In this study, we examined the load–velocity relationship in the hexagonal bar deadlift exercise in women. Twenty-seven resistance-trained women were recruited. Participants performed a progressive load test up to the one-repetition maximum (1RM) load for determining the individual load–velocity relationship in the hexagonal bar deadlift exercise. Bar velocity was measured in every repetition through a linear encoder. A very strong and negative relationship was found between the %1RM and bar velocity for the linear (R 2 = .94; standard error of the estimation = 5.43% 1RM) and second-order polynomial (R 2 = .95) regression models. The individual load–velocity relationship provided even better adjustments (R 2 = .98; coefficient of variation = 1.77%) than the general equation. High agreement level and low bias were found between actual and predicted 1RM for the general load–velocity relationship (intraclass correlation coefficient = .97 and 95% confidence interval [0.90, 0.99]; bias = −2.59 kg). In conclusion, bar velocity can be used to predict 1RM with high accuracy during hexagonal bar deadlift exercise in resistance-trained women.
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Load–Velocity Relationship to Estimate the One-Repetition Maximum in the Hexagonal Bar Deadlift Exercise in Women
Petrus Gantois, Drumond Gilo, Ana Denise, Alejandro Muñoz-López, Fábio Yuzo Nakamura, and Fabiano de Souza Fonseca
Three Simulated Goalball Games in the Same Day Cause Central Fatigue and Can Impair Game Technical Performance
Jônatas Augusto Cursiol, Tarine Botta de Arruda, Fábio Yuzo Nakamura, and Ricardo Augusto Barbieri
The purpose of this study was to investigate the effects of three simulated goalball games on neuromuscular, physiological, perceptual, and technical parameters. Ten male players underwent assessments before and immediately after each game. Heart rate was recorded at rest and during all games that were entirely filmed for further technical performance analysis. Exercise significantly decreased knee extensor muscles peak force and percentage of voluntary activation after the second and third games, indicating the presence of central fatigue. Heart rate responses remained predominantly in a range equivalent to moderate activity intensity in all games. In addition, perceptual parameters were associated with reduced frequency of throws and density of actions. These findings suggest significant implications for the management of physical training, game strategy during a competition, and fixture change from three to two games per day.
Reliability of Heart Rate Variability in Children: Influence of Sex and Body Position During Data Collection
Carla Cristiane Silva, Maurizio Bertollo, Felipe Fossati Reichert, Daniel Alexandre Boullosa, and Fábio Yuzo Nakamura
Purpose:
To examine which body position and indices present better reliability of heart rate variability (HRV) measures in children and to compare the HRV analyzed in different body positions between sexes.
Method:
Twenty eutrophic prepubertal children of each sex participated in the study. The RR intervals were recorded using a portable heart rate monitor twice a day for 7 min in the supine, sitting, and standing positions. The reproducibility was analyzed using the intraclass correlation coefficient (ICC; two way mixed) and within-subject coefficient of variation (CV).Two-way ANOVA with repeated measures was used to compare the sexes.
Results:
High levels of reproducibility were indicated by higher ICC in the root-mean-square difference of successive normal RR intervals (RMSSD: 0.93 and 0.94) and Poincaré plot of the short-term RR interval variability (SD1: 0.92 and 0.94) parameters for boys and girls, respectively, in the supine position. The ICCs were lower in the sitting and standing positions for all HRV indices. In addition, the girls presented significantly higher values than the boys for SDNN and absolute high frequency (HF; p < .05) in the supine position.
Conclusions:
The supine position is the most reproducible for the HRV indices in both sexes, especially the vagal related indices.
Microdosing: Old Wine in a New Bottle? Current State of Affairs and Future Avenues
José Afonso, Fábio Yuzo Nakamura, Ivan Baptista, Gonçalo Rendeiro-Pinho, João Brito, and Pedro Figueiredo
Purpose: Microdosing of exercise aims to deliver smaller daily training doses but at a higher weekly frequency, adding up to a similar weekly volume as in nonmicrodosed training. This commentary critically discusses this concept, which appears to be a rebranding of the “old” distributed practice of motor learning. Development: We propose that microdosing should relate to the minimal dose that develops or at least maintains the selected capacities or skills as this training dose matters to practitioners, especially during the in-season period. Moreover, microdosing has been applied mainly to develop strength and endurance, but abilities such as sprinting and changing direction could also be microdosed, as well as technical–tactical skills. Conclusions: The concept of microdosing should be reframed to avoid redundancy with the concept of distributed practice while providing valuable information concerning the minimum doses that still generate the intended effects and the thresholds that determine whether a dose is “micro” or not.
Determining the Relationship Between Internal Load Markers and Noncontact Injuries in Young Elite Soccer Players
Javier Raya-González, Fabio Yuzo Nakamura, Daniel Castillo, Javier Yanci, and Maurizio Fanchini
Purpose: To examine the association and predictive ability of internal load markers with regard to noncontact injuries in young elite soccer players. Methods: Twenty-two soccer players (18.6 [0.6] y) who competed in the Spanish U19 League participated in the study. During a full season, noncontact injuries were recorded and, using session rating of perceived exertion, internal weekly load (sum of load of all training sessions and matches for each week) and acute:chronic workload ratio (typically, acute = current week and chronic = rolling 4-wk average) were calculated. A generalized estimating equation analysis was used to examine the association of weekly and acute:chronic load-ratio markers with a noncontact injury in the subsequent week. Load variables were also analyzed for predictive ability with receiver operating characteristic curve and area under the curve. Results: No association was found for weekly load (odds ratio = 1.00; 90% confidence interval, 0.99–1.00) and acute:chronic load ratio (odds ratio = 0.16; 90% confidence interval, 0.01–1.84) with respect to injury occurrence. In addition, the analyzed load markers showed poor ability to predict injury occurrence (area under the curve < .50). Conclusions: The results of this study suggest that internal load markers are not associated with noncontact injuries in young soccer players and present poor predictive capacity with regard to the latter.
Hemodynamic Effects of Intermittent Pneumatic Compression on Athletes: A Double-Blinded Randomized Crossover Study
Filipe Maia, Marta V.B. Machado, Gustavo Silva, Fábio Yuzo Nakamura, and João Ribeiro
Purpose: There are multiple postexercise recovery technologies available in the market based on the assumption of blood-flow enhancement. Lower-limb intermittent pneumatic compression (IPC) has been widely used, but the available scientific evidence supporting its effectiveness remains scarce, requiring a deeper investigation into its underlying mechanisms. The aim of this study was to assess the hemodynamic effects caused by the use of IPC at rest. Methods: Twenty-two soccer and track and field athletes underwent two 15-minute IPC protocols (moderate- [80 mm Hg] and high-pressure [200 mm Hg]) in a randomized order. Systolic peak velocity, end-diastolic peak velocity, arterial diameter, and heart rate were measured before, during (at the eighth minute), and 2 minutes after each IPC protocol. Results: Significant effects were observed between before and during (eighth minute) the IPC protocol for measures of systolic (P < .001) and end-diastolic peak velocities (P < .001), with the greater effects observed during the high-pressure protocol. Moreover, 2 minutes after each IPC protocol, hemodynamic variables returned to values close to baseline. Arterial diameter presented significant differences between pressures during the IPC protocols (P < .05), while heart rate remained unaltered. Conclusion: IPC effectively enhances transitory blood flow of athletes, particularly when applying high-pressure protocols.
Isometric Midthigh-Pull Testing: Reliability and Correlation With Key Functional Capacities in Young Soccer Players
Vincenzo Rago, Fábio Yuzo Nakamura, Carlos Suarez-Balsera, Javier Arnaiz-Lastras, and Pedro Figueiredo
Purpose: We examined the reliability of force parameters derived from the isometric midthigh pull (IMTP) and their correlation with the functional capacities of young soccer players. Methods: Data were collected from 20 young professional soccer players within and between 2 sessions (after 1 wk) using a 1000-Hz force plate. Results: Performance outputs in all IMTP parameters were consistent and showed moderate to excellent reliability (intraclass correlation coefficient = .72–1.00) within and between sessions. However, all parameters reported a marginal ability to detect chronic changes in performance (smallest worthwhile change [SWC] < standard error of measurement [SEM]) except for peak vertical force (PF) parameters, which showed good usefulness (SWC > SEM). Absolute PF was correlated with the countermovement-jump (CMJ) total impulse (CMJ-TI; r = .54), whereas relative PF (to body mass) was correlated with CMJ height, CMJ peak power, and the last speed of the 30:15 Intermittent Fitness Test (V IFT; r = .40 to .63). IMTP time-dependent forces were correlated with CMJ-TI (r = .52 to .62). The IMTP impulse parameters were positively correlated with CMJ-TI (r = .48 to .58) and negatively with V IFT (r = −.44 to −.38). None of the IMTP parameters were correlated either with the CMJ mean propulsive force or with any linear acceleration times. Conclusions: All IMTP parameters can be adopted by practitioners involved with testing young soccer players based on their acceptable reliability criteria. However, caution should be taken when interpreting the time-dependent variables based on their marginal usefulness when assessing performance. Generally, a greater PF was associated with a greater vertical power based on its correlation to CMJ.
Impact of Generalized Versus Individualized Load–Velocity Equations on Velocity-Loss Magnitude in Bench-Press Exercise: Mixed-Model and Equivalence Analysis
Miguel Sánchez-Moreno, Beatriz Bachero-Mena, Juan Sánchez-Valdepeñas, Fabio Yuzo Nakamura, and Fernando Pareja-Blanco
Purpose: This study analyzed the influence of 2 velocity-based training-load prescription strategies (general vs individual load–velocity equations) on the relationship between the magnitude of velocity loss (VL) and the percentage of repetitions completed in the bench-press exercise. Methods: Thirty-five subjects completed 6 sessions consisting of performing the maximum number of repetitions to failure against their 40%, 60%, and 80% of 1-repetition maximum (1RM) in the Smith machine bench-press exercise using generalized and individualized equations to adjust the training load. Results: A close relationship and acceptable error were observed between percentage of repetitions completed and the percentage of VL reached for the 3 loading magnitudes and the 2 load-prescription strategies studied (R 2 from .83 to .94; standard error of the estimate from 7% to 10%). A simple main effect was observed for load and VL thresholds but not for load-prescription strategies. No significant interaction effects were revealed. The 40% and 60% 1RM showed equivalence on data sets and the most regular variation, whereas the 80% 1-repetition maximum load showed no equivalence and more irregular variation. Conclusion: These results suggest that VL is a useful variable to predict percentage of repetitions completed in the bench-press exercise, regardless of the strategy selected to adjust the relative load. However, caution should be taken when using heavy loads.
Characterization of the Sprint and Repeated-Sprint Sequences Performed by Professional Futsal Players, According to Playing Position, During Official Matches
Fabio Giuliano Caetano, Murilo José de Oliveira, Ana Lorena Marche, Fábio Yuzo Nakamura, Sergio Augusto Cunha, and Felipe Arruda Moura
The purposes of this study were to investigate sprints and to characterize repeated-sprint sequences (RS) performed by athletes during professional futsal matches. We analyzed 97 players during 5 official matches using the DVideo automatic tracking system. The sprints were analyzed during the first and second halves according to playing position, and RS were categorized according to the number of sprints and the time between them. The results showed an increase (F[1, 2520] = 3.96; P = .046) in the sprint duration from the first (mean = 3.1 ± 1.3) to the second half (mean = 3.2 ± 1.2). However, no differences were found for other variables (distance covered, peak velocity, initial velocity, recovery time between sprints, and sprints performed per minute) or among playing positions. In addition, when considering RS, the results showed that RS comprising two sprints interspersed with a maximum of 15 seconds of recovery were significantly more frequent than other RS. The findings of this study characterizing the sprinting features of futsal players can help coaches to plan physical training and assessments according to the requirements of the sport.
The Effects of Neuromuscular Training on Sand Versus Hard Surfaces on Physical Fitness in Young Male Tennis Players
Jaime Fernandez-Fernandez, Fábio Yuzo Nakamura, Daniel Boullosa, Francisco Javier Santos-Rosa, Alba Herrero-Molleda, Urs Granacher, and David Sanz-Rivas
Purpose: To examine the effects of a neuromuscular training program combining plyometric exercises with acceleration, deceleration, and change-of-direction drills conducted on sand or hard surfaces on the fitness qualities of young male tennis players. Methods: Thirty-one young male players were allocated to a training group performing 12 training sessions on sand or hard surfaces, during a 6-week period. Tests included linear sprint (10-m acceleration with 5-m split times), change of direction (modified 5-0-5 test), vertical jumps (countermovement jump and the 10/5 repeated-jump test), isometric hip abduction and adduction strength, and dynamic balance (Y-balance test). Perceived training loads and muscle soreness were assessed during the intervention. Results: Both training strategies were similarly effective in improving the analyzed fitness components. Group × time interaction effects were noticed, with countermovement jump (P = .032), repeated-jump test (P = .029), and reactive strength index (P = .008) favoring hard surfaces and 5-m sprint (P = .009), dynamic balance (P < .05), adduction strength (P < .05), and abduction strength (P < .001) indices favoring sand. Furthermore, the sand group promoted greater perceived training loads and muscle soreness (P < .05) than the hard group across the intervention period. Conclusion: Neuromuscular training strategies characterized by a relatively low volume (∼35 min), conducted on sand or hard surfaces, promoted similar improvements in the fitness qualities of young tennis players, with selected surface-interaction effects. Training on sand can cause transiently higher training loads and persistently higher muscle soreness, suggesting the need for an adequate familiarization period.