Institute for Research in Rehabilitation

Sion, Switzerland

Institute for Research in Rehabilitation

Sion, Switzerland
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Faiss R.,University of Lausanne | Von Orelli C.,University of Lausanne | Deriaz O.,Institute for Research in Rehabilitation | Millet G.P.,University of Lausanne
International Journal of Sports Physiology and Performance | Year: 2014

Purpose: Hypoxia is known to reduce maximal oxygen uptake (VO2max) more in trained than in untrained subjects in several lowland sports. Ski mountaineering is practiced mainly at altitude, so elite ski mountaineers spend significantly longer training duration at altitude than their lower-level counterparts. Since acclimatization in hypobaric hypoxia is effective, the authors hypothesized that elite ski mountaineers would exhibit a VO2max decrement in hypoxia similar to that of recreational ski mountaineers. Methods: Eleven elite (E, Swiss national team) and 12 recreational (R) ski mountaineers completed an incremental treadmill test to exhaustion in normobaric hypoxia (H, 3000 m, FIO2 14.6% ± 0.1%) and in normoxia (N, 485 m, FIO2 20.9% ± 0.0%). Pulse oxygen saturation in blood (SpO2), VO2max, minute ventilation, and heart rate were recorded. Results: At rest, hypoxic ventilatory response was higher (P < .05) in E than in R (1.4 ± 1.9 vs 0.3 ± 0.6 L · min-1 · kg-1). At maximal intensity, SpO2 was significantly lower (P < .01) in E than in R, both in N (91.1% ± 3.3% vs 94.3% ± 2.3%) and in H (76.4% ± 5.4% vs 82.3% ± 3.5%). In both groups, SpO2 was lower (P < .01) in H. Between N and H, VO2max decreased to a greater extent (P < .05) in E than in R (-18% and -12%, P < .01). In E only, the VO2max decrement was significantly correlated with the SpO2 decrement (r = .74, P < .01) but also with VO2max measured in N (r = .64, P < .05). Conclusion: Despite a probable better acclimatization to altitude, VO2max was more reduced in E than in R ski mountaineers, confirming previous results observed in lowlander E athletes. © 2014 Human Kinetics, Inc.

Le Carre J.,Institute for Research in Rehabilitation | Lamon S.,Deakin University | Leger B.,Institute for Research in Rehabilitation
Frontiers in Genetics | Year: 2014

Since the discovery of microRNAs (miRNAs), different approaches have been developed to label, amplify and quantify miRNAs. The TaqMan® technology, provided by Applied Biosystems (ABIs), uses a stem-loop reverse transcription primer system to reverse transcribe the RNA and amplify the cDNA. This method is widely used to identify global differences between the expression of 100s of miRNAs across comparative samples. This technique also allows the quantification of the expression of targeted miRNAs to validate observations determined by whole-genome screening or to analyze few specific miRNAs on a large number of samples. Here, we describe the validation of a method published by ABIs on their web site allowing to reverse transcribe and pre-amplify multiple miRNAs and snoRNAs simultaneously. The validation of this protocol was performed on human muscle and plasma samples. Fast and cost efficient, this method achieves an easy and convenient way to screen a relatively large number of miRNAs in parallel. © 2014 Le Carré, Lamon and Léger.

Praz C.,University of Lausanne | Praz C.,Institute for Research in Rehabilitation | Leger B.,Institute for Research in Rehabilitation | Kayser B.,University of Lausanne
European Journal of Applied Physiology | Year: 2014

Purpose: Multi-hour ski mountaineering energy balance may be negative and intake below recommendations.Methods: Athletes on the ‘Patrouille des Glaciers’ racecourses (17 on course Z, 27 km, +2,113 m; 11 on course A, 26 km, +1,881 m) volunteered. Pre-race measurements included body mass, stature, VO2max, and heart rate (HR) vs VO2 at simulated altitude; race measurements HR, altitude, incline, location, and food and drink intake (A). Energy expenditure (EE) was calculated from altitude corrected HR derived VO2.Results: Race time was 5 h 7 min ± 44 min (mean ± SD, Z) and 5 h 51 min ± 53 min (A). Subjects spent 19.2 ± 3.2 MJ (Z), respectively, 22.6 ± 2.9 MJ (A) during the race. Energy deficit was −15.5 ± 3.9 MJ (A); intake covered 20 ± 7 % (A). Overall energy cost of locomotion (EC) was 9.9 ± 1.3 J m−1 kg−1 (Z), 8.0 ± 1.0 J m−1 kg−1 (A). Uphill EC was 11.7 ± 1 J m−1 kg−1 (Z, 13 % slope) and 15.7 ± 2.3 J m−1 kg−1 (A, 19 % slope). Race A subjects lost −1.5 ± 1.1 kg, indicating near euhydration. Age, body mass, gear mass, VO2max and EC were significantly correlated with performance; energy deficit was not.Conclusions: Energy expenditure and energy deficit of a multi-hour ski mountaineering race are very high and energy intake is below recommendations. © 2014, Springer-Verlag Berlin Heidelberg.

Reynard F.,Clinique romande de readaptation SUVACare | Terrier P.,Clinique romande de readaptation SUVACare | Terrier P.,Institute for Research in Rehabilitation
Experimental Brain Research | Year: 2015

While vision obviously plays an essential role in orienting and obstacle avoidance, its role in the regulation of dynamic balance is not yet fully understood. The objective of this study was to assess dynamic stability while blindfolded, under optimal conditions that minimized the fear of falling. The hypothesis was that visual deprivation could be compensated for by using other sensory strategies to stabilize gait. One hundred healthy adults (aged 20–69 years) participated in the study. They were previously accustomed to blindfolded treadmill walking wearing a safety harness. Their preferred walking speeds (PWS) were assessed with eyes open (PWSEO) and with eyes closed (blindfolded, PWSEC). Three five-minute tests were performed: (A) normal walking at PWSEO, (B) blindfolded walking at PWSEC, and (C) normal walking at PWSEC. Trunk acceleration was measured with a lightweight inertial sensor. Dynamic stability was assessed by using (1) acceleration root mean square (RMS), which estimates the variability of the signal, and hence, the smoothness of the trunk movement and (2) local dynamic stability (LDS), which reflects the efficiency of the motor control to stabilize the trunk. Although walking at PWSEC with eyes open (comparing conditions A and C) had a slight impact on gait stability (relative difference: RMS +4 %, LDS −5 %), no destabilizing effect of visual deprivation (B vs. C, RMS −4 %, LDS −1 %) was observed. Therefore, it is concluded that when reassuring conditions are offered to individuals while walking, they are able to adopt alternative sensory strategies to control dynamic equilibrium without the help of vision. © 2014, Springer-Verlag Berlin Heidelberg.

Reynard F.,Clinique romande de readaptation SUVACare | Terrier P.,Institute for Research in Rehabilitation
Journal of Biomechanics | Year: 2014

Repetitive falls degrade the quality of life of elderly people and of patients suffering of various neurological disorders. In order to prevent falls while walking, one should rely on relevant early indicators of impaired dynamic balance. The local dynamic stability (LDS) represents the sensitivity of gait to small perturbations: divergence exponents (maximal Lyapunov exponents) assess how fast a dynamical system diverges from neighbor points. Although numerous findings attest the validity of LDS as a fall risk index, reliability results are still sparse. The present study explores the intrasession and intersession repeatability of gait LDS using intraclass correlation coefficients (ICC) and standard error of measurement (SEM). Ninety-five healthy individuals performed 5min treadmill walking in two sessions separated by 9 days. Trunk acceleration was measured with a 3D accelerometer. Three time scales were used to estimate LDS: over 4-10 strides (λ4-10), over one stride (λ1) and over one step (λ0.5). The intrasession repeatability was assessed from three repetitions of either 35 strides or 70 strides taken within the 5min tests. The intersession repeatability compared the two sessions, which totalized 210 strides. The intrasession ICCs (70-strides estimates/35-strides estimates) were 0.52/0.18 for λ4-10 and 0.84/0.77 for λ1 and λ0.5. The intersession ICCs were around 0.60. The SEM results revealed that λ0.5 measured in medio-lateral direction exhibited the best reliability, sufficient to detect moderate changes at individual level (20%). However, due to the low intersession repeatability, one should average several measurements taken on different days in order to better approximate the true LDS. © 2013 Elsevier Ltd.

Terrier P.,Institute for Research in Rehabilitation | Reynard F.,Clinique romande de readaptation SUVACare
Gait and Posture | Year: 2015

Falls during walking are a major health issue in the elderly population. Older individuals are usually more cautious, walk more slowly, take shorter steps, and exhibit increased step-to-step variability. They often have impaired dynamic balance, which explains their increased falling risk. Those locomotor characteristics might be the result of the neurological/musculoskeletal degenerative processes typical of advanced age or of a decline that began earlier in life. In order to help determine between the two possibilities, we analyzed the relationship between age and gait features among 100 individuals aged 20-69. Trunk acceleration was measured during a 5-min treadmill session using a 3D accelerometer. The following dependent variables were assessed: preferred walking speed, walk ratio (step length normalized by step frequency), gait instability (local dynamic stability, Lyapunov exponent method), and acceleration variability (root mean square [RMS]). Using age as a predictor, linear regressions were performed for each dependent variable. The results indicated that walking speed, walk ratio and trunk acceleration variability were not dependent on age (R2<2%). However, there was a significant quadratic association between age and gait instability in the mediolateral direction (R2=15%). We concluded that most of the typical gait features of older age do not result from a slow evolution over the life course. On the other hand, gait instability likely begins to increase at an accelerated rate as early as age 40-50. This finding supports the premise that local dynamic stability is likely a relevant early indicator of falling risk. © 2014 Elsevier B.V.

Terrier P.,Institute for Research in Rehabilitation
Annals of Biomedical Engineering | Year: 2016

In human locomotion, sensorimotor synchronization of gait consists of the coordination of stepping with rhythmic auditory cues (auditory cueing, AC). AC changes the long-range correlations among consecutive strides (fractal dynamics) into anti-correlations. Visual cueing (VC) is the alignment of step lengths with marks on the floor. The effects of VC on the fluctuation structure of walking have not been investigated. Therefore, the objective was to compare the effects of AC and VC on the fluctuation pattern of basic spatiotemporal gait parameters. Thirty-six healthy individuals walked 3 × 500 strides on an instrumented treadmill with augmented reality capabilities. The conditions were no cueing (NC), AC, and VC. AC included an isochronous metronome. For VC, projected stepping stones were synchronized with the treadmill speed. Detrended fluctuation analysis assessed the correlation structure. The coefficient of variation (CV) was also assessed. The results showed that AC and VC similarly induced a strong anti-correlated pattern in the gait parameters. The CVs were similar between the NC and AC conditions but substantially higher in the VC condition. AC and VC probably mobilize similar motor control pathways and can be used alternatively in gait rehabilitation. However, the increased gait variability induced by VC should be considered. © 2016 Biomedical Engineering Society

Terrier P.,Institute for Research in Rehabilitation | Deriaz O.,Institute for Research in Rehabilitation
Frontiers in Physiology | Year: 2013

It has been observed that times series of gait parameters [stride length (SL), stride time (ST), and stride speed (SS)], exhibit long-term persistence and fractal-like properties. Synchronizing steps with rhythmic auditory stimuli modifies the persistent fluctuation pattern to anti-persistence. Another non-linear method estimates the degree of resilience of gait control to small perturbations, i.e., the local dynamic stability (LDS). The method makes use of the maximal Lyapunov exponent, which estimates how fast a non-linear system embedded in a reconstructed state space (attractor) diverges after an infinitesimal perturbation. We propose to use an instrumented treadmill to simultaneously measure basic gait parameters (time series of SL, ST, and SS from which the statistical persistence among consecutive strides can be assessed), and the trajectory of the center of pressure (from which the LDS can be estimated). In 20 healthy participants, the response to rhythmic auditory cueing (RAC) of LDS and of statistical persistence [assessed with detrended fluctuation analysis (DFA)] was compared. By analyzing the divergence curves, we observed that long-term LDS (computed as the reverse of the average logarithmic rate of divergence between the 4th and the 10th strides downstream from nearest neighbors in the reconstructed attractor) was strongly enhanced (relative change +73%). That is likely the indication of a more dampened dynamics. The change in short-term LDS (divergence over one step) was smaller (+3%). DFA results (scaling exponents) confirmed an antipersistent pattern in ST, SL, and SS. Long-term LDS (but not short-term LDS) and scaling exponents exhibited a significant correlation between them (r = 0.7). Both phenomena probably result from the more conscious/voluntary gait control that is required by RAC. We suggest that LDS and statistical persistence should be used to evaluate the efficiency of cueing therapy in patients with neurological gait disorders. © 2013 Terrier and Dériaz.

Rossano C.,Institute for Research in Rehabilitation | Terrier P.,Institute for Research in Rehabilitation
Trials | Year: 2016

Background: After a lesion to the central nervous system, many patients suffer from reduced walking capability. In the first rehabilitation phase, repeated walking exercises facilitate muscular strength and stimulate brain plasticity and motor relearning. However, marked limping, an unsteady gait, and poor management of obstacle clearance may persist, which increases a patient's risk of falling. Gait training with augmented reality has been recommended to improve gait coordination. The objective of this study is to test whether a gait rehabilitation program using augmented reality is superior to a conventional treadmill training program of equivalent intensity. Methods/design: The GASPAR trial (Gait Adaptation for Stroke Patients with Augmented Reality) is a pragmatic, parallel-arm, single-center, nonblind, superiority randomized control trial in neurorehabilitation. The setting is a rehabilitation clinic in Switzerland. The planned number of participants is 70-100. The intervention uses instrumented treadmills equipped with projectors that display shapes on the walking surface. The principle is that patients must adapt their gait to the image that unfolds in front of them. Specific exercises for gait symmetry, coordination enhancement, and gait agility are provided. The program includes twenty 30-min sessions spanning 4 weeks. The comparator group receives standard treadmill training of a similar frequency and intensity. The main outcome to be measured in the trial is walking speed, which is assessed with the 2-min Walk Test. Moreover, gait parameters are recorded during the gait training sessions. Other outcomes are balance control (Berg Balance Scale) and the fear of falling (Falls Efficacy Scale). The statistical analyses will compare the baseline assessment for each participant (before the intervention) with a post-intervention assessment (taken a few days after the end of the program). Furthermore, a follow-up assessment will take place 3 months after discharge. Discussion: The study results will provide new knowledge about recovery in neurological patients and will contribute to the design of better rehabilitation programs to accompany this process. The findings will also help health care funders to decide whether treadmills equipped with augmented reality capabilities are a worthwhile investment. Trial registration: ID: NCT02808078, registered on 16 June 2016. © 2016 The Author(s).

Terrier P.,Institute for Research in Rehabilitation | Reynard F.,Institute for Research in Rehabilitation
Journal of Applied Biomechanics | Year: 2014

Local dynamic stability (stability) quantifies how a system responds to small perturbations. Several experimental and clinical findings have highlighted the association between gait stability and fall risk. Walking without shoes is known to slightly modify gait parameters. Barefoot walking may cause unusual sensory feedback to individuals accustomed to shod walking, and this may affect stability. The objective was therefore to compare the stability of shod and barefoot walking in healthy individuals and to analyze the intrasession repeatability. Forty participants traversed a 70 m indoor corridor wearing normal shoes in one trial and walking barefoot in a second trial. Trunk accelerations were recorded with a 3D-accelerometer attached to the lower back. The stability was computed using the finite-time maximal Lyapunov exponent method. Absolute agreement between the forward and backward paths was estimated with the intraclass correlation coefficient (ICC). Barefoot walking did not significantly modify the stability as compared with shod walking (average standardized effect size: +0.11). The intrasession repeatability was high (ICC: 0.73-0.81) and slightly higher in barefoot walking condition (ICC: 0.81-0.87). Therefore, it seems that barefoot walking can be used to evaluate stability without introducing a bias as compared with shod walking, and with a sufficient reliability. © 2014 Human Kinetics, Inc.

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