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The Cognitive Function and Taekwondo-Specific Kick Performance of Taekwondo Athletes at Different Hydration Statuses

Ai-Chi Zheng, Cheng-Shiun He, Chi-Cheng Lu, Bao-Lien Hung, Kuei-Ming Chou, and Shih-Hua Fang

Purpose: Successful participation in taekwondo (TKD) requires athletes to possess quick decision-making abilities and demonstrate technical proficiency during competition. Dehydration, occurring during both training and competition, is widely recognized to have various negative effects. Methods: This study investigated the impact of different levels of dehydration on cognitive function, as measured by the Vienna Test System, and the specific performance of kicking techniques among TKD athletes. Using a randomized crossover design, 12 participants were involved in the study. Before and after 1 hour of training at 80% of maximal heart rate, participants were weighed and provided urine samples. All participants were randomly assigned to 3 different hydration conditions: the euhydrated (EUH) group had unrestricted access to fluid consumption, while the hypohydrated (HYP) and severely HYP (S-HYP) groups experienced reductions of 2.0% and 4.0% of their initial body weight, respectively. Results: The EUH group exhibited better reaction speed in reaction-time test-form S1 than the HYP and S-HYP groups. Notably, the EUH group demonstrated a significantly higher success rate in the front-side kick (EUH 98%, HYP 90%, S-HYP 88%; P < .05). However, the success rates of back roundhouse kick and free head kick were similar among the 3 statuses. Furthermore, postexercise heart rates were found to be significantly higher in the HYP and S-HYP groups compared with the EUH group. Conclusions: This study provides insight into the negative effects of dehydration on cognitive function and TKD-specific performance. It is recommended that TKD athletes maintain optimal hydration levels during training and competition to ensure optimal performance.

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Volume 19 (2024): Issue 5 (May 2024)

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Quantifying Hitting Load in Racket Sports: A Scoping Review of Key Technologies

Quim Brich, Martí Casals, Miguel Crespo, Machar Reid, and Ernest Baiget

Purpose: This scoping review aims to identify the primary racket and arm-mounted technologies based on inertial measurement units that enable the quantification of hitting load in racket sports. Methods: A comprehensive search of several databases (PubMed, SPORTDiscus, Web of Science, and IEEE Xplore) and Google search engines was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping reviews guidelines. Included records primarily focused on monitoring hitting load in racket sports using commercialized racket or arm-mounted inertial sensors through noncompetitive and competitive racket-sports players. Results: A total of 484 records were identified, and 19 finally met the inclusion criteria. The largest number of systems found were compatible with tennis (n = 11), followed by badminton (n = 4), table tennis (n = 2), padel (n = 1), and squash (n = 1). Four sensor locations were identified: grip-attached (n = 8), grip-embedded (n = 6), wrist (n = 3), and dampener sensors (n = 2). Among the tennis sensors, only 4 out of the 11 (36.4%) demonstrated excellent reliability (>.85) in monitoring the number of shots hit either during analytic drills or during simulated matches. None of the other racket-sports sensors have undergone successful, reliable validation for hitting-volume quantification. Conclusions: Despite recent advancements in this field, the quantification of hitting volume in racket sports remains a challenge, with only a limited number of tennis devices demonstrating reliable results. Thus, further progress in technology and research is essential to develop comprehensive solutions that adequately address these specific requirements.

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The Limitations of Systematic Reviews With Meta-Analyses in Sport Science

Daniel Boullosa, David Behm, Sebastián Del Rosso, Moritz Schumann, Kenji Doma, and Carl Foster

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“You Are Not Wrong About Getting Strong:” An Insight Into the Impact of Age Group and Level of Competition on Strength in Spanish Football Players

Marcos A. Soriano, Víctor Paredes, Paul Comfort, Ester Jiménez-Ormeño, Francisco Areces-Corcuera, Verónica Giráldez-Costas, César Gallo-Salazar, Diego A. Alonso-Aubín, María Menchén-Rubio, and John J. McMahon

Objective: This study aimed to compare the maximum and rapid force production of Spanish football players and explore the differences between age group and level of competition. Methods: A cross-sectional study was developed to evaluate the peak force (PF), relative PF, and rate of force development over 250 ms (RFD0−250) during the isometric midthigh pull between groups of football players based on age group (senior vs junior) and level of competition (national vs regional). Using a portable isometric rig, 111 football players performed 2 isometric midthigh-pull trials on a force plate. Two-way analysis of variance with Bonferroni post hoc correction was applied, and statistical significance was set at P ≤ .05. The PF, relative PF, and RFD0−250 0, 25, 50, 75, and 100 percentiles were also calculated and descriptively reported, separated by age group and level of competition. Results: The analysis of variance revealed a significant main effect of the level of competition for the PF (P < .001), relative PF (P = .003), and RFD0−250 (P < .001). There was a significant main effect of age group for the PF (P < .001). There was a significant interaction effect of the age group × level of competition for relative PF (P = .014). National players were stronger than regional players on the PF and RFD0−250 (P < .001). Senior players were stronger than junior players for the PF (P < .001). Conclusions: Maximum and rapid force production are crucial for Spanish football players as they progress in both level of competition and age group. Practitioners should encourage young football players to prioritize strength development to improve their athletic performance.

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Peak Performance: Characteristics and Key Factors in the Development of the World Top-8 Swimmers Based on Longitudinal Data

Yuming Chen, Chenbin Huang, Hui Chen, Ting Huang, Christine Su, and Jiexing Chen

Purpose: This study aimed to investigate the peak performance characteristics of the world top-8 swimmers and the key factors involved in the journey toward achieving better peak performance. Methods: The results of the world top-8 swimmers from 2001 to 2022 were collected from the World Aquatics performance database. Progression to peak performance was tracked with individual quadratic trajectories (1191 cases). Utilizing k-means clustering to group competitive feature variables, this study investigated key developmental factors through a binary logistic regression model, using the odds ratio (OR) to represent whether a factor was favorable (OR > 1) or unfavorable (OR < 1). Results: Significant differences (P < .001) in the peak age between men (23.54/3.80) and women (22.31/4.60) were noticed, while no significant differences (P > .05) in the peak-performance window for both sexes appeared. Peak performance occurred at later ages for the sprint for both sexes, and women had a longer duration in peak-performance window for sprint (P < .05). Peak-performance occurred at later ages for the breaststroke and butterfly for both sexes (P < .05). Binary logistic regression revealed that high first-participation performance (OR = 1.502), high major-competition performance (OR = 4.165), early first-major-competition age (OR = 1.441), participation frequency above 4 times/year in both phase 2 (4.3–8.0 times/y, OR = 3.940; 8.1–20.0 times/y, OR = 5.122) and phase 3 (4.1–7.5 times/y: OR = 5.548; 7.7–15.0 times/y: OR = 7.526), and a career length of 10 years or more (10–15 y, OR = 2.102; 16–31 y, OR = 3.480) were favorable factors for achieving better peak performance. Conclusions: Peak performance characteristics varied across sex, swimming stroke, and race distance in the world top-8 swimmers. Meanwhile, the research indicated that certain specific developmental factors were key conditions for the world top-8 swimmers to achieve better peak performance in the future.

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Which Strength Manifestation Is More Related to Regional Swimmers’ Performance and In-Water Forces? Maximal Neuromuscular Capacities Versus Maximal Mechanical Maintenance Capacity

Sergio Miras-Moreno, Óscar López-Belmonte, Amador García-Ramos, Raúl Arellano, and Jesús J. Ruiz-Navarro

Purpose: To explore the association of the load–velocity (L-V) relationship variables and ability to maintain maximal mechanical performance during the prone bench-pull exercise with sprint swimming performance and in-water forces. Methods: Eleven competitive adult male swimmers (50-m front crawl World Aquatics points: 488 [66], performance level 4) performed 1 experimental session. The L-V relationship variables (L 0 [ie,  maximal theoretical load at 0 velocity]; v 0 [ie, maximal theoretical velocity at 0 load], and A line [ie, area under the L-V relationship]) and maximal mechanical maintenance capacity were assessed at the beginning of the session. Afterward, sprint swimming performance and in-water force production were tested through a 50-m front-crawl all-out trial and 15-s fully-tethered swimming, respectively. Results: Only v 0 presented high positive associations with 50-m time and swimming kinematics (r > .532; P < .046). The L 0, v 0, and A line showed very high positive associations with the in-water forces during tethered swimming (r > .523; P < .049). However, the ability to maintain maximal mechanical performance, assessed by the mean velocity decline during the prone bench pull, was only significantly correlated with stroke rate (r = −.647; P = .016) and stroke index (r = .614; P = .022). Conclusions: These findings indicate that maximal neuromuscular capacities, especially v 0, have a stronger correlation with swimming performance and in-water force production than the ability to maintain maximal mechanical performance in level 4 swimmers.

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Multi-Ingredient Preworkout Supplementation Compared With Caffeine and a Placebo Does Not Improve Repetitions to Failure in Resistance-Trained Women

Mariah Snyder, Christi Brewer, and Katrina Taylor

There has been an increase in the use of commercially available multi-ingredient preworkout supplements (MIPS); however, there are inconsistencies regarding the efficacy of MIPS in resistance-trained women. Purpose: To determine the effect of varying doses of MIPS compared with caffeine only (C) and a placebo (PL) on resistance-training performance in trained women. Methods: Ten women (21.5 [2.3] y) completed 1-repetition-maximum tests at baseline for leg press and bench press. A within-group, double-blind, and randomized design was used to assign supplement drinks (ie, PL, C, MIPS half scoop [MIPS-H], and MIPS full scoop [MIPS-F]). Repetitions to failure were assessed at 75% and 80% to 85% of 1-repetition maximum for bench and leg press, respectively. Total performance volume was calculated as load × sets × repetitions for each session. Data were analyzed using a 1-way repeated-measures analysis of variance and reported as means and SDs. Results: There were no differences in repetitions to failure for bench press (PL: 14.4 [3.2] repetitions, C: 14.4 [2.9] repetitions, MIPS-H: 14.2 [2.6] repetitions, MIPS-F: 15.1 [3.1] repetitions; P = .54) or leg press (PL: 13.9 [7.8] repetitions, C: 10.8 [5.9] repetitions, MIPS-H: 13.1 [7.1] repetitions, MIPS-F: 12.4 [10.7] repetitions; P = .44). Furthermore, there were no differences in total performance volume across supplements for bench press (PL: 911.2 [212.8] kg, C: 910.7 [205.5] kg, MIPS-H: 913.6 [249.3] kg, MIPS-F: 951.6 [289.6] kg; P = .39) or leg press (PL: 4318.4 [1633.6] kg, C: 3730.0 [1032.5] kg, MIPS-H: 4223.0 [1630.0] kg, MIPS-F: 4085.5 [2098.3] kg; P = .34). Conclusions: Overall, our findings suggest that caffeine and MIPS do not provide ergogenic benefits for resistance-trained women in delaying muscular failure.

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Sport Science, Geopolitics, and How Each of Us Can Make a Difference

Jos J. de Koning, Carl Foster, David B. Pyne, Ralph Beneke, and Øyvind Sandbakk

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The Relationship of Open- and Closed-Kinetic-Chain Rate of Force Development With Jump Performance Following Anterior Cruciate Ligament Reconstruction

Megan C. Graham, Kelsey A. Reeves, Tereza Janatova, and Brian Noehren

Purpose: To determine between-limbs differences in isometric rate of force development (RFD) measured during open- (OKC) and closed-kinetic-chain (CKC) strength testing and establish which method had the strongest relationship to single-leg vertical-jump performance and knee mechanics after anterior cruciate ligament (ACL) reconstruction. Methods: Subjects (n = 19) 1 to 5 years from ACL reconstruction performed isometric knee extensions (OKC), unilateral isometric midthigh pulls (CKC), and single-leg vertical jumps on the ACL-involved and -noninvolved limbs. Between-limbs differences were assessed using paired t tests, and the relationship between RFD, jump performance, and knee mechanics was assessed using correlation coefficients (r; P ≤ .05). Results: There were significant between-limbs differences in OKC RFD (P = .008, d = −0.69) but not CKC RFD. OKC RFD in the ACL-involved limb had a strong association with jump height (r = .64, P = .003), knee-joint power (r = .72, P < .001), and peak knee-flexion angle (r = .72, P = .001). CKC RFD in the ACL-involved limb had a strong association with jump height (r = .65, P = .004) and knee-joint power (r = .67, P = .002) but not peak knee-flexion angle (r = .40, P = .09). Conclusions: While both OKC and CKC RFD were strongly related to jump performance and knee-joint power, OKC RFD was able to detect between-limbs RFD asymmetries and was strongly related to knee-joint kinematics. These findings indicate that isometric knee extension may be optimal for assessing RFD after ACL reconstruction.