Dennis Landin

Acute effects of passive muscle stretching on sprint performance

The results of previous research have shown that passive muscle stretching can diminish the peak force output of subsequent maximal isometric, concentric and stretch-shortening contractions. The aim of this study was to establish whether the deleterious effects of passive stretching seen in laboratory settings would be manifest in a performance setting. Sixteen members (11 males, 5 females) of a Division I NCAA track athletics team performed electronically timed 20 m sprints with and without prior stretching of the legs. The experiment was done as part of each athletes Monday work-out programme. Four different stretch protocols were used, with each protocol completed on a different day. Hence, the test period lasted 4 weeks. The four stretching protocols were no-stretch of either leg (NS), both legs stretched (BS), forward leg in the starting position stretched (FS) and rear leg in the starting position stretched (RS). Three stretching exercises (hamstring stretch, quadriceps stretch, calf stretch) were used for the BS, FS and RS protocols. Each stretching exercise was performed four times, and each time the stretch was maintained for 30 s. The BS, FS and RS protocols induced a significant (P  < 0.05) increase (∼0.04 s) in the 20 m time. Thus, it appears that pre-event stretching might negatively impact the performance of high-power short-term exercise.

The Role of Verbal Cues in Skill Learning

Verbal cues are concise phrases, often just one or two words, that are used as an alternate method of communicating task information. Research in motor learning and sport pedagogy has examined the effects of verbal cues in directing attention to critical task stimuli and information, recalling series of motor activities, and initiating movement sequences. The purpose of this paper is to address the theoretical bases of verbal cues, review recent cueing research, and offer suggestions for designing and implementing verbal cues in physical education and sport settings.

The influence of self-talk on the performance of skilled female tennis players

Abstract This paper reports on the development and implementation of a self-talk (ST) strategy designed to improve the volleying skill of collegiate tennis players (N = 5). A two-word ST strategy was developed, implemented, and evaluated using a single-case, multiple-baseline design. Dependent measures were movement patterns and outcome scores. After intervention, four players displayed immediate, positive changes with no overlapping datapoints on movement patterns. Notable improvements in outcome scores were also observed in all players, however, overlapping datapoints occurred for three players. Visual inspection of plotted values was supplemented by quantitative analysis using one-way ANOVAs to analyze four datapoints: the two baseline days just prior to intervention, and the two days immediately post intervention. Significant differences were found between phases, with both movement pattern and outcome scores higher following intervention. Qualitative data were collected via surveys and interviews. Pl...

Static stretching impairs sprint performance in collegiate track and field athletes

Previous research has shown that static stretching (SS) can diminish the peak force output of stretch-shortening cycle actions while performing a dynamic warm-up (DW) protocol has been shown to enhance performance in similar activities. The purpose of this study was to establish whether the deleterious effects of SS would wash out the performance enhancements obtained from the DW. Eleven males and 11 females, who were athletes of a NCAA Division I track team, performed a DW followed with either a SS or rest (NS) condition. After warm-up was completed, three 40 m sprints were performed to investigate the effects of the SS condition on sprint performance when preceded by DW. Time(s) were obtained from timing gates placed at 0, 20, and 40 m respectively. Testing was conducted over 2 days with a 1 week washout period. Testing order was balanced to eliminate possible order effect. Time for the NS versus the SS group was significantly faster for the second 20 m with a time of 2.41 versus 2.38 seconds (P ≤ .05), and for the entire 40 m with a time of 5.6 ± 0.4 versus 5.7 ± 0.4 seconds (P ≤ .05). The results of this study suggest that performing a SS protocol following a DW will inhibit sprint performance in collegiate athletes.

Practice Schedule Effects on the Performance and Learning of Low- and High-Skilled Students: An Applied Study

This study examined the effects of practice schedule manipulations implemented in an instructional setting on the performance and learning of low- and high-skilled students. College undergraduates (N = 83) enrolled in 5 tennis classes completed a pretest on the forehand and backhand ground strokes, practiced these skills under a blocked or alternating schedule, and then completed a posttest. Results indicated that practice schedule effects on learning were influenced by student ability. Low-skilled students assigned to the blocked schedule had higher posttest scores than those assigned to the alternating schedule, whereas no significant differences were found for high-skilled students. These findings are discussed in relation to previous applied and laboratory-based findings and as a means for manipulating practice difficulty in teaching physical education.

A Comparison of Three Practice Schedules along the Contextual Interference Continuum

T he organization of practice sessions is recognized as one of the most important functions teachers and coaches perform (Silverman, 1990; Vickers, 1990). However, as noted by Newel1 and McDonald (1992), despite considerable interest among researchers and practitioners, clear guidelines for organizing practice sessions have yet to be formulated. Magill (1992) has argued that the practice schedule research provides a knowledge base from which guidelines can be developed. This research, ongoing for over a decade, has compared the effects of practice schedules, which represent levels of contextual interference, on the performance and learning of motor skills. Predominately laboratory based, this research has produced an impressive set of findings (for a review, see Magill & Hall, 1990). However, replication of these findings in applied settings has been difficult, and questions regarding the applicability of contextual interference have been raised (Newel1 & McDonald, 1992).

Effects of a Learning Model and Augmented Feedback on Tennis Skill Acquisition

This experiment investigated the effects of observing a learning model and receiving augmented verbal feedback on the acquisition and retention of the tennis volley. Female undergraduate students were randomly assigned to four groups: (a) AFB--received augmented verbal feedback from an instructor, (b) LMFB--monitored a learning models trials and feedback, (c) LMFB+AFB--monitored a learning models trials and feedback and received verbal feedback from an instructor, and (d) Control--received neither treatment. Subjects were pretested, given 50 acquisition trials, and then a retention test. Outcome and movement pattern dependent variables were employed. Repeated measures analyses indicated that all three experimental groups were significantly better than the Control group on movement pattern and outcome, with the greatest success experienced by the LMFB+AFB group. Findings are discussed relative to previous research findings and implications for practitioners.

The Effects of Variable Practice on the Performance of a Basketball Skill

(1993). The Effects of Variable Practice on the Performance of a Basketball Skill. Research Quarterly for Exercise and Sport: Vol. 64, No. 2, pp. 232-237.

The Effects of Self-Talk and Augmented Feedback on Learning the Tennis Forehand

This study compared the effects of self-talk strategy (ST) and knowledge of performance (KP) feedback on learning the forehand tennis groundstroke. Three experimental groups met during their regular tennis class for seven days to examine the interactions between ST and feedback (FB). The instructors (N = 3) taught three groups of eight randomly assigned participants using scripted lessons, one group under each condition (ST with KP, ST without KP, and KP only). Four dependent measures: (a) outcome scores, (b) movement sequence scores, (c) percentage of correct trials, and (d) feedback statement analyses were examined separately. The movement sequence scores of the participants using ST strategy significantly exceeded those of the FB group. An examination of the percentage of correct trials during acquisition revealed the positive impact of ST early in the learning process, and displayed reasons for the marked differences in KP provided to each group. The findings indicate that ST can enhance learning the tennis forehand even when KP is unavailable.

The function of gastrocnemius as a knee flexor at selected knee and ankle angles

The gastrocnemius has been viewed as an important contributor at the knee joint as a joint flexor and stabilizer across all the knee and ankle joint angles. The purpose of this study was to investigate the influence of knee and ankle joint angles on the knee flexor function of the gastrocnemius. Seventeen participants were tested on a Biodex dynamometer with the gastrocnemius muscle selectively stimulated at a standardized level of electrical current. The results indicated that both ankle and knee joint angle influence the knee joint flexion moment produced by the gastrocnemius. Further analysis revealed that the flexion moment was greatest with the knee joint straight (180 degrees ) across all ankle joint angles. The greatest reduction in knee flexion moment occurred between 180 and 165 degrees of knee angle. No significant difference was observed in the knee flexion moment between 165 degrees and 115 degrees knee flexion, and little knee flexion moment was observed at knee angles of 90 degrees and 75 degrees. The dramatic reduction of moment between 180 degrees and 165 degrees knee angle is possibly due to the change of moment arm while the little moment production during extreme flexion (90 degrees and 75 degrees ) may be due to the reduction of muscle length.