The effects of bungy weight training on muscle function and functional performance

Eccentric strength training is thought to be important for improving functional performance. A form of training that may enhance the eccentric training stimulus is the attachment of a rubber bungy to the strength-training apparatus in such a way that the return velocity and, therefore, the force required to decelerate the load at the end of the eccentric phase are increased. To determine the effects of elastic bungy training, we performed two studies. In the first, we examined the electromyographic (EMG) and kinematic characteristics of three different squat techniques: traditional squat, non-bungy jump squat and bungy jump squat. In the second study, we examined whether jump squat training with and without the attachment of a rubber bungy to an isoinertial supine squat machine affects muscle function, multidirectional agility, lunge ability and single leg jump performance. The EMG activity of the vastus lateralis and gastrocnemius muscles was recorded. An instrumented isoinertial supine squat machine was used to measure maximal strength and various force, velocity and power measures in both studies. Participants were randomly assigned to one of three groups: a control group and two weight-trained groups, one of which performed bungy squat jumps and one of which performed non-bungy squat jumps. The two experimental groups performed 10 weeks of ballistic weight training. The kinematic and EMG characteristics of the bungy and non-bungy squat techniques differed significantly from those of the traditional squat on all the variables measured. The only difference between the bungy squat and non-bungy squat training was greater EMG activity during the later stages (70-100%) of the eccentric phase of the bungy squat condition. The 10 weeks of bungy squat and non-bungy squat jump weight training were found to be equally effective in producing improvements in a variety of concentric strength and power measures (10.6-19.8%). These improvements did not transfer to improved performance for the single leg jump and multidirectional agility. However, bungy weight training did lead to a significant improvement in lunge performance (21.5%) compared with the other groups.     

Learning and teaching axiomatic geometry

Summary To sum up, we have examined the various difficulties-mathematical, conceptual, and logical-involved in learning and teaching axiomatic geometry. Taking as a typical axiomatic approach one that couples Emil Artin's treatment of affine geometry with Choquet's handling of the basic order and orthogonality phenomena of Euclidean geometry, we have tried to identify these difficulties in some detail. We have noted that this particular approach isolates the graver difficulties, separating them from one another in such a way that they can be mastered by comparatively simple techniques. For both student and teacher the burden is shifted to the fuller understanding of certain fundamental concepts, such as that of a geometrical transformation, which permit making an early contact with algebra-specifically, with group theory-in the spirit of Descartes and Felix Klein. We have proposed an organization of the school program in geometry from grade K or grade 1 through grade 12 aimed at gradually acquainting the student with these basic concepts and their technical uses as they emerge from the persistent contemplation of the physical, mathematical, and logical facts. We have stated our conviction that by the 10th grade students should be prepared to understand the strategy and the significance of the axiomatic approach, and by the 11th and 12th grades to carry through that approach in adequate detail. We have taken explicitly into account the need to arrange the school geometry program in such a way that students can reach terminal points appropriate to their capacities, needs, and interests. We must emphasize that what has been presented here is no more than a rough outline, to be filled out on the basis of further psychological, mathematical and curricular investigations. I am confident that these suggestions can mature into a school geometry program not only far more significant intellectually and technically than those now commonly offered but also one easier to learn and to teach. This is not just a matter of personal belief, because many elements of the proposed program have actually been tried out in one form or another with success. What is now needed is a grand effort to assemble the tested and untested parts into an experimental whole.     

Adapting to changing task demands: variability in children's response to manipulations of resistance and cadence during pedaling

Reduction in performance variability is characteristic of skill acquisition during childhood. Less understood is the role of variability in adaptive skill. The purpose of this study was to determine children's capacity for adapting to changing task requirements. Children ages 4-14 years and adults rode a stationary ergometer at different levels of cadence and resistance. Younger children were less successful in meeting task requirements. When they did succeed, the younger children were more variable. However, no interactions were found. Variability did not change with resistance, and all groups showed increasing variability as cadence increased. It was concluded that in spite of a weaker synergy (more variability), children were adept to changes in task demand within tested limits.