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

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

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

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

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

VERTICAL JUMP CHARACTERISTICS FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

The purpose of this study was to compare two-legged countermovement vertical jump characteristics between operated and non-operated lower limbs of twelve recreational athletes who had undergone unilateral ACL surgical reconstruction. A control group of eight uninjured athletes was employed. Bilateral vertical ground reaction forces, joint angles, moments and powers patterns were measured and statistically analysed. The examination of the angular kinematics revealed for the injured limb a significant reduction of the knee and ankle extension angles at the take off and an ankle ROM reduction. Examining peak moments and powers the injured knee exhibited significant lower values. The reduction of the knee peak power seems to be compensated in most of the subjects by an increase of the omolateral ankle peak power

Quantitative Comparison of Locomotor Performance in Different Race Walkers

Biomechanics of track and field activities has been investigated by many authors. A literature overview on race walking points out various analyses on: supporting energy (Zarrough et al. 1974), mechanical energy variations (Marchetti et at. 1983), potential versus kinetic energy variations (Ralston and Lukin, 1969), muscular work efficiency (Marchetti et at. 1983), Payne (1979) reported the ground reaction components measured during race walking while some aspects of the related biomechanics were discussed by Boccardi et al. (1978) by displaying a vectorial representation of the ground reaction evolution. As the trainers know well, the primary needs of the race walkers involve something more than a general description of the basic executive mechanism. The athletes have to solve a very complex problem: walk under restrictive Jules for a time varying from 18 to more than 200 minutes at a speed that is usually more than two times higher the threshold at which a man begins running naturally (Cavagna et at., 1977). Such goal is obtained through a proper modification of the normal motor-patterns aimed to the best use of the endurance qualities. By the way, the critical importance of optimal motor efficiency to reduce any possible noisy factor is evident. The aim of this study is to quantify locomotor performances of two homogeneous groups of differently ranked walkers. The vectorial representation of the ground reaction force is used to identify and compare typical biomechanical features associating with the athletic level. A further data processing, including normalization and statistical estimation of the differences between the results from the two groups. leads to a practical and powerful tool for the investigation of motorcoordination and asymmetry in race walking