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(1) Background: The aim of this paper is to analyze the acute effects of different velocity loss (VL) thresholds during a full squat (SQ) with blood-flow restriction (BFR) on strength performance, neuromuscular activity, metabolic response, and muscle contractile properties. (2) Methods: Twenty strength-trained men performed four protocols that differed in the VL achieved within the set (BFR0: 0% VL; BFR10: 10% VL; BFR20: 20% VL; and BFR40: 40% VL). The relative intensity (60% 1RM), recovery between sets (2 min), number of sets (3), and level of BFR (50% of arterial occlusion pressure) were matched between protocols. Tensiomyography (TMG), blood lactate, countermovement jump (CMJ), maximal voluntary isometric SQ contraction (MVIC), and performance with the absolute load required to achieve 1 m·s −1 at baseline measurements in SQ were assessed before and after the protocols. (3) Results: BFR40 resulted in higher EMG alterations during and after exercise than the other protocols (p < 0.05). BFR40 also induced greater impairments in TMG-derived variables and BFR10 decreased contraction time. Higher blood lactate concentrations were found as the VL within the set increased. BFR0 and BFR10 showed significantly increased median frequencies in post-exercise MVIC. (4) Conclusions: High VL thresholds (BFR40) accentuated metabolic and neuromuscular stress, and produced increased alterations in muscles’ mechanical properties. Low VL could potentiate post-exercise neuromuscular activity and muscle contractile properties.

This study explored the effects of 4 bench-press (BP) training programs with different velocity-loss (VL) thresholds (0%, 15%, 25%, and 50%) on strength gains and neuromuscular adaptations. Methods: Forty-six resistance-trained men (22.8 [4.4] y) were randomly assigned into 4 groups that differed in the VL allowed within the set: 0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50). Training loads (40%–55% 1-repetition maximum), frequency (2 sessions/wk), number of sets (3), and interset recovery (4 min) were identical for all groups. Participants completed the following tests before and after an 8-week (16-session) BP training program: (1) maximal isometric test, (2) progressive loading test, and (3) fatigue test in the BP exercise. During all tests, triceps brachii muscle electromyography was assessed. Results: After completing the resistance-training program, no significant group × time interactions were noticed for isometric and dynamic BP strength variables. The dose–response relationship exhibited an inverted U-shaped relationship pattern, with VL25 showing the greatest effect sizes for almost all strength variables analyzed. The total number of repetitions performed during the training program increased as the VL magnitude increased. Conclusions: The group that trained with high VL threshold (50%), which performed a total of 876 repetitions, did not experience additional strength gains compared with those experienced by the 0%, 15%, and 25% of VL groups, which performed significantly fewer repetitions (48, 357, and 547, respectively). These findings suggest that when light loads (40%–55% 1-repetition maximum) are used, low and moderate VL thresholds (0%–25%) provide a higher training efficiency.

Purpose: To investigate the effect of different resistance training (RT) protocols with 5 equated volume load on acute mechanical and metabolic responses. Methods: In a 6 randomized order, eighteen men performed 8 different training protocols in the bench 7 press exercise consisting of (sets, repetitions, intensity, and inter-set recoveries): 3x16, 8 40% 1RM, 2 and 5 minutes; 6x8, 40% 1RM, 2 and 5 minutes; 3x8, 80% 1RM, 2 and 5 9 minutes; and 6x4, 80% 1RM, 2 and 5 minutes. Volume load was equalized between 10 protocols (1920 AU). Velocity loss and effort index (EI) attained during the session were 11 calculated. Movement velocity against the 60% 1RM and blood lactate concentration pre 12 post exercise were used to assess the mechanical and metabolic responses, respectively. 13 Results: RT protocols performed with heavy load (80% 1RM) resulted in a lower (P<.05) 14 total number of repetitions (ES=-2.44) and volume load (ES=-1.79) than the scheduled 15 ones when longer set configurations and shorter rest periods were used in the same 16 protocol (i.e., higher training density protocols). Protocols including higher number of 17 repetitions per set and shorter rest times induced higher velocity loss, EI, and lactate 18 concentrations than the rest of protocols. Conclusions: Our results suggest that RT 19 protocols with similar volume load but different training variables (i.e., intensity, number 20 of sets and repetitions, rest between sets) produce different responses. Implementing 21 shorter number of repetitions per set and longer rest interval length are recommended to 22 reduce the intra-session and post-session fatigue.

Purpose: To compare the effect of 4 velocity-loss (VL) thresholds—0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)—on strength gains, neuromuscular adaptations, and muscle hypertrophy during the bench press (BP) exercise using intensities ranging from 55% to 70% of 1-repetition maximum (1RM). Methods: Fifty resistance-trained men were randomly assigned to 4 groups that followed an 8-week (16 sessions) BP training program at 55% to 70% 1RM but differed in the VL allowed in each set (VL0, VL15, VL25, and VL50). Assessments performed before (pre) and after (post) the training program included (1) cross-sectional area of pectoralis major muscle, (2) maximal isometric test, (3) progressive loading test, and (4) fatigue test in the BP exercise. Results: A significant group × time interaction was found for 1RM (P = .01), where all groups except VL0 showed significant gains in 1RM strength (P < .001). The VL25 group attained the greatest gains in 1RM strength and most load–velocity relationship parameters analyzed. A significant group × time interaction was observed for EMG root mean square in pectoralis major (P = .03) where only the VL25 group showed significant increases (P = .02). VL50 showed decreased EMG root mean square in triceps brachii (P = .006). Only the VL50 group showed significant increases in cross-sectional area (P < .001). Conclusions: These findings indicate that a VL threshold of about 25% with intensities from 55% to 70% 1RM in BP provides an optimal training stimulus to maximize dynamic strength performance and neuromuscular adaptations, while higher VL thresholds promote higher muscle hypertrophy.

El presente trabajo, tiene como principal objetivo la revisión de dos medios de entrenamiento en niños (autocargas y cargas externas), para evidenciar que método de entrenamiento es el más adecuado para dichos sujetos. Además, se conocerán los beneficios que tiene este tipo de práctica deportiva, así como las principales indicaciones y errores que se deben de tener en cuenta a la hora de planificar un entrenamiento de fuerza en edad escolar. También encontraremos y daremos solución a las principales controversias del entrenamiento de fuerza presentes en la sociedad actual, con el fin de promover una práctica segura y beneficiosa para los más jóvenes. Se hará especial énfasis en las variables del entrenamiento de fuerza, volumen e intensidad, pero sobre todo en los dos medios de entrenamiento (autocargas y cargas externas) que se pueden aplicar a niños, para conocer tanto aspectos positivos como negativos de cada uno de ellos. Tras él análisis de los diversos estudios, los resultados mostraron que el entrenamiento con cargas externas generó mayores beneficios en niños, por tanto, se ha propuesto al final de dicha revisión una propuesta de iniciación al entrenamiento de fuerza para el tren inferior con cargas externas, conociendo y teniendo en cuenta, aspectos de seguridad y de control, sobre las diferentes variables que influyen en el entrenamiento de fuerza en niños., The main objective of this work is to review two training methods for children (body-weight training and weight training), in order to demonstrate which training method is the most suitable for these subjects. In addition, the benefits of this type of sports practice will be known, as well as the main indications and errors that should be taken into account meanwhile training children. We will also find and solve the main controversies of strength training present in today's society, in order to promote a safe and beneficial practice for the youngest. Special emphasis will be placed on the variables of strength, volume and intensity training, but above all on the two means of training (body-weight training and weight training) that can be applied to children, to know both positive and negative aspects of each of them. Focusing on the analysis of the various studies, the results showed that weight training generated greater benefits in children, therefore, it has been proposed at the end of this review a recommendation for initiation to strength training for the lower train with weight training, knowing and taking into account some aspects of safety and control on the different variables that influence strength training in children.