BASES Position Statement on Guidelines for Resistance Exercise in Young People

Abstract

Despite the performance concerns of dehydration in other sports, there are currently no data on the effects of rapid weight-loss on the physical and cognitive performance of jockeys in a sport-specific context. In a randomised crossover design, eight Great Britain (GB) male licensed jockeys were assessed for chest strength, leg strength, simulated riding performance (assessed by maximum pushing frequency on a mechanical riding simulator during the final two furlongs of a simulated 2 mile race) and simple reaction time after performing 45 min of exercise, during which euhydration was maintained (Control trial) or induced 2% dehydration (Rapid Weight-Loss trial). Reductions in both chest (–13.8 ± 3.03% vs. 0.62 ± 1.04%) and leg strength (–4.8 ± 4.8% vs. –0.56 ± 2.5%) were greater in Rapid Weight-Loss compared with Control (P < 0.01 and P = 0.04, respectively). Similarly, reductions in simulated riding performance were also greater (P = 0.05) in Rapid Weight-Loss (–2.8 ± 4.0%) compared with Control (–0.07 ± 1.5%), whereas there were no significant changes (P = 0.14) in simple reaction time. We conclude that a 2% reduction in body mass, as achieved by 45 min of moderate-intensity exercise undertaken in a sweatsuit (a common method of inducing acute dehydration by jockeys), significantly impairs maximum pushing frequency during a simulated race. In addition, the observed reductions in strength may also increase the occupational hazards associated with race riding.     

Embedding with multiple knowledge sources to improve innovation performance: the learning experience of Motorola in Brazil

This article explores how a subsidiary of a multi-national enterprise (MNE) in an emerging economy embeds with multiple knowledge sources, both in its corporate network (internal) and in the host country (external), to create the capability to undertake innovative activities. Drawing on first-hand and intra-firm field evidence over the lifetime of a subsidiary in the information and communications technology industry in Brazil (1996–2009) the article finds that: (1) Within 10 years, the case subsidiary attained advanced, near-world leading innovation performance in three technological functions: project management, software engineering and product and solutions; (2) This was an outcome of how the firm simultaneously engaged in knowledge-intensive linkages based on increased frequency of use and improved quality over time, with specific internal and external counterparts; (3) However, some counterparts and linkages were more effective than others in contributing to the subsidiary's innovation performance. Drawing on a novel approach that examines the relationship between dual embeddedness and innovative performance, this article extends our understanding of embeddedness as part of knowledge-seeking strategies of MNE-subsidiaries. It also provides new insights to deepen the analysis of the nuances of subsidiaries’ multiple embeddedness, especially in emerging economies.     

从墨家和平思想看中国和平发展战略的思想渊源与现代重构

中国和平发展战略思想是墨家及中国传统思想家朴素的和平思想的现代转型与重构,是马克思主义和平发展思想在当代的继承与发展.探究梳理墨家及中国传统文化中的和平思想精髓,对于继承和弘扬马克思主义和平发展思想精华,把握中国和平发展战略思想的意蕴要旨具有重要意义.     

Comment on ‘Ventilation and blood lactate increase exponentially during incremental exercise’ : A reply

Oar force and oar angle data resulting from a 6‐min maximal rowing ergometer test undertaken by novice (n = 9), good (n ‐ 23) and national (n = 9) level male rowers, were used to identify biomechanical performance variables which accurately discriminated between rowers of differing ability levels. The variables included two work capacity measures, mean propulsive power output per kilogram of body mass (W kg^‐1) and propulsive work consistency (%), and two skill variables, stroke‐to‐stroke consistency (%) and stroke smoothness (%). Discriminant function analysis indicated the presence of two functions, both of which clearly indicated the importance of mean propulsive power output per kilogram of body mass as a discriminating variable. Function 2 gave greater weight to stroke‐to‐stroke consistency and stroke smoothness than function 1; however, function 1 was the most powerful discriminator. Classification procedures were used to predict the ability level to which a rower most likely belonged and involved defining the ‘distance’ between each rower and each ability level centroid, with the rower being classified into the ‘nearest’ ability level. These procedures indicated that 100% of the elite, 73.9% of the good, 88.9% of the novice and 82.9% of all rowers were correctly classified into their respective skill levels. Stepwise discriminant analysis included the variables in the following order: mean propulsive power output per kilogram of body mass, stroke‐to‐stroke consistency, stroke smoothness and propulsive work consistency (P < 0.001). The results of this study indicate that biomechanical performance variables related to rowing capacity and skill may be identified and used to discriminate accurately between rowers of differing skill levels, and that, of these variables, propulsive work consistency is the least effective discriminator.     

Age,Physical Activity,Physical Fitness,Body Composition,and Incidence of Orthopedic Problems

Abstract

The incidence of orthopedic problems was examined in 5, 582 men and women who attended the Cooper Clinic in Dallas, Texas between 1974 and 1982. The effects of age, physical activity, physical fitness, and body mass index (EMI) on the occurrence of these problems were examined using a proportional hazards approach. The expected risk of orthopedic problems per person-year was 0.045 for men and 0.046 for women. For men, physical fitness, BMI, and physical activity were associated with orthopedic problems, while for women, physical activity was the main predictor. Age was not a factor for either gender. The effect of change in physical fitness, physical activity, and BMI was examined in a subset of 2, 325 persons with more than one visit to the clinic. For women, physical activity and a decrease in BMI were associated with orthopedic problems, while for men none of those factors were significant. Again, age was not a factor in either group. The absence of any age effect on the occurrence of problems suggests that with regard to orthopedic problems, moderate amounts of physical activity in generally healthy persons may be recommended without special consideration as to age.     

Lactate and Phosphagen Levels in Muscle Immediately after a Maximum 300 m Run at Sea Level

Abstract

The relative effectiveness of six intensive training programs on the development of four selected skills was studied, with emphasis on limited time encountered within the semester organizational plan. One hundred and twenty college freshmen men volunteers were randomly assigned to training groups of 30 members each, which met for two sessions a week for 16 weeks.

Results indicated that: (a) direct practice jumping, alone or combined with repetitive sprinting or weight training, was significantly superior to weight training alone on standing broad jump development; (b) direct practice of a zigzag run was superior to both weight training and repetitive sprinting; and (c) when group acquisition of “adequate” skill is the objective, performance improvements educed over the first nine weeks were great enough to question the merits of persisting at an activity over a full semester. Only the zigzag run was adversely affected by the spring vacation cessation of training.     

Effect of cluster set configurations on power clean technique

Abstract

The purpose of this investigation was to examine the effects of cluster set configurations on power clean technique. Ten male, recreational weightlifters performed three sets of six repetitions at 80% of one repetition max with 0 (P0), 20 (P20) or 40 seconds (P40) inter-repetition rest. During the first and second set of P0, the catch and first pull were in a more forward position during repetition 6 as compared to repetition 1, respectively. During the second set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the second pull and the loop. During the third set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the first pull, transition, and beginning of the second pull. No differences in horizontal displacement were found between repetitions 1 and 6 during P20. During each set of P0, vertical displacement decreased between repetitions 1 and 6 (1.02 ± 0.07 m vs. 0.94 ± 0.06 m; Mean ± s). Cluster set configurations led to the maintenance of vertical displacement throughout all sets. The results demonstrate cluster set configurations with greater than 20 seconds inter-repetition rest maintain weightlifting technique to a greater extent than a traditional set configuration.     

Interactions among Dietary Pattern,Physical Activity and Skinfold Thickness

Abstract

This study was designed to assess the effects of a specifically designed perceptual-motor training program on the level of perceptual-motor development, self-concept, and academic ability of kindergarten children. Subjects for the study were 40 kindergarten children randomly assigned to 1 of 2 groups. Each group received the same kindergarten program with one exception, the experimental group was exposed to a specifically designed perceptual-motor program 30 min daily for 5 mo, while the control group received a free play period for 30 min daily. Results of the study indicated that the data tended to support the specificity of training concept. The variables showing the greatest change were the perceptual-motor tests which measured changes on specific aspects of the training program. There appeared to be some immediate transfer to academic abilities but this was not pronounced enough to suggest that perceptual-motor training was of real benefit in developing academic abilities for normal kindergarten children. In addition the follow-up test indicated no long term effects on academic performance.     

The Construct and Concurrent Validity of a 12-Minute Crawl Stroke Swim as a Field Test of Swimming Endurance

This study investigated the construct and concurrent validity of a 12-minute crawl stroke swim as a field test of swimming endurance. A sample of 42 male college students who ranged from certified life savers to competitive swimmers were administered three tests. The first, a multistage swimming endurance test, required that a tethered subject swim to exhaustion under a linear progressive increase in workload. The second measure was the crawl stroke count for two lengths of a 25-yard pool. The third test was a 12-minute crawl stroke swim for distance with total distance and distance covered each minute recorded for each subject. Alpha factor analysis of the 12 minute intervals of the crawl stroke swim produced one factor which demonstrated that swimming performance was internally consistent during the 12-minute swim. There was a correlation of .898 (p < .01) between the 12-minute swim and the tethered swim test. Cross validity procedures demonstrated a high degree of stability for the correlation between the 12-minute swim and the tethered swim and for resulting regression statistics. The construct validity was established for both the multistage test and the 12-minute swim using the known groups approach. On the basis of the data the 12-minute swim is a valid field test for swimming endurance for the population studied.     

Cognitive Style and Learner Strategy Interaction in the Performance of Primary and Related Maze Tasks

Abstract

The effect of designated learning strategies and reflective versus impulsive cognitive styles on performance in a maze learning task was investigated. Twenty-four female subjects were randomly assigned to a strategy or control group. The strategies group was provided with three potentially effective strategies (imagery, rhythm, and feedback) as identified by an information processing task analysis procedure. The Matching Familiar Figures test further classified subjects within the two groups according to their preferred styles of responding. Eleven primary task trials were administered with direct view of maze and four related task trials were completed with an indirect view of it. Traversal speed and time in the incorrect pathways were analyzed with a 2 × 2 × 7 (Strategies × Cognitive Styles × Trial Blocks) repeated measures ANOVA. A significant three-way interaction was found for both dependent measures. As hypothesized, during the primary task the control reflective subjects traversed the maze more slowly than the control impulsive subjects. However, the strategies reflective subjects completed the maze with the same speed as strategies impulsives. The incorrect pathways × time interaction revealed that the control reflective subjects spent less time in the incorrect pathways during the related task than the control impulsives. No significant differences were found for strategies reflectives or impulsives. These findings indicate that, for this maze task that emphasized speed, the performance of reflective and impulsive subjects was facilitated by appropriate learning strategies.