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621.
We tested the hypothesis that quiet eye, the final fixation before the initiation of a movement in aiming tasks, is used to scale the movement's parameters. Two groups of 12 participants (N = 24) threw darts to targets in the horizontal and vertical axes under conditions of higher (random) or lower (blocked) target variability. Supporting our predictions, random practice and target changes in the vertical axis led to longer quiet eye duration than did blocked practice and target changes in the horizontal axis. Our data suggest that quiet eye is not simply a mediating factor in accuracy, but is responsive to the task's programming demands, being influenced by the necessity to reparameterize the movement from one trial to the next. 相似文献
622.
Terry J. Housh William G. Thorland Gerald D. Tharp Glen O. Johnson Craig J. Cisar 《Research quarterly for exercise and sport》2013,84(4):347-350
Abstract Sixty-two elite adolescent (age: 16.39 ± 1.62 yrs) female track and field athletes volunteered to be measured isokinetically for peak torque of the leg flexors and extensors. The sample included 16 throwers, 11 jumpers, 12 middle-distance runners (> 400 m), and 23 sprinters. A Cybex II isokinetic dynamometer was used to measure dominant leg strength at 180°/sec. One-way ANOVA revealed significant between group differences for absolute flexion and extension (Nm), extension/body weight (Nm/Kg), and extension/lean body weight (Nm/Kg). Scheffe post-hoc comparisons showed that, for absolute leg extension strength, throwers were stronger than middle-distance runners (by 54.4%), sprinters (35.6%), and jumpers (23.6%). For absolute leg flexion movements, throwers were stronger than middle distance runners (37.4%) and sprinters (32.1%). Jumpers had greater extension peak torque values than middle-distance runners relative to body weight (14.0%), and throwers were stronger than middle-distance runners for extension/lean body weight (14.9%)). No other comparisons were significant. However, when strength was expressed relative to body weight or lean body weight, there were few differences between events for flexion or extension. Given that absolute strength scores were correlated with body weight and lean body weight, peak torque/body weight or peak torque/lean body weight may be more sensitive than absolute values as indicators of underlying factors (such as training status or fiber type composition) responsible for the differences in muscular strength between groups. 相似文献
623.
Terry J. Housh Glen O. Johnson Roger A. Hughes Craig J. Cisar William G. Thorland 《Research quarterly for exercise and sport》2013,84(3):240-243
Abstract The purpose of this investigation was to determine the yearly changes in body composition as well as absolute and relative isokinetic forearm flexion and extension strength of high school wrestlers. Evaluations of body composition (underwater weighing) were performed on 27 high school wrestlers prior to three consecutive seasons. In addition, isokinetic forearm flexion and extension strength values at 180°/s (Cybex II) were available for 20 of the subjects. The mean ages at the times of laboratory testing were 15.5 (± .5), 16.5 (± .5), and 17.5 (± .5) years. Repeated measures ANOVA or ANCOVA with Tukey post-hoc comparisons were used to locate significant (p<.05) differences across age for height, body weight, relative fat, body density, fat weight, fat-free weight, absolute muscular strength, and muscular strength covaried for body weight and fat-free weight. There were yearly increases in all variables except fat weight, forearm flexion covaried for fat-free weight and forearm extension covaried for fat-free weight. The results of this study indicated that the improved wrestling performance and the increase in weight classification which normally occurs during high school are, in part, a function of yearly changes in body composition and muscular strength. 相似文献
624.
Dona J. Housh Terry J. Housh Sonja M. Bauge 《Research quarterly for exercise and sport》2013,84(4):406-409
Abstract Laboratory research in motor learning has consistently demonstrated higher retention and!or transfer when practice occurs under conditions of high contextual variety (e.g., Lee &; Magill, 1983; Newell &; Shapiro, 1976; Shea of Morgan, 1979;). In the present study, an attempt was made to determine whether a contextual variety effect could be demonstrated in a standard physical education instructional setting. During practice trials on the long and short badminton serves, male and female subjects performed under either blocked (i.e., all trials of one serve followed by all trials of the other) or varied (i.e., alternating trials of long and short serves) conditions. Retention and transfer tests (i.e., using the service area opposite that employed during the practice phase) were administered at the end of the badminton unit. Although little difference was observed in the performance of the two groups during practice, alternating-trial subjects demonstrated significantly higher retention of the short serve and significantly higher transfer of both serves than blocked-trial subjects. The performance of male and female subjects was not differentially influenced by practice structure conditions. It was concluded that a practice schedule that requires performers to change their plan of action from trial to trial may facilitate the retention and transfer of motor skills in applied instructional settings. 相似文献
625.
Abstract Forty-four subjects were given an all-out run test on a motor driven treadmill. The times for attaining heart rates of 150, 160, 170, 180 beats per minute were recorded along with measurements of ventilation, oxygen uptake and carbon dioxide production. The correlations between heart rate times and the all-out run times increased with the heart rate, a correlation of .85 calculated at the rate of 180 beats per minute. Using criteria established by Balke, it was demonstrated that the 180 heart rate serves as a valid cut-off point in measuring circulorespiratory capacity under variable exercise stress conditions. 相似文献
626.
What are the longitudinal cognitive profiles of Hong Kong Chinese children with specific reading difficulties in Chinese only, in English only, or both? A total of 16 poor readers each of Chinese (PC) and English (PE) and 8 poor readers of both orthographies (PB) were compared to a control sample (C) of 16 children; all were drawn from a statistically representative sample of 154 Hong Kong Chinese children tested at ages 5 to 9 years. PE and PB children's mothers had lower education levels than did the other groups. With children's ages and mothers' education levels statistically controlled, the PE, PC, and PB groups were significantly lower than the C group on phonological awareness. The PB and PE groups also scored significantly lower than the others on English vocabulary across years, whereas the PC and PB groups were significantly poorer than the C and PE groups on morphological awareness across years. Finally, the PB group was significantly slower than the other groups on speed naming at every age tested, underscoring the potential importance of automaticity in reading across orthographies. Findings highlight the need to consider the issue of how to identify reading difficulties in a second language. 相似文献
627.
Fifteen-day-old rats made random choices in a T-maze, while adult levels of alternation (approximately 70%) were noted among 30-day-olds. Also, younger pups were insensitive to a lengthening of the intertrial interval, unlike older animals whose rate of alternation decreased when a 1-h delay was interposed between arm entries. These findings are consistent with the hypothesis that hippocampal development is a factor in the ontogeny of postweaning locomotion. The unsystematic pattern of goal-arm selections among 15-day-olds suggests that ontongenetic variation in the utilization of stimuli may underlie developmental shifts in spontaneous alternation. 相似文献
628.
Although going to college may be viewed as a rite of passage for many students, some groups of students often face unique challenges in their pursuit of a college degree. One group of students that we are trying to gain a better understanding of is first-generation students, those whose parents did not graduate from college. This article presents the results of a study that investigated longitudinal effects of being a first-generation student on attrition. Results indicated that first-generation students were more likely to depart than their counterparts over time. After controlling for factors such as race, gender, high school grade point average (GPA), and family income, the risk of attrition in the first year among first-generation students was 71% higher than that of students with two college-educated parents. 相似文献
629.
Terry W. Belke 《Learning & behavior》1992,20(4):401-406
Four pigeons were exposed to multiple schedules with concurrent variable interval (VI) components and then tested for preference transfer. Half of the pigeons were trained on a multiple concurrent VI 20-sec, VI 40-sec/cuncurrent VI 4G-sec5 VI 80-sec schedule. The remaining pigeons were trained on a multiple concurrent VI 80-sec, VI 40-sec/concurrent VI 40-sec, VI 20-sec schedule-After stability criteria for time and response proportions were simultaneously met, four preference transfer tests were conducted with the stimuli associated with the VI 40-sec schedules. During the transfer tests, each pigeon allocated a greater proportion of responses (M=0,79) and time (M=0.82) to the stimulus associated with the VI 40-sec schedule that was paired with the VI 80-sec schedule than lo the VI 40-sec schedule stimulus paired with the VI 20-sec schedule. Absolute reinforcement rates on the two VI 40 sec schedules were approximately equal and unlikely to account for the observed preference. Nor was the preference consistent with the differences in local reinforcement rates associated with the two stimuli. Instead, the results were interpreted in terms of the differential value that stimuli acquire as a function of previous pairings with alternative schedules of reinforcement. 相似文献
630.
Terry F. Pettijohn 《Learning & behavior》1977,5(4):370-372
Forty sexually mature Mongolian gerbils served as subjects in a study designed to examine responsiveness to samples of urine. In a two-choice comparison situation in the home cage, each isolated gerbil was tested for amount of time spent with each urine sample during a 3-min period. Male gerbils spent significantly more time with estrus female urine than nonestrus female gerbil urine, and with nonestrus female gerbil urine than with either male gerbil urine or water. Female gerbils did not respond differentially to any of the stimuli. Neither sex discriminated between gerbil and hamster urine of either sex. Results suggest that female gerbil urine communicates sexual identity and, especially, sexual readiness to the male gerbil. 相似文献