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Villeneuve-d'Ascq, France

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. Source

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. Source

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. Source

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. Source

Casanova R.,Aix - Marseille University | Borg O.,Aix - Marseille University | Borg O.,Oxylane Research | Bootsma R.J.,Aix - Marseille University
Journal of Sports Sciences | Year: 2015

Abstract: Using plain white and chequered footballs, we evaluated observers’ sensitivity to rotation direction and the effects of ball texture on interceptive behaviour. Experiment 1 demonstrated that the maximal distance at which observers (n = 8) could perceive the direction of ball rotation decreased when rotation frequency increased from 5 to 11 Hz. Detection threshold distances were nevertheless always larger for the chequered (decreasing from 47 to 28 m) than for the white (decreasing from 15 to 11 m) ball. In Experiment 2, participants (n = 7) moved laterally along a goal line to intercept the two balls launched with or without ±4.3 Hz sidespin from a 30-m distance. The chequered ball gave rise to shorter movement initiation times when trajectories curved outward (±6 m arrival positions) or did not curve (±2 m arrival positions). Inward curving trajectories, arriving at the same ±2 m distances from the participants as the non-curving trajectories, evoked initial movements in the wrong direction for both ball types, but the amplitude and duration of these reversal movements were attenuated for the chequered ball. We conclude that the early detection of rotation permitted by the chequered ball allowed modulation of interception behaviour without changing its qualitative characteristics. © 2015 Taylor & Francis. Source

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