Vastus Lateralis Muscle Size Is Differently Associated With the Different Regions of the Squat Force-Velocity and Load-Velocity Relationships, Rate of Force Development, and Physical Performance Young Men.

ABSTRACT: Cornejo-Daza, PJ, Sánchez-Valdepeñas, J, Rodiles-Guerrero, L, Páez-Maldonado, JA, Ara, I, León-Prados, JA, Alegre, LM, Pareja-Blanco, F, and Alcazar, J. Vastus lateralis muscle size is differently associated with the different regions of the squat force-velocity and load-velocity relationships, rate of force development, and physical performance young men. J Strength Cond Res 38(3): 450-458, 2024-The influence that regional muscle size and muscle volume may have on different portions of the force-velocity (F-V) and load-velocity (L-V) relationships, explosive force, and muscle function of the lower limbs is poorly understood. This study assessed the association of muscle size with the F-V and L-V relationships, rate of force development (RFD) and maximal isometric force in the squat exercise, and vertical jump performance via countermovement jump (CMJ) height. Forty-nine resistance-trained young men (22.7 ± 3.3 years old) participated in the study. Anatomical cross-sectional area (ACSA) of the vastus lateralis (VLA) muscle was measured using the extended field of view mode in an ultrasound device at 3 different femur lengths (40% [distal], 57.5% [medial], and 75% [proximal]), and muscle volume was estimated considering the VLA muscle insertion points previously published and validated in this study. There were significant associations between all muscle size measures (except distal ACSA) and (a) forces and loads yielded at velocities ranging from 0 to 1.5 m·s -1 ( r = 0.36-0.74, p < 0.05), (b) velocities exerted at forces and loads ranging between 750-2,000 N and 75-200 kg, respectively ( r = 0.31-0.69, p < 0.05), and (c) RFD at 200 and 400 milliseconds ( r = 0.35-0.64, p < 0.05). Proximal and distal ACSA and muscle volume were significantly associated with CMJ height ( r = 0.32-0.51, p < 0.05). Vastus lateralis muscle size exhibited a greater influence on performance at higher forces or loads and lower velocities and late phases of explosive muscle actions. Additionally, proximal ACSA and muscle volume showed the highest correlation with the muscle function measures.

Effects of different phenylcapsaicin doses on neuromuscular activity and mechanical performance in trained male subjects: a randomized, triple-blinded, crossover, placebo-controlled trial.

Objective: This study aimed to examine the effects of phenylcapsaicin (PC) supplementation on strength performance and neuromuscular activity in young trained male subjects. Materials and methods: A total of 25 trained subjects [full-squat (SQ) one repetition maximum (1RM) = 125.6 ± 21.0 kg] were enrolled in this randomized, triple-blinded, crossover, placebo-controlled trial. The subjects performed a first session and a post-24 h session for each condition. In the first session, the subjects ingested a high dose of PC (HD, 2.5 mg), a low dose (LD, 0.625 mg), or a placebo (PLA). Their performance in SQ was assessed under a 3% × 8 × 70% 1RM protocol in the first session. Their performances in countermovement jump (CMJ), SQ with 60% 1RM, and isometric squat were measured before and after the SQ protocol in both sessions. The neural activity of the vastus lateralis (VL) and vastus medialis (VM) was recorded via surface electromyography (EMG) and averaged in both sessions. Results: Significant differences between the conditions were reported for lifting velocity, velocity loss, and the 60% load in dynamic SQ (p range = 0.02-0.04). Electrical changes were not identified for any outcome, although neural activity changed across time (p range ≤0.001-0.006). A significant condition × time effect was observed in CMJ compared to PLA (p ≤0.001) and LD (p ≤0.001). Intra-set analyses revealed higher velocities in HD compared to those in LD (p = 0.01) and PLA (p range = 0.004-0.008). Conclusion: Therefore, PC may improve the strength performance and attenuate the mechanical fatigue induced by resistance training in SQ and CMJ exercises.

A novel equation that incorporates the linear and hyperbolic nature of the force-velocity relationship in lower and upper limb exercises.

The purpose of this study is to provide a force-velocity (F-V) equation that combines a linear and a hyperbolic region, and to compare its derived results to those obtained from linear equations. A total of 10 cross-training athletes and 14 recreationally resistance-trained young men were assessed in the unilateral leg press (LP) and bilateral bench press (BP) exercises, respectively. F-V data were recorded using a force plate and a linear encoder. Estimated maximum isometric force (F0), maximum muscle power (Pmax), and maximum unloaded velocity (V0) were calculated using a hybrid (linear and hyperbolic) equation and three different linear equations: one derived from the hybrid equation (linearhyb), one applied to data from 0 to 100% of F0 (linear0-100), and one applied to data from 45 to 100% of F0 (linear45-100). The hybrid equation presented the best fit to the recorded data (R2 = 0.996 and 0.998). Compared to the results derived from the hybrid equation in the LP, significant differences were observed in F0 derived from linear0-100; V0 derived from linearhyb, linear0-100 and linear45-100; and Pmax derived from linearhyb and linear45-100 (all p < 0.05). For the BP, compared to the hybrid equation, significant differences were found in F0 derived from linear0-100; and V0 and Pmax derived from linearhyb, linear0-100 and linear45-100 (all p < 0.05). An F-V equation combining a linear and a hyperbolic region showed to fit adequately recorded F-V data from ~ 20 to 100% of F0, and overcame the limitations shown by linear equations while providing relevant results.

Acute Mechanical, Neuromuscular, and Metabolic Responses to Different Set Configurations in Resistance Training.

ABSTRACT: Piqueras-Sanchiz, F, Cornejo-Daza, PJ, Sánchez-Valdepeñas, J, Bachero-Mena, B, Sánchez-Moreno, M, Martín-Rodríguez, S, García-García, Ó, and Pareja-Blanco, F. Acute mechanical, neuromuscular, and metabolic responses to different set configurations in resistance training. J Strength Cond Res 36(11): 2983-2991, 2022-The aim of this study was to investigate the effect of set configuration on mechanical performance, neuromuscular activity, metabolic response, and muscle contractile properties. Sixteen strength-trained men performed 2 training sessions in the squat exercise consisting of (a) 3 sets of 8 repetitions with 5 minutes rest between sets (3 × 8) and (b) 6 sets of 4 repetitions with 2 minutes rest between sets (6 × 4). Training intensity (75% one repetition maximum), total volume (24 repetitions), total rest (10 minutes), and training density were equalized between protocols. A battery of tests was performed before and after each protocol: (a) tensiomyography (TMG), (b) blood lactate and ammonia concentration, (c) countermovement jump, and (d) maximal voluntary isometric contraction in the squat exercise. Force, velocity, and power output values, along with electromyography data, were recorded for every repetition throughout each protocol. The 6 × 4 protocol resulted in greater mechanical performance (i.e., force, velocity, and power) and lower neuromuscular markers of fatigue (i.e., lower root mean square and higher median frequency) during the exercise compared with 3 × 8, particularly for the last repetitions of each set. The 3 × 8 protocol induced greater lactate and ammonia concentrations, greater reductions in jump height, and greater impairments in TMG-derived velocity of deformation after exercise than 6 × 4. Therefore, implementing lower-repetition sets with shorter and more frequent interset rest intervals attenuates impairments in mechanical performance, especially in the final repetitions of each set. These effects may be mediated by lower neuromuscular alterations, reduced metabolic stress, and better maintained muscle contractile properties.

Dose-Response Relationship Between Velocity Loss During Resistance Training and Changes in the Squat Force-Velocity Relationship.

PURPOSE: This study aimed to compare the adaptations provoked by various velocity loss (VL) thresholds used in resistance training on the squat force-velocity (F-V) relationship. METHODS: Sixty-four resistance-trained young men were randomly assigned to one of four 8-week resistance training programs (all 70%-85% 1-repetition maximum) using different VL thresholds (VL0 = 0%, VL10 = 10%, VL20 = 20%, and VL40 = 40%) in the squat exercise. The F-V relationship was assessed under unloaded and loaded conditions in squat. Linear and hyperbolic (Hill) F-V equations were used to calculate force at zero velocity (F0), velocity at zero force (V0), maximum muscle power (Pmax), and force produced at mean velocities ranging from 0.0 to 2.0 m·s-1. Changes in parameters derived from the F-V relationship were compared among groups using linear mixed models. RESULTS: Linear equations showed increases in F0 (120.7 N [89.4 to 152.1]) and Pmax (76.2 W [45.3 to 107.2]) and no changes in V0 (-0.02 m·s-1 [-0.11 to 0.06]) regardless of VL. Hyperbolic equations depicted increases in F0 (120.7 N [89.4 to 152.1]), V0 (1.13 m·s-1 [0.78 to 1.48]), and Pmax (198.5 W [160.5 to 236.6]) with changes in V0 being greater in VL0 and VL10 versus VL40 (both P < .001). All groups similarly improved force at 0.0 to 2.0 m·s-1 (all P < .001), although in general, effect sizes were greater in VL10 and VL20 versus VL0 and VL40 at velocities ≤0.5 m·s-1. CONCLUSIONS: All groups improved linear and hyperbolic F0 and Pmax and hyperbolic V0 (except VL40). The dose-response relationship exhibited an inverted U-shape pattern at velocities ≤0.5 m·s-1 with VL10 and VL20 showing the greatest standardized changes.

Comparison of linear, hyperbolic and double-hyperbolic models to assess the force-velocity relationship in multi-joint exercises.

AbstractThis study assessed the validity of linear, hyperbolic and double-hyperbolic models to fit measured force-velocity (F-V) data in multi-joint exercises and the influence of muscle excitation on the F-V relationship. The force-joint angle and F-V relationships were assessed in 10 cross-training athletes and 14 recreationally resistance-trained subjects in the unilateral leg press (LP) and bilateral bench press (BP) exercises, respectively. A force plate and a linear encoder were installed to register external force and velocity, respectively. Muscle excitation was assessed by surface EMG recording of the quadriceps femoris, biceps femoris and gluteus maximus muscles during the unilateral LP. Linear, Hill's (hyperbolic) and Edman's (double-hyperbolic) equations were fitted to the measured F-V data and compared. Measured F-V data were best fitted by double-hyperbolic models in both exercises (p < 0.05). F-V data deviated from the rectangular hyperbola above a breakpoint located at 90% of measured isometric force (F0) and from the linearity at ≤45% of F0 (both p < 0.05). Hyperbolic equations overestimated F0 values by 13 ± 11% and 6 ± 6% in the LP and BP, respectively (p < 0.05). No differences were found between muscle excitation levels below and above the breakpoint (p > 0.05). Large associations between variables obtained from linear and double-hyperbolic models were noted for F0, maximum muscle power, and velocity between 25% and 100% of F0 (r = 0.70-0.99; all p < 0.05). The F-V relationship in multi-joint exercises was double-hyperbolic, which was unrelated with lower muscle excitation levels. However, linear models may be valid to assess F0, maximal muscle power and velocity between 25% and 100% of F0.

Effects of velocity loss in the bench press exercise on strength gains, neuromuscular adaptations, and muscle hypertrophy.

OBJECTIVE: This study aimed to compare the effects of four velocity-based training (VBT) programs in bench press (BP) between a wide range of velocity loss (VL) thresholds-0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)-on strength gains, neuromuscular adaptations, and muscle hypertrophy. METHODS: Sixty-four resistance-trained young men were randomly assigned into four groups (VL0, VL15, VL25, and VL50) that differed in the VL allowed in each set. Subjects followed a VBT program for 8-weeks using the BP exercise. Before and after the VBT program the following tests were performed: (a) cross-sectional area (CSA) measurements of pectoralis major (PM) muscle; (b) maximal isometric test; (c) progressive loading test; and (d) fatigue test. RESULTS: Significant group x time interactions were observed for CSA (P < .01) and peak root mean square in PM (peak RMS-PM, P < .05). VL50 showed significantly greater gains in CSA than VL0 (P < .05). Only the VL15 group showed significant increases in peak RMS-PM (P < .01). Moreover, only VL0 showed significant gains in the early rate of force development (RFD, P = .05), while VL25 and VL50 improved in the late RFD (P ≤ .01-.05). No significant group × time interactions were found for any of the dynamic strength variables analyzed, although all groups showed significant improvements in all these parameters. CONCLUSION: Higher VL thresholds allowed for a greater volume load which maximized muscle hypertrophy, whereas lower VL thresholds evoked positive neuromuscular-related adaptations. No significant differences were found between groups for strength gains, despite the wide differences in the total volume accumulated by each group.

Velocity Loss as a Critical Variable Determining the Adaptations to Strength Training.

PURPOSE: This study aimed to compare the effects of four resistance training (RT) programs with different velocity loss (VL) thresholds: 0% (VL0), 10% (VL10), 20% (VL20), and 40% (VL40) on sprint and jump performance, muscle strength, neuromuscular, muscle hypertrophy, and architectural adaptations. METHODS: Sixty-four young resistance-trained men were randomly assigned into four groups (VL0, VL10, VL20, and VL40) that differed in the VL allowed in each set. Subjects followed an RT program for 8 wk (two sessions per week) using the full-squat (SQ) exercise, with similar relative intensity (70%-85% 1-repetition maximum), number of sets (3), and interset recovery period (4 min). Before and after the RT program, the following tests were performed: 1) muscle hypertrophy and architecture of the vastus lateralis (VLA), 2) tensiomyography, 3) 20-m running sprint, 4) vertical jump, 5) maximal voluntary isometric contraction in SQ, 6) progressive loading test in SQ, and 7) fatigue test. RESULTS: No between-group differences existed for RT-induced gains in sprint, jump, and strength performance despite the differences in the total volume performed by each group. VL20 and VL40 showed significant increases (P < 0.001) in muscle hypertrophy (group-time interaction, P = 0.06). However, only VL40 exhibited a significant slowing (P < 0.001) of the delay time in the VLA muscle (group-time interaction, P = 0.05). Moreover, VL40 showed a significant decrease in the early rate of force development (P = 0.04). CONCLUSIONS: Higher VL thresholds (i.e., VL20 and VL40) maximized hypertrophic adaptations, although an excessive VL during the set (i.e., VL40) may also induce negative neuromuscular adaptations. Therefore, moderate VL thresholds should be chosen to maximize strength adaptations and to prevent negative neuromuscular adaptations.

Time Course of Recovery Following Resistance Exercise with Different Loading Magnitudes and Velocity Loss in the Set.

The aim of this study was to compare the time course of recovery following four different resistance exercise protocols in terms of loading magnitude (60% vs. 80% 1RM-one-repetition maximum) and velocity loss in the set (20% vs. 40%). Seventeen males performed four different protocols in full squat exercise, which were as follows: (1) 60% 1RM with a velocity loss of 20% (60-20), (2) 60% 1RM with a velocity loss of 40% (60-40), (3) 80% 1RM with a velocity loss of 20% (80-20), and (4) 80% 1RM with a velocity loss of 40% (80-40). Movement velocity against the load that elicited a 1 m·s-1 velocity at baseline measurements (V1-load), countermovement jump (CMJ) height, and sprint time at 20 m (T20) were assessed at Pre, Post, 6 h-Post, 24 h-Post, and 48 h-Post. Impairments in V1-load were significantly higher for 60-40 than other protocols at Post (p < 0.05). The 60-20 and 80-40 protocols exhibited significant performance impairments for V1-load at 6 h-Post and 24 h-Post, respectively (p < 0.05). CMJ height remained decreased for 60-20 and 60-40 until 24 h-Post (p < 0.001⁻0.05). Regarding T20, the 80-40 protocol resulted in higher performance than 60-40 at 24 h-Post and the 80-20 protocol induced a greater performance than 60-40 protocol at 48 h-Post (p < 0.05). A higher velocity loss during the set (40%) and a lower relative load (60% 1RM) resulted in greater fatigue and slower rate of recovery than lower velocity loss (20%) and higher relative load (80% 1RM).