Understanding the track and field sprint start through a functional analysis of the external force features which contribute to higher levels of block phase performance

This study aimed to identify the continuous ground reaction force (GRF) features which contribute to higher levels of block phase performance. Twenty-three sprint-trained athletes completed starts from their preferred settings during which GRFs were recorded separately under each block. Continuous features of the magnitude and direction of the resultant GRF signals which explained 90% of the variation between the sprinters were identified. Each sprinter’s coefficient score for these continuous features was then input to a linear regression model to predict block phase performance (normalised external power). Four significant (p < 0.05) predictor features associated with GRF magnitude were identified; there were none associated with GRF direction. A feature associated with greater rear block GRF magnitudes from the onset of the push was the most important predictor (β = 1.185), followed by greater front block GRF magnitudes for the final three-quarters of the push (β = 0.791). Features which included a later rear block exit (β = 0.254) and greater front leg GRF magnitudes during the mid-push phase (β = 0.224) were also significant predictors. Sprint practitioners are encouraged, where possible, to consider the continuous magnitude of the GRFs produced throughout the block phase in addition to selected discrete values.     

The role of the teacher with substance-abusing adolescents in secondary schools

Before choosing to become involved with students who currently are abusing psychoactive substances, teachers must consider not only the potential consequences and payoffs to them professionally, but also what specifically they can do to help adolescents. This article presents some of the philosophical problems, and suggests potential solutions of how to relate to students who engage in potentially self-destructive, drug-related behavior. There is a need for teachers to become quasi-counselors and consultants, since they are the first line of defense against substance use and abuse.     

Incorporating a vocational component into a school psychological evaluation: A case example

Vocational assessment services increasingly are being provided to handicapped secondary school students as a result of recent federal legislation. This article describes the need for such services and describes a vocationally oriented psychological evaluation completed on a handicapped adolescent by a school psychologist. The relevance of traditionally derived school psychological assessment data in vocational programming, the value of expanding assessment batteries to include vocationally specific assessment techniques, and the writing of vocationally oriented psychological reports are discussed.     

Correlates of vocational practice among school psychologists

This study surveyed 362 school psychologists to: (a) identify the percentages of school psychologists who have had some involvement in the practices of vocational assessment, vocational counseling, consultation with vocational education teachers, and vocational program or curriculum development, and (b) identify factors that are associated with such vocational involvement. Results indicated that 30–40% of those school psychologists surveyed reported some involvement in vocational assessment, vocational counseling, and consultation with vocational education teachers, while only 12% indicated involvement with vocational program or curriculum development. Sex, experience, salary, perceived control over role functioning, and involvement in practices other than traditional assessment were found to be associated with increased involvement in vocational activities. Results also indicated that school psychologists who were certified guidance counselors, and who were members of the American Association of Counseling and Development, were more likely to be involved in vocational practices than were school psychologists who were not so certified or affiliated. Results are discussed in terms of their implication for involving greater numbers of school psychologists in vocational practices.     

Hypertext and Instructional Design: Some Preliminary Guidelines

Hypertext is a nonlinear way of presenting content consisting of nodes and links that a person can access using a variety of search and browsing strategies. In this article, we focus on the use of hypertext as an instructional tool. We compare hypertext instruction with traditional instructional formats. We offer some initial guidelines relating to guidance and control, development and implementation, multiuser management, user interface, and content representation. The paper concludes with a discussion of limitations of learner control as an instructional strategy, and the need for careful instructional design of hypertext instructional programs.     

Lower limb joint kinetics during the first stance phase in athletics sprinting: three elite athlete case studies

Abstract

This study analysed the first stance phase joint kinetics of three elite sprinters to improve the understanding of technique and investigate how individual differences in technique could influence the resulting levels of performance. Force (1000 Hz) and video (200 Hz) data were collected and resultant moments, power and work at the stance leg metatarsal-phalangeal (MTP), ankle, knee and hip joints were calculated. The MTP and ankle joints both exhibited resultant plantarflexor moments throughout stance. Whilst the ankle joint generated up to four times more energy than it absorbed, the MTP joint was primarily an energy absorber. Knee extensor resultant moments and power were produced throughout the majority of stance, and the best-performing sprinter generated double and four times the amount of knee joint energy compared to the other two sprinters. The hip joint extended throughout stance. Positive hip extensor energy was generated during early stance before energy was absorbed at the hip as the resultant moment became flexor-dominant towards toe-off. The generation of energy at the ankle appears to be of greater importance than in later phases of a sprint, whilst knee joint energy generation may be vital for early acceleration and is potentially facilitated by favourable kinematics at touchdown.     

Surprise and change: Variations in the strength of present and absent cues in causal learning

It is said that “absence makes the heart grow fonder.” But, when and why does an absent event become salient to the heart or to the brain? An absent event may become salient when its nonoccurrence is surprising. Van Hamme and Wasserman (1994) found that a nonpresented but expected stimulus can actually change its associative status—and in the opposite direction from a presented stimulus. Associative models like that of Rescorla and Wagner (1972) focus only on presented cues; so, they cannot explain this result. However, absent cues can be permitted to change their value by assigning different learning parameters to present and absent cues. Van Hamme and Wasserman revised the Rescorla-Wagner model so that the α parameter is positive for present cues, but negative for absent cues; now, changes in the associative strength of absent cues move in the opposite direction as presented ones. This revised Rescorla-Wagner model can thus explain such otherwise vexing empirical findings as backward blocking, recovery from overshadowing, and backward conditioned inhibition. Moreover, the revised model predicts new effects. For example, explicit information about the absence of nonpresented cues should increase their salience (that is, their negative α value should be larger), leading to stronger associative changes than when no explicit mention is made of cue absence. Support for this prediction is detailed in a new causal judgment experiment in which participants rated the effectiveness of different foods’ triggering a patient’s allergic reaction. Overall, these and other findings encourage us to view human causal learning from an associative perspective.     

Response rate is not an effective mediator of learned stimulus equivalence in pigeons

We explored response rate as a possible mediator of learned stimulus equivalence. Five pigeons were trained to discriminate four clip art pictures presented during a 10-sec discrete-trial fixed interval (FI) schedule: two paired with a one-pellet reinforcer, which supported a low rate of responding, and two paired with a nine-pellet reinforcer, which supported a high rate of responding. After subjects associated one stimulus from each of these pairs with a discriminative choice response, researchers presented two new clip art stimuli during a 10-sec FI: one trained with a differential reinforcement of low rate schedule (DRL) after the FI and the other trained with a differential reinforcement of high rate schedule (DRH) after the FI. Each of the stimuli that were withheld during choice training was later shown to see if the choice responses would transfer to these stimuli. The results suggest that response rate alone does not mediate learned stimulus equivalence.