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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.

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Absence of Monotony and Strain Effects on Referees’ Physical Performance During International Basketball Federation World Cup Basketball Competition

Rūtenis Paulauskas, Alejandro Vaquera, and Bruno Figueira

Purpose: The study aimed to conduct a comparative analysis of physical performance indicators and assess the levels of performance monotony and strain experienced by basketball referees. Methods: The study involved the participation of 12 basketball referees (mean age: 40.0 [4.9] y) affiliated with the International Basketball Federation. The investigation was carried out throughout 2 density tournaments, wherein the maximum heart rate, average heart rate, performance monotony, and performance strain were documented for 3 variables. Results: The findings indicated significant variations in the mean heart rate, maximum heart rate, total distance monotony, total distance strain, the total number of sprints monotony, the total number of sprints strain, calories monotony, and calories strain (P < .05). Decreasing the density of elite-level basketball competitions has been observed to reduce the monotony and strain experienced by referees. However, this action does not increase motion distance or speed zones. Conclusions: The environmental stressors experienced by senior-level athletes (World Cup) differ from those encountered by younger athletes (World Cup Under 19). Further investigation is required to ascertain the potential effects of competition monotony and strain on decision-making processes and the overall quality of refereeing.

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Erratum. Absence of Monotony and Strain Effects on Referees’ Physical Performance During International Basketball Federation World Cup Basketball Competition

International Journal of Sports Physiology and Performance

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Is the 5-Minute Time-Trial Cycling Test a Valid Predictor of Maximal Oxygen Uptake? An External Cross-Validation Study

Fernando Klitzke Borszcz, Artur Ferreira Tramontin, Ricardo Dantas de Lucas, and Vitor Pereira Costa

Purpose: This study aimed to cross-validate a recently proposed equation for the prediction of maximal oxygen uptake ( V ˙ O 2 max ) in cycling exercise by using the average power output normalized by the body mass from a 5-minute time trial (RPO5-min) as the independent variable. Further, the study aimed to update the predictive equation using Bayesian informative prior distributions and meta-analysis. Methods: On different days, 49 male cyclists performed an incremental graded exercise test until exhaustion and a 5-minute time trial on a stationary cycle ergometer. We compared the actual V ˙ O 2 max with the predicted value obtained from the RPO5-min, using a modified Bayesian Bland–Altman agreement analysis. In addition, this study updated the data on the linear regression between V ˙ O 2 max and RPO5-min, by incorporating information from a previous study as a Bayesian informative prior distribution or via meta-analysis. Results: On average, the predicted V ˙ O 2 max using RPO5-min underestimated the actual V ˙ O 2 max by −6.6 mL·kg–1·min–1 (95% credible interval, −8.6 to −4.7 mL·kg–1·min–1). The lower and upper 95% limits of agreement were −17.2 (−22.7 to −12.3) and 3.8 (−1.0 to 9.5) mL·kg–1·min–1, respectively. When the current study’s data were analyzed using the previously published data as a Bayesian informative prior distribution, the accuracy of predicting sample means was found to be better when compared with the data combined via meta-analyses. Conclusions: The proposed equation presented systematic bias in our sample, in which the prediction underestimated the actual V ˙ O 2 max . We provide an updated equation using the previous one as the prior distribution, which could be generalized to a greater audience of cyclists.