著者

Chris Bailey Kimitake Sato Ryan Alexander Chieh-Ying Chiang Michael H. Stone

出版者

Active Aging Research Center

雑誌

Journal of Trainology (ISSN:21865264)

巻号頁・発行日

vol.2, no.1, pp.1-5, 2013-04-24 (Released:2015-05-04)

参考文献数

20

被引用文献数

49 50

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Objectives: The purpose of this study was to identify the relationship between isometric force production symmetry and jumping performance in weighted and un-weighted static and countermovement jumps (SJ and CMJ). Design: Bivariate correlation between isometric force production symmetry and vertical jump performance variables. Methods: Collegiate athletes were evaluated for this study (n=36). Subjects performed SJ, CMJ, and isometric mid-thigh pulls (IMTP). Jumps were analyzed for jump height (JH) and peak power (PP). IMTP was analyzed for peak force (PF) for left and right sides, and values were calculated to produce a peak force symmetry index (PF-SI) score. Correlational statistics were performed examining the relationship between PF-SI and jump variables. Results: Moderate statistically significant negative correlations were observed between PF-SI and all jump variables, indicating that as asymmetry increases jump performance decreases. SJ correlations weakened in weighted conditions (JH r=-0.52 @ 0 kg/r=-0.39 @ 20 kg, PP r=-0.43 @ 0 kg/r=-0.34 @ 20 kg), but CMJ produced similar correlations for both conditions (JH r=-0.47 @ 0 kg/r=-0.49 @ 20 kg, PP r=-0.28 @ 0 kg/r=-0.34 @ 20 kg). Unlike the SJ, which only contains the propulsive or concentric portion of the jump, the CMJ also contains the eccentric portion and performance contributions of the stretch-shortening cycle (SSC). The addition of the SSC may play a role in the maintaining the magnitude of asymmetry in the CMJ weighted condition. Conclusions: The results indicate that force production asymmetry may be detrimental to bilateral vertical jumping performance. The findings should be considered for further investigation on sport-specific tasks.

著者

George K. Beckham Hugh S. Lamont Kimitake Sato Michael W. Ramsey Gregory Haff G. Michael H. Stone

出版者

Active Aging Research Center

雑誌

Journal of Trainology (ISSN:21865264)

巻号頁・発行日

vol.1, no.2, pp.32-35, 2012-11-12 (Released:2015-05-04)

参考文献数

10

被引用文献数

22 35

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Objectives: To determine if force differences exist between isometric pulling positions corresponding to key positions of the deadlift. Design: Cross-sectional evaluation of isometric strength Methods: 14 powerlifters performed isometric pulls on a force plate at 3 key positions related to the deadlift (at the floor, just above the patella, and 5-6 cm short of lockout) and in the mid thigh pull position (MTP). A 1x4 repeated measures ANOVA was used to ascertain differences between the various pulling positions tested. Bonferroni-adjusted paired samples t-tests were used post-hoc. Results: Forces generated at each bar height were significantly different (F(3,39) = 51.058, p<0.05, η2=0.80). Paired samples t-tests showed significant differences between positions, revealing a trend of greater force generation at increasing heights for positions corresponding to the deadlift. Force generated in the mid thigh pull position was significantly higher than any other position. Conclusion: In positions corresponding to the deadlift, force generation increases at higher bar heights.

著者

Kevin M. Carroll Kimitake Sato George K. Beckham Travis Triplett N. Cameron V. Griggs Michael H. Stone

出版者

Active Aging Research Center

雑誌

Journal of Trainology (ISSN:21865264)

巻号頁・発行日

vol.6, no.1, pp.9-12, 2017-01-26 (Released:2017-04-25)

参考文献数

16

被引用文献数

6

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Objectives: The purpose of this study was to examine the relationship of velocities in the back squat between one repetition maximum (1RM) and submaximally loaded repetition maximum (RM) conditions, specifically in regard to what has been described as the minimal velocity threshold (MVT). The MVT describes a minimum concentric velocity that an individual must reach or surpass in order to successfully complete a repetition. Design: To test the presence of a MVT, participants were tested for 1RM and RM back squat ability. The mean concentric veloci ties (MCV) of the last successful repetition of each condition were then compared. Methods: Fourteen male participants familiar with the back squat volunteered to participate in the current study (age = 25.0 y ± 2.6, height = 178.9 cm ± 8.1, body mass = 88.2 kg ± 15.8). The mean concentric velocity (MCV) during the last successful repetition from each testing condition was considered for the comparison. Results: Results indicated a non-significant negative relationship of MCV between the 1RM and RM conditions (r = -0.135), no statistical difference between testing conditions (p = 0.266), with a small-to-moderate effect size (d = 0.468). Conclusions: The results of this study suggest that MVT should be further investigated to enhance its use in the practical setting. Additionally, coaches considering using a velocity-based approach for testing athletes should use data from either 1RM or RM conditions, but not both interchangeably. Coaches should be cautious when considering group averages or comparing velocity data between athletes, which may not be appropriate based on our results.

著者

Jeremy A. Gentles William G. Hornsby Howard S. Gray Jonathan A. Miller Andrew R. Dotterweich Charles A. Stuart Michael H. Stone

出版者

Active Aging Research Center

雑誌

Journal of Trainology (ISSN:21865264)

巻号頁・発行日

vol.4, no.1, pp.25-31, 2015-06-18 (Released:2015-07-06)

参考文献数

47

被引用文献数

3

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Objectives: This study investigated chronic changes in cell free DNA (cf-DNA) throughout a collegiate soccer season. The relationship between cf-DNA, C-reactive protein (CRP), creatine kinase (CK), testosterone (T), cortisol (C), testoster one-cortisol ratio (T:C), body mass and body composition were also examined. Design: Longitudinal study design with repeated measures and group comparisons. Methods: Twenty three NCAA Division I male soccer players were divided into two groups. Starters were placed in Group 1 (G1) and non-starters were placed in Group 2 (G2). cf-DNA, CRP, CK, T, C, T:C, body mass and body composition were taken three times, corresponding to pre-season, approximately mid-season and immediately after the concluding the season. Results: In G1, cf-DNA, CRP, CK, cf-DNA %∆, CRP %∆ and, CK %∆ were all statistically higher at T2 and T3 than T1. In G2, CRP %∆ was statistically higher at T2 than T1. In G2, cf-DNA %∆, CRP %∆ and CK %∆ were higher at T2 and T3 than T1. Conclusions: This suggests that cf-DNA may be a useful marker that can reflect accumulated soccer training and competi tive stressors.