Duane Knudson

Stretching has no effect on tennis serve performance.

&NA; Knudson, D.V., G.J. Noffal, R.E. Bahamonde, J.A. Bauer, and J.R. Blackwell. Stretching has no effect on tennis serve performance. J. Strength Cond. Res. 18(3):654–656. 2004.—Stretching prior to vigorous physical activity has been shown to decrease high‐force muscular performance, but little is known about the effect of stretching on speed and accuracy movements. Serving percentage and radar measurements of ball speed were studied to examine the acute effect of stretching on tennis serve performance. Eighty‐three tennis players from beginning level to advanced volunteered to serve following traditional (T) warm‐up and traditional plus stretching (S) conditions. Service speeds and service percentage of each condition were measured. Dependent t‐tests showed nonsignificant effects of stretching on service speed (p = 0.06) or accuracy (p = 0.35), and this lack of an effect was similar for all skill levels, age, and gender. The large sample and good statistical power in this study indicated that these observations are not likely type II errors. There was no short‐term effect of stretching in the warmup on the tennis serve performance of adult players, so adding stretching to the traditional 5‐minute warm‐up in tennis does not affect serve performance.

Use of deterministic models in sports and exercise biomechanics research

A deterministic model is a modeling paradigm that determines the relationships between a movement outcome measure and the biomechanical factors that produce such a measure. This review provides an overview of the use of deterministic models in biomechanics research, a historical summary of this research, and an analysis of the advantages and disadvantages of using deterministic models. The deterministic model approach has been utilized in technique analysis over the last three decades, especially in swimming, athletics field events, and gymnastics. In addition to their applications in sports and exercise biomechanics, deterministic models have been applied successfully in research on selected motor skills. The advantage of the deterministic model approach is that it helps to avoid selecting performance or injury variables arbitrarily and to provide the necessary theoretical basis for examining the relative importance of various factors that influence the outcome of a movement task. Several disadvantages of deterministic models, such as the use of subjective measures for the performance outcome, were discussed. It is recommended that exercise and sports biomechanics scholars should consider using deterministic models to help identify meaningful dependent variables in their studies.

Comparison of Three Methods of Estimating Energy Expenditure: Caltrac, Heart Rate, and Video Analysis

This study examined the accuracy of a new device (Caltrac) in estimating energy expenditure via acceleration measurements. Energy expenditure of 20 high school students during basketball class activity (average length = 37 min) was estimated using the Caltrac, heart rate recording, and video analysis. Heart rate recording and video analysis estimates of energy expenditure were determined from heart rate, caloric expenditure curves, and an activity rating scale, respectively. The following estimates of caloric expenditure (M +/- SD) were found: heart rate recording = 196 +/- 73 greater than Caltrac = 163 +/- 49 greater than film analysis = 123 +/- 30 kcal (p less than .05). Laboratory simulations of the basketball activity revealed that the Caltrac energy expenditure was not significantly different from the actual energy expenditure (p greater than .05). The heart rate recording and video analysis estimates of energy expenditure were significantly (p less than .05) higher and lower, respectively, than the actual energy expenditure. The Caltrac is a lightweight, low-cost device that provides a relatively accurate estimate of energy expenditure in free-ranging activities, such as basketball.

The Canadian Assessment of Physical literacy: Development of a model of children's capacity for a healthy, active lifestyle through a Delphi process

BACKGROUND The Canadian Assessment of Physical Literacy (CAPL) was conceptualized as a tool to monitor childrens physical literacy. The original model (fitness, activity behavior, knowledge, motor skill) required revision and relative weights for calculating/interpreting scores were required. METHODS Nineteen childhood physical activity/fitness experts completed a 3-round Delphi process. Round 1 was open-ended questions. Subsequent rounds rated statements using a 5-point Likert scale. Recommendations were sought regarding protocol inclusion, relative importance within composite scores and score interpretation. RESULTS Delphi participant consensus was achieved for 64% (47/73) of statement topics, including a revised conceptual model, specific assessment protocols, the importance of longitudinal tracking, and the relative importance of individual protocols and composite scores. Divergent opinions remained regarding the inclusion of sleep time, assessment/ scoring of the obstacle course assessment of motor skill, and the need for an overall physical literacy classification. CONCLUSIONS The revised CAPL model (overlapping domains of physical competence, motivation, and knowledge, encompassed by daily behavior) is appropriate for monitoring the physical literacy of children aged 8 to 12 years. Objectively measured domains (daily behavior, physical competence) have higher relative importance. The interpretation of CAPL results should be reevaluated as more data become available.

Advancing Kinesiology Through Improved Peer Review

Peer review of scholarship is essential to journal quality, evidence, knowledge advancement, and application of that knowledge in any field. This commentary summarizes recent literature on issues related to peer-review quality and current review practice in kinesiology and provides recommendations to improve peer review in kinesiology journals. We reviewed the literature on the characteristics of peer review in scientific journals and describe the status of peer review in kinesiology journals. Although the majority of scholars and editors strongly support the peer-review process, systematic research in several disciplines has shown somewhat positive but mixed results for the efficacy of peer review in evaluating the quality of and improving research reports. Past recommendations for improvement have focused on agreement between reviewers, standards for evaluating quality, and clarification of the editorial team roles. Research on interventions, however, indicates that improving reviewer performance is difficult. The specific research on peer review in kinesiology is limited. Six recommendations to improve peer review are proposed: publishing clear evaluation standards, establishing collaborative evaluation procedures and editorial team roles, utilizing online submission data to help improve reviewer comments, creating author appeals procedures, protecting reviewer time commitments, and improving reviewer recognition. There is considerable variation in peer-review criteria and procedures in kinesiology, and implementing several reasonable improvements may advance knowledge development and the field of kinesiology.

Authorship and Sampling Practice in Selected Biomechanics and Sports Science Journals

In some biomedical sciences, changes in patterns of collaboration and authorship have complicated the assignment of credit and responsibility for research. It is unclear if this problem of “promiscuous coauthorship” or “hyperauthorship” (defined as six or more authors) is also apparent in the applied research disciplines within sport and exercise science. This study documented the authorship and sampling of patterns of original research reports in three applied biomechanics (Clinical Biomechanics, Journal of Applied Biomechanics, and Sports Biomechanics) and five similar subdisciplinary journals within sport and exercise science (International Journal of Sports Physiology and Performance, Journal of Sport Rehabilitation, Journal of Teaching Physical Education, Measurement in Physical Education and Exercise Sciences, and Motor Control). Original research reports from the 2009 volumes of these biomechanics and sport and exercise journals were reviewed. Single authorship of papers was rare (2.6%) in these journals, with the mean number of authors ranging from 2.7 to 4.5. Sample sizes and the ratio of sample to authors varied widely, and these variables tended not to be associated with number of authors. Original research reports published in these journals in 2009 tended to be published by small teams of collaborators, so currently there may be few problems with promiscuous coauthorship in these subdisciplines of sport and exercise science.

Teaching practices of the undergraduate introductory biomechanics faculty: a North American survey

Instruction and assessment strategies of undergraduate introductory biomechanics instructors have yet to be comprehensively examined. The purpose of this study was to identify the current instruction and assessment practices of North American undergraduate introductory biomechanics instructors and equipment needed for effective instruction in lecture and laboratory sessions. One hundred and sixty-five respondents (age: 42.5 ± 10.3 years) who currently teach or have taught an introductory biomechanics course in North America were recruited by electronic mail. Subjects completed a web-based survey, consisting of 60 open- and closed-ended questions. Pearsons correlation coefficients were used to assess relationships between instructors familiarity with either the Biomechanics Concept Inventory or the NASPE Guidelines for Undergraduate Biomechanics, and instructor and course characteristics (number of years teaching, age, faculty rank, number of quizzes given, etc.) A number of variables were significantly (p < 0.05) correlated. Answers to open-ended questions were processed using content analysis, with results categorized in content areas including: instructor and course characteristics; lecture instruction; assessment and equipment; laboratory instruction; assessment and equipment; and instructors perspectives. Many active learning strategies for lecture and laboratory instruction were identified by faculty. Limited student preparation and limited resources were noted as the instructors most common challenges.

Effect of type 3 (oversize) tennis ball on serve performance and upper extremity muscle activity.

Abstract This study investigated the effect of the larger diameter (Type 3) tennis ball on performance and muscle activation in the serve. Sixteen male advanced tennis players performed serves using regular size and Type 3 tennis balls. Ball speed, surface electromyography, and serve accuracy were measured. There were no significant differences in mean initial serve speeds between balls, but accuracy was significantly greater (19.3%) with the Type 3 ball than with the regular ball. A consistent temporal sequence of muscle activation and significant differences in mean activation of different muscles were observed. However, ball type had no effect on mean arm muscle activation. These data, combined with a previous study, suggest that play with the larger ball is not likely to increase the risk of overuse injury, but serving accuracy may increase compared to play with the regular ball.This study investigated the effect of the larger diameter (Type 3) tennis ball on performance and muscle activation in the serve. Sixteen male advanced tennis players performed serves using regular size and Type 3 tennis balls. Ball speed, surface electromyography, and serve accuracy were measured. There were no significant differences in mean initial serve speeds between balls, but accuracy was significantly greater (19.3%) with the Type 3 ball than with the regular ball. A consistent temporal sequence of muscle activation and significant differences in mean activation of different muscles were observed. However, ball type had no effect on mean arm muscle activation. These data, combined with a previous study, suggest that play with the larger ball is not likely to increase the risk of overuse injury, but serving accuracy may increase compared to play with the regular ball.

Pre- and post-impact muscle activation in the tennis volley: effects of ball speed, ball size and side of the body

Aim: To examine the pre- and post-impact activation of five upper extremity muscles in the tennis volley across conditions of ball speed, ball type and side of the body. Methods: A repeated measures design in a biomechanics laboratory setting was used. A total of 24 recreational tennis players (mean (SD) age 24 (5) years, height 176 (10) cm, mass 76 (13) kg) were recruited from a university. Participants performed tennis volleys under 18 ball conditions: three ball speeds (slow, medium and fast), with three ball types (two oversize and one regular size) each from two sides (forehand and backhand). Average normalised electromyographic levels of the flexor carpi radialis, extensor carpi radialis, triceps brachii, anterior/middle deltoid and posterior/middle deltoid of the hitting arm during pre- and post-impact phases (200 ms before and after ball–racquet impact, respectively) were assessed. Results: For the pre-impact phase, a significant muscle and side interaction (p<0.001) and significant main effects for speed (p = 0.002) and muscle (p<0.001) were observed. For the post-impact phase, significant interactions were observed for ball type and side (p = 0.002), ball speed and side (p = 0.011) and muscle and side (p = 0.001), as well significant main effects for muscle (p<0.001), speed (p = 0.035) and side (p<0.001). Conclusion: Oversize tennis balls do not significantly increase upper extremity muscle activation compared to regular size balls during a tennis volley. The highest post-impact activation was observed in the ECR indicating a vigorous wrist stabilisation role that could irritate players with lateral epicondylalgia.

Impact and prestige of kinesiology-related journals1

Abstract This study documented the major factors of scholarly influence of kinesiology journals: impact and prestige. Four citation-based biblometric indicators were extracted for kinesiology journals from three databases: Thompson-Reuters Journal Citation Reports, SCImago Journal and Country Rank, and Eigenfactor.org. Two metrics (Eigenfactor™ and Hirsch index) estimated journal prestige, while SCImago Journal Rank and the Impact Factor estimated impact. Correlations and curve fits confirmed the impact and prestige structure in kinesiology journals that has been reported in other fields. Combined impact and prestige scores showed some journals with high influence, but about twenty percent of the journals with ratings of either impact or prestige higher (0.5 SD) than the other. Kinesiology journals may make different contributions to the knowledge generation and storage roles of scholarly publications.