EFFECT OF STRETCH REFLEX BLOCKAGE ON THE KINETICS AND KINEMATICS OF THREE JUMPERS PERFORMANCES

It has been postulated that the stretch reflex enhances force production in walking (Capady & Stein, 1986), running (Deitz, 1981), hopping (Melvill-Jones & Watt, 1971) and jumping (Bosco, et a1., 1982). In addition, it is widely accepted that the elastic component of muscles plays an important role in dynamic activities such as jumping. For example, during eccentric contraction ofthe jump, energy may be stored in the series elastic components which can be re-used during the subsequent concentric contraction. In fact, evidence from isolated muscle, as well as from intact muscle in humans, has been presented to show that the elastic energy storage contributed to enhanced work, force, velocity, and power of the positive phase of muscle contraction (e.g., Cavagna, 1965, 1971 a,b). All of the enhanced performances during the positive phase was attributed to fast stretching of a muscle prior to the shortening. It is well known that in stretching a muscle the muscle spindle will be stretched during which a volley of discharge is carried by an afferent path to evoke the stretch reflex. It was concluded that EMG activity in the extensor muscle is much higher in a countermovement jump (CMJ) than in a squat jump. Thus, the enhanced performance produced by a CMJ is related to a combination of elastic energy storage and the stretch reflex (Bosco, et a1., 1982)

THE IMPACT OF FATIGUE ON IDENTIFYING BIOMECHANIC POTENTIAL SOCCER KICKING RISK FACTORS FOR JORDANIAN JUNIOR SOCCER PLAYERS

INTRODUCTION: In soccer there are many incidences of injuries due to either bad technique or shear force at a joint and to great extend of repeating kicks which causes fatigue occurrences .In reality, junior players in soccer could be exposed to many and various kicking positioning in which a joint can be in a situation were risk factors greatly pronounced and such circumstances can be hazardous. Predicting and identifying those risk factors in early stage (Backous et al,1988) may be useful for both the young athlete and the coach to modify based on biomechanical analysis of their kicking techniques, especially after fatigue prevailed

THE IMPACT OF FATIGUE ON IDENTIFYING BIOMECHANIC POTENTIAL SOCCER KICKING RISK FACTORS FOR JORDANIAN JUNIOR SOCCER PLAYERS

INTRODUCTION: In soccer there are many incidences of injuries due to either bad technique or shear force at a joint and to great extend of repeating kicks which causes fatigue occurrences .In reality, junior players in soccer could be exposed to many and various kicking positioning in which a joint can be in a situation were risk factors greatly pronounced and such circumstances can be hazardous. Predicting and identifying those risk factors in early stage (Backous et al,1988) may be useful for both the young athlete and the coach to modify based on biomechanical analysis of their kicking techniques, especially after fatigue prevailed

KINEMATICAL PARAMETERS CONTRIBUTION TO THE FLIGHT HEIGHT USING ONE-FOOT OR TWO-FOOT TAKE-OFF

The purpose of this study was to investigate which of the kinematics parameters most contribute to vertical flight heights. Eight subjects were filmed using Sony digital camera with 25 images from the sagittal plane during execution of the following vertical jump conditions: free two-foot take-off, free one-foot take-off, fixed arm two-foot take-off, and fixed arm one-foot take-off. Arm swing contribution, leg swing contribution, height of centre of gravity at take-off (HCGTO), vertical velocity at take-off, arm’s angular momentum, work, and power were analyzed in each condition using stick figures according to Clauser, McConville, and Young (1969). Correlation and regression analysis indicated that HCGTO contributed the most to the flight heights in all conditions

Visual Perception of Biomechanical Characteristics of Walking, Jumping, and Landing

Visual perception of biological systems is one important aspect which has been considered by researchers in understanding human motion. The term «biological motion» was used by Johansson (1971, 1973) to distinguish human movement patterns from the motion of rigid inanimate objects previously utilized in visual motion perception. The emphasis, however, has been on the need for distinguishing three types of motion to describe perceived kinematic relations: the relative motion of elements to each other in the configuration, the common motion of the whole configuration relative to the observer, and the absolute motion of each element in dynamic display [Cutting and Proffitt (1982)]. Based on data collected using a video-recorder, reflective tape and high powered light for producingpoint-light displays, Cutting and Proffitt (1982) concluded that relative motion is automatically minimized by the visual system. Moreover, Johansson (1971, 1973) showed that all movement pattern of walking and running can be visually identified by observers without seeing the total picture. Using a similar technique, observers were able to visually recognize gender and friends by their walking patterns (Cutting and Kozlowzki, 1977; Cutting, 1978), ones' own identity (Beardsworth and Buckner, 1981), the weight of lifted objects (Runeson and Frykholm, 1983), and to the extent that evaluation of technical skill execution was sucessfully judged (Scully, 1986). Based on the principle that relative motion is automatically minimized by the visual system, Johansson (1973), concluded that previous learning of motion patterns do not determine the perception of walking. An important factor, however, is a highly mechanical, automatic type of visual data treatment. In addition, Runeson and Frykholm (1981) stated that the dynamic variable of the event (weight of the box), is well specified in the kinematic pattern and hence the visual system is efficient in picking up such information. Identifying cues by visual information may not be sufficient, however, to distinguish discrete skills (ie., jumping and landing) and/or continuous skills (ie., walking), especially, if the direction of the movement is reversed and if the total picture is seen as an absolute motion which includes the relative and common motion (Cutting and Proffitt, 1982). Therefore, this study was conducted to test the hypotheses that experience and familiarity are important factors in visual perception of kinematic patterns and that kinetics cannot be determined effectively by observation of kinematics. The purpose of this study is to determine: (1) the ability to visually perceive differences between a continuous skill (walking forward vs. backwards): (2) a discrete skill (jumping vs. landing); (3) the actual kinetic differences in the movement; and (4) whether individuals can distinguish between movement patterns, despite the kinetic differences, while the true pattern is reversed

E-Learning Readiness of Jordanian Universities

E-learning became very important to the universities success and it considered as one of the key success factors, in which it’s enhanced the competitive advantage and help in competing strongly in the market. Using Information technologies and sharing tools will add value to the educational process and by using these tools; the universities will have the power of innovation and creativity. E-learning helps in developing, managing and maintaining the students knowledge, on the other hand, it enhances the performance and learning capacity to remain innovation and competitive. This paper is measuring the readiness of the Jordanian universities for e-learning. It presents the main findings of a survey conducted to evaluate the e-learning readiness. The survey helped in analyzing three levels used for the measurement: ICT infrastructure, universities lecturers and students’ readiness, and the maturity of the external environment. Keywords: E-learning, IT infrastructure, Demand, External Environment, and HR readiness

Techno-Economical Optimization for River Nile Container Ships

This work introduces a procedure for the preliminary design of a self-propelled container ship working between Cairo and Aswan through the River Nile. The characteristics of the navigation route from Cairo to Aswan are investigated to defi ne the constraints on dimensions and speed of the River Nile container ships. Also, the dimensions of some existing inland ships are collected and investigated to set limits on the dimensional ratios of such ships. Two empirical formulae, for the determination of ship steel weight and power prediction in the preliminary design stage of conventional self propelled inland container ships, are proposed. This problem is handled as a single objective constrained optimization problem using a specially developed computer program (CACSO). As the required freight rate refl ects the major goal of any commercial ship, it is considered as the objective function for this optimization process. A sensitivity study is carried out to indicate the relative dependence of the objective function on a variety of factors to which the objective function may be sensitive

THE MOST ECONOMICAL CONFIGURATION OF PUSHED BARGE CONVOY SYSTEM THROUGH CAIRO-ASWAN WATERWAY

In the recent years, as a result of the economical situation in Egypt, fuel price is rapidly increased. Consequently, the cost of cargo transport is also increased. Therefore, the aim of the present paper is to check the feasibility of a pushed barge convoy system working through Cairo-Aswan waterway as an alternative mean of cargo transport in order to encourage the transport companies to transport their cargoes through river Nile which is considered the cheapest transport mode in Egypt. In this paper, the current situation of the river transport and the characteristics of the Egyptian inland waterways network are reviewed and investigated to identify the navigation problems and constraints which affect the navigation through Cairo-Aswan waterway. The basic concept of ship controllability is reviewed to clarify the maneuver characteristics of a pushed barge convoy system in shallow waterways. Also, different configurations for pushed barge convoy system are proposed and the required power of each configuration is calculated using a specially developed computer program. A technical and operational measure called transport efficiency is used as a criterion to get the most economical configuration of the desired pushed barge convoy system. Finally, a comparison between the pushed barge convoy system and the existing river transport means in Egypt is made to clarify the feasibility of using pushed barge convoy system through Cairo-Aswan waterway

Iatrogenic colorectal Kaposi sarcoma complicating a refractory ulcerative colitis in a human immunodeficiency negative-virus patient

Kaposi sarcoma is a mesenchymal tumor associated to a human herpes virus-8. It often occurs in human immunodeficiency virus-positive subjects. Colorectal localization is rare. We report the case of a colorectal Kaposi sarcoma complicating a refractory ulcerative colitis treated with surgery after the failure of immunomodulator therapy in a human immunodeficiency virus-negative heterosexual man.Key words: Kaposi’s Sarcoma, ulcerative colitis, Human Herpes Virus-8, Infliximab, immunosuppressio