Monitoring Of Sprinters' Motor Coordination Through Vertical Jump Exercises

Vertical jumping exercises are widely used in sport activities to estimate the motor condition of the athletes. Common methodologies, based on devices designed to compute the jumping height, seem to be not adequate in order to monitor the motor coordination status as function of training programs. This is particularly true when high level athletes, practising sports where functional qualities must be maximally developed, are considered. The aim of this study is to analyse the motor coordination patterns by means of mechanical net moments and powers, expressed at the main lower limb joints, during vertical jumping exercises. Subjects of the study were nine male sprinters (range of best performance on 100 m. = 10".4 - 10".8). The athletes were asked to jump as high as possible while keeping the hands on their hips, and performed jumps either with the thrust of both legs or the thrust of one leg. Data of four trials per condition and legs were recorded. Kinematic data, concerning the spatial position of ten anatomical landmarks . (five per each leg), were recorded by means of an optoelectronic system (ELITE) with a sampling rate of 100 Hz. Simultaneously ground reaction forces were measured with a Kistler force platform at the sampling rate of 1000 Hz. The internal joint centers, such as the corresponding moments and powers, were estimated by using a special software (SAFLO) which inputs were anthropometric, kinematic and kinetic data. When necessary, non parametric statistics (Spearman rank correlation coefficient, Wi1coxon-MannWhitney test) were used to avoid the assumption of normal distribution of the underlying population. By considering intra-individual data the results show quite low subject variability in kinematics and ground reaction forces for all trial conditions. There is an appreciable variability of moment and power maxima at all the joints and this variability is not random but has high degree of covariance. Furthermore asymmetries have been evidenced between the mechanical output at the same joint both during bilateral and unilateral exercises. By considering interindividual data it has been found a wide spectrum of motor strategies evidenced by peaks amplitude and time sequence distribution. This biomechanical approach seems to be an appropriate tool to quantify important motor differences, not evidenced by the measurement of the gravity center displacement

A 3-D KINEMATIC STUDY OF TWO POPULAR FLEXIBILITY TESTS

INTRODUCTION. Flexibility is the intrinsic property of body tissues which determines the range of motion achievable without injury in a Joint or group of joints Goniometers are often used to measure the range of motion of the joints. These devices have been criticized and their reliability questioned.. Part of the problem is with the instruments and part with the procedure for using them. To deeply understand the phenomenon of flexibility more accurate, precise, multiaxial measurements are desirable By using an automatic motion analyzer (accuracy 1/3000 the field of view), it was the purpose of this study to perform a 3-D analysis of two popular flexibility tests When possible, the data were compared with those obtained by standard goniometers. METHODS Four recreational athletes (age range: 24-40 yr.) were the subjects of this study They were required to perform the sit and reach test and the passive single-straight-leg raising test. Both the tests are usually used as a test for hamstring tightness even if the sit and reach test combines back and hamstring flexibility Before the measurements the subjects warm-up by performing 10 minutes of slow jogging, and slow stretching movements Ten trials for each exercise were executed with one-minute rest period between trials. Kinematic data were recorded by means of an optoelectronic system (ELITE) with a sampling rate of 100 Hz. Markers were placed on: C7, T3, T6, T9, T12, L3, and S1 to mark the spine; sacroiliac spines, iliac crests, great trochanters, femoral condiles, malleola, and fifth metatarsal heads to mark the pelvis and the lower limbs; acromions, elbows and wrists to mark the arms. The position of the internaI joint centers of the hip, knee and ankle were estimated from the position of external landmarks using a special software which inputs were anthropometric and kinematic data. The back profile was modelled using a cubic spline. RESULTS. Mean and standard deviation values of the hip range of motion during the sit and reach and the straight-leg raising test are outlined in table 1 and 2, respectively. The results showed significant bilateral differences for most of the parameters examined suggesting that evaluative procedures requiring controlateral comparisons may be inaccurate. The dynamic examination of the sit and reach exercise revealed large intersubjects differences in the way to come to the full extended position evidentiating a different degree of spine mobility among the subjects The comparison with standard goniometer measurements showed differences up to 24 degrees in the hip range of motion CONCLUSION. In summary, the model presented in this work: gives a good representation of the subjects during all the phases of the flexibility tests; provides a direct quantification of the range of motion in degrees; allows the measurement of several joints and joint actions, the control of compensatory movements, and a permanent record of the trials

MULTIFACTORIAL ANALYSIS OF SHOOTING ARCHERY

In archery shooting there is a fixed sequence of movements the shooter performs bow holding, drawing, full draw, aiming, release and follow through stage This sequence allows the archer to get highly reproducible releases for achieving and maintaining good results. This implies the following: I ) the programming of the proper movement sequence during the different phases, 2) the control of body segments action; 3) the body and bow equilibrium maintenance. In such a complex motor task which involves multijoint coordination, a distinctive feature of the motor system is maximally exploited, namely the potential to execute the same motor task through different combination of motor equivalent actions. It was the purpose of this study the identification of the various strategies utilised by a group of different skilled archers and the evaluation of the role that skill has in movement execution This requires a simultaneous investigation of different kinds of variables, including kinematics, forces and EMG. Twelve archers of Italian Archery Federation were the subjects of this study. According to their FITA scores they were classified as intermediate (n = 7: FlTA scores ranging from 1180 to 1300) and high level archers (n = 5; FlTA scores > 1300). Twenty shoots for each archer were recorded and analysed. Electromiographic (EMG), kinematics and force platfor~n data were acqu~red 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 brachial 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; shoulders, elbows, wrists and hands to mark the arms; 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 1000 Hz. Despite-the apparent intra and intersubject similarities in performing the shoots. slight differences were observed in both kinematics and EMG pattern. Results indicate that while there are common elements that are present in all subjects, strategies .vary in some ways that can be attributed to the skill and in others that may not attributed to the skill For example, the ways to come to full drawing position as well as EMG activity appear to be idiosyncratic, as each subject showed a unique configuration Among the disparities that may attributed to the skill. differences in the relative duration of the shooting phases, in arm and bow stability, and degree of activation of biceps brachial seem to be the most relevant

GROUND REACTION FORCE PATTERNS FOR THE EVALUATION OR MOTOR RECOVERY IN ATHLETES AFFECTED BY KNEE INJURIES

INTRODUCTION Vertical jump is an exercise widely adopted to evaluate some motor characteristics of the athletes. Vertical component of the ground reaction force (VGRF) is often used to gain more information regarding efficiency and motor coordination of the lower limbs. The aim of this study is to evaluate vertical jump performances of subjects afflicted by ACL injury, by means of VGRF patterns. METHODS Ten healthy rugby players (HP) were the sample of this study, together with four subjects who present a ACL pathology (PP), due to a previous injury. At the time of the acquisition all the pathological subjects had been reintegrated in the team training and competitive programs. The subjects were asked to perform 20 two-legged vertical jumps, as high as possible, keeping one foot at a time over a Kistler force platform. Arms were behind their back, in order to minimize the contribution of the upper part of the body to the thrust of the legs. Ground reaction forces were recorded by means of a force platform at the sampling rate of 1000 Hz, and data were normalized in amplitude to the body mass. Jumping height was computed through the flight time. RESULTS In agreement with previous studies, a common pattern in the GRF for HP subjects was observed; the typical VGRF time course was characterized by an initial decrease of the force until a minimum, followed by two maxima with a further relative minimum in between, the first peak is the absolute maximum. Amplitude and timing of these parameters were examined for the analysis. The mean jump height evidenced statistical diierences only between one PP subject and the mean jump height of the HP group. By considering VGRF amplitude, significative differences have been found only between the amplitude of the first minimum (healthy = 0.25 BW, pathological = 0.36 BW) while no differences were found between the absolute maxima. By considering the timing of the different phases it has been observed that PP group show a longer delay between the initial minimum and the first maximum. As far as the VGRF time course is concerned, we noted for PP subjects individual behaviors in comparison with the average pattern of the HP. Furthermore, the presence of a strong asymmetry between the curves of the healthy and pathological limb, were observed. CONCLUSIONS Jumping height does not seem to be a parameter useful in designating motor impairments in subjects with ACL injuries. However, as far as the VGRF is concerned, intra and inter individual significative differences may be observed. A common characteristics of PP group is the reduced capacity to perform the eccentric phase. While the amplitude of the maxima is similar, VGRF patterns of the PP group show individual characteristics and appreciable asymmetries between the two legs. These results allow to speculate about compensatory motor actions and confm that the majority of the PP subjects were from a complete motor recovery

INFLUENCE OF AN ERGOLINE BICYCLE ERGOMETER ON BODY SEGMENT KINEMATICS AND POSTURE

INTRODUCTION Bicycle erogmeters have been the most used modality in the investigation of physiological and biomechanical parameters in cycling, for their ease of calibration and adaptation to various body size. In addition, the possibility to apply rackg type saddles, handlebars, and pedals allows the athlete to more closely replicates road racing condition in laboratory. There is, however, very little information about the effects of these devices on body kinematics. By a simultaneous right and left 3-D kinematic analysis, the purpose of this study was to compare body segment kinematics and posture of five experienced cyclists while pedaling on their own racing bicycle and on a widely used bicycle ergometer. METHODS Five experienced road cyclists were the subjects of this study. Each athlete first pedaled on his own bicycle mounted on rollers fitted with a variable-load device and then, performed on an electronically braked cycle erogmeter (Ergoline, Germany) which was mechanically modified to allow the athletes to correctly adjust the seat and handlebar, and to use their nonnal cycling shoes and cleats. Using the ELm system motion analyzer (four 100 Hz-TV cameras), the 3-D coordinates of small retoreflective markers glued onto 19 anatomical repere points were recorded with the subjects pedaling at 90-95 rpm. RESULTS As it can be seen in the table, considering lower limb joint motion in the sagittal plane, sigdcant differences between the two pedaling conditions were found in the ankle range of motion (ROM) and in maximum (MAX) and minimum (MIN) angular hip flexion. Others relevant differences were evident examining joint rotation center trajectories in the frontal plane, with the foot and shank performing farther from the bicycle frame using the Ergoline. In most of the subjects this resulted in an excessive transverse/frontal knee motion. The pelvis is significantly less anteroversed on the bicycle ergometer with more pelvic tilt in the frontal and horizontal plane. CONCLUSION The use of the examined ergometer significantly altered lower limb and pelvis kinematics in the frontal plane compared to standard bicycle. This must be considered when this device is used for training andlor to collect physiological and biomechanical data

GENDER DIFFERENCES IN JOINT MOMENTAND POWER MEASUREMENTS DURING VERTICAL JUMP EXERCISES

INTRODUCTION Gender differences are apparent not only in the absolute maximum force level but also in the rates at which the force and/or power is produced(Koml et al., 1978). The predominant requirement for success in a large number of athletic skills IS explosive power. For the lower body, this IS perhaps best exemplified by vertical jump. Vertical jumps a complex ballistic multi-joint movement, where the musculature around the hip, knee and ankle joints collectively operate to produce patterned movements. The purpose of this study was to assess the effect of gender on the mechanical output of the lower limb joints (moments and powers), during vertical jumping exercise. Methods: Eight male (age 22.4 yrs) and eight female ( age 21.7yrs) athletes served as subjects. After 20 min. of standard warm-up, the subjects performed 20 maximal vertical jumps with the arms behind the back. The 3-D coordinates of ten anatomical landmarks ( five per leg) were detected by the opt electronic ELITE system (Ferringno & Pedotti, 1985) with a sampling frequency of 100 HzS simultaneously, the GRF signals were measured and acquired with a sampling frequency of 500 Hz. Internal joint centres and the corresponding moments and powers were estimated from anthropometric and kinematic data using a special software package Group differences were assessed by the Wilcoxon signed rank test Statistical significance was assessed at

SIMPLIFIED 3-D MODEL FOR THE CALCULATION OF BODY SEGMENT KINEMATIC ASYMMETRIES IN CYCLING

INTRODUCTION The analysis of lower limb kinematics in cycling has generally been confined in the sagittal plane by using data obtained with a 2-D analysis Furthermore, when asymmetries were evaluated this was done by detecting data from one leg at time and subsequently comparing the scores obtained from the two sides in different trials. The present work provides a three-dimensional model for the calculation of body segment kinematics, by measuring the 3-D coordinates of a reduced number of external markers. METHODS Subjects of this study were 8 professional road cyclists, (age 25.1 ± 40 yr., body mass: 68.6 ± 6.4 kg), usually covering more than 25.000 km/year The subjects used their own bicycle mounted on rollers fitted with an air-operated variable-load device. Data were recorded at three levels of external load (Iow, medium and high) The ELITE system motion analyzer was used with 4 TV cameras paired on the two sides of the cyclist. Sampling frequency was 100 Hz Size of the passive retroreflective markers was 10 mm in diameter. The 3-D body coordinates (iliac crest, great trochanter, femoral condile, malleolus, fifth metatarsal head) and some anthropometric measures of the subject were the input of a mathematical model designed to describe the spatial kinematics of seven rigid segments belonging to the lower limbs (feet, shanks, thighs and pelvis). RESULTS Tables 1 and 2 show the mean and the standard deviation of some of the variables used for the analysis They have been computed by grouping right and left patterns of the whole group As it can be seen, when the load changes there is an evident trend of some variables. For example, the range of motion decreases at the hip joint, when the load Increases, conversely it increases at the knee and at the ankle joint. The individual examination revealed as the majority of athletes were characterized by significant left-right differences in the selected lower leg angles and in some linear kinematic parameters. These asymmetries appear to be subject, joint and pedalling modality dependent. CONCLUSION The method presented here seems to be an useful tool to assess and to evaluate biomechanical data during cycling. The proposed kinematic model gives indeed a good representation of the cyclist during his action. In particular the possibility to collect simultaneously data from both sides of the body appears to be very informative about asymmetries characterizing cyclists

EFFECTS OF PLANTAR ORTHOSIS ON DYNAMIC PLANTAR PRESSURE MEASUREMENTS IN RUNNERS

During the past years, the use of custom-made plantar orthoses (POs) has been sharply increased among athletes. Concurrently, a great effort has been dedicated by orthotic designers and manufacturers to improve the quality of their products. Only recently, however, systems that allow dynamic plantar pressure measurements within shoes have become available. Data and information provided by these devices can potentially reveal information about both the structure and the function of the foot and may also be used to evaluate the effectiveness of specifically designed POs on plantar foot pressure. By analyzing the pressure distribution in different plantar areas and the centre of force path as well, the aim of this work was to examine the efficacy of specific custom-made POs in athletes wearing their own running shoes. For this purpose, eleven runners were randomly selected among a population of competitive athletes wearing POs. The orthosis had been made by different laboratories using different casting methods. Each subject performed two separate running trials at 12 km/h on a motorized treadmill: one trial wearing his own custom-orthotics in the shoes, and one trial without. In the two experimental conditions, data for at least six strides for each foot was collected. The Fscan inshoe pressure measurement system was used to measure piantar pressure during all trials. The system used an ultra-thin flexible and trimmable sensor with 960sensing locations distributed evenly across the entire plantar surface. These food sensors can be customized to the individual needs and sizing of each subject. According to previous studies, the results of trials with and without orthosis appeared to show a sensitivity to this change in condition. In many ofthe examined parameters, significant changes have been found between the two experimental conditions. However, in three cases, although inserts are thoughtto redistribute and decrease local plantar pressure beneath the foot, Pos significantly increased pressure in particular areas of the metatarsal region. Furthermore, in two subjects, a dramatic pressure increase had been found in the lateral portion of the midfoot suggesting an overcorrection of the medial arch support. In four subjects the effect of POs was not significant in each of the examined parameters. In only three subjects, the centre of force path was found to deviate significantly with POs

3-D KINEMATIC ANALYSIS OF CANOEING ON A SIMULATOR: DIFFERENCES BETWEEN ELITE, INTERMEDIATE AND NOVICE CANOISTS

Using 3-D kinematic analysis, this paper identified kinematic variables that govern successful performance in canoeing on a simulator. The presence of side-to-side asymmetries in selected linear and angular variables was investigated. Elite, intermediate and novice canoeists participated. Similar to previously results for symmetrical cyclic sport activities like cross-country skiing, running and cycling, elite athletes evidenced higher movement amplitude and a more symmetric behavior compared with intermediate and novice paddlers. The less experienced athletes evidenced more accentuated saddle and pelvis movements in the frontal plane. Aerobic and anaerobic capacities and technical skills developed over years of training may explain the reported difference

LOWER LIMB KINETIC VARIABILITY IN VERTICAL JUMPING

For more that 50 years vertical jumping exercises have been widely used in sport practice as a measure of power not only to predict athletic ability but also to obtain indications on same near-muscular and motor characteristics of the athletes. The most interesting work in this area has been done by a research group at the Free University of Amsterdam. The studies of these authors evidenced very elegantly that kinetic analysis provides potentially more diagnostic information force derived indices. However, what the majority of previous studies on human extremely large intra subject variability of the joint kinetic variables. So far, no attempts have been made to gain more insight into the variability inherent in moment and power selected measurements in vertical jumping exercises. To the best of our knowledge, in fact, all the studies employed on or more homogeneous subject groups and presented data describing the average performance groups. Furthermore, frequently, when mean values of kinetic parameters for a group were calculated, only the highest jump of each subject was selected for the calculation. The present experiments were devised to gain more insight into the variability of aforementioned biomechanical parameters in order to determine the appropriate number of trails necessary to obtain a stable mean for these parameters and to investigate the interday variability. Eight recreational athletes were the subjects of this study. In two different test sessions, each subject performed 25 double-legged countermovement vertical jumps without the arm swing. Kinematic data, concerning the spatial position often anatomical landmarks (five per each leg), were recorded by means of an optoelectronic system (ELITE) with a sampling rate of 100 Hz. Simultaneously, ground reaction forces were measured with a Kistler force platform at the sampling rate of 1000 Hz. The internal joint centres, such as the corresponding moments and powers, were estimated by using a special software (SAFLO) which inputs were anthropometric, kinematic and kinetic data. Preliminary results show that, considering all the subjects, power mean value stability ranges from 11 to 16 trials. Interday correlation was higher for hip and ankle and lower for knee values. These results suggest the need to adopt multiple trial protocols to reach reliable results suitable for identifying meaningful performance differences