Muscle Hypertrophy Response Is Affected by Previous Resistance Training Volume in Trained Individuals

Conceptualizing a load and volume autoregulation integrated velocity model to minimize neuromuscular fatigue and maximize neuromuscular adaptations in resistance training

Resistance training (RT) load and volume are considered crucial variables to appropriately prescribe and manage for eliciting the targeted acute responses (i.e., minimizing neuromuscular fatigue) and chronic adaptations (i.e., maximizing neuromuscular adaptations). In traditional RT contexts, load and volume are generally pre-prescribed; thereby, potentially yielding sub-optimal outcomes. A RT concept that individualizes programming is autoregulation: a systematic two-step feedback process involving, (1) monitoring performance and its constituents (fitness, fatigue, and readiness) across multiple time frames (short-, moderate-, and long-term); and (2) adjusting programming (i.e., load and volume) to elicit the targeted goals (i.e., responses and adaptations). A growing body of load and volume autoregulation research has accelerated recently, with several meta-analyses suggesting that autoregulation may provide a small advantage over traditional RT. Nonetheless, the existing literature has typically conceptualized these current autoregulation methods as standalone practices, which has limited their extensive utility in research and applied settings. The primary purpose of this review was three-fold. Initially, we synthesized the current methods of load and volume autoregulation, while disseminating each method's main advantages and limitations. Second, we conceptualized a theoretical Integrated Velocity Model (IVM) that integrates the current methods for a more holistic perspective of autoregulation that may potentially augment its benefits. Lastly, we illustrated how the IVM may be compared to the current methods for future directions and how it may be implemented for practical applications. We hope that this review assists to contextualize a novel autoregulation framework to help inform future investigations for researchers and practices for RT professionals.

Increasing set volume relative to baseline does not augment skeletal muscle adaptations when compared to maintenance of baseline training volume in recreationally trained individuals

PURPOSE

This study compared the effects of prescribing an increased number of sets relative to baseline (ITV) to a maintenance of baseline training volume (BTV), in previously trained individuals.

METHODS

Forty-two adults with more than 6 months of elbow flexion resistance training experience had each arm randomized to either the ITV or BTV condition. Participants performed 2-weekly sessions of unilateral standing dumbbell elbow flexion exercise for 12 weeks, 8 of which were supervised. Muscle thickness of the elbow flexors at 50, 60, and 70% the distance of the upper arm and one repetition-maximum (1RM) strength for the unilateral standing dumbbell elbow flexion exercise were assessed pre- and post-intervention.

RESULTS

For the 50% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = 0.022 (95% CI - 0.096, 0.140)]. However, there was evidence that both conditions observed a greater change compared to the control. For the 60% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = - 0.010 (95% CI - 0.155, 0.96)]. However, there was evidence that both conditions observed a greater change compared to the control. For the 70% site, there was no evidence that the changes were different between BTV and ITV [∆BTV vs ∆ITV (cm) = 0.004 (95% CI - 0.092, 0.101)]. However, there was evidence that both conditions observed a greater change compared to the control. For changes in 1RM, there was evidence that the change was greater in the BTV [∆BTV vs ∆Control (kg) = 1.915 (95% CI 1.219, 2.611)] and ITV [∆ITV vs ∆Control (kg) = 1.780 (95% CI 1.084, 2.475)] conditions compared to control.

CONCLUSION

Prescribing an increased dose of sets relative to baseline did not augment muscular adaptations when compared to a maintenance of BTV, in recreationally trained individuals. Both training conditions were similarly effective in promoting significant increases in muscle thickness and 1RM strength of the elbow flexors.

Protein supplementation optimizes muscle strength and hypertrophic responses induced by low-load training with blood flow restriction in resistance-trained individuals

BACKGROUND & AIMS

Low-load blood flow restriction (LL-BFR) training induces favorable changes in muscle hypertrophy and strength. However, the potential additive effect of LL-BFR and protein supplementation on these outcomes remains unclear.

METHODS

Twenty-four recreationally resistance-trained men were randomly assigned to either a protein (PRO) or placebo (PLA) supplementation group in a 2:1 ratio. After being submitted to maximum dynamic strength (1-RM) and elbow flexors muscles cross-sectional area (EFCSA) assessments at baseline, participants were enrolled in a 3-week unilateral LL-BFR training (4 days per week, 4 sets of 15 repetitions, 30 % 1-RM) for the elbow flexors muscles in the incline dumbbell curl exercise. Psychological outcomes (rate of perceived exertion, pain and muscle soreness) were obtained at the first and last training session. EFCSA and 1-RM were reassessed after LL-BFR, with EFCSA being assessed at 45 %, 65 % and 85 % of humerus length.

RESULTS

Psychological responses to LL-BFR improved in PRO and PLA (both p < 0.05), with no significant between-group differences (all comparisons, p > 0.05). A significant improvement in 1-RM was detected for PRO (+7.2 %, p = 0.0002), but not PLA (+3.5 %, p = 0.156). PRO experienced significant increases in EFCSA at 45 % (+7.5 %, p = 0.021), 65 % (+5.2 %, p = 0.033) and 85 % lengths (+8.4 %, p = 0.002), while PLA experienced increases only at the 85 % length (+5.9 %, p = 0.045). Absolute increases in 1-RM were greater for PRO vs. PLA (p = 0.039), whereas increases in EFCSA tended to be greater for PRO vs. PLA at 45 % (p = 0.086) and 65 % lengths (p = 0.072).

CONCLUSION

Our results showed that protein supplementation optimized the LL-BFR-induced muscle strength and hypertrophy improvements in trained individuals under comparable psychological responses.

The Effect of Proximity-To-Failure on Perceptual Responses to Resistance Training

Perceptual responses may influence how much pleasure or displeasure an individual experiences during or following resistance training (RT). Resistance-trained males (n = 12) and females (n = 6) completed an 8-week intervention involving two RT sessions per week. The lower limbs of each participant were randomised to perform the leg press and leg extension exercises either to (i) momentary muscular failure (FAIL) or (ii) a perceived 2-RIR and 1-RIR, respectively, for the entire intervention. In weeks one, four, and eight, post-set ratings of perceived discomfort (RPD), and post-session ratings of perceived exertion (RPE) and general feelings via feeling scale (FS) were measured. Data were analysed with Bayesian mixed-effect models. When averaged over all time points measured, results showed slightly greater RPD for FAIL [5.1 (HDI: 4.2-6.0); pd = 100%] versus RIR [4.1 (HDI: 3.2-5.1); pd = 100%], greater RPE for FAIL [5.4 (HDI: 4.6-6.3); pd = 100%] versus RIR [4.3 (HDI: 3.5-5.1); pd = 100%], and more positive general feelings for RIR [1.2 (HDI: 0.7-1.8); pd = 100%] versus FAIL [0.3 (HDI: -0.3 to 0.8); pd = 86%]. Overall, assessing perceptual responses may help inform RIR prescription to promote desired outcomes whilst limiting negative feelings that may compromise long-term adherence.

Does increasing the resistance-training volume lead to greater gains? The effects of weekly set progressions on muscular adaptations in females

We investigated the effect of increasing the number of sets per week every fortnight versus performing a constant set volume on muscular adaptations over 12 weeks. Thirty females (RT experience 2.1 ± 1.0 years) were randomly assigned to a constant group (CG, n = 9) that performed 22 sets per week, a two-set progression group (2SG, n = 11), or a four-set progression group (4SG, n = 10). Forty-five degree leg press one-repetition maximum (1RM), vastus lateralis cross-sectional area (VL-CSA), and the sum of proximal, middle and distal lateral thigh muscle thickness (∑MT) were assessed at baseline and after the intervention. We observed that the 4SG and 2SG conditions showed greater improvements in 1RM than the CG (p < 0.001, p = 0.032, respectively), with no differences between 4SG and 2SG (p = 0.118). Regarding VL-CSA, the 4SG group showed greater increases than the CG (p = 0.029) but not than the 2SG (p = 0.263), whereas no differences between the 2SG and CG (p = 0.443) were observed. There were no differences between groups for ∑MT (p = 0.783). While all groups demonstrated improvements in the measured outcomes, our findings suggest that increasing weekly sets may offer additional benefits for 1RM and vastus lateralis cross-sectional area. However, no additional benefits were observed for ∑MT.

Training volume increases or maintenance based on previous volume: the effects on muscular adaptations in trained males

This study investigated the effects of increasing previous resistance training (RT) weekly set volume by 30% (G30) and 60% (G60) on muscle hypertrophy and strength. Fifty-five resistance-trained men were randomly allocated to the experimental groups, whereas 29 completed the study, as follows: control group (CON): n = 10, G30: n = 10, and G60: n = 9. Participants underwent a lower body RT program twice a week for 8 wk. We assessed pre- and poststudy thigh region-of-interest fat-free mass (ROI-FFM), anterior thigh muscle thickness (MT) at two sites: proximal (PMT) and distal (DMT) and their sum (ΣMT), one-repetition maximum (1RM), and strength-endurance via repetitions to failure (RTF) at 70% of 1RM. ROI-FFM and MT demonstrated a significant increase from pre- to posttraining (main time effect, P < 0.001) (ΔΣMT CON: 1.07 cm, G30: 0.76 cm, and G60: 0.70 cm; ΔROI-FFM CON: 1.57 kg, G30: 0.47 kg, and G60: 1.55 kg). All groups increased back squat 1RM (P < 0.0001). However, the main group effect (P < 0.0268) indicated that the CON group showcased a greater overall 1RM (174.7 kg), than the G30 (159.0 kg) and G60 (149.0 kg). Only the G30 group increased RTF at the posttest (CON: 0.13 reps, G30: 5.45 reps, and G60: -0.41 reps) (P < 0.0263). Our findings suggest that trained males can experience significant muscle growth and strength adaptations while maintaining their previous weekly set number above a certain weekly set volume threshold.NEW & NOTEWORTHY Increasing previous resistance training volume by 30% (G30), 60% (G60), or maintenance (CON) on muscular adaptations in trained individuals. Interestingly, CON group resulted in the greatest overall 1RM strength, whereas G30 showed the highest increase in repetitions to failure, with no differences between groups in muscle mass size. These findings suggest that more is not always better for muscle adaptations in a trained cohort, highlighting muscle growth across a wide range of weekly set numbers.

Changes in muscle cross-sectional area during two menstrual cycles may not be exclusively attributed to resistance training

This study investigated the impact of menstrual cycle (MC) phases and resistance training (RT) on muscle cross-sectional area (CSA) in two MCs utilizing a within-subject design. Twenty women with regular MCs had their legs randomly allocated to either the control (CON) or RT condition, which included 16 training sessions over two MCs. CSA, estradiol (E2), and progesterone (P4) were assessed during the menstruation (M), ovulation (O), and luteal (L) phases in the first (M1, O1, L1) and second (M2, O2, L2) MCs and at the beginning of the third MC (M3). P4 values were significantly higher during the luteal phase than during menstruation (P < 0.0001) and ovulation (P < 0.0001). No significant differences in E2 concentrations were observed between the MC phases (P = 0.08). For the RT condition, the CSA showed significant increases at O2, L2, and M3 compared to baseline (M1) (all P < 0.0001). No significant changes were observed for the CON condition during the two MCs (P > 0.05). However, RT condition showed a significant change in average CSA across two MCs. Additionally, individual analyses revealed that 19 participants showed variation in CSA above or below the minimum detectable difference during the two MCs. These findings suggest that changes in muscle CSA observed during two MCs may not be exclusively attributed to RT.

Dose-response effects of 8-week resistance training on body composition and muscular performance in untrained young women: A quasi-experimental design

BACKGROUND

The purpose of this study was to investigate the effects of 8-week resistance training with different training volumes on body composition, maximum strength, peak power, and muscle thickness in non-training women.

METHODS

This was a 3-arm, prospectively designed, randomized controlled trial. A total of 45 adult women aged 20.7 ± 1 years, the mean heights of the participants were 166 ± 0.07 cm, body weight was measured as 54.5 ± 8.8 kg, and body mass index was 19.9 ± 2.1 kg/m2. They were randomized to low-volume training resistance training (LVT; n = 15, 3 sessions of 12 exercises per week), moderate-volume training resistance training (MVT; n = 15; 4 sessions of 12 exercises per week), and high-volume resistance training (HVT; n = 15; 5 sessions of 12 exercises per week) for 8 weeks. The muscle thickness (MT) of the vastus lateralis was assessed at baseline and 8 weeks later using a portable ultrasound device.

RESULTS

A total of 39 adult women completed the study, with 2 participants from each group lost to follow-up. All experimental groups 1RM increased (P = .001, effect size (ES) = 0.463) All groups showed improved muscle thickness (MT) (P = .001) and CMJ (P = .004). The group × time interaction is statistically significant (P = .001) suggests that the changes in muscle thickness over time differ significantly between the different training volume groups (ηp²) is 0.368.

CONCLUSION

In untrained young women, resistance training improved muscle hypertrophy, maximal strength, power, and body composition in untrained young women. However, 4 sessions MVT per week were superior to LVT and HVT sessions, suggesting a nonlinear dose-response relationship favoring moderate volume over low or high volumes, at least in previously untrained young women.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT06449300).

Resistance training-induced changes in muscle proteolysis and extracellular matrix remodeling biomarkers in the untrained and trained states

PURPOSE

Resistance training (RT) induces muscle growth at varying rates across RT phases, and evidence suggests that the muscle-molecular responses to training bouts become refined or attenuated in the trained state. This study examined how proteolysis-related biomarkers and extracellular matrix (ECM) remodeling factors respond to a bout of RT in the untrained (UT) and trained (T) state.

METHODS

Participants (19 women and 19 men) underwent 10 weeks of RT. Biopsies of vastus lateralis were collected before and after (24 h) the first (UT) and last (T) sessions. Vastus lateralis cross-sectional area (CSA) was assessed before and after the experimental period.

RESULTS

There were increases in muscle and type II fiber CSAs. In both the UT and T states, calpain activity was upregulated and calpain-1/-2 protein expression was downregulated from Pre to 24 h. Calpain-2 was higher in the T state. Proteasome activity and 20S proteasome protein expression were upregulated from Pre to 24 h in both the UT and T. However, proteasome activity levels were lower in the T state. The expression of poly-ubiquitinated proteins was unchanged. MMP activity was downregulated, and MMP-9 protein expression was elevated from Pre to 24 h in UT and T. Although MMP-14 protein expression was acutely unchanged, this marker was lower in T state. TIMP-1 protein levels were reduced Pre to 24 h in UT and T, while TIMP-2 protein levels were unchanged.

CONCLUSION

Our results are the first to show that RT does not attenuate the acute-induced response of proteolysis and ECM remodeling-related biomarkers.

Application of Artificial Intelligence to Automate the Reconstruction of Muscle Cross-Sectional Area Obtained by Ultrasound

PURPOSE

Manual reconstruction (MR) of the vastus lateralis (VL) muscle cross-sectional area (CSA) from sequential ultrasound (US) images is accessible, is reproducible, and has concurrent validity with magnetic resonance imaging. However, this technique requires numerous controls and procedures during image acquisition and reconstruction, making it laborious and time-consuming. The aim of this study was to determine the concurrent validity of VL CSA assessments between MR and computer vision-based automated reconstruction (AR) of CSA from sequential images of the VL obtained by US.

METHODS

The images from each sequence were manually rotated to align the fascia between images and thus visualize the VL CSA. For the AR, an artificial neural network model was utilized to segment areas of interest in the image, such as skin, fascia, deep aponeurosis, and femur. This segmentation was crucial to impose necessary constraints for the main assembly phase. At this stage, an image registration application, combined with differential evolution, was employed to achieve appropriate adjustments between the images. Next, the VL CSA obtained from the MR ( n = 488) and AR ( n = 488) techniques was used to determine their concurrent validity.

RESULTS

Our findings demonstrated a low coefficient of variation (CV) (1.51%) for AR compared with MR. The Bland-Altman plot showed low bias and close limits of agreement (+1.18 cm 2 , -1.19 cm 2 ), containing more than 95% of the data points.

CONCLUSIONS

The AR technique is valid compared with MR when measuring VL CSA in a heterogeneous sample.

N of 1: Optimizing Methodology for the Detection of Individual Response Variation in Resistance Training

Most resistance training research focuses on inference from average intervention effects from observed group-level change scores (i.e., mean change of group A vs group B). However, many practitioners are more interested in training responses (i.e., causal effects of an intervention) on the individual level (i.e., causal effect of intervention A vs intervention B for individual X). To properly examine individual response variation, multiple confounding sources of variation (e.g., random sampling variability, measurement error, biological variability) must be addressed. Novel study designs where participants complete both interventions and at least one intervention twice can be leveraged to account for these sources of variation (i.e., n of 1 trials). Specifically, the appropriate statistical methods can separate variability into the signal (i.e., participant-by-training interaction) versus the noise (i.e., within-participant variance). This distinction can allow researchers to detect evidence of individual response variation. If evidence of individual response variation exists, researchers can explore predictors of the more favorable intervention, potentially improving exercise prescription. This review outlines the methodology necessary to explore individual response variation to resistance training, predict favorable interventions, and the limitations thereof.

Ladder-based resistance training with the progression of training load altered the tibial nerve ultrastructure and muscle fiber area without altering the morphology of the postsynaptic compartment

Scientific evidence regarding the effect of different ladder-based resistance training (LRT) protocols on the morphology of the neuromuscular system is scarce. Therefore, the present study aimed to compare the morphological response induced by different LRT protocols in the ultrastructure of the tibial nerve and morphology of the motor endplate and muscle fibers of the soleus and plantaris muscles of young adult Wistar rats. Rats were divided into groups: sedentary control (control, n = 9), a predetermined number of climbs and progressive submaximal intensity (fixed, n = 9), high-intensity and high-volume pyramidal system with a predetermined number of climbs (Pyramid, n = 9) and lrt with a high-intensity pyramidal system to exhaustion (failure, n = 9). myelinated fibers and myelin sheath thickness were statistically larger in pyramid, fixed, and failure. myelinated axons were statistically larger in pyramid than in control. schwann cell nuclei were statistically larger in pyramid, fixed, and failure. microtubules and neurofilaments were greater in pyramid than in control. morphological analysis of the postsynaptic component of the plantar and soleus muscles did not indicate any significant difference. for plantaris, the type i myofibers were statistically larger in the pyramid and fixed compared to control. the pyramid, fixed, and failure groups for type ii myofibers had larger csa than control. for soleus, the type i myofibers were statistically larger in the pyramid than in control. pyramid and fixed had larger csa for type ii myofibers than control and failure. the pyramid and fixed groups showed greater mass progression delta than the failure. We concluded that the LRT protocols with greater volume and progression of accumulated mass elicit more significant changes in the ultrastructure of the tibial nerve and muscle hypertrophy without endplate changes.

Chronic Effects of Inter-Set Static Stretching on Morphofunctional Outcomes in Recreationally Resistance-Trained Male and Female

Purpose: The purpose of this study was to compare the effects of resistance training (RT) with inter-set static stretching (IS) versus traditional RT (TRT) on morphofunctional outcomes in recreationally resistance-trained male and female. Methods: Twenty-two recreationally-trained subjects were allocated to IS group (n = 12) or TRT (n = 10) and completed eight weeks of RT. The only difference between the groups was that IS group included static stretching between sets, while the TRT rested between the sets. Ultrasound images, dynamic and isometric strength tests for the elbow flexors and elbow extensors were evaluated pre- and post-intervention period. Results: Total training volume (TTV) was greater in TRT than IS (p = .031). TRT and IS caused similar increases in maximal dynamic and isometric strength. Fascicle length of the brachialis increased following TRT (p = .033); muscle thickness and the pennation angle of the distal portion of the triceps brachii increased following IS (p = .035 and p = .007, respectively). There were no significant changes in thickness and architecture for biceps brachii in either group. There were no significant differences between groups for any muscle strength and morphology outcome. Conclusion: IS negatively affects TTV but does not affect muscle strength and architecture of recreationally resistance-trained male and female.

Effects of Different Weekly Set Progressions on Muscular Adaptations in Trained Males: Is There a Dose-Response Effect?

PURPOSE

This study investigated the effect of progressively adding sets for the lower limb every 2 wk versus performing a constant set volume in resistance-trained males.

METHODS

Thirty-one resistance-trained males (age = 24.4 ± 2.9 yr, height = 175.5 ± 6.5 cm, body mass = 80.1 ± 9.4 kg, body fat = 14.4% ± 3.1%, resistance training [RT] experience = 5.1 ± 2.2 yr; one-repetition maximum [1RM] barbell back squat: body mass ratio = 1.7 ± 0.1 a.u.) were randomly allocated into a constant group (CG, n = 10), a four-set progression group (4SG, n = 10) or a six-set progression group (6SG, n = 11). After a 2-wk washout period and another 2-wk familiarization period, participants performed a lower-limb training program twice a week for 12 wk. Maximum dynamic strength (1RM) in the barbell back squat, vastus lateralis cross-sectional area, and the sum of lateral thigh muscle thickness at 30%, 50%, and 70% of the femur length were assessed at baseline and after the 12-wk training program.

RESULTS

Regarding 1RM, multiple comparisons revealed that 6SG elicited higher muscle strength gains than 4SG ( P = 0.002) and CG ( P < 0.0001), and 4SG had greater improvements than CG ( P = 0.023). Cross-sectional area and sum of lateral thigh muscle thickness showed no between-group differences ( P = 0.067 and P = 0.076, respectively). However, an inspection of 95% confidence intervals suggests a potential dose-response relationship, with results appearing to plateau in the higher volume conditions.

CONCLUSIONS

Our results suggest that progressively adding four or six sets per week every 2 wk elicited greater lower-limb strength in resistance-trained individuals over a 12-wk training period. Although our findings indicate a possible small benefit for higher volume conditions regarding hypertrophic adaptations in this population, the limited certainty of our findings warrants caution.

Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals

This study examined the influence of resistance training (RT) proximity-to-failure, determined by repetitions-in-reserve (RIR), on quadriceps hypertrophy and neuromuscular fatigue. Resistance-trained males (n = 12) and females (n = 6) completed an 8-week intervention involving two RT sessions per week. Lower limbs were randomised to perform the leg press and leg extension exercises either to i) momentary muscular failure (FAIL), or ii) a perceived 2-RIR and 1-RIR, respectively (RIR). Muscle thickness of the quadriceps [rectus femoris (RF) and vastus lateralis (VL)] and acute neuromuscular fatigue (i.e., repetition and lifting velocity loss) were assessed. Data was analysed with Bayesian linear mixed-effect models. Increases in quadriceps thickness (average of RF and VL) from pre- to post-intervention were similar for FAIL [0.181 cm (HDI: 0.119 to 0.243)] and RIR [0.182 cm (HDI: 0.115 to 0.247)]. Between-protocol differences in RF thickness slightly favoured RIR [-0.036 cm (HDI: -0.113 to 0.047)], but VL thickness slightly favoured FAIL [0.033 cm (HDI: -0.046 to 0.116)]. Mean volume was similar across the RT intervention between FAIL and RIR. Lifting velocity and repetition loss were consistently greater for FAIL versus RIR, with the magnitude of difference influenced by the exercise and the stage of the RT intervention.

Lean mass sparing in resistance-trained athletes during caloric restriction: the role of resistance training volume

Many sports employ caloric restriction (CR) to reduce athletes’ body mass. During these phases, resistance training (RT) volume is often reduced to accommodate recovery demands. Since RT volume is a well-known anabolic stimulus, this review investigates whether a higher training volume helps to spare lean mass during CR. A total of 15 studies met inclusion criteria. The extracted data allowed calculation of total tonnage lifted (repetitions × sets × intensity load) or weekly sets per muscle group for only 4 of the 15 studies, with RT volume being highly dependent on the examined muscle group as well as weekly training frequency per muscle group. Studies involving high RT volume programs (≥ 10 weekly sets per muscle group) revealed low-to-no (mostly female) lean mass loss. Additionally, studies increasing RT volume during CR over time appeared to demonstrate no-to-low lean mass loss when compared to studies reducing RT volume. Since data regarding RT variables applied were incomplete in most of the included studies, evidence is insufficient to conclude that a higher RT volume is better suited to spare lean mass during CR, although data seem to favor higher volumes in female athletes during CR. Moreover, the data appear to suggest that increasing RT volume during CR over time might be more effective in ameliorating CR-induced atrophy in both male and female resistance-trained athletes when compared to studies reducing RT volume. The effects of CR on lean mass sparing seem to be mediated by training experience, pre-diet volume, and energy deficit, with, on average, women tending to spare more lean mass than men. Potential explanatory mechanisms for enhanced lean mass sparing include a preserved endocrine milieu as well as heightened anabolic signaling.

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

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” (<12 weekly sets), “moderate” (12-20 weekly sets) and “high” volume (>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.

The Effect of Load and Volume Autoregulation on Muscular Strength and Hypertrophy: A Systematic Review and Meta-Analysis

Background

Autoregulation has emerged as a potentially beneficial resistance training paradigm to individualize and optimize programming; however, compared to standardized prescription, the effects of autoregulated load and volume prescription on muscular strength and hypertrophy adaptations are unclear. Our objective was to compare the effect of autoregulated load prescription (repetitions in reserve-based rating of perceived exertion and velocity-based training) to standardized load prescription (percentage-based training) on chronic one-repetition maximum (1RM) strength and cross-sectional area (CSA) hypertrophy adaptations in resistance-trained individuals. We also aimed to investigate the effect of volume autoregulation with velocity loss thresholds ≤ 25% compared to > 25% on 1RM strength and CSA hypertrophy.

Methods

This review was performed in accordance with the PRISMA guidelines. A systematic search of MEDLINE, Embase, Scopus, and SPORTDiscus was conducted. Mean differences (MD), 95% confidence intervals (CI), and standardized mean differences (SMD) were calculated. Sub-analyses were performed as applicable.

Results

Fifteen studies were included in the meta-analysis: six studies on load autoregulation and nine studies on volume autoregulation. No significant differences between autoregulated and standardized load prescription were demonstrated for 1RM strength (MD = 2.07, 95% CI – 0.32 to 4.46 kg, p = 0.09, SMD = 0.21). Velocity loss thresholds ≤ 25% demonstrated significantly greater 1RM strength (MD = 2.32, 95% CI 0.33 to 4.31 kg, p = 0.02, SMD = 0.23) and significantly lower CSA hypertrophy (MD = 0.61, 95% CI 0.05 to 1.16 cm², p = 0.03, SMD = 0.28) than velocity loss thresholds > 25%. No significant differences between velocity loss thresholds > 25% and 20–25% were demonstrated for hypertrophy (MD = 0.36, 95% CI – 0.29 to 1.00 cm², p = 0.28, SMD = 0.13); however, velocity loss thresholds > 25% demonstrated significantly greater hypertrophy compared to thresholds ≤ 20% (MD = 0.64, 95% CI 0.07 to 1.20 cm², p = 0.03, SMD = 0.34).

Conclusions

Collectively, autoregulated and standardized load prescription produced similar improvements in strength. When sets and relative intensity were equated, velocity loss thresholds ≤ 25% were superior for promoting strength possibly by minimizing acute neuromuscular fatigue while maximizing chronic neuromuscular adaptations, whereas velocity loss thresholds > 20–25% were superior for promoting hypertrophy by accumulating greater relative volume.

Protocol Registration The original protocol was prospectively registered (CRD42021240506) with the PROSPERO (International Prospective Register of Systematic Reviews).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00404-9.

Individual Muscle Adaptations in different Resistance Training Systems in Well-Trained Men

Using a within-subject design we compared the individual responses between drop-set (DS) vs. traditional resistance training (TRAD) (n=16) and crescent pyramid (CP) vs. TRAD (n=15). Muscle cross-sectional area (CSA), leg press and leg extension 1 repetition maximum (1-RM) were assessed pre and post training. At group level, CSA increased from pre to post (DS: 7.8% vs. TRAD: 7.5%, P=0.02; CP: 7.5% vs. TRAD: 7.8%, P=0.02). All protocols increased the 1-RM from pre to post for leg press (DS: 24.9% vs. TRAD: 26.8%, P < 0.0001; CP: 27.3% vs. TRAD:2 6.3%, P < 0.0001) and leg extension (DS: 17.1% vs. TRAD: 17.3%, P < 0.0001; CP: 17.0% vs. TRAD: 16.6%, P < 0.0001). Individual analysis for CSA demonstrated no differences between protocols in 15 subjects. For leg press 1-RM, 5 subjects responded more to TRAD, 2 to DS and 9 similarly between protocols. In TRAD vs. CP, 4 subjects responded more to CP, 1 to TRAD and 10 similarly between protocols. For leg extension 1-RM 2 subjects responded more to DS, 3 to TRAD and 11 similarly between protocols. Additionally, 2 subjects responded more to CP, 2 to TRAD and 11 similarly between protocols. In conclusion, all protocols induced similar individual responses for CSA. For 1-RM, some subjects experience greater gains for the protocol performed with higher loads, such as CP.

Equating Resistance-Training Volume Between Programs Focused on Muscle Hypertrophy

Calculating resistance-training volume in programs focused on muscle hypertrophy is an attempt to quantify the external workload carried out, then to estimate the dose of stimulus imposed on targeted muscles. The volume is usually expressed in some variables that directly affected the total training work, such as the number of sets, repetitions, and volume-load. These variables are used to try to quantify the training work easily, for the subsequent organization and prescription of training programs. One of the main uses of measures of volume quantification is seen in studies in which the purpose is to compare the effects of different training protocols on muscle growth in a volume-equated format. However, it seems that not all measures of volume are always appropriate for equating training protocols. In the current paper, it is discussed what training volume is and the potentials and shortcomings of each one of the most common ways to equate it between groups depending on the independent variable to be compared (e.g., weekly frequency, intensity of load, and advanced techniques).

Does Varying Repetition Tempo in a Single-Joint Lower Body Exercise Augment Muscle Size and Strength in Resistance-Trained Men?

Pearson, J, Wadhi, T, Barakat, C, Aube, D, Schoenfeld, BJ, Andersen, JC, Barroso, R, Ugrinowitsch, C, and De Souza, EO. Does varying repetition tempo in a single-joint lower body exercise augment muscle size and strength in resistance-trained men? J Strength Cond Res XX(X): 000-000, 2021-This study compared the effects of FAST and SLOW eccentric repetition tempo in a single exercise volume-matched intervention on muscle thickness (MT) and strength in resistance-trained men. Using a within-subject design, 13 subjects had each leg randomly assigned to SLOW (1-0-3) or FAST (1-0-1) repetition tempo. Subjects underwent an 8-week strength-training (ST) intervention performed twice weekly. Unilateral leg-extension one repetition-maximum (1RM) and anterior thigh MT at the proximal (MTP) and distal (MTD) portions were assessed via ultrasound imaging at baseline and after 8 weeks of RT. Rating of perceived exertion (RPE) assessments of the training sessions (i.e., 16 per leg) were averaged for further analysis. Both legs similarly increased MTP (estimated differences: FAST: 0.24 cm, 3.6%; SLOW: 0.20 cm, 3.1%). However, for MTD, analysis of covariance analysis showed a leg effect (p = 0.02) in which absolute pre-to-post change was greater in FAST compared with SLOW (estimated differences: FAST 0.23 cm, 5.5%; SLOW: 0.13 cm, 2.2%). For 1RM, both legs similarly increased maximum strength (estimated differences: FAST: 9.1 kg, 17.0%; SLOW: 10.4 kg, 22.1%, p <= 0.0001). The SLOW group had a higher RPE than FAST (8.59 vs. 7.98, p = 0.002). Despite differences in RPE, our results indicate that both repetition tempos produced similar muscular adaptations. However, they also suggest that the FAST tempo may provide a small hypertrophic advantage at the distal quadriceps. From a practical standpoint, strength and conditioning professionals may implement a FAST tempo at least in one single-joint exercise during an 8-week training period to enhance regional hypertrophic adaptations in trained individuals.

Creatine Supplementation Does Not Influence the Ratio Between Intracellular Water and Skeletal Muscle Mass in Resistance-Trained Men

The authors aimed to compare the effects of creatine (Cr) supplementation combined with resistance training on skeletal muscle mass (SMM), total body water, intracellular water (ICW), and extracellular water (ECW) in resistance-trained men as well as to determine whether the SMM/ICW ratio changes in response to the use of this ergogenic aid. Twenty-seven resistance-trained men received either Cr (n = 14) or placebo (n = 13) over 8 weeks. During the same period, subjects performed two split resistance training routines four times per week. SMM was estimated from appendicular lean soft tissue assessed by dual-energy X-ray absorptiometry. Total body water, ICW, and ECW were determined by spectral bioelectrical impedance. Both groups showed improvements (p < .05) in SMM, total body water, and ICW, with greater values observed for the Cr group compared with placebo. ECW increased similarly in both groups (p < .05). The SMM/ICW ratio did not change in either group (p > .05), whereas the SMM/ECW ratio decreased only in the Cr group (p < .05). A positive correlation was observed (p < .05) between SMM and ICW changes (r = .71). The authors' results suggest that the increase in muscle mass induced by Cr combined with resistance training occurs without alteration of the ratio of ICW to SMM in resistance-trained men.

Effects of Six Weeks of High-Intensity Functional Training on Physical Performance in Participants with Different Training Volumes and Frequencies

High-intensity functional training (HIFT) is characterized by presenting high volumes and training intensities with constantly varied exercises. The aim of this study was to analyze the internal training load and the effects of high-intensity functional training on physical performance in subjects with different training volumes and frequencies. A total of 31 volunteers involved in high-intensity functional training (14 men and 17 women) were divided according to their training volumes and frequencies (high training-volume and frequency-HTVF; (n = 17) (nine women and eight men; age: 31.0 ± 6.3 years; height: 168.8 ± 8.1 cm, body weight: 73.6 ± 11.9 kg; BMI: 25.96 kg/m²) and moderate training volume and frequency-MTVF; (n = 14) (eight women and six men; age: 26.6 ± 4.7 years; height: 167.2 ± 8.6 cm, body weight: 75.8 ± 18.0 kg; BMI: 27.33 kg/m²)). The internal training load was determined using the session-rating of perceived exertion method. The monotony index (MI) and training strain (TS) were used to determine training variability during the training weeks. Countermovement vertical jump height, 20-m sprinting and handgrip strength were assessed at baseline and after six weeks of training. There was a time effect for MI ((F_{(5, 145)} = 5.942; p = 0.0001)), TS ((F_{(5, 145)} = 5.734; p = 0.0001)), weekly internal training load ((F_{(4.006, 116.87)} = 4.188; p = 0.003)) and mean weekly internal training load ((F_{(4.006, 116.87)} = 4.188; p = 0.003)). There was no increase in performance in either group for countermovement vertical jump height ((F_(1,29) = 6.081; p = 0.050)), sprinting ((F_(1,29) = 1.014; p = 0.322)), right handgrip strength ((F_(1,29) = 2.522; p = 0.123)) or left handgrip strength ((F_(1,29) = 2.550; p = 0.121)). The current findings suggest that six weeks of high-intensity functional training was not able to increase performance in either group. Therefore, different volumes and frequencies do not seem to influence the increase in physical performance of HIFT practitioners.

Effect of resistance training to muscle failure vs non-failure on strength, hypertrophy and muscle architecture in trained individuals

The aim of this study was to compare the effects of resistance training to muscle failure (RT-F) and non-failure (RT-NF) on muscle mass, strength and activation of trained individuals. We also compared the effects of these protocols on muscle architecture parameters. A within-subjects design was used in which 14 participants had one leg randomly assigned to RT-F and the other to RT-NF. Each leg was trained 2 days per week for 10 weeks. Vastus lateralis (VL) muscle cross-sectional area (CSA), pennation angle (PA), fascicle length (FL) and 1-repetition maximum (1-RM) were assessed at baseline (Pre) and after 20 sessions (Post). The electromyographic signal (EMG) was assessed after the training period. RT-F and RT-NF protocols showed significant and similar increases in CSA (RT-F: 13.5% and RT-NF: 18.1%; P < 0.0001), PA (RT-F: 13.7% and RT-NF: 14.4%; P < 0.0001) and FL (RT-F: 11.8% and RT-NF: 8.6%; P < 0.0001). All protocols showed significant and similar increases in leg press (RT-F: 22.3% and RT-NF: 26.7%; P < 0.0001) and leg extension (RT-F: 33.3%, P < 0.0001 and RT-NF: 33.7%; P < 0.0001) 1-RM loads. No significant differences in EMG amplitude were detected between protocols (P > 0.05). In conclusion, RT-F and RT-NF are similarly effective in promoting increases in muscle mass, PA, FL, strength and activation.