Assessment of Back-Squat Performance at Submaximal Loads: Is the Reliability Affected by the Variable, Exercise Technique, or Repetition Criterion?

This study aimed to compare the between-session reliability of different performance variables during 2 variants of the Smith machine back-squat exercise. Twenty-six male wrestlers performed 5 testing sessions (a 1-repetition maximum [1RM] session, and 4 experimental sessions [2 with the pause and 2 with the rebound technique]). Each experimental session consisted of performing 3 repetitions against 5 loads (45–55–65–75–85% of the 1RM). Mean velocity (MV), mean power (MP), peak velocity (PV), and peak power (PP) variables were recorded by a linear position transducer (GymAware PowerTool). The best and average scores of the 3 repetitions were considered for statistical analyses. The coefficient of variation (CV) ranged from 3.89% (best PV score at 55% 1 RM using the pause technique) to 10.29% (average PP score at 85% 1 RM using the rebound technique). PP showed a lower reliability than MV, MP, and PV (CVratio ≥ 1.26). The reliability was comparable between the exercise techniques (CVratio = 1.08) and between the best and average scores (CVratio = 1.04). These results discourage the use of PP to assess back-squat performance at submaximal loads. The remaining variables (MV, MP, or PV), exercise techniques (pause or rebound), and repetition criteria (best score or average score) can be indistinctly used due to their acceptable and comparable reliability

Prediction of One Repetition Maximum Using Reference Minimum Velocity Threshold Values in Young and Middle-Aged Resistance-Trained Males

Background: This study determined the accuracy of different velocity-based methods when predicting one-repetition maximum (1RM) in young and middle-aged resistance-trained males. Methods: Two days after maximal strength testing, 20 young (age 21.0 ± 1.6 years) and 20 middleaged (age 42.6 ± 6.7 years) resistance-trained males completed three repetitions of bench press, back squat, and bent-over-row at loads corresponding to 20–80% 1RM. Using reference minimum velocity threshold (MVT) values, the 1RM was estimated from the load-velocity relationships through multiple (20, 30, 40, 50, 60, 70, and 80% 1RM), two-point (20 and 80% 1RM), high-load (60 and 80% 1RM) and low-load (20 and 40% 1RM) methods for each group. Results: Despite most prediction methods demonstrating acceptable correlations (r = 0.55 to 0.96), the absolute errors for young and middle-aged groups were generally moderate to high for bench press (absolute errors = 8.2 to 14.2% and 8.6 to 20.4%, respectively) and bent-over-row (absolute error = 14.9 to 19.9% and 8.6 to 18.2%, respectively). For squats, the absolute errors were lower in the young group (5.7 to 13.4%) than the middle-aged group (13.2 to 17.0%) but still unacceptable. Conclusion: These findings suggest that reference MVTs cannot accurately predict the 1RM in these populations. Therefore, practitioners need to directly assess 1RM

Análisis de la operativa de sistemas de recarga para autobuses eléctricos

Improving air quality is one of the main challenges facing urban mobility in the 21st century; electric vehicles have proven to have the potential to be the solution to this problem. The public transport that will change most will be the bus; the technology upgrade of the vehicles will be accompanied by the enhancement in the network performance. This work seeks to analyse the new electric recharge operations and determine the conditions that guarantee a regular service. Thus, based on classic models for the calculation of the stops capacity, it seeks to incorporate the electrical needs and determine the necessary infrastructure to maintain the service throughout the day with on-street recharging. Given the limited capacity of the batteries, this operation must always be completed; for this reason, the irregularities in bus arrivals are taken into account and gap times will be introduced to mitigate their effects. This will determine the performance metrics for regular lines with electric buses without disturbing their schedules. Finally, the agency costs are estimated against the current alternative of motor buses; considering the social costs of transportation. The results should facilitate decision-making in the substitution of traditional networks. Thanks to the data provided by Transports Metropolitans de Barcelona (TMB) and participants in the Zero Emissions bUs Systems (ZeEUS) project, the analysis of the H6 and H16 lines of the new Barcelona bus network is carried out. The results will show that, nowadays, electric buses are completely viable in regular services.La mejora de la calidad del aire es uno de los principales retos a los que se enfrenta la movilidad urbana en el siglo XXI; los vehículos eléctricos han demostrado tener el potencial de ser la solución a este problema. El modo de transporte público que más cambios sufrirá será el autobús; la actualización de la tecnología de los vehículos vendrá acompañada de mejoras en la operativa de la red. Este trabajo busca analizar las nuevas operaciones de recarga eléctrica y determinar las condiciones que garanticen un servicio regular. De este modo, partiendo de modelos clásicos del cálculo de la capacidad de las paradas, se busca incorporar las necesidades eléctricas y determinar la infraestructura necesaria para mantener el servicio a lo largo de la jornada mediante recargas en el recorrido. Dada la limitada capacidad de las baterías, esta operación siempre debe completarse; por este motivo se tienen en cuenta las irregularidades en las llegadas de autobuses y se introducen márgenes de tiempo para mitigar sus efectos. Con esto, se determinarán los parámetros de servicio para líneas regulares con autobuses eléctricos sin perturbar sus horarios. Finalmente, se estima el coste para el operador del autobús eléctrico frente a la alternativa actual de autobuses con motores de combustión; considerando los costes sociales del transporte. Los resultados deberán facilitar la toma de decisiones en la sustitución de las redes tradicionales. Gracias a los datos aportados por Transports Metropolitans de Barcelona (TMB) y participantes en el proyecto Zero Emissions bUs Systems (ZeEUS), se lleva a cabo el análisis de las líneas H6 y H16 de la nueva red de bus de Barcelona. Los resultados mostrarán que, en la actualidad, los autobuses eléctricos son completamente viables en los servicios regulares

Ballistic, maximal strength and strength-endurance performance of male handball players: Are they affected by the evaluator’s sex?

This study aimed to elucidate whether ballistic, maximal strength and strength-endurance performances are affected by the sex of the evaluator. Sixteen young male handball players attended two testing sessions that only differed in the sex of the evaluators (2 women vs. 2 men). The two sessions were performed in a counterbalanced order. Ballistic performance (countermovement jump height and throwing velocity), maximal strength performance (squat and bench press [BP] one-repetition maximum [1RM]), and strength-endurance performance (number of repetitions-to-failure in BP and average velocity of the set in the squat) were assessed in both sessions. BP 1RM was greater in the presence of women evaluators (p = 0.036, ES = 0.09), whereas no differences were observed for the remaining variables (p � 0.254, ES � 0.19). Low correlations (r median [range] = -0.074 [-0.693, 0.326]) were observed between the different performance tests for the percent differences between both testing sessions. The sex of the evaluators has minimal influence on a number of physical traits in young male handball players when they are tested in the presence of other members of the team, while the low correlations indicate that a higher performance in one test under the presence of women does not imply a higher performance under the presence of women in other performance tests

The Acute and Chronic Effects of Implementing Velocity Loss Thresholds During Resistance Training: A Systematic Review, Meta‑Analysis, and Critical Evaluation of the Literature

Background Velocity loss (VL) experienced in a set during resistance training is often monitored to control training volume and quantify acute fatigue responses. Accordingly, various VL thresholds are used to prescribe resistance training and target different training adaptations. However, there are inconsistencies in the current body of evidence regarding the magnitude of the acute and chronic responses to the amount of VL experienced during resistance training. Objective The aim of this systematic review was to (1) evaluate the acute training volume, neuromuscular, metabolic, and perceptual responses to the amount of VL experienced during resistance training; (2) synthesize the available evidence on the chronic effects of different VL thresholds on training adaptations; and (3) provide an overview of the factors that might differentially influence the magnitude of specific acute and chronic responses to VL during resistance training. Methods This review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Five databases were searched, and studies were included if they were written in English, prescribed resistance training using VL, and evaluated at least one (1) acute training volume, neuromuscular, metabolic, or perceptual response or (2) training adaptation. Risk of bias was assessed using a modified Cochrane Collaboration’s tool for assessing the risk of bias in randomized trials. Multilevel and multivariate meta-regressions were performed where possible. Results Eighteen acute and 19 longitudinal studies met the inclusion criteria, of which only one had more than one risk of bias item assessed as high risk. Based on the included acute studies, it seems that the number of repetitions per set, blood lactate concentration, and rating of perceived exertion generally increase, while countermovement jump height, running sprint times, and velocity against fixed loads generally decrease as VL increases. However, the magnitude of these effects seems to be influenced, among other factors, by the exercise and load used. Regarding training adaptations, VL experienced during resistance training did not influence muscle strength and endurance gains. Increases in VL were associated with increases in hypertrophy (b = 0.006; 95% confidence interval [CI] 0.001, 0.012), but negatively affected countermovement jump (b = − 0.040; 95% CI − 0.079, − 0.001), sprint (b = 0.001; 95% CI 0.001, 0.002), and velocity against submaximal load performance (b = − 0.018; 95% CI − 0.029, − 0.006). Conclusions A graded relationship exists between VL experienced during a set and acute training volume, neuromuscular, metabolic, and perceptual responses to resistance training. However, choice of exercise, load, and individual trainee characteristics (e.g., training history) seem to modulate these relationships. The choice of VL threshold does not seem to affect strength and muscle endurance gains whereas higher VL thresholds are superior for enhancing hypertrophy, and lower VL thresholds are superior for jumping, sprinting, and velocity against submaximal loads performance.CAU

A study on the lateralization of the effect of musical imagery on spontaneous otoacoustic emissions

It has been suggested that different pathways through the brain are followed depending on the type of information that is being processed. Although it is now known that there is a continuous exchange of information through both hemispheres, language is considered to be processed by the left hemisphere, where Broca?s and Wernicke?s areas are located. On the other hand, music is thought to be processed mainly by the right hemisphere. According to Sininger Y.S. & Cone- Wesson, B. (2004), there is a similar but contralateral specialization of the human ears; due to the fact that auditory pathways cross-over at the brainstem. A previous study showed an effect of musical imagery on spontaneous otoacoustic emissions (SOAEs) (Perez-Acosta and Ramos-Amezquita, 2006), providing evidence of an efferent influence from the auditory cortex on the basilar membrane. Based on these results, the present work is a comparative study between left and right ears of a population of eight musicians that presented SOAEs. A familiar musical tune was chosen, and the subjects were trained in the task of evoking it after having heard it. Samples of ear-canal signals were obtained and processed in order to extract frequency and amplitude data on the SOAEs. This procedure was carried out before, during and after the musical image creation task. Results were then analyzed to compare the difference between SOAE responses of left and right ears. A clear asymmetrical SOAEs response to musical imagery tasks between left and right ears was obtained. Significant changes of SOAE amplitude related to musical imagery tasks were only observed on the right ear of the subjects. These results may suggest a predominant left hemisphere activity related to a melodic image creation task

The influence of skull shape modularity on internal skull structures: a 3D-Pilot study using bears

In order to capture the phenotypic variation of the internal skull structures, such as the sinuses or the brain, it is necessary to perform CT scans in a large number of specimens, which is difficult and expensive. Therefore, while the external morphology of the mammalian cranium has been the subject of many morphometric studies, the internal structures of the cranium have been comparatively less studied. Here, we explore how the variation of external shape reflects the morphology of internal structures. We use the family Ursidae (Carnivora, Mammalia) as a case study because bears have a wide variability of cranial morphologies in part associated with different trophic ecologies. To do this, we digitized a set of landmarks in 3D with a Microscribe G2X from the external surface of the cranium in a wide sample of bears. Additionally, the crania of seven bear species were CT-scanned and prepared digitally to visualize the 3D models of the external cranium morphology and of internal structures. Subsequently, we divided the landmarks into two modules, splanchnocranium and neurocranium, and we perform a two-block partial least squares analysis (2B PLS) to explore the intraspecific (static) morphological changes associated with the covariation between them. These morphological changes were visualized using the morphing technique with the 3D models, looking at both the external shape and the internal structures. In addition, we inferred the volume of the sinuses and of the brain in each hypothetical model. Our results show that the first two PLS axes are associated externally with changes in the basicranial angle, face length and cranium height and width. Concerning the internal structures, there are parallel changes in dorso-ventral and medio-lateral expansion of sinuses and brain, accompanied by their corresponding changes in volume. In contrast, the third PLS axis is related to opposite changes in the volume of sinuses and brain. These preliminary results suggest that the opposite relationship between sinuses and brain volumes in the bear cranium is not as evident as expected, at least at intraspecific level.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Distinct predatory behaviors in scimitar- and dirk-toothed sabertooth cats

Over the Cenozoic, large cat-like forms have convergently evolved into specialized killers of ‘megaherbivores’ that relied on their large, and laterally-compressed (saber-like) canines to rapidly subdue their prey [1-5]. Scimitar- and dirk-toothed sabertooths are distinct ecomorphs that differ in canine tooth length, degree of serration, and postcranial features indicative of dissimilar predatory behavior [6-13]. Despite these differences, it is assumed that they used a similar ‘canine-shear’ bite to kill their prey [14,15]. We investigated the killing behavior of the scimitar-toothed Homotherium serum and the dirk-toothed Smilodon fatalis using a comparative sample of living carnivores and a new quantitative approach to the analysis of skull function. For the first time, we quantified differences in the relative amount and distribution of cortical and trabecular bone in coronal sections of skulls to assess relative skull stiffness and flexibility [16-19]. We also use finite element analysis to simulate various killing scenarios that load skulls in ways that likely favor distinct proportions of cortical versus trabecular bone across the skull. Our data reveal that S. fatalis had an extremely thick skull and relatively little trabecular bone, consistent with a large investment in cranial strength for a stabbing canine-shear-bite. However, H. serum had more trabecular bone, and likely deployed an unusual predatory behavior more similar to the clamp-and-hold technique of the lion than S. fatalis. These data broaden the killing repertoire of sabertooths and highlight the degree of ecological specialization among members of the large carnivore guild during the Late Pleistocene of North America

The Bench Press Grip Width Does Not Affect the Number of Repetitions Performed at Different Velocity Loss Thresholds

Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the University of Granada Institutional Review Board (approval: 491/CEIH/2018).We would like to thank all the authors who participated in the data collection.This study aimed (I) to compare the number of repetitions that can be completed to failure (XRM) and before reaching a 15%, 30%, or 45% velocity loss threshold (XVLT) in the bench press exercise performed using different grip widths, and (II) to examine the inter-individual variability in the percentage of completed repetitions with respect to the XRM when the set volume is prescribed based on a fixed number of repetitions (FNR) and several velocity loss thresholds (VLT). Nineteen men performed four separate sessions in a random order where there was a single set of repetitions completed to failure against 75% of the one-repetition maximum during the Smith machine bench press exercise using a narrow, medium, wide, or self-selected grip widths. The XRM (p = 0.545) and XVLTs (p ≥ 0.682) were not significantly affected by grip width. A high and comparable inter-individual variability in the percentage of completed repetitions with respect to the XRM was observed when using both an FNR (median CV = 24.3%) and VLTs (median CV = 23.5%). These results indicate that Smith machine bench press training volume is not influenced by the grip width and that VLTs do not allow a more homogeneous prescription of the set volume with respect to the XRM than the traditional FNR