CRITICAL ISSUES IN APPLIED SPORT BIOMECHANICS RESEARCH

Applied sport biomechanics represents one of the most challenging fields of biomechanics of human movement. High-speed sport movements require thorough biomechanical analysis to have a good understanding of the different aspects of the techniques especially when working with elite athletes. Through the presentation of some studies carried out at the Bioengineering Center of Milan over the last five years this paper outlines same critical issues in applied sport movement researches. In particular, we investigated the operational feasibility and the reliability of the resulting quantitative kinematics analysis of using free-floating video cameras with variable optics for field three-dimensional sport movement analysis. In other experiments the critical issue of accuracy and reliability of the biomechanical measures was studied

EFFECT OF DIFFERENT HANDLEBAR HAND POSITIONS ON FAST BRAKE LEVER REACHING MOVEMENTS IN CYCLING

INTRODUCTION: The aim of the present study was to evaluate the effect of different kinds of handlebar hand positions on fast brake lever reaching movements. The assumption motivating this study was that riding positions that provide quick access to brake levers allow athletes to more easily manage the braking operation when they are forced to suddenly decrease bicycle speed or change direction to avoid an unexpected obstacle. METHODS: Three high-level road cyclists were the subjects of this study. Each athlete was tested while pedaling on his own racing bicycle mounted on a magnetic braked roller simulator. The bikes were equipped with a Cinelli Spinaci clipon handlebar. While pedaling, the athletes were asked to reach, as quickly as possible, the brake levers and try to brake the wheels’ rotation in the shortest possible time. Seven handlebar starting hand positions were predefined and investigated, including the placement of the hands on the clip-on handlebar. The subjects performed the braking actions in response to external stimuli (visual and acoustic) and were free to choose when to start the movement. For each of the experimental conditions, data for 10 trials were acquired. The ELITE motion analysis system was used at a sampling rate of 100 Hz to collect the 3-D kinematic variables of the right upper limb segments with respect to the handlebar and right brake lever frame. Five retro-reflective markers were glued on the subjects’ skin, and markers were located on sticks fixed to the right brake lever and to the handlebar. To account for bicycle movements, the measured coordinates were referred, by trigonometry, to a reference system whose origin was the handlebar marker. The time the rider took to reach the right brake lever was defined as the time from the first detectable movement of the marker fixed on the third finger of the right hand (distal end of the 2nd phalanx) until the first movement of the brake lever marker. The effect of the different handlebar hand positions on brake lever reaching times was analyzed with one-way ANOVA. The existence of significant differences between conditions was then tested using the Newman Keuls post hoc test. RESULTS: The results of the data analysis were as follows: • In each of the examined experimental conditions, the time the athletes took to reach the brake levers (lower than 300 ms) represented a small fraction of the total time necessary to stop a bicycle after an emergency signal was perceived. • Hand positions slightly affected the access time to the brake levers that, on the average, ranged from 150 ms to 280 ms. Lower values were measured when the hands were placed very close to the brake lever mounts. • Riding with the hands placed on the clip-on handlebar lead to brake lever reaching- times as high as those measured for other traditional positions with the hand placed on the top of the handlebar

A PROCEDURE FOR QUANTITATIVE KINEMATIC ANALYSIS IN RUNNING ON TREADMILL

The purpose of this paper is to describe and test a method and a special developed software package capable of doing a complete 3-D kinematic analysis in treadmill running, including the assessment of kinematic asymmetries by a simultaneous right and left analysis. A pilot study using 8 recreational runners demonstrated that accurate and repeatable quantitative data can be collected and analyzed with the procedure. Comparison of specific kinematic data with literature studies revealed same significant difference in total joint range of motion. Some measurements and samples plots are also presented and discussed. The method and the user friendly software presented here seems to be an useful tool for scientists, trainers and athletes to assess and evaluate biomechanical data during running

NONLINEAR ANALYSIS OF RACE WALKING GAIT: MOVEMENT VARIABILITY, ENTROPY AND MOTOR SKILLS ASSESSMENT

The aim of this study was to explore the issue of motor skills characterisation, by assessing the regularity of motor patterns during race walking gait. Seven competitive race walkers’ action was analysed through an optoelectronic system and a force platform. Sample entropy, a nonlinear dynamics tool, was adopted to evaluate the regularity of a selection of kinematic and kinetic variables. Results allowed to characterise athletic skill and to evidence the changes that may occur over time. In particular, the subtle anomalies of an injured subject were detected. Sample entropy appeared a valid means for individual monitoring in sports and gave clues for possible injury prevention

BIOVARIABILlTY: THE STARTING POINT FOR DEVELOPING RELIABLE MOTOR FEED-BACK PROCEDURES IN SPORTS

Modem technologies allow multifactorial analyses of sports movement. Their output might be used as a reliable feed-back for sports motor applications, but individual variability must be assessed first, to gain more insight on treating data, interpreting results and presenting suggestions. Former studies evidenced important aspects of multijoint coordination and successfully interpreted the role of many kinematic/kinetic measures. Nevertheless they didn't examine biovariability extensively. In this work a common, Widely-studied field test (vertical jump) was chosen to evaluate intralintersubject variance. Results showed a considerable variability in many kinematic and kinetic parameters. Some suggestions on treating data are proposed. Some indications of possible applications are presented

FATIGUE EFFECTS ON SHOOTING ARCHERY PERFORMANCE

As archery competitions normally last many hours requiring a great deal of shoots, the athletes are usually subjected to a deterioration of muscle performance Deterioration of mechanical performance of one or more muscles, which are not able to maintain longer the desired force level, may be related to technique and motor strategy changes Although these modification are probably very subtle, their effect may produce undesirable impact on arrow scores It was the purpose of this study to analyse the possible effect of muscular fatigue on strategy used by athletes to accomplish the task. An additional objective was to determine whether or not fatigue effects are somewhat dependent on skill level of athletes. Twelve archers of Italian Archery Federation were the subjects of this study. According to their FITA scores they were classified as intermediate (n = 7; FITA scores ranging from 1.180 to 1300) and top level archers (n = 5; FITA scores > 1300). 15 shoots for each archer were recorded and analysed at firstly. After these measurements a fatigue protocol was performed. The athletes come to a full drawing position and remained in the aiming phase for 20 s. Each athlete performed six series of ten repetition with rest interval of 20 s. between the sets. Immediately following the fatigue protocol, the subjects performed other 15 shoots. EMG, kinematics and force platform data were acquired and processed using the ELITE motion analysis system An electrical device attached to the bow was used to detect the moment of clicker closure, arrow release. and contact-loss of the arrow with the bowstring Surface EMG was collected from the finger flexor muscles and biceps of the drawing arm and from upper and lower back muscles, with a sampling rate of 1000 Hz. Markers were placed on. the temporal bone and the mandibular joint to mark the head: the shoulders. elbows. wrists and hands to mark the arms; the iliac crests, knees. ankles, and third metatarsal heads to mark the lower limbs. In addition. three markers were placed on the backbone and other three were attached to the bow. Ground reaction forces and centre of pressure displacements were measured with a Kistler force platform at a sampling rate of I000 Hz. In each subject no significant variation in performance scores was evident. In all the subjects a significant increase in bow lateral sway were observed after the fatigue protocol. The increase was much more evident in less skilled subjects. Furthermore, the results showed that less skilled subjects displayed longer aiming phase duration after fatigue protocol

A BIOMECHANICAL COMPARISON BETWEEN RACEWALKING AND NORMAL WALKING STANCE PHASE

The purpose of this study was to understand the peculiarities of lower limbs kinematics and kinetics during racewalking stance, by comparing it with normal walking gait. Four young but skilled athletes were analysed through a motion analysis system and a force platform. Results were expressed in terms of average kinetics and kinematics curves. Many differences emerged between the two walking modes, most of which can be reconducted to the rules that govern this sport. These observations might be useful, both for trainers and practitioners, to gain more insight in racewalking technique and proficiency, but they are just a first step toward an effective application “on the field”. In fact, an individual analysis might discover the athlete’s distinctive biomechanical characteristics and consequently might help in setting better training methodologies

SADDLE PRESSURE DISTRIBUTION IN CYCLING: COMPARISON AMONG SADDLES OF DIFFERENT DESIGN AND MATERIALS

This study compared saddle pressure distribution patterns in a group of experienced cyclists riding their own bicycle mounting different saddle models. Two traditional flat surface saddles incorporating different shock-absorbent materials in the perineal area and two innovative saddles with a hole in the perineal area were evaluated. The T-Scan system was utilised to measure the saddle pressure distribution. Each subject showed an individual pressure distribution pattern when using the same saddle. The use of the different saddles resulted in same significant changes in the saddle pressure amplitude and distribution pattern in all the subjects examined. In general, the flat surfaced saddles showed a more uniform pressure distribution with less pressure on the anterior part and more on the posterior part compared with the saddle with a perineal hole

APPLICATION IN SPORTS OF THE "ELITE": A SYSTEM FOR REAL TIME PROCESSING OF TV SIGNALS

Competitive sport requires a deep engagement of the athletes that have to improve continuously physical and technical qualities with heavy programs of training. The help of the coaches is an important tool both to plan the training and to perform it correctly. The coach evaluates the work of the athlete with quantitative and qualitative inspections. Quantitatively he measures the actual performance or useful parameters (time, length, height) obtaining information on the total efficiency of the athlete. Qualitatively he analyzes the technical aspects of the sport. The analysis is done by a direct visual inspection or by video tape records. The final result is a synthesis of sensations that, through experience and knowledge, becomes practical suggestions. When the same analysis is quantitative, the intervention may he more complete as the coach is supported by powerful information: knowledge of quantities not easy or possible to be detected by visual inspection (velocities, accelerations, forces), accurate description of each phase of the movement, data storage allowing objective comparison in time

PRINCIPAL COMPONENT ANALYSIS OF KNEE ANGLE WAVEFORMS DURING RACE WALKING

This study aimed at understanding whether principal component analysis (PCA) may be useful to characterize race-walkers abilities at different performance levels. Seven young race-walkers of national and international rank were recruited. PCA was applied for classifying and detecting the structure of knee sagittal angle. This statistical technique allowed extracting multidimensional features that capture the greatest variation in race walking data. The scores, i.e. the projections of the original data on the components, revealed to be good discriminative factors for performance level detection. Finally, the underlying linear structure of the principal components provided a biomechanical interpretation of motor skill. The best athletes were able to correctly lock the knee during the mid-stance; the worst ones tended to bend the knee prematurely