Oxylane Research

Saint-Georges-de-Mons, France

Oxylane Research

Saint-Georges-de-Mons, France
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Gerrett N.,Loughborough University | Ouzzahra Y.,Loughborough University | Ouzzahra Y.,University of Luxembourg | Redortier B.,Oxylane Research | And 2 more authors.
Physiology and Behavior | Year: 2015

Regional differences in thermal sensation to a hot or cold stimulus are often limited to male participants, in a rested state and cover minimal locations. Therefore, magnitude sensation to both a hot and cold stimulus were investigated during rest and exercise in 8 females (age: 20.4±1.4years, mass: 61.7±4.0kg, height: 166.9±5.4cm, VO2max: 36.8±4.5ml·kg-1·min-1). Using a repeated measures cross over design, participants rested in a stable environment (22.3±0.9°C, 37.7±5.5% RH) whilst a thermal probe (25cm2), set at either 40°C or 20°C, was applied in a balanced order to 29 locations across the body. Participants reported their thermal sensation after 10s of application. Following this, participants cycled at 50% VO2max for 20min and then 30% VO2max whilst the sensitivity test was repeated. Females experienced significantly stronger magnitude sensations to the cold than the hot stimulus (5.5±1.7 and 4.3±1.3, p<0.05, respectively). A significant effect of location was found during the cold stimulation (p<0.05). Thermal sensation was greatest at the head then the torso and declined towards the extremities. No significant effect of location was found in response to the hot stimulation and the pattern across the body was more homogenous. In comparison to rest, exercise caused a significant overall reduction in thermal sensation (5.2±1.5 and 4.6±1.7, respectively, p<0.05). Body maps were produced for both stimuli during rest and exercise, which highlight sensitive areas across the body. © 2015.

Filingeri D.,Loughborough University | Redortier B.,Oxylane Research | Hodder S.,Loughborough University | Havenith G.,Loughborough University
Neuroscience Letters | Year: 2013

Cold sensations are suggested as the primary inducer of the perception of skin wetness. However, limited data are available on the effects of skin cooling. Hence, we investigated the role of peripheral cold afferents in the perception of wetness. Six cold-dry stimuli (producing skin cooling rates in a range of 0.02-0.41. °C/s) were applied on the forearm of 9 female participants. Skin temperature and conductance, thermal and wetness perception were recorded. Five out of 9 participants perceived wetness as a result of cold-dry stimuli with cooling rates in a range of 0.14-0.41. °C/s, while 4 did not perceive skin wetness at all. Although skin cooling and cold sensations play a role in evoking the perception of wetness, these are not always of a primary importance and other sensory modalities (i.e. touch and vision), as well as the inter-individual variability in thermal sensitivity, might be equally determinant in characterising this perception. © 2013 Elsevier Ireland Ltd.

Filingeri D.,Loughborough University | Redortier B.,Oxylane Research | Hodder S.,Loughborough University | Havenith G.,Loughborough University
Neuroscience | Year: 2014

The central integration of thermal (i.e. cold) and mechanical (i.e. pressure) sensory afferents is suggested as to underpin the perception of skin wetness. However, the role of temperature and mechanical inputs, and their interaction, is still unclear. Also, it is unknown whether this intra-sensory interaction changes according to the activity performed or the environmental conditions. Hence, we investigated the role of peripheral cold afferents, and their interaction with tactile afferents, in the perception of local skin wetness during rest and exercise in thermo-neutral and warm environments. Six cold-dry stimuli, characterized by decreasing temperatures [i.e. -4, -8 and -15°C below the local skin temperature (Tsk)] and by different mechanical pressures [i.e. low pressure (LP): 7kPa; high pressure (HP): 10kPa], were applied on the back of 8 female participants (age 21±1years), while they were resting or cycling in 22 or 33°C ambient temperature. Mean and local Tsk, thermal and wetness perceptions were recorded during the tests. Cold-dry stimuli produced drops in Tsk with cooling rates in a range of 0.06-0.4°C/s. Colder stimuli resulted in increasing coldness and in stimuli being significantly more often perceived as wet, particularly when producing skin cooling rates of 0.18°C/s and 0.35°C/s. However, when stimuli were applied with HP, local wetness perceptions were significantly attenuated. Wetter perceptions were recorded during exercise in the warm environment. We conclude that thermal inputs from peripheral cutaneous afferents are critical in characterizing the perception of local skin wetness. However, the role of these inputs might be modulated by an intra-sensory interaction with the tactile afferents. These findings indicate that human sensory integration is remarkably multimodal. © 2013 IBRO.

Theurel J.,Aix - Marseille University | Theurel J.,University of Burgundy | Crepin M.,Aix - Marseille University | Foissac M.,Oxylane Research | Temprado J.J.,Aix - Marseille University
Scandinavian Journal of Medicine and Science in Sports | Year: 2012

The present study aimed to test the influence of the pedalling technique on the occurrence of muscular fatigue and on the energetic demand during prolonged constant-load cycling exercise. Subjects performed two prolonged (45min) cycling sessions at constant intensity (75% of maximal aerobic power). In a random order, participants cycled either with their preferred technique (PT) during one session or were helped by a visual force-feedback to modify their pedalling pattern during the other one (FB). Index of pedalling effectiveness was significantly (P<0.05) improved during FB (41.4±5.5%); compared with PT (36.6±4.1%). Prolonged cycling induced a significant reduction of maximal power output, which was greater after PT (-15±9%) than after FB (-7±12%). During steady-state FB, vastus lateralis muscle activity was significantly (P<0.05) reduced, whereas biceps femoris muscles activities increased compared with PT. Gross efficiency (GE) did not significantly differ between the two sessions, except during the first 15min of exercise (FB: 19.0±1.9% vs PT: 20.2±1.9%). Although changes in muscular coordination pattern with feedback did not seem to influence GE, it could be mainly responsible for the reduction of muscle fatigue after prolonged cycling. © 2011 John Wiley & Sons A/S.

Goislard De Monsabert B.,Aix - Marseille University | Rossi J.,Aix - Marseille University | Rossi J.,Oxylane Research | Berton E.,Aix - Marseille University | Vigouroux L.,Aix - Marseille University
Medicine and Science in Sports and Exercise | Year: 2012

PURPOSE: The aim of this study was to estimate muscle and joint forces during a power grip task. Considering the actual lack of quantification of such internal variables, this information would be essential for sports sciences, medicine, and ergonomics. This study also contributed to the advancement of scientific knowledge concerning hand control during power grip. METHODS: A specially designed apparatus combining both an instrumented handle and a pressure map was used to record the forces at the hand/handle interface during maximal exertions. Data were processed such that the forces exerted on 25 hand anatomical areas were determined. Joint angles of the five fingers and the wrist were also computed from synchronized kinematic measurements. These processed data were used as input of a hand/wrist biomechanical model, which includes 23 degrees of freedom and 42 muscles to estimate muscle and joint forces. RESULTS: Greater forces were applied on the distal phalanges of the long fingers compared with the middle and the proximal ones. Concomitantly, high solicitations were observed for FDP muscles. A large cocontraction level of extensor muscles was also estimated by the model and confirmed previously reported activities and injuries of extensor muscles related to the power grip. Quantifying hand internal loadings also resulted in new insights into the thumb and the wrist biomechanics. Output muscle tension ratios were all in smaller ranges than the ones reported in the literature. CONCLUSIONS: Including wrist and finger interactions in this hand model provided new quantification of muscle load sharing, cocontraction level, and biomechanics of the hand. Such information could complete future investigations concerning handle ergonomics or pathomechanisms of hand musculoskeletal disorders. Copyright © 2012 by the American College of Sports Medicine.

Filingeri D.,Loughborough University | Redortier B.,Oxylane Research | Hodder S.,Loughborough University | Havenith G.,Loughborough University
Skin Research and Technology | Year: 2015

Background/purpose: In the absence of humidity receptors in human skin, the perception of skin wetness is considered a somatosensory experience resulting from the integration of temperature (particularly cold) and mechanical inputs. However, limited data are available on the role of the temperature sense. Methods: Wet and dry stimuli at 4°C and 8°C above local skin temperature were applied on the back of seven participants (age 21 ± 2 years) while skin temperature and conductance, thermal and wetness perceptions were recorded. Results: Resting local skin temperature was always increased by the application of the stimuli (+0.5-+1.4°C). No effect of stimulus wetness was found on wetness perceptions (P > 0.05). The threshold (point '-2 slightly wet' on the wetness scale) to identify a clearly perceived wetness was never reached during any stimulations and participants did not perceive that some of the stimuli were wet. Overall, warm temperature stimuli suppressed the perception of skin wetness. Conclusion: We conclude that it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs (amongst which coldness seems dominant) which drives the perception of skin wetness during the initial contact with a wet surface. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Ouzzahra Y.,Loughborough University | Havenith G.,Loughborough University | Redortier B.,Oxylane Research
Journal of Thermal Biology | Year: 2012

Although several studies have compared thermal sensitivity between body segments, little is known on regional variations within body segments. Furthermore, the effects of exercise on the thermal sensation resulting from a cold stimulus remain unclear. The current experiment therefore aimed to explore inter- and intra-segmental differences in thermal sensitivity to cold, at rest and during light exercise. Fourteen male participants (22.3±3.1 years; 181.6±6.2cm; 73.7±10.3kg) were tested at rest and whilst cycling at 30% VO 2max. Sixteen body sites (front torso=6; back=6; arms=4) were stimulated in a balanced order, using a 20°C thermal probe (25cm 2) applied onto the skin. Thermal sensations resulting from the stimuli were assessed using an 11-point cold sensation scale (0=not cold; 10=extremely cold). Variations were found within body segments, particularly at the abdomen and mid-back where the lateral regions were significantly more sensitive than the medial areas. Furthermore, thermal sensations were significantly colder at rest compared to exercise in 12 of the 16 body sites tested. Neural and hormonal factors were considered as potential mechanisms behind this reduction in thermal sensitivity. Interestingly, the distribution of cold sensations was more homogenous during exercise. The present data provides evidence that thermal sensitivity to cold varies within body segments, and it is significantly reduced in most areas during exercise. © 2012 Elsevier Ltd.

Rossi J.,Aix - Marseille University | Rossi J.,Oxylane Research | Vigouroux L.,Aix - Marseille University | Barla C.,Oxylane Research | Berton E.,Aix - Marseille University
Scandinavian Journal of Medicine and Science in Sports | Year: 2014

The effects of tennis racket grip size on the forces exerted by muscles affecting lateral epicondylalgia (LE) were assessed in this study. Grip forces and joint moments applied on the wrist were quantified under three different handle size conditions, with and without induced muscle fatigue for intermediate and advanced players. The obtained experimental results were then used as input data of a biomechanical model of the hand. This simulation aimed to quantify the impact of grip strength modulation obtained in the experiment on the wrist extensor muscle forces. Our results show that there is an optimal grip diameter size defined as the handle inducing a reduced grip force during the stroke, in both fatigued and non-fatigued sessions. The results of the simulation suggested that extensor muscles were highly employed during forehand strokes, which confirms that the mechanical overuse of extensor tendons is a potential risk factor for tennis elbow occurrence. The handle grip size appeared to be a significant factor to reduce this extensor tendon loading. This suggests that grip size should be taken into account by players and designers in order to reduce the mechanical risk factors of overuse injury occurrence. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Filingeri D.,Loughborough University | Fournet D.,Oxylane Research | Hodder S.,Loughborough University | Havenith G.,Loughborough University
Journal of Neurophysiology | Year: 2014

Although the ability to sense skin wetness and humidity is critical for behavioral and autonomic adaptations, humans are not provided with specific skin receptors for sensing wetness. It has been proposed that we “learn” to perceive the wetness experienced when the skin is in contact with a wet surface or when sweat is produced through a multisensory integration of thermal and tactile inputs generated by the interaction between skin and moisture. However, the individual roles of thermal and tactile cues and how these are integrated peripherally and centrally by our nervous system is still poorly understood. Here we tested the hypothesis that the central integration of coldness and mechanosensation, as subserved by peripheral A-nerve afferents, might be the primary neural process underpinning human wetness sensitivity. During a quantitative sensory test, we found that individuals perceived warm-wet and neutral-wet stimuli as significantly less wet than cold-wet stimuli, although these were characterized by the same moisture content. Also, when cutaneous cold and tactile sensitivity was diminished by a selective reduction in the activity of A-nerve afferents, wetness perception was significantly reduced. Based on a concept of perceptual learning and Bayesian perceptual inference, we developed the first neurophysiological model of cutaneous wetness sensitivity centered on the multisensory integration of cold-sensitive and mechanosensitive skin afferents. Our results provide evidence for the existence of a specific information processing model that underpins the neural representation of a typical wet stimulus. These findings contribute to explaining how humans sense warm, neutral, and cold skin wetness. © 2014 the American Physiological Society.

Chambon N.,Aix - Marseille University | Chambon N.,Oxylane Research | Delattre N.,Oxylane Research | Gueguen N.,Oxylane Research | And 2 more authors.
Gait and Posture | Year: 2014

Many studies have highlighted differences in foot strike pattern comparing habitually shod runners who ran barefoot and with running shoes. Barefoot running results in a flatter foot landing and in a decreased vertical ground reaction force compared to shod running. The aim of this study was to investigate one possible parameter influencing running pattern: the midsole thickness. Fifteen participants ran overground at 3.3ms-1 barefoot and with five shoes of different midsole thickness (0mm, 2mm, 4mm, 8mm, 16mm) with no difference of height between rearfoot and forefoot. Impact magnitude was evaluated using transient peak of vertical ground reaction force, loading rate, tibial acceleration peak and rate. Hip, knee and ankle flexion angles were computed at touch-down and during stance phase (range of motion and maximum values). External net joint moments and stiffness for hip, knee and ankle joints were also observed as well as global leg stiffness. No significant effect of midsole thickness was observed on ground reaction force and tibial acceleration. However, the contact time increased with midsole thickness. Barefoot running compared to shod running induced ankle in plantar flexion at touch-down, higher ankle dorsiflexion and lower knee flexion during stance phase. These adjustments are suspected to explain the absence of difference on ground reaction force and tibial acceleration. This study showed that the presence of very thin footwear upper and sole was sufficient to significantly influence the running pattern. © 2014 Elsevier B.V.

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