A THREE-DIMENSIONAL KINEMATIC ANALYSIS OF HANDBALL THROWS

INTRODUCTION: The success of a shot in a game of team handball depends very often on the throwing velocity. One of the most important factors affecting ball's velocity is the technique of motion. This technique can be improved by the training process, but for the high performance players that progress is very difficult to achieve. In order to improve the efficiency of that process scientists and coaches should define the most important characteristics of the throwing technique and then develop them during training. The first step leading to this goal is to identify the main parameters of the handball throwing technique. The purpose of this study was to quantify selected kinematic variables of the handball throwing and, in particular, to establish the relationships between athletes' movement patterns and throwing velocity. METHODS: Ten high-performance handball field players took part in the experiment. The average values of basic parameters of physical characteristics of the subjects were: 86.5±9.8 kg body mass, 1.89±0.09 m body height and 22.4±1.8 years of age. The subjects were video taped by two cameras at 60 Hz (CamCoder Panasonic) throwing on the spot from the distance of 7m (penalty shot) to the goal. The cameras were placed perpendicularly at the distances of 14.3 m to the right of, and 31.0 m behind the player. Three-dimensional coordinates of 16 points of each subject with a ball were calculated by combining the images from both cameras. Each throw was digitized and analyzed using the Ariel Performance Analysis System (APAS). Fifty sequences were digitized: 30 frames prior to and 20 frames after the release of the ball. Statistical analysis of the results was carried out with the use of Statistica v. 5.0 software. RESULTS: The following kinematic parameters were defined: duration of the movement, linear and angular displacement of the body parts, and their derivatives - linear and angular velocities. The throwing technique analysis was based on the values of those parameters. The results show that the huge differences of throwing technique parameter values exist even among the high performance handball players. The linear velocity of the ball was 24.45 m/s ± 1.97 m/s (range: 21.11 m/s ¸ 28.50 m/s), horizontal linear displacement of the hand with a ball (XY plane) - 1.74 m ± 0.14m (1.60 m ¸ 2.10 m) and rotational energy of shoulder - 286 J ± 109 J (95 J ¸ 511 J). CONCLUSIONS: The parameters describing the performance were used to estimate the efficiency of the throwing technique. The differences between the values of trunk momentum and the momenta of distal parts of upper limb (arm, forearm, wrist) appeared to be one of the most important factors in the evaluation of throwing technique

THE INFLUENCE OF SELECTED BODY DIMENSIONAL PARAMETERS ON THE MECHANICAL PARAMETERS OF THE VERTICAL JUMP

INTRODUCTION: The purpose of the present study was to determine the influence of body fat, as well as selected limb lengths and proportions, on the maximal mechanical power and height of the countermovement jump. The effect of countermovement depth, body mass and jump height on maximal power, known from our previous study, was taken into consideration as well. METHODS: Untrained physical education students (56 female and 38 male) volunteered to take part in the CMJ jumping test, consisting of 3 jumps of different countermovement depths performed at one-minute intervals on a computerized Kistler force plate. Results of the highest jump were selected for each subject for further processing. The following variables were included in the statistical analysis: the maximal mechanical power (Pmax) developed during take-off, the height of the jump (h), the counter-movement depth (d), body mass (m) and height (H), lengths of the foot (F), shank (S), leg (L), trunk (T), shank to leg length ratio (s) and fat mass. The Shapiro-Wilk test was used to examine the distributions of the tested variables. Pearson’s correlation matrix and multiple regression analysis were employed to identify the relationships between the tested variables. RESULTS AND CONCLUSIONS: In both female and male groups the multiple regression procedure (the forward stepwise method) pointed the height of the jump, the countermovement depth and the body mass as variables having an effect on maximal power. Significant effects of the fat mass and the shank-to-leg length ratio on the height of jumps were found. REFERENCES: Aura, O., Viitasalo, J. T. (1989). Biomechanical Characteristics of Jumping. Intertional Journal of Sport Biomechanics 5, 89-98. Bobbert, M. F., Gerritsen, K. G. M., Litjens, M. C. A., Van Soest, A. J. (1995). Explanation of Differences in Jump Height Between Countermovement and Squat Jumps. Book of Abstracts. XV ISB Congress. Jyväskylä Dowling, J. J., Vamos, L. (1993). Identification of Kinetic and Temporal Factors Related to Vertical Jump Performance. J. Appl. Biomech. 9, 95-110. Harley, R. A., Doust, J. H. (1994). Effects of Different Degrees of Knee Flexion During Continuous Vertical Jumping on Power Output Using the Bosco Formula. Journal of Sports Sciences 12, 2, 139-140. Gajewski, J., Janiak, J., Eliasz, J., Wit, A. (1996). Determinants of the Maximal Mechanical Power Developed During the Countermovement Jump. In J. Abrantes (Ed.), XIV International Symposium on Biomechanics in Sports (pp.420-423). Lisbon

Inter-individual similarities and variations in muscle forces acting on the ankle joint during gait

Muscle forces acting over the ankle joint play an important role in the forward progression of the body during gait. Yet despite the importance of ankle muscle forces, direct in-vivo measurements are neither possible nor practical. This makes musculoskeletal simulation useful as an indirect technique to quantify the muscle forces at work during locomotion. The purpose of this study was to: 1) identify the maximum peaks of individual ankle muscle forces during gait; 2) investigate the order over which the muscles are sorted based on their maximum peak force. Three-dimensional kinematics and ground reaction forces were measured during the gait of 10 healthy subjects, and the data so obtained were input into the musculoskeletal model distributed with the OpenSim software. In all 10 individuals we observed that the soleus muscle generated the greatest strength both in dynamic (1856.1N) and isometric (3549N) conditions, followed by the gastrocnemius in dynamic conditions (1232.5N). For all other muscles, however, the sequence looks different across subjects, so the k-means clustering method was used to obtain one main order over which the muscles’ peak-forces are sorted. The results indicate a common theme, with some variations in the maximum peaks of ankle muscle force across subjects

A SIMPLE MATHEMATICAL MODEL OF A SINGLE SCULLING TECHNIQUE

The results in sport in rowing depend on the two most important factors, such as the athlete physical features and the techniques of motion. The assessment and optimisation of rowing techniques are possible only when one disposes the reliable mathematical model predicting the results of the regatta that is the time of covering an assumed distance. A single scull participating in the 2000 meters distance regatta is our subject. The purpose of this study is to create a simplified mathematical model to simulate the rowing boat dynamics. The boat-rower system is treated as a material point here. The oar has a prescribed angular motion vs. oarlock depending on the time. The hydrodynamics force distribution to be developed on the oar’s blade has been modelled here. Then, the boat motion was described by a single nonlinear ordinary differential equation (NODE). The proposed simple model gives the possibilities of fast and reliable simulation of the single sculling technique and forecasts the result of rowing regattas

First signs of elderly gait for women

Background: The aims of this study have been twofold: to attempt to reduce the number of spatiotemporal parameters used for describing gait through the factor analysis and component analysis; and to explore the critical age of decline for other gait parameters for healthy women. Material and Methods: A total of 106 women (aged ≥ 40 years old (N = 76) and ≤ 31 years old (N = 30)) were evaluated using a pressure-sensitive mat (Zebris Medical System, Tübingen, Germany) for collecting spatiotemporal gait parameters. Results: The factor analysis identified 2 factors – labelled Time and Rhythm – that accounted for 72% of the variation in significant free-gait parameters; the principal component analysis identified 4 of these parameters that permit full clinical evaluation of gait quality. No difference was found between the groups in terms of the values of parameters reflecting the temporal nature of gait (Rhythm), namely step time, stride time and cadence, whereas significant differences were found for total double support phase (p < 0.001). Next, seeking evidence of a critical decline in gait, we selected 3 parameters: total double support, stride time and velocity. We concluded that the women taking part in the experiment manifested significant signs of senile gait after the age of 60 years old, with the first symptoms thereof already manifesting themselves after 50 years of age. Conclusions: We show that among 26 spatiotemporal parameters that may be used for characterizing gait, at least a half of them may be omitted in the assessment of gait correctness; a finding that may be useful in clinical practice. The finding that the onset of senile gait occurs in the case of women after the age of 60 years old, in turn, may be useful in evaluating the ability for performing types of physical work that mainly require ambulation. Med Pr 2017;68(4):441–44

Effect of Drop Foot on Spatiotemporal, Kinematic, and Kinetic Parameters during Gait

Background. The complexity of the structure and function of a living body can be affected by disorders and can cause various dysfunctions. Objective. The aim of this study was to determine compensatory mechanisms in subjects with drop foot during gait. Methods. The study evaluated 10 subjects with drop foot (DF) whose results were compared to a group of 10 healthy controls (C). Spatiotemporal, kinematic, and kinetic parameters during the gait cycle were collected using Vicon system synchronized with Kistler platforms. Results. Spatiotemporal, kinematic, and kinetic parameters were significantly different between the analysed groups. In the DF group, the subjects walked almost 47% slower and performed 60% less steps per minute compared to the C group. The main problem in the DF group was insufficient ankle dorsiflexion in the 0–10% of the gait cycle. Mean values in the groups during the first 10% of the gait cycle were as follows: DF (−10.42 ± 5.7°) and C (−2.37 ± 1.47°), which affected the substantial differences in the values of muscle torque: DF (0.2 ± 0.1 Nm/kg) and C (−0.26 ± 0.06 Nm/kg). Conclusions. Comparative analysis for joint angles and torques demonstrated that the mechanism of compensation is the most noticeable in the knee joint and less in the hip joint

Finished Genome of the Fungal Wheat Pathogen Mycosphaerella graminicola Reveals Dispensome Structure, Chromosome Plasticity, and Stealth Pathogenesis.

The plant-pathogenic fungus Mycosphaerella graminicola (asexual stage: Septoria tritici) causes septoria tritici blotch, a disease that greatly reduces the yield and quality of wheat. This disease is economically important in most wheat-growing areas worldwide and threatens global food production. Control of the disease has been hampered by a limited understanding of the genetic and biochemical bases of pathogenicity, including mechanisms of infection and of resistance in the host. Unlike most other plant pathogens, M. graminicola has a long latent period during which it evades host defenses. Although this type of stealth pathogenicity occurs commonly in Mycosphaerella and other Dothideomycetes, the largest class of plant-pathogenic fungi, its genetic basis is not known. To address this problem, the genome of M. graminicolawas sequenced completely. The finished genome contains 21 chromosomes, eight of which could be lost with no visible effect on the fungus and thus are dispensable. This eight-chromosome dispensome is dynamic in field and progeny isolates, is different from the core genome in gene and repeat content, and appears to have originated by ancient horizontal transfer from an unknown donor. Synteny plots of the M. graminicola chromosomes versus those of the only other sequenced Dothideomycete, Stagonospora nodorum, revealed conservation of gene content but not order or orientation, suggesting a high rate of intra-chromosomal rearrangement in one or both species. This observed “mesosynteny” is very different from synteny seen between other organisms. A surprising feature of the M. graminicolagenome compared to other sequenced plant pathogens was that it contained very few genes for enzymes that break down plant cell walls, which was more similar to endophytes than to pathogens. The stealth pathogenesis of M. graminicola probably involves degradation of proteins rather than carbohydrates to evade host defenses during the biotrophic stage of infection and may have evolved from endophytic ancestors

Long-term effects of evolocumab in participants with HIV and dyslipidemia: results from the open-label extension period

Objectives: People with HIV (PWH) are at an increased risk of atherosclerotic cardiovascular disease. Suboptimal responses to statin therapy in PWH may result from antiretroviral therapies (ARTs). This open-label extension study aimed to evaluate the long-term safety and efficacy of evolocumab up to 52\u200aweeks in PWH. Design: This final analysis of a multinational, placebo-controlled, double-blind, randomized phase 3 trial evaluated the effect of monthly subcutaneous evolocumab 420\u200amg on low-density lipoprotein cholesterol (LDL-C) during the open-label period (OLP) following 24\u200aweeks of double-blind period in PWH with hypercholesterolemia/mixed dyslipidemia. All participants enrolled had elevated LDL-C or nonhigh-density lipoprotein cholesterol (non-HDL-C) and were on stable maximally tolerated statin and stable ART. Methods: Efficacy was assessed by percentage change from baseline in LDL-C, triglycerides, and atherogenic lipoproteins. Treatment-emergent adverse events (TEAEs) were examined. Results: Of the 467 participants randomized in the double-blind period, 451 (96.6%) received at least one dose of evolocumab during the OLP (mean age of 56.4\u200ayears, 82.5% male, mean duration with HIV of 17.4\u200ayears). By the end of the 52-week OLP, the overall mean (SD) percentage change in LDL-C from baseline was -57.8% (22.8%). Evolocumab also reduced triglycerides, atherogenic lipid parameters (non-HDL-C, apolipoprotein B, total cholesterol, very-low-density lipoprotein cholesterol, and lipoprotein[a]), and increased HDL-C. TEAEs were similar between placebo and evolocumab during the OLP. Conclusion: Long-term administration of evolocumab lowered LDL-C and non-HDL-C, allowing more PWH to achieve recommended lipid goals with no serious adverse events. Trail registration: NCT02833844. Video abstract: http://links.lww.com/QAD/C441