Avaliação da vibração no sistema mão-braço em operadores de máquinas de corte de grama

É grande a quantidade de equipamentos e máquinas operadas por pessoas de forma manual que executam as mais diversas tarefas. Parafusar, martelar, lixar, cortar, serrar, entre outros, são algumas destas tarefas que podem ser executadas com o auxílio de maquinário. Todas estas máquinas expõem seus usuários a certos níveis de ruído e de vibração durante sua utilização. Especificamente na área de corte de vegetais, há uma série de outras máquinas que auxiliam na poda, plantio e colheita de vegetais, que da mesma forma também induzem vibração no sistema mão-braço de quem os utilizam, podendo esta exposição ser danosa à sua saúde dependendo de sua intensidade e de seu tempo de exposição. Este trabalho propõe a construção de um dispositivo de monitoramento da vibração no sistema mão-braço, com medição simultânea para as duas mãos, em operadores de cortadores de grama em uma situação usual de atividade diária a fim de avaliar os seus níveis de vibração e riscos associados a esta atividade. O trabalho também propõe a adaptação de códigos para a gravação, processamento e comparação das vibrações frente a Normas Brasileiras de Higiene Ocupacional assim como Normas Internacionais específicas. Ao final, são indicados quais os riscos relativos a tal operação e recomendações para mitigar esta exposição das situações que foram avaliadas.There is a large amount of equipment and machines manually operated by people that perform the most diverse tasks. Screwing, hammering, sanding, cutting, sawing, among others, are some of these tasks that can be performed with the help of machines. All of these machines expose their users to certain levels of noise and vibration during the use. Specifically in the cutting vegetables area, there are a number of other machines that assist in the pruning, planting and harvesting of vegetables, which likewise also induce vibration in the hand-arm system of those who use them, and this exposure can be harmful and unhealthy depending on your intensity and the exposure time. This paper proposes the construction of a vibration monitoring device in the hand-arm system, simultaneous measurement for both hands, in lawn mower operators in a usual situation of daily activity in order to assess their vibration levels and risks associated with this activity. The paper also proposes the adaptation of codes for recording, processing and comparing vibrations against Brazilian Occupational Hygiene Standards as well as International Standards. At the end, it is indicated the risks related to such an operation and recommendations to mitigate this exposure of the situations that were evaluated are suggested

INVESTIGATION OF A THEORETICAL MODEL FOR THE ROTATIONAL SHOT PUT TECHNIQUE

This study aimed to investigate the causal relationships among biomechanical variables for achieving high release velocity in male shot putter and create a theoretical model for the rotational shot put technique. The throwing motions of 22 male shot putters were videotaped and analysed using the 3D DLT method. Path analysis was used to examine causal relationships among biomechanical variables. The examined model consisted of three kinetic and eight kinematic variables that significantly related to a higher release velocity directly or indirectly. Two key factors were identified in shot put performance with the rotational technique: (1) increasing of impulse of the shot at delivery phase, and (2) creating greater linear and angular momentum before delivery. Future research should confirm or extend this potential causal mechanism of contributors to shot release velocity

Kinematic characteristics of barefoot sprinting in habitually shod children

Background. Anecdotally, a wide variety of benefits of barefoot running have been advocated by numerous individuals. The influence of the alterations in the properties of the shoe on the running movement has been demonstrated in adults at submaximal jogging speeds. However, the biomechanical differences between shod and barefoot running in children at sprinting speeds and the potential developmental implications of these differences are still less examined. The purpose was to determine the potential differences in habitually shod children's sprint kinematics between shod and barefoot conditions. Methods. Ninety-four children (51 boys and 43 girls; 6-12 years-old; height, 135.0 ± 0.12 m; body mass, 29.0 ± 6.9 kg) performed 30 m maximal sprints from standing position for each of two conditions (shod and barefoot). To analyze sprint kinematics within sagittal plane sprint kinematics, a high-speed camera (300 fps) was set perpendicular to the runway. In addition, sagittal foot landing and take-offimages were recorded for multiple angles by using five high-speed cameras (300 fps). Spatiotemporal variables, the kinematics of the right leg (support leg) and the left leg (recovery leg), and foot strike patterns: rear-foot strike (RFS), mid-foot strike (MFS), and forefoot strike (FFS) were investigated. The paired t -test was used to test difference between shod and barefoot condition. Results. Barefoot sprinting in habitually shod children was mainly characterized by significantly lower sprint speed, higher step frequency, shorter step length and stance time. In shod running, 82% of children showed RFS, whereas it decreased to 29% in barefoot condition. The touch down state and the subsequent joint movements of both support and recovery legs during stance phase were significantly altered when running in condition with barefoot. Discussion. The acute effects of barefoot sprinting was demonstrated by significantly slower sprinting speeds that appear to reflect changes in a variety of spatiotemporal parameters as well as lower limb kinematics. It is currently unknown whether such differences would be observed in children who typically run in bare feet and what developmental benefits and risks may emerge from increasing the proportion of barefoot running and sprinting in children. Future research should therefore investigate potential benefits that barefoot sprinting may have on the development of key physical fitness such as nerve conduction velocity, muscular speed, power, and sprinting technique and on ways to minimize the risk of any acute or chronic injuries associated with this activity. © 2018 Mizushima et al

CLASSIFICATION OF THE DISCUS THROW TECHNIQUE

The purpose of this study is to classify discus throwers based on the velocity components at release and to investigate their throwing biomechanics. Forty-six male discus throwers were classified into 2 groups through cluster analysis. Twenty-two throwers were classified into a horizontal dominant group, while the remaining 24 throwers were classified into a vertical dominant group. There were no significant differences in the throwing distance and resultant release velocity between the groups. The right leg angle at release and the displacement of the centre of gravity (vertical direction) were significantly greater in vertical dominant group. These results indicated the horizontal dominant group drove their right leg forward to increase the horizontal velocity, while the vertical dominant group lifted their body upward direction to increase the vertical velocity

COMPARISON OF WORLD ELITE AND JAPANESE ELITE THROWERS IN THE DISCUS THROW

The aim of this study is to clarify the differences between world elite and Japanese elite throwers in the discus throw by comparing their hip-shoulder and shoulder-arm separation angles. The performances of 12 male world elite discus throwers (the World group) and 12 male Japanese elite discus throwers (the National group) were analysed. The hip-shoulder and shoulder-arm separation through the throwing motion were greater in the World group than in the National group. In the World group, the hip-shoulder separation reached its local maximum at the middle of 2nd single support phase, and the shoulder-arm separation reached its local maximum around left-foot touchdown to the ground; whereas in the National group, the former reached its local maximum in the first half of 2nd single support phase, and the latter reached its local maximum in the middle of the delivery phase. Although the shoulder led hip in both the World and National groups, the shoulder led the arm in the National group and the arm led the shoulder in the World group at release. These results showed that the World group released the discus in front of the shoulder while utilising the kinematic-chain appropriately, while the National group released the discus with the arm still trailing behind the shoulder

Níveis de riscos e Vibração Mão-Braço (VMB) em máquinas de corte de grama

Existe um grande número de equipamentos e máquinas que são operados manualmente por humanos e que expõem seus usuários a determinados níveis de ruído e vibração, durante o uso, tais como: parafusar, forjar, retificar, aparar, serrar, entre outros. Particularmente, na área de corte de gramas, existe uma gama de máquinas portáteis que auxiliam na poda, plantio e colheita, causando vibrações no sistema mão-braço para a pessoa que utiliza essas máquinas, e essa exposição pode ser prejudicial à saúde, dependendo de sua intensidade e seu tempo de exposição. Este trabalho demonstra a construção de um monitor de vibração no sistema mão-braço, durante as atividades diárias de um operador de cortador de grama, enquanto medições simultâneas são feitas em ambas as mãos para avaliar os níveis de vibração. Finalmente, os riscos associados a isso são identificados, e recomendações para mitigá-los são apresentadas para a situação em avaliação