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Indirect measurement of disc hydration can be obtained through measures of spinal height using stadiometry. However, specialised stadiometers for this are often custom-built and expensive. Generic wall-mounted stadiometers alternatively are common in clinics and laboratories. This study examined the reliability of a custom set-up utilising a wall-mounted stadiometer for measurement of spinal height using custom built wall mounted postural rods. Twelve participants with non-specific chronic low back pain (CLBP; females n = 5, males n = 7) underwent measurement of spinal height on three separate consecutive days at the same time of day where 10 measurements were taken at 20 s intervals. Comparisons were made using repeated measures analysis of variance for 'trial' and 'gender'. There were no significant effects by trial or interaction effects of trial x gender. Intra-individual absolute standard error of measurement (SEM) was calculated for spinal height using the first of the 10 measures, the average of 10 measures, the total shrinkage, and the rate of shrinkage across the 10 measures examined as the slope of the curve when a linear regression was fitted. SEMs were 3.1 mm, 2.8 mm, 2.6 mm and 0.212, respectively. Absence of significant differences between trials and the reported SEMs suggests this custom set-up for measuring spinal height changes is suitable use as an outcome measure in either research or clinical practice in participants with CLBP.

International audience; Pumice flows are potentially destructive volcanic events that derive from eruption column collapse and whose dynamics are poorly understood. The challenges in studying these flows include the lack of constraints on the dynamics, kinematics and initial conditions that control their emplacement. We present a morphological study of the distal deposits (lobes) of the pumice flows resulting from the 1993 eruption at Lascar, Chile. The surface geometry of the lobes was measured in detail using a LiDAR device, which allowed for detailed characterisation of their morphology, consisting of central channel and lateral levees, and terminal frontal snout. In particular we find that the ratio of channel/levee height as a function of the ratio of the distance between levees/total width of the lobe has a characteristic curve for these pumice flow lobes. Our analysis of several of the Lascar pumice lobe deposits (south east sector) identified several dimensionless groups of the available parameters which, when compared against published results from both experimental and numerical investigations, allowed us to constrain crucial kinematic and dynamic information on the terminal phase of the pumice flows. Notably, we estimate the velocity of the terminal phase of pumice flows to be 5-10 m/s. Froude numbers of 1.5-2 are comparable with values found for experimental granular flows. Height-width aspect ratios for the levee-channel section of the pumice lobes are similar to those for experimental flows although these same aspect ratios for the snout are much larger for the natural deposits than their small-scale analogues. Finally, we discuss the possible emplacement dynamics of the terminal Lascar 1993 pumice flows. A pseudo-Reynolds number based on the velocity estimation is found to be up to 100 times larger for the pumice flows than experimental-scale flows. This suggests that the flow-retarding frictional forces for large-scale flows are relatively unimportant compared to flows at smaller scales. Mechanical effects such as fluidisation, mobilisation of material lying on the slopes over which they propagate and lubrication due to polydispersivity could provide an explanation for their ability to propagate on shallow slopes (6-11°).