Use of machine-learning and load–velocity profiling to estimate 1-Repetition maximums for two variations of the bench-press exercise

The purpose of the current study was to compare the ability of five different methods to estimate eccentric–concentric and concentric-only bench-press 1RM from load–velocity profile data. Smith machine bench-press tests were performed in an eccentric–concentric (n= 192) and a concentric-only manner (n= 176) while mean concentric velocity was registered using a linear position transducer. Load–velocity profiles were derived from incremental submaximal load (40–80% 1RM) tests. Five different methods were used to calculate 1RM using the slope, intercept, and velocity at 1RM (minimum velocity threshold—MVT) from the load–velocity profiles: calculation with individual MVT, calculation with group average MVT, multilinear regression without MVT, regularized regression without MVT, and an artificial neural network without MVT. Mean average errors for all methods ranged from 2.7 to 3.3 kg. Calculations with individual or group MVT resulted in significant overprediction of eccentric–concentric 1RM (individual MVT: difference = 0.76 kg, p= 0.020, d= 0.17; group MVT: difference = 0.72 kg, p= 0.023, d= 0.17). The multilinear and regularized regression both resulted in the lowest errors and highest correlations. The results demonstrated that bench-press 1RM can be accurately estimated from load–velocity data derived from submaximal loads and without MVT. In addition, results showed that multilinear regression can be used to estimate bench-press 1RM. Collectively, the findings and resulting equations should be helpful for strength and conditioning coaches as they would help estimating 1RM without MVT data

Effects of resistance training on the body fat in obese people: systematic review

La obesidad, una de las enfermedades más preocupantes hoy en día, ha impulsado la búsqueda de nuevas estrategias interdisciplinares entre la comunidad científica. Una línea de investigación de actual relevancia es la que analiza en qué medida un programa de intervención con cargas tiene efecto sobre la reducción de la obesidad. En este trabajo se revisa la producción bibliográfica hasta el año 2011 que ha investigado el efecto de los programas basados única y exclusivamente en entrenamiento con cargas, sobre la grasa corporal en personas obesas. Los resultados son divergentes, pues la mitad de estudios concluyen que el entrenamiento con cargas reduce la grasa corporal y la otra mitad no, si bien en ningún estudio se ha incrementado significativamente la grasa corporal de los participantes. Se aportan cuáles han sido los parámetros de entrenamiento y se sugieren pautas para la investigación a corto plazo sobre este particularNowadays obesity is a disease of high prevalence, that’s why scientific community is interested to research it. A line of relevant investigation is to analyze effects of strength training on reduction of obesity. This paper reviews the bibliographic research until the year 2011 which analyzed if the strength training reduces body fat of obese people. Results found are divergent. Half of studies conclude that training with loads reduces body fat and the other half do not. However, there are not studies where participants increased their body fat. At the same time, this study reports about some strength training parameters and about guidelines for future research in this topi

The implementation of velocity-based training paradigm for team sports: Framework, technologies, practical recommendations and challenges

While velocity-based training is currently a very popular paradigm to designing and monitoring resistance training programs, its implementation remains a challenge in team sports, where there are still some confusion and misinterpretations of its applications. In addition, in contexts with large squads, it is paramount to understand how to best use movement velocity in different exercises in a useful and time-efficient way. This manuscript aims to provide clarifications on the velocity-based training paradigm, movement velocity tracking technologies, assessment procedures and practical recommendations for its application during resistance training sessions, with the purpose of increasing performance, managing fatigue and preventing injuries. Guidelines to combine velocity metrics with subjective scales to prescribe training loads are presented, as well as methods to estimate 1-Repetition Maximum (1RM) on a daily basis using individual load–velocity profiles. Additionally, monitoring strategies to detect and evaluate changes in performance over time are discussed. Finally, limitations regarding the use of velocity of execution tracking devices and metrics such as “muscle power” are commented upon. Funding: This research received no external funding

Monitoring and study of the relationships between training load, force production, fatigue and performance in high-level distance runners

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Formación de Profesorado y Educación, Departamento de Educación Física, Deporte y Motricidad Humana. Fecha de lectura: 30-04-201

Effect of visual stimuli on the jumping ability of amateur soccer players

In soccer, high levels of strength applied in short durations are crucial for various performance-related actions such as accelerations, decelerations, sprints, jumps, and changes of direction. These actions often occur in the presence of visual stimuli that require attention and rapid reaction. Recent training methodologies propose integrating visual stimuli to enhance sport-specific physical abilities. However, limited research has investigated the impact of visual stimuli on explosive force production abilities. Therefore, this study aimed to analyse the influence of reacting to non-specific visual stimuli on seated and counter-movement vertical jump performance. Seventeen senior amateur soccer players (age: 22.9 ± 2.8 years; height: 172.0 ± 8.5 cm; weight: 71.1 ± 7.3 kg) were recruited as participants for this study. Participants performed seated vertical jumps (SJsit-90º) and counter-movement vertical jumps (CMJ) under two conditions: with reaction to a visual stimulus (REAC) and without reaction (VOL). The order of the conditions was counterbalanced across participants. The statistical analysis revealed a significant decrease in the height of SJsit-90º in the REAC condition compared to the VOL condition (HeightVOL-REAC = 1.88 ± 2.16 cm; p < .001). Although a similar trend was observed, no significant differences were found in CMJ height between conditions (HeightVOL-REAC = 0.70 ± 0.63 cm; p = .277). It is concluded that the inclusion of non-specific visual stimuli to react to significantly and negatively affects the ability to apply force measured through seated vertical jumps. These findings emphasize the importance of considering the potential detrimental effects of external visual stimuli on explosive force production when designing training protocols for soccer players

Validity and Reliability of Strategy Metrics to Assess Countermovement Jump Performance Using the Newly Developed My Jump Lab Smartphone Application

The aim of the present study was to analyse the validity and reliability of the newly developed My Jump Lab smartphone app, which includes the option to calculate time to take-off and the reactive strength index modified (RSI_Mod-calculated as jump height divided by time to take-off), in addition to jump height. Twenty-seven postgraduate sport science students attended a single test session and performed three maximal effort countermovement jumps (CMJ) on twin force plates, whilst concurrently being filmed using the app. Results showed no significant differences in jump height between measurement methods (g = 0.00) or RSI_Mod (g =-0.49), although a significant difference was evident for time to take-off (g = 0.68). When a correction factor was applied to time to take-off data, no meaningful differences were evident (g = 0.00), which also had a knock-on effect for RSI_Mod (g = 0.10). Bland-Altman analysis showed near perfect levels of agreement for jump height with a bias estimate of 0.001 m, whilst time to take-off reported a bias estimate of 0.075 s initially and, 0.000 s once the correction factor was applied. For RSI_Mod, bias estimate was initially-0.048, and 0.006 once calculated with the corrected time to take-off data. Pearson's r correlations were: 0.98 for jump height, 0.81 for time to take-off, and 0.85 for RSI_Mod. Based on the findings from the present study, and with the inclusion of the newly embedded correction factor, My Jump Lab can now be used as both a valid and reliable means of measuring time to take-off and RSI_Mod in the CMJ

A Systematic Review of the Effects of Different Resistance Training Volumes on Muscle Hypertrophy

[EN] The main goal of this study was to compare responses to moderate and high training volumes aimed at inducing muscle hypertrophy. A literature search on 3 databases (Pubmed, Scopus and Chocrane Library) was conducted in January 2021. After analyzing 2083 resultant articles, studies were included if they met the following inclusion criteria: a) studies were randomized controlled trials (with the number of sets explicitly reported), b) interventions lasted at least six weeks, c) participants had a minimum of one year of resistance training experience, d) participants' age ranged from 18 to 35 years, e) studies reported direct measurements of muscle thickness and/or the cross-sectional area, and f) studies were published in peer-review journals. Seven studies met the inclusion criteria and were included in the qualitative analysis, whereas just six were included in the quantitative analysis. All participants were divided into three groups: "low" (20 weekly sets). According to the results of this meta-analysis, there were no differences between moderate and high training volume responses for the quadriceps (p = 0.19) and the biceps brachii (p = 0.59). However, it appears that a high training volume is better to induce muscle mass gains in the triceps brachii (p = 0.01). According to the results of this review, a range of 12-20 weekly sets per muscle group may be an optimum standard recommendation for increasing muscle hypertrophy in young, trained men

Mutational analysis of Escherichia coli GreA protein reveals new functional activity independent of antipause and lethal when overexpressed

There is a growing appreciation for the diverse regulatory consequences of the family of proteins that bind to the secondary channel of E. coli RNA polymerase (RNAP), such as GreA, GreB or DksA. Similar binding sites could suggest a competition between them. GreA is characterised to rescue stalled RNAP complexes due to its antipause activity, but also it is involved in transcription fidelity and proofreading. Here, overexpression of GreA is noted to be lethal independent of its antipause activity. A library of random GreA variants has been used to isolate lethality suppressors to assess important residues for GreA functionality and its interaction with the RNA polymerase. Some mutant defects are inferred to be associated with altered binding competition with DksA, while other variants seem to have antipause activity defects that cannot reverse a GreA-sensitive pause site in a fliC::lacZ reporter system. Surprisingly, apparent binding and cleavage defects are found scattered throughout both the coiled-coil and globular domains. Thus, the coiled-coil of GreA is not just a measuring stick ensuring placement of acidic residues precisely at the catalytic centre but also seems to have binding functions. These lethality suppressor mutants may provide valuable tools for future structural and functional studies