47 research outputs found
Behaviour of an instrumented anthropomorphic dummy during full scale drop tests.
No full textThe aim of this work was to study the behaviour of an instrumented anthropomorphic dummy during full scale drop tests. The dummy presented triaxial accelerometers at head and chest and multiaxial load cells at the thighs. Drops were performed on a wooden floor inclined at 16° from horizontal. Kinematics of drop landing in sagittal plane was filmed with a high speed camera. Peak values of acceleration and thigh loads were recorded to provide a validation of a numerical model of the dummy including stiffness properties of the skis and boots
Comparative analysis of muscle activation patterns between skiing on slopes and on training devices
No full textThe increasing popularity of ski as winter sport and the difficulties related to its accessibility and environmental conditions led to the development of specific trainingdevices for practise, both for improving technique and for training after injuries.
In particular the aim of this work was to study the efficacy of two trainingdevices: Skimagic®and Skier’s Edge®, comparing their functionality to ski on natural snow.
The efficacy of trainingdevices was investigated after comparing the EMG activationpatterns of snow skiing with the other two training conditions; good correlation of activationpatterns should correspond to a better simulation of the skiing movement
COMPARATIVE EVALUATION OF TWO SKIING SIMULATORS AS FUNCTIONAL TRAINING DEVICES FOR RECREATIONAL SKIERS
No full textThe aims of this study were to examine two ski simulators, Skimagic and Skier's Edge, and to evaluate their efficacy as functional training devices for skiers. Vertical ground reaction forces, knee flexion angle kinematics and muscles activity were recorded on these devices and compared with those measured in similar condition while skiing on snow. Five ski instructors performed three randomized testing sessions (snow, Skimagic and Skier's Edge). During the testing sessions, vertical ground reaction forces were recorded by means of pressure insoles in synchronisation with a portable data logger that collected values of knee flexion-extension and EMG activation of rectus femoris and vastus medialis. EMG activations and ground reaction forces measured while skiing on simulators were lower than on snow. Although less overall EMG activation was present on the simulators, the pattern of EMG activity was closer to real snow on Skimagic than on Skiers' Edge. Results of the present study suggested that the two devices are not effectively applicable for strength training. However, based on the recorded EMG patterns, the Skimagic treadmill is potentially suitable to act as a functional training device for recreational skiers provided that an increase of speed and slope on Skimagic could induce a closer matching of the studied biomechanical parameters with the snow skiing conditions
Biomechanical comparison of shorts with different pads: An Insight into the Perineum Protection Issue
No full textAn intensive use of the bicycle may increase the risk of erectile dysfunction and the compression of the perineal area has been showed to be a major mechanism leading to sexual alterations compromising the quality of life. Manufacturers claim that pads contribute to increase cyclists perineal protection ensuring a high level of comfort. To investigate the influence of various cycling pads with regard to perineal protection and level of comfort. Nine club road cyclists rode 20 min on a drum simulator, located at the Nutrition and Exercise Physiology Laboratory, at a constant speed and gear ratio wearing the shorts with 3 cycling pads of different design and thickness: basic (BAS), intermediate (INT), and endurance (END). Kinematics and pressure data were recorded at min 5, 15, and 20 of the test using a motion capture system and a pressure sensor mat. The variables of interest were: 3-dimensional pelvis excursions, peak pressure, mean pressure, and vertical force. The comfort level was assessed with a ranking order based on the subjects' perception after the 20-min trials and measuring the vertical ground reaction force under the anterior wheel as well as the length of the center of pressure (COP) trajectory on the saddle. Results showed that the vertical force and the average value of mean pressure on the saddle significantly decreased during the 20-min period of testing for BAS and END. Mean peak pressure on the corresponding perineal cyclist area significantly increased only for BAS during the 20-min period. Interestingly objective comfort indexes measured did not match cyclists subjective comfort evaluation. The lower capacity of BAS to reduce the peak pressure on the corresponding perineal area after 20 min of testing, together with its positive comfort evaluation, suggest that a balance between protection and perceived comfort should be taken into account in the choice of the pad. Hence, the quantitative approach of objective comfort indexes introduced in this study could be helpful for manufacturers in the development of their protective pads
Different intensities of basketball drills affect jump shot accuracy of expert and junior players
No full textBackground In basketball a maximum accuracy at every game intensity is required while shooting. The aim of the present study was to investigate the acute effect of three different drill intensity simulation protocols on jump shot accuracy in expert and junior basketball players. Materials & Methods Eleven expert players (age 26 ± 6 yrs, weight 86 ± 11 kg, height 192 ± 8 cm) and ten junior players (age 18 ± 1 yrs, weight 75 ± 12 kg, height 184 ± 9 cm) completed three series of twenty jump shots at three different levels of exertion. Counter Movement Jump (CMJ) height was also measured after each series of jump shots. Exertion’s intensity was induced manipulating the basketball drills. Heart rate was measured for the whole duration of the tests while the rating of perceived exertion (RPE) was collected at the end of each series of shots. Results Heart rate and rating of perceived exertion (RPE) were statistically different in the three conditions for both expert and junior players. CMJ height remained almost unchanged in both groups. Jump shot accuracy decreased with increasing drills intensity both in experts and junior players. Expert players showed higher accuracy than junior players for all the three levels of exertion (83% vs 64%, p < 0.001; 75% vs 57%, p < 0.05; 76% vs 60%, p < 0.01). Moreover, for the most demanding level of exertion, experts showed a higher accuracy in the last ten shots compared to the first ten shots (82% vs 70%, p < 0.05). Discussion Experts coped better with the different exertion’s intensities, thus maintaining a higher level of performance. The introduction of technical short bouts of high-intensity sport-specific exercises into skill sessions should be proposed to improve jump shot accuracy during matches
Development of a servohydraulic roller test bench for indoor evaluation of the vibrational comfort of bicycle components
No full textOne of the most important parameters evaluated by racing and trekking cyclists is vibrational comfort: as generally accepted, it is closely correlated to the response of bicycle components in combination with the cyclist's characteristics. Vibration transmissibility of wheels and saddles was recently studied during lab tests using a wooden dummy bottom resting on the saddle or in road tests on an instrumented racing bicycle at different speeds on different surfaces. The use of shakers is also well established in the evaluation of cyclist's posture effects on the overall bicycle behaviour. In fact, in previous works, either a servohydraulic actuator was applied to the seatpost of a bicycle frame hinged at the front wheel axle with a cycling tester, or two electrodynamic shakers were applied under the wheels of a fully equipped bicycle, with a cyclist sitting statically on the saddle. In the present study, the combination of a servohydraulic actuator and a roller type bench allowed to overcome the limitations of the former experiences. Random vibrations were input to the bicycle-cyclist complex by means of rollers supporting the rear wheel while cyclists were cycling unrestrained on the rollers. The test bench setup and tuning approach are presented for comparison with results available from previous bench and road tests
Varying negative work assistance at the ankle with a soft exosuit during loaded walking
No full textBackground: Only very recently, studies have shown that it is possible to reduce the metabolic rate of unloaded and loaded walking using robotic ankle exoskeletons. Some studies obtained this result by means of high positive work assistance while others combined negative and positive work assistance. There is no consensus about the isolated contribution of negative work assistance. Therefore, the aim of the present study is to examine the effect of varying negative work assistance at the ankle joint while maintaining a fixed level of positive work assistance with a multi-articular soft exosuit. Methods: We tested eight participants during walking at 1.5 ms-1with a 23-kg backpack. Participants wore a version of the exosuit that assisted plantarflexion via Bowden cables tethered to an off-board actuation platform. In four active conditions we provided different rates of exosuit bilateral ankle negative work assistance ranging from 0.015 to 0.037 W kg-1and a fixed rate of positive work assistance of 0.19 W kg-1. Results: All active conditions significantly reduced metabolic rate by 11 to 15% compared to a reference condition, where the participants wore the exosuit but no assistance was provided. We found no significant effect of negative work assistance. However, there was a trend (p =.08) toward greater reduction in metabolic rate with increasing negative work assistance, which could be explained by observed reductions in biological ankle and hip joint power and moment. Conclusions: The non-significant trend of increasing negative work assistance with increasing reductions in metabolic rate motivates the value in further studies on the relative effects of negative and positive work assistance. There may be benefit in varying negative work over a greater range or in isolation from positive work assistance
Differences in electromyographic activity of biceps brachii and brachioradialis while performing three variants of curl
No full textBackground. Dumbbell curl (DC) and barbell curl in its two variants, straight (BC) or undulated bar (EZ) are typical exercises to train the elbow flexors. The aim of the study was to verify if the execution of these three variants could induce a selective electromyographic (EMG) activity of the biceps brachii (BB) and brachioradialis (BR). Methods. Twelve participants performed one set of ten repetitions at 65% of their 1-RM for each variant of curl. Pre-gelled electrodes were applied with an inter-electrode distance of 24mmon BB and BR. An electrical goniometer was synchronously recorded with EMG signals to determine the concentric and eccentric phases of each variant of curl. Results. We detected higher activation profile of both BB (P < 0:05) and BR (P < 0:01) during the EZ compared to the DC. Higher levels of activation was found during the concentric phase for only the BR performed with an EZ compared to DC (P < 0:001) and performing BC compared to DC (P < 0:05). The eccentric phase showed a higher activation of the BB muscle in EZ compared to DC (P < 0:01) and in BC compared to DC (P < 0:05). The BR muscle showed a higher activation performing EZ compared to DC (P < 0:01). Discussion. The EZ variant may be preferred over the DC variant as it enhances BB and BR EMG activity during the whole range of motion and only in the eccentric phase. The small difference between BC and EZ variants of the BB and BR EMG activity makes the choice between these two exercises a matter of subjective comfort
An unusual cause of pneumonia in a child. Eur. Respir. J. 2005; 26 (49): 630s.
No full textA case of rare pneumonia in children is described by the author
