The use of an Edge Load Profile static bench for the qualification of alpine skis

Abstract The work reports the results of several tests performed on a set of commercial skis ranging from racing to recreational skis by means of a special bench designed for evaluating the Edge Load Profile produced by a ski when pressed against a bed of calibrated load cells. The test bench is equipped with 21 uniaxial load cells of 100 mm width and with a linear actuator able to press any type of alpine ski at edging angles ranging from 0i to +/- 70i. The Edge Load Profiles were presented along a normalized ski length and their shapes were compared within each category of skis. The bench output was clearly revealing the presence of critical spots along the ski where either the contact to the ground was missing or some non-uniform peaks were present. The experiences here presented confirm the appropriateness of the Edge Load Profile bench as tool for the skis qualification process and its continuous design improvement

A METHOD FOR THE PERFORMANCE EVALUATION OF JUMPING HEADERS IN SOCCER

The aim of the present work was to develop a method for the evaluation of soccer heading performance in jumping headers by means of a stereophotogrammetric system. Three non-professional players were involved in this pilot study. The attention was focused on the following variables: the player’s jump height at the impact instant, the ball velocity variation and the initial ball angle after the impact with the forehead of the player. The analysis of these parameters permitted to characterize the biomechanical technique and the performance ability of each player in such a way that a trainer can define individual procedures to improve the efficacy of this fundamental skill in soccer. Finally an Elevation Index (E.I.) was developed to compare the players performances and to draft a ranking between them

Methods for evaluating the radial structural behaviour of racing bicycle wheels

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A method for evaluating the vibrational response of racing bicycles wheels under road roughness excitation

Abstract The aim of the work was the development of a method for measuring and comparing the vibrational response of different racing rear wheels to the excitation caused by riding on irregular road surfaces. Four different rear wheels were selected for the study. Vertical accelerations at rear wheel axis and at the seatpost were measured during field tests performed while cruising on different road surfaces at different constant speeds. Frequency analysis of acceleration signals was performed using random signal analysis methods. The results show that the ranking between comfort properties of different wheels varies with the road surface roughness and the cruising speed considered

Biomechanical comparison of shorts with different pads: An Insight into the Perineum Protection Issue

An 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

Development of instrumented downhill bicycle components for field data collection

Abstract A downhill bicycle was equipped with strain gauge bridges at the most significant safety components, stroke sensors at the suspensions and accelerometers at the front axle. A set of 7 channels was applied on the frame, 4 channels were applied to the rear swing arm, 6 channels to the front fork, 2 channels to the front and rear brakes and a customized load cell was connected to the rear damper. Each channel was calibrated during static laboratory tests and the calibration constants or matrices were used to convert the measured signals into functional loads applied to the components. Tests were performed involving an expert downhill racer on a competition track. The peak values collected during the study would allow for the definition of static overload tests on the bicycle safety components; the time histories collected in the field will allow evaluating the field loads spectra to be used in the fatigue life prediction of the components and defining the standard fatigue tests to verify the minimum required fatigue strength of the most important components of such an extreme sport discipline

EVALUATION OF SPRINT BIOMECHANICS BY MEANS OF AN INSTRUMENTED TRAINING SLEDGE IN SOCCER

The aim of the study was the functional evaluation of sprint biomechanics by means of an instrumented training sledge in a soccer field. In particular, peak values of the horizontal ground reaction force generated in the first 6 thrusts were estimated after measuring the instantaneous cable tension and the sledge acceleration with a data acquisition system installed on the sledge. Three soccer players were asked to perform 3 couples of 30m sprints (starting once with the left and once with the right leg) while pulling the training sledge: the sledge mass increased in three levels (11.5kg, 16.5kg, 21.5kg). The athletes performed also Bosco tests in monolateral CMJ. Differences in force values between the two legs were more evident after the sledge functional testing in the field than after Bosco monolateral CMJ: the method can suggest functional training procedures to improve the strength of the weak leg and running coordination

Full scale impact testing of ski safety barriers using an instrumented anthropomorphic dummy

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Behaviour of an instrumented anthropomorphic dummy during full scale drop tests

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Vibrational analysis of a flexible bicycle stem during indoor in-vivo cycling on a two rollers servohydraulic test bench

Introduction. Comfort is an important parameter correlated to bicycle usability and depends deeply on vibrations and human perception. The most of vibrations is generated by the interaction between road and wheels and sensed at hands and seat [1][2]. Different approaches were used to evaluate the in-vivo behaviour of different bycicle postures and components, including vibrational excitation applied to the wheels [2],[3]. The present work presents results obtained from a full scale roller bench test [3] on a flexible stem supposed to improve the riding comfort. External vibrations were applied to both wheels using a two rollers servohydraulic test bench [3] with a random load function generator corresponding to road types defined by the ISO 8608: 2016. Methods. A specific flexible stem (Shockstop produced by Redshift), designed to reduce accelerations transmitted to the hands by selectable elastomeric shock-absorbing inserts (SOFT, MEDIUM, HARD), was compared to a standard rigid stem (Deda zero 100 Alluminum). Three road profiles (A= Airport runways and super highways; B= Normal pavements; C= Unpaved and damaged roads, ISO 8608: 2016) were applied to the cyclist in two postures (Posture1-Hands on upper handlebar brakes, Posture2-Hands on handlebar drops). Results. Table 1 reports the Comfort index and Transmission index percent variations respect to the RIGID stem (Red cells represent lower performance). As it can be seen, based on CI the Flexible stems seems to improve comfort in both postures and stem hardness with lower roas harshness, but gives not favourable results in Posture 1 with road C. The transmission index TI seems to give opposite results than the CI in Posture 1, whereas shows better agreement in posture 2. Conclusions. The study shows the suitability of the roller test bench for the stationary analysis of comfort related component in bicycle. The significance of the two parameters CI and TI deserve comparison with a larger number of subjects and their subjective evaluation