Daniela Ciprandi

Dribbling determinants in sub-elite youth soccer players

Abstract Dribbling speed in soccer is considered critical to the outcome of the game and can assist in the talent identification process. However, little is known about the biomechanics of this skill. By means of a motion capture system, we aimed to quantitatively investigate the determinants of effective dribbling skill in a group of 10 Under-13 sub-elite players, divided by the median-split technique according to their dribbling test time (faster and slower groups). Foot-ball contacts cadence, centre of mass (CoM), ranges of motion (RoM), velocity and acceleration, as well as stride length, cadence and variability were computed. Hip and knee joint RoMs were also considered. Faster players, as compared to slower players, showed a 30% higher foot-ball cadence (3.0 ± 0.1 vs. 2.3 ± 0.2 contacts · s−1, P < 0.01); reduced CoM mediolateral (0.91 ± 0.05 vs. 1.14 ± 0.16 m, P < 0.05) and vertical (0.19 ± 0.01 vs. 0.25 ± 0.03 m, P < 0.05) RoMs; higher right stride cadence (+20%, P < 0.05) with lower variability (P < 0.05); reduced hip and knee flexion RoMs (P < 0.05). In conclusion, faster players are able to run with the ball through a shorter path in a more economical way. To effectively develop dribbling skill, coaches are encouraged to design specific practices where high stride frequency and narrow run trajectories are required.

Dynamic balance in elite karateka.

In karate, balance control represents a key performance determinant. With the hypothesis that high-level athletes display advanced balance abilities, the purpose of the current study was to quantitatively investigate the motor strategies adopted by elite and non-elite karateka to maintain balance control in competition. The execution of traditional karate techniques (kihon) in two groups of elite Masters (n = 6, 31 ± 19 years) and non-elite Practitioners (n = 4, 25 ± 9 years) was compared assessing body center of mass (CoM) kinematics and other relevant parameters like step width and angular joint behavior. In the considered kihon sequence, normalized average CoM height was 8% lower (p < 0.05), while CoM displacement in the horizontal direction was significantly higher in Masters than in Practitioners (2.5 vs. 1.9 m, p < 0.05), as well as CoM average velocity and rms acceleration (p < 0.05). Step width was higher in Masters in more than half of the sequence steps (p < 0.05). Results suggest that elite karateka showed a refined dynamic balance control, obtained through the increase of the base of support and different maneuvers of lower limbs. The proposed method could be used to objectively detect talented karateka, to measure proficiency level and to assess training effectiveness.

Primary bladder neck obstruction may be determined by postural imbalances

Primary bladder neck obstruction (PBNO) is a frequent under-investigated urological condition in which the bladder neck fails to open adequately during voiding. In the majority of cases no known etiological factor can be found. In this study we propose a new hypothesis to explain the origin of the disease in young male patients with no neurological disorders. We suggest a possible role of an unbalanced biomechanics of the pelvis on urethral sphincters activity and on functional bladder capacity. To support the proposed hypothesis, we present pilot gait analysis data of young male patients with primary bladder neck obstruction.

Rowing technique determinants: a comparison between international and national level rowers

Rowing is a motor skill that requires high levels of consistency, coherence, accuracy and continuity, particularly at an elite level [1]. The rowing stroke consists of two phases: the drive, during which force is applied to the blade in order to move the boat relative to the water, and the recover, during which the rowers return to their former position [2]. The goal of the current study was to investigate the kinematic differences between rowers of International Level (IL) and National level (NL), in order to identify parameters that have the potential to characterise the best ergometer rowing technique. With this objective, we analysed three IL (age: 18.3 (0.5) [years]; height: 183.0 (8.8) [cm]; weight: 76.3 (8.9) [kg]), and thirteen NL rowers (22.2 (1.9) [years]; 182.5 (4.7) [cm]; 77.1 (7.4) [kg]), using a motion capture system (BTS SpA, Italy). Duration of the stroke phases, Range of Motion (RoM) of the knee 3D trajectories, length of the body Centre of Mass trajectory (COMd) and the curvature of the wrist path during the stroke (Index of Curvature, IC) were compared using the Mann-Whitney U test. The findings showed that the IL rowers presented a non-significant decrease of the drive phase duration (IL: 0.94 (0.04) [s]; NL: 1.05 (0.08) [s]; p= 0.122), higher Knee Rom (IL: 0.68 (0.04) [m]; NL: 0.51 (0.02) [m]; p= 0.018) in the Anterior-Posterior direction, a higher COMd (IL: 2.62 (0.12) [m]; NL: 1.74 (0.15) [m]; p=0.026) and a higher IC (IL 0.984(0.003); NL: 0.980(0.003); p=0.040). In conclusion, the stroke duration, the amplitude of the movement in the Anterior-Posterior direction and the control of the wrist path seem to be associated with high-level performances; the findings suggest that IL rowers present a better command of technique, timing and power, compared to NL rowers.

Can experience in karate be estimated by Principal Component Analysis

Karate is a Japanese martial art that involves repeated and technically demanding sequences of strikes and defences. In kata competition selected movements are organised in fixed sequences of varying duration and complexity. The evaluation of kata is usually made by subjective scoring from coaches and judges, who employ a qualitative, global assessment. Holistic quantitative evaluations of karate performance are still unavailable. Based on previous findings (1), we hypothesise that the multi-joint motion patterns that enable complex techniques are experience-dependent. If this were true, we would seek to find which motion pattern could be more sensible to the experience level. To test this hypothesis, a method based on the Principal Component Analysis (PCA) appears well-suited to detect the “synergies” or “coordinative structures” by which the motor system organises a movement (2). PCA can provide a quantitative global analysis of stylistic differences in technique. In this study we aimed at: describing the fundamental multi-joint synergies of a karate performance, under the hypothesis that the latter are skill-dependent; estimate karateka’s experience level, expressed as years of practice. A motion capture system recorded traditional karate techniques of ten professional and amateur karateka. At any time point, the 3D-coordinates of body markers gave posture vector that were normalised, concatenated from all karateka and submitted to a first PCA. Five principal movements described both gross movement synergies and individual difference, explaining 91% of the overall variance. A second PCA followed by linear regression estimated the years of practice using principal movements (eigenpostures and weighting curves) and centre-of-mass kinematics (error: 3.71 ys; R2=0.91, p<0.001). Principal movements and eigenpostures varied among different karateka and as a function of experience. This approach provides a framework to develop visual tools for the analysis of motor synergies in karate, allowing to detect the multi-joint motor patterns that should be specifically trained to increase performance.

Three-dimensional analysis of balance control strategies in elite karateka

In karate, balance control represents a key performance determinant (1). Balance stability was reported to be related to a refined control of the center of mass (CoM) displacement (2). The aim of the current study was to quantitatively investigate the motor strategies adopted by elite and non-elite karateka to maintain balance control. We analyzed the execution of traditional karate techniques (kata) in two groups: elite Masters (n=6, 31±19 years) and non-elite Practitioners (n=4, 25±9 years). On each participant, the three-dimensional coordinates of 14 reflective markers (landmarks: right and left tragion, acromion, olecranum, radius styloid process, great trochanter, femur lateral epicondyle, lateral malleolus) were recorded by nine infrared cameras of an optoelectronic motion analyzer with a 120 Hz sampling rate. Kinematic parameters assessed were: CoM, step width, joints range of motions. CoM kinematics was computed according to the segmental centroid method (3). In the 11 steps of kata, CoM height was 8% lower (p<0.05, Mann-Whitney non parametric U-test), CoM average velocity and rms acceleration were approximately 35% higher (p<0.05) and step width was higher (p<0.05) in Masters. There was a significant difference between groups in CoM height and step width in seven and six out of the 11 steps, respectively. CoM vertical displacements resulted almost equal along the vertical direction, while in the horizontal direction it was significantly (p<0.05) higher in Masters than in Practitioners. Results suggest that elite karateka developed a refined body balance control, obtained through the increase of the base of support and different maneuvers of lower limbs. The proposed method could be used to objectively detect talented karateka, to measure proficiency level and to assess training effectiveness.

The face in Down’s syndrome: indices of overall size and harmony in Sudanese vs Italian subjects

The study aimed to provide quantitative information about the facial soft-tissues of Italian and Northern Sudanese subjects with Down’s syndrome (DS) by using summary anthropometric measurements representative of facial size and harmony. The 3D coordinates of soft-tissue facial landmarks were obtained by a computerized digitizer in 54 Italian subjects with DS (20 females, 34 males, aged 13-52 years), in 64 Northern Sudanese subjects with DS (18 females, 46 males, aged 5-34 years), in 578 healthy Italian, and 653 healthy Northern Sudanese reference subjects, matched for sex and age. From the landmarks, 16 facial dimensions were calculated. Data from subjects with DS were compared to those collected in reference individuals by computing z-scores. Two summary anthropometric measurements for quantifying craniofacial variations were obtained: the mean z-score (an index of overall facial size), and its standard deviation, or the craniofacial variability index (an index of facial harmony) [1]. In subjects with DS, facial size was significantly smaller, and craniofacial variability was significantly larger than in normal individuals; 93% of Italian and 81% of Northern Sudanese subjects with DS had one or both values outside the normal interval. Overall, Italian subjects with DS differed more from the norm than Northern Sudanese ones. In the Northern Sudanese subjects, the mean z-scores and the CVI decreased significantly with age. The facial soft-tissue structures of subjects with DS differed from those of normal controls of the same age, sex and ethnic group: a reduced facial size was coupled with a global anomalous relationship between individual measurements. The alterations in soft-tissue facial dimensions were different in the two ethnic groups and partially influenced by age.

Dribbling skill determinants in youth soccer players

Dribbling and pass-kick are the most frequently performed techniques during match play. While an extensive knowledge is available about kicking biomechanics, little is known about dribbling kinematics. Given that dribbling performance can assist in the talent identification process [1], we aim at finding the biomechanics determinants of this technique. A motion analysis system recorded the 3-D coordinates of 21 reflective markers placed upon the body of 10 youth sub-elite soccer players (12.6±0.37 years, 42.9±6.15 kg, 1.54 ± 0.07 m). Each participant performed 5 slalom-dribbling tests consisting of a 180° turning and four changes of direction. Since dribbling speed is a separating performance factor, players were split into two groups of 5 according to the execution time (“fast” and “slow”). Center of Mass (CoM) trajectory, Range of Motion (RoM), velocity and acceleration were computed along the three directions [2]. Mann-Whitney’s non-parametric tests were used for comparisons. Fast and slow players did not differ in terms of age, weight, body height, BMI, playing position and number of foot-ball contacts (p>0.05). While CoM average velocity and root mean square acceleration were similar in the two groups, CoM mediolateral and craniocaudal RoM were significantly lower (p<0.05) in faster players. Skilled players took less time in completing the test because they were able to drive the ball while running through a shorter path. Their CoM vertical and lateral displacements were significantly lower, meaning that, at a higher skill level, dribbling technique is delivered in a more effective and economical way.