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Garrett S. Bullock, Taylor Chapman, Thomas Joyce, Robert Prengle, Taylor Stern and Robert J. Butler

Context: Dominican Republic (DR) players have different training norms, which can affect their resiliency and performance. The variance among DR players’ training regimens may be influenced by the degree of training incorporating fundamental movement patterns. Objective: To examine differences in fundamental movement patterns in United States (US)–born versus DR-born professional baseball players. Design: Cross-sectional cohort. Setting: Professional baseball athletic training room. Participants: One hundred forty-two players (76 DR-born and 66 US-born) who were recently selected by a Major League Baseball team. Intervention: Subjects completed the Functional Movement Screen using the standardized 7 movement tests and the 3 isolated clearing tests. Main Outcome Measures: The primary variables studied were composite score, left and right asymmetry, and individual movement standard scores. Two-way chi-squared analysis was utilized for the statistical analysis with statistical significance being identified at P < .05. Results: DR players had a larger number of 1s (7.8% vs 3.0%) and 3s (10.5% vs 1.5%) on the right-sided hurdle step and a greater percentage of 3s (82.8% vs 60.6%) on right-sided shoulder mobility. US players had a larger percentage of 3s (33.3% vs 13.4%) and a lower percentage of 1s (2.2% vs 15.1%) on the active straight leg raise and a greater percentage of passable scores (≥2; 99.5% vs 65.8%) on the trunk stability push-up. Conclusion: This study suggests that fundamental movement competency differs between US- and DR-born professional baseball players. Based on these movement competency differences, a player’s country of origin may be taken into account to create an effective training program.

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Kristie-Lee Taylor, Will G. Hopkins, Dale W. Chapman and John B. Cronin

The purpose of this study was to calculate the coefficients of variation in jump performance for individual participants in multiple trials over time to determine the extent to which there are real differences in the error of measurement between participants. The effect of training phase on measurement error was also investigated. Six subjects participated in a resistance-training intervention for 12 wk with mean power from a countermovement jump measured 6 d/wk. Using a mixed-model meta-analysis, differences between subjects, within-subject changes between training phases, and the mean error values during different phases of training were examined. Small, substantial factor differences of 1.11 were observed between subjects; however, the finding was unclear based on the width of the confidence limits. The mean error was clearly higher during overload training than baseline training, by a factor of ×/÷ 1.3 (confidence limits 1.0–1.6). The random factor representing the interaction between subjects and training phases revealed further substantial differences of ×/÷ 1.2 (1.1–1.3), indicating that on average, the error of measurement in some subjects changes more than in others when overload training is introduced. The results from this study provide the first indication that within-subject variability in performance is substantially different between training phases and, possibly, different between individuals. The implications of these findings for monitoring individuals and estimating sample size are discussed.

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Kristie-Lee Taylor, John Cronin, Nicholas D. Gill, Dale W. Chapman and Jeremy Sheppard

Purpose:

This investigation aimed to quantify the typical variation for kinetic and kinematic variables measured during loaded jump squats.

Methods:

Thirteen professional athletes performed six maximal effort countermovement jumps on four occasions. Testing occurred over 2 d, twice per day (8 AM and 2 PM) separated by 7 d, with the same procedures replicated on each occasion. Jump height, peak power (PP), relative peak power (RPP), mean power (MP), peak velocity (PV), peak force (PF), mean force (MF), and peak rate of force development (RFD) measurements were obtained from a linear optical encoder attached to a 40 kg barbell.

Results:

A diurnal variation in performance was observed with afternoon values displaying an average increase of 1.5–5.6% for PP, RPP, MP, PV, PF, and MF when compared with morning values (effect sizes ranging from 0.2–0.5). Day to day reliability was estimated by comparing the morning trials (AM reliability) and the afternoon trials (PM reliability). In both AM and PM conditions, all variables except RFD demonstrated coefficients of variations ranging between 0.8–6.2%. However, for a number of variables (RPP, MP, PV and height), AM reliability was substantially better than PM. PF and MF were the only variables to exhibit a coefficient of variation less than the smallest worthwhile change in both conditions.

Discussion:

Results suggest that power output and associated variables exhibit a diurnal rhythm, with improved performance in the afternoon. Morning testing may be preferable when practitioners are seeking to conduct regular monitoring of an athlete’s performance due to smaller variability.