Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

We monitored the displacement and seismic activity of an unstable vertical rock slice in a natural limestone cliff of the southeast Vercors massif, southeast France, during the months preceding its collapse. Displacement measurements showed an average acceleration of the movement of its top, with clear increases in the displacement velocity and in the discrete seismic event production rate during periods where temperature falls, with more activity when rainfall or frost occurs. Crises of discrete seismic events produce high amplitudes in periodograms, but do not change the high frequency base noise level rate. We infer that these crises express the critical crack growth induced by water weakening (from water vapor condensation or rain) of the rock strength rather than to a rapid change in applied stresses. Seismic noise analysis showed a steady increase in the high frequency base noise level and the emergence of spectral modes in the signal recorded by the sensor installed on the unstable rock slice during the weeks preceding the collapse. High frequency seismic noise base level seems to represent subcritical crack growth. It is a smooth and robust parameter whose variations are related to generalized changes in the rupture process. Drop of the seismic noise amplitude was concomitant with the emergence of spectral modes – that are compatible with high-order eigenmodes of the unstable rock slice – during the later stages of its instability. Seismic noise analysis, especially high frequency base noise level analysis may complement that of inverse displacement velocity in early-warning approaches when strong displacement fluctuations occur

Effects of a primary rehabilitation programme on arterial vascular adaptations in an individual with paraplegia

AbstractObjectiveEvaluation of the effects of 6 weeks of wheelchair endurance training on arterial stiffness in an individual with paraplegia.MethodsA 22-year-old male patient with complete (ASIA A) paraplegia (T11) was tested before and after training (30minutes three times per week). Physical performance and cardiorespiratory response were evaluated during a maximal progressive test. Heart rate (HR), blood pressure, stroke volume and arterial carotid–wrist and carotid–ankle pulse wave velocity (PWV) were measured at rest.ResultsMaximal responses registered (maximal tolerated power, V˙O2 peak) during the exercise test were increased after training. At rest, HR as PWV decreased, whereas cardiac output and blood pressure remained constant.ConclusionContinuous exposure of the subject to a repeated high intensity exercise bout for 6 weeks elevated fitness level. Such a regular practice might also constitute a major way to trigger vascular remodelling beyond to the trained body part

Evaluation of «CODESNA HRV», software dedicated to analysis of heart rate variability and his use in sport domain

La Variabilidad de la Frecuencia Cardiaca (VFC) es un método simple y no-invasivo que permite la evaluación del sistema cardiovascular y de su regulación extrínseca por el Sistema Nervioso Autónomo SNA. Usualmente, éste método es utilizado en el ámbito deportivo como marcador biológico cuantificador de adaptaciones fisiológicas logradas posterior a cargas de entrenamiento, buscando evitar sobre-cargas o sobre-entrenamiento en los atletas. En consecuencia, estudios han desarrollado herramientas para el análisis de la VFC, sin embargo, actualmente no existe un instrumento para análisis dinámicos, en tiempo real y diferenciando vías simpática y parasimpática. En respuesta, el software CODESNA HRV pro-pone un nuevo sistema de tratamiento de información que responde a las necesidades planteadas

Does Characterizing Global Running Pattern Help to Prescribe Individualized Strength Training in Recreational Runners?

This study aimed to determine if concurrent endurance and strength training that matches the global running pattern would be more effective in increasing running economy (RE) than non-matched training. The global running pattern of 37 recreational runners was determined using the Volodalen <sup>®</sup> method as being aerial (AER) or terrestrial (TER). Strength training consisted of endurance running training and either plyometric (PLY) or dynamic weight training (DWT). Runners were randomly assigned to a matched (n = 18; DWT for TER, PLY for AER) or non-matched (n = 19; DWT for AER, PLY for TER) 8 weeks concurrent training program. RE, maximal oxygen uptake V̇O <sub>2</sub> max) and peak treadmill speed at V̇O <sub>2</sub> max (PTS) were measured before and after the training intervention. None of the tested performance related variables depicted a significant group effect or interaction effect between training and grouping (p ≥ 0.436). However, a significant increase in RE, V̇O <sub>2</sub> max, and PTS (p ≤ 0.003) was found after the training intervention. No difference in number of responders between matched and non-matched groups was observed for any of the performance related variables (p ≥ 0.248). In recreational runners, prescribing PLT or DWT according to the global running pattern of individuals, in addition to endurance training, did not lead to greater improvements in RE

Greater fatigability in knee-flexors vs. knee-extensors after a standardized fatiguing protoco

The present study aimed to investigate the effects of a standardized fatiguing protocol on central and peripheral fatigue in knee-flexors and knee-extensors. Thirteen healthy men (age: 23\u2009\ub1\u20093 years; height: 1.78\u2009\ub1\u20090.09 m; body-mass: 73.6\u2009\ub1\u20099.2\u2005kg) volunteered for the present study. Maximal voluntary contraction (MVC), Electromyography (EMG) activity, voluntary activation level (VAL) as an index of central fatigue and twitch potentiation as an index of peripheral fatigue were measured before and after the fatiguing protocol. The fatiguing protocol consisted of a 0.6 duty-cycle to exhaustion (6\u2005s isometric contraction, 4\u2005s recovery) at 70% MVC. After the fatiguing protocol, MVC decreased in both (Effect-size (ES)\u2009=\u20091.14) and knee-extensors (ES\u2009=\u20091.14), and EMG activity increased in both knee-flexors (ES\u2009=\u20092.33) and knee-extensors (ES\u2009=\u20091.54). Decreases in VAL occurred in knee-flexors (ES\u2009=\u20090.92) but not in knee-extensors (ES\u2009=\u20090.04). Decreases in potentiation occurred in both knee-flexors (ES\u2009=\u20090.84) and knee-extensors (ES\u2009=\u20090.58). The greater central occurrence of fatigue in knee-flexors than in knee-extensors may depend on the different muscle morphology and coupled with a greater tolerance to fatigue in knee-extensors. The present data add further insight to the complicated knee-flexors-to-knee-extensors strength relationship and the mechanisms behind the different occurrence of fatigue

The match-play sprint performance of elite senior hurlers during competitive games

The typical sprint profile in elite hurling has yet to be established. The purpose of this study was to investigate the sprinting demands of elite hurling competition and characterize the sprinting patterns of different playing positions. GPS (10-Hz, STATSports Viper) were used to collect data from 51 hurlers during 18 games. The total sprint ( 6522 km\ub7h-1) distance (TSD), the number of sprints (NOS) classified as length (<20 m, 6520 m) and relative speed thresholds (<80%, 80-90%, >90%), the between-sprint duration and the number of repeated-sprint bouts ( 652 sprints in 6460 s) were analyzed. The NOS was 22.2 \ub1 6.8 accumulating 415 \ub1 140 m TSD. The NOS <20 m, 6520 m was 14.0 \ub1 4.7 and 8.1 \ub1 3.6 respectively. The NOS <80%, 80-90% and >90% was 10.6 \ub1 4.3, 8.2 \ub1 3.6, 3.4 \ub1 2.4 respectively. The between-sprint duration and the repeated-sprint bouts were 208 \ub1 86 s and 4.5 \ub1 2.6 respectively. TSD (ES = -0.20), NOS (ES = -0.34), NOS <20 m (ES = -0.33), 6520 m (ES = -0.24), 80-90% (ES = -0.35) >90% (ES = -0.13) and repeated-sprint bouts (ES = -0.28) decreased between-halves. Full-backs performed a lower NOS <80% than half-backs (ES = -0.66) and a shorter mean duration of sprints than half-backs (ES = -0.75), midfielders (ES = -1.00) and full-forwards (ES = -0.59). These findings provide a sprint profile of elite hurling match-play that coaches should consider to replicate the sprint demands of competition in training

Investigation of finger reflectance photoplethysmography in volunteers undergoing a local sympathetic stimulation

Optical sensors used in clinical applications have gained great popularity over the last few decades, especially the photoplethysmographic (PPG) technique used in estimating arterial blood oxygen saturation in the well-known medical devices called pulse oximeters. In this study we investigate the photoplethysmogram further in an effort to understand its origin better, as there is a significant void in the current knowledge on the PPG quantitative measurement. The photoplethysmographic signal provides a heart rhythm pulsating AC component, and a non-pulsating DC component. The signal is commonly believed to originate from tissue volume changes only and hasn't been investigated intensively. This in vivo study examines the source of the PPG signal in relation to pulse amplitude and pulse rhythm while volunteers undergo a right hand ice immersion. It was found that the PPG signal is sensitive in detecting the sympathetic stimulation which corresponds to volumetric and heart rate changes. During the immersion, AC pulse amplitudes (PA) from both hands decreased significantly, while DC levels increased significantly in the right hand and non-significantly in the left hand. Also, a significant decrease in the pulse repetition time (PRT) was observed. Using blood pressure-flow theories, these results suggest that there are possibly other factors in the blood flow regulation that alter the blood optical density which contributes to the detected signal. Further studies need to investigate PPGs in relation to blood optical density and the dynamics of the pulsatile flow effects besides volumetric changes. Such investigations might explore further applications of the PPG in medicine