2D characterization of near-surface V P/V S: surface-wave dispersion inversion versus refraction tomography

International audienceThe joint study of pressure (P-) and shear (S-) wave velocities (Vp and Vs ), as well as their ratio (Vp /Vs), has been used for many years at large scales but remains marginal in near-surface applications. For these applications, and are generally retrieved with seismic refraction tomography combining P and SH (shear-horizontal) waves, thus requiring two separate acquisitions. Surface-wave prospecting methods are proposed here as an alternative to SH-wave tomography in order to retrieve pseudo-2D Vs sections from typical P-wave shot gathers and assess the applicability of combined P-wave refraction tomography and surface-wave dispersion analysis to estimate Vp/Vs ratio. We carried out a simultaneous P- and surface-wave survey on a well-characterized granite-micaschists contact at Ploemeur hydrological observatory (France), supplemented with an SH-wave acquisition along the same line in order to compare Vs results obtained from SH-wave refraction tomography and surface-wave profiling. Travel-time tomography was performed with P- and SH- wave first arrivals observed along the line to retrieve Vtomo p and Vtomo s models. Windowing and stacking techniques were then used to extract evenly spaced dispersion data from P-wave shot gathers along the line. Successive 1D Monte Carlo inversions of these dispersion data were performed using fixed Vp values extracted from Vtomo p the model and no lateral constraints between two adjacent 1D inversions. The resulting 1D Vsw s models were then assembled to create a pseudo-2D Vsw s section, which appears to be correctly matching the general features observed on the section. If the pseudo-section is characterized by strong velocity incertainties in the deepest layers, it provides a more detailed description of the lateral variations in the shallow layers. Theoretical dispersion curves were also computed along the line with both and models. While the dispersion curves computed from models provide results consistent with the coherent maxima observed on dispersion images, dispersion curves computed from models are generally not fitting the observed propagation modes at low frequency. Surface-wave analysis could therefore improve models both in terms of reliability and ability to describe lateral variations. Finally, we were able to compute / sections from both and models. The two sections present similar features, but the section obtained from shows a higher lateral resolution and is consistent with the features observed on electrical resistivity tomography, thus validating our approach for retrieving Vp/Vs ratio from combined P-wave tomography and surface-wave profiling

Lactate & Cardiopulmonary Responses to Simulated Arm-Pulling & Leg-Kicking in Collegiate & Recreational Swimmers

Investigations into the changes due to training the metabolism of the arms or the legs in swimmers of diffferent training status are limited. The purpose of this study was to compare the lactate and cardiopulmonary responses tto simulated arm-pulling and leg-kicking in collegiate and recreational swimmers. Sixteen males (9 collegiate swimmers; SW, 7 recreational swimmers; RSW, mean ± SD; age 22 ± 3 years, body mass 81±9kg, stature 1.84±0.06m), gave written consent and performed continuous incremental exercise tests using either simulated front-crawl arm-pulling or leg-kicking. Lactate concentration (HLa) and oxygen consumption (V02)) were determined at 20 W intervals and at exhaustion (HLapeak; V02 peak)-The exercise intensity at a lactate concentration of 4 mM (EI4mM) and at exhaustion (EIpeak) for arm-pulling and leg-lkicking were also established. The arm:leg ratios for EI4mM, HLapeak and V02 peak were computed. The results showed that (for arm-pulling, the SW had higher EI4mM (P = 0.02), Elpeak (P = 0.006), but lower HLapeak (P = 0.03) compared to the RSW. For leg-kicking, none of the responses differed significantly. These results suggest that it is rather the metabolism and local musclle endurance of the arms that are enhanced with competitive swimming endurance

The relationship between blood lactate and heart rate responses to swim bench exercise and women’s competitive water polo

The aim of this study was to explore the relationship between physiological responses to dry-land testing and to water polo playing. Eight female water polo players (mean +/- s: age 26.7 +/- 5.7 years, height 169 +/- 6 cm, body mass 65.3 +/- 7.0 kg) participated in two assessments. The first involved a discontinuous incremental arm test to exhaustion on an isokinetic swim bench. Blood lactate was determined from finger-prick blood samples and heart rate was recorded at increasing exercise intensities. The highest (peak) values for blood lactate (5.1 +/- 0.2 mmol 1-1), exercise intensity (79 +/- 5.2 W) and heart rate (146 +/- 6 beats min-1) were recorded at exhaustion. Also, the exercise intensity and heart rate at a blood lactate concentration of 4 mmol 1-1 were established. The second assessment involved determination of blood lactate and heart rate immediately after each quarter of a different water polo game for each subject. The mean ( sx ) blood lactate and heart rate for each quarter of the game were as follows: 3.5 +/- 0.4, 4.3 +/- 0.5, 4.3 +/- 0.7 and 4.6 +/- 0.5 mmol l-1; 138 +/- 10, 149 +/- 12, 151 +/- 9 and 154 +/- 8 beats min-1, respectively. None of the peak values on the swim bench correlated with blood lactate or heart rate responses to game-playing. However, the mean exercise intensity at 4 mmol l-1 lactate (64 +/- 5 W) correlated with the fourth quarter values of both blood lactate concentration (r = -0.82, P = 0.01) and heart rate (r = -0.93, P < 0.001). These results show that submaximal metabolic responses to exercise on a swim bench are closely correlated with metabolic responses to water polo game-playing

Peak Oxygen Uptake Responses to Free and Simulated Swimming Using Different Body Segments.

Simulated swimming has been a useful tool in training and in assessment of physiological responses of swimmers. However, the extent to which oxygen uptake responses to simulated swimming compare to respective responses during free swimming is not yet known. The purpose of this study was to compare oxygen uptake responses in free and simulated swimming using different body segments. Five men (mean ± SD; mass: 67.2 ±5.3 kg, stature: 1.74 ± 0.06 m, age: 19.1 ± 3.4 years) and four women (mass: 62.2 ± 3.1 kg, stature: 1.63 ± 0.04 m, age: 17.3 ± 4.1 years) club swimmers performed six incremental exercise tests to exhaustion. These tests comprised whole-stroke, arms-only and legs-only free and simulated swimming. Oxygen uptake (VO2) was determined throughout the tests and at exhaustion ( VO2peak) using a portable telemetric system. VO2peak during whole-stroke free swimming was 10.4 ± 2.0% higher than during simulated swimming (P&lt;0.05), whereas VO2peak during arms-only and legs-only free swimming did not differ from that of simulated swimming. These results suggest that oxygen uptake responses to arms-only and legs-only simulated swimming compare favourably with respective responses to free swimming, yet, there are still limitations to simulation of whole-stroke freestyle swimming in the laboratory

Effects of arms-only swimming training on performance, movement economy and aerobic power.

Context: Forward propulsion in freestyle swimming is predominantly achieved through arm action. Few studies have assessed the effects of arm training on arm power and swimming performance, yet there have not been any investigations on the effects of arms-only swimming training on swimming performance and physiological responses to arm exercise. Purpose: To investigate the changes in arms-only and fullstroke swimming performance, movement economy and aerobic power after an armsonly swimming training program. Methods: Fifteen male county level swimmers were assigned either to an experimental (ES, n = 8) or control group (CS, n = 7). For six weeks ES performed arms-only freestyle swimming exercises for 20% of their weekly training distance three times per week, whereas CS performed their usual swimming training. Before and after the training program, both groups performed a) two time trials, 186 m using arms-only (186ARMS) and 372 m using full-stroke (372FULL) freestyle swimming, and b) an incremental arm-pulling exercise test. The time to complete the trials was recorded. Peak oxygen uptake (VO2peak), peak exercise intensity (EIpeak) submaximal oxygen uptake at 60 W (VO2-60) and exercise intensity at ventilatory threshold (VTW) were determined from the exercise test. Results: After training, ES had improved in 186ARMS (−14.2 ± 3.6%, P = .03), VO2-60 (−22.5 ± 2.3%, P = .04), EIpeak (+17.8 ± 4.2%, P = .03), and VTW (+18.9 ± 2.3%, P = .02), but not in VO2peak (P = .09) or in 372FULL (P = .07). None of the measures changed in CS (P &gt; .05). Conclusion: Arms-only swimming training at 20% of the weekly training distance is an effective method to improve arm conditioning during the preparatory phase of the annual training cycle

The effects of arms-or legs-only training on indices of swimming performance and dry-land endurance in swimmers

This study compared arm and leg performance and dry-land endurance before and after a 6-week swimming training programme. Fourteen club swimmers (mean± s; age 16 ± 5 years, stature 1.70 ± 0.08 m, mass 60 ± 10 kg), gave informed consent and were assigned to arms-only (ARMS) or legs-only (LEGS) training. Two types of testing were performed before and after the programme. First, simulated arm-pulling and leg-kicking ramp tests to exhaustion from which dry-land endurance was assessed as total exercise time (TETarms = TETlegs); second, 200m arms- (200arms), legs-only (200legs) and 400m full stroke (400full) time trials from which distance per pull and kick (DPP, DPK) were calculated from video recordings. MANOVA with repeated measures showed that for ARMS, TET = 200arms and DPP improved, whereas for LEGS only 200legs and DPK were enhanced after training (P<0.05). The results suggest that arms- and legs-only training produce changes in limb-specific local muscle endurance or technique and does not necessarily translate into improved whole stroke middle distance swimming performance

Multimaterial bioresorbable optical fibers for theranostics

The design, fabrication and characterization of phosphate based bioresorbable optical fibers is reported. Applications in diffuse optics, pH sensing and temperature sensing have been demonstrated paving the way to the use for a new generation of implantable and degradable devices for theranostics