz whole body vibration. Vibration slightly reduced plasma glucose (30 min: vibration 4.59 +/- 0.21, control 4.74 +/- 0.22 mM, p=0.049) and increased plasma norepinephrine concentrations (60 min: vibration 1.29 +/- 0.18, control 1.01 +/- 0.07 nM, p=0.038), but did not change the circulating concentrations of other hormones. These results demonstrate that vibration exercise transiently reduces plasma glucose, possibly by increasing glucose utilization by contracting muscles. Since hormonal responses, with the exception of norepinephrine, are not affected by acute vibration exposure, this type of exercise is not expected to reduce fat mass in obese subjects.

Complex response function of magnetic resonance spectrometers.

A vectorial analysis of magnetic resonance spectrometers, based on traveling wave resonators and including the reference arm and the automatic control of frequency, has been developed. The proposed model, valid also for stationary wave resonators, gives the response function of the spectrometer for any working condition, including scalar detectors with arbitrary response law and arbitrary excitation frequency. The purely dispersive and purely absorptive linear responses are discussed in detail for different scalar detectors. The developed approach allows for optimizing the performances of the spectrometer and for obtaining the intrinsic lineshape of the sample in a very broad range of working conditions. More complex setups can be modeled following the proposed scheme.

High-field, multifrequency EPR spectroscopy using whispering gallery dielectric resonators.

High-field/high frequency EPR spectroscopy measurements are shown. Experiments were carried out at 240- and 316-GHz frequencies. The employed apparatus uses a novel combination of far infrared molecular lasers and of probehead exploiting dielectric resonators working in the whispering gallery modes. This approach constitutes a relatively simple method of multifrequency EPR spectroscopy and opens appealing perspectives in high-sensitivity EPR spectroscopy up to the THz regime.