Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men

Comparison of Periodized and Non-Periodized Resistance Training on Maximal Strength: A Meta-Analysis

BACKGROUND

Periodization is a logical method of organizing training into sequential phases and cyclical time periods in order to increase the potential for achieving specific performance goals while minimizing the potential for overtraining. Periodized resistance training plans are proposed to be superior to non-periodized training plans for enhancing maximal strength.

OBJECTIVE

The primary aim of this study was to examine the previous literature comparing periodized resistance training plans to non-periodized resistance training plans and determine a quantitative estimate of effect on maximal strength.

METHODS

All studies included in the meta-analysis met the following inclusion criteria: (1) peer-reviewed publication; (2) published in English; (3) comparison of a periodized resistance training group to a non-periodized resistance training group; (4) maximal strength measured by 1-repetition maximum (1RM) squat, bench press, or leg press. Data were extracted and independently coded by two authors. Random-effects models were used to aggregate a mean effect size (ES), 95% confidence intervals (CIs) and potential moderators.

RESULTS

The cumulative results of 81 effects gathered from 18 studies published between 1988 and 2015 indicated that the magnitude of improvement in 1RM following periodized resistance training was greater than non-periodized resistance training (ES = 0.43, 95% CI 0.27-0.58; P < 0.001). Periodization model (β = 0.51; P = 0.0010), training status (β = -0.59; P = 0.0305), study length (β = 0.03; P = 0.0067), and training frequency (β = 0.46; P = 0.0123) were associated with a change in 1RM. These results indicate that undulating programs were more favorable for strength gains. Improvements in 1RM were greater among untrained participants. Additionally, higher training frequency and longer study length were associated with larger improvements in 1RM.

CONCLUSION

These results suggest that periodized resistance training plans have a moderate effect on 1RM compared to non-periodized training plans. Variation in training stimuli appears to be vital for increasing maximal strength, and longer periods of higher training frequency may be preferred.

Trained females exhibit less fatigability than trained males after a heavy knee extensor resistance exercise session

PURPOSE

We examined differences between trained males and females in measures of muscular fatigability and central motor output after a resistance exercise session.

METHODS

Sixteen trained males (n = 8) and females (n = 8) participated in the study. Knee extensor maximal torque and rate of torque development were measured before and after the exercise session, and the twitch interpolation technique was used during the maximal efforts to derive measures of voluntary activation and muscle contractility by supramaximal stimulation of the femoral nerve using 10 and 100 Hz doublets. Surface electromyograms were recorded during all maximal efforts to examine maximal and rate of quadriceps muscle activation.

RESULTS

After exercise, maximal torque was reduced for both sexes by 26.3 ± 12.5% (p < 0.001). Absolute and relative vRTD was reduced only for males after exercise (p < 0.05). The early (0-50 ms) rate of muscle activation rise was similarly reduced for both sexes between 2.6 and 16.4% s^-1 (p < 0.01), but males experienced an average decrease of 82.5 ± 72.1% s^-1 for the maximal rate of muscle activation compared to no change for females (p = 0.02). Males had greater reductions (p < 0.05) for maximal twitch amplitudes and rate of twitch development (- 51.1 ± 21.5% and - 49.9 ± 22.8%, respectively) compared to females (- 35.8 ± 13.7% and - 31.5 ± 14.0%, respectively).

CONCLUSIONS

These findings suggest that trained females are resistant to reductions in rapid torque development, despite similar reductions in maximal torque, after resistance exercise, with this result explained by better-maintained muscle contractility and maximal rate of muscle activation compared to males.

The effects of chronic betaine supplementation on body composition and performance in collegiate females: a double-blind, randomized, placebo controlled trial

BACKGROUND

Betaine supplementation has been shown to improve body composition and some metrics of muscular performance in young men; but, whether betaine enhances body composition or performance in female subjects is currently unknown. Therefore, the purpose of this study was to investigate the interaction between resistance training adaptation and chronic betaine supplementation in females.

METHODS

Twenty-three young women (21.0 ± 1.4 years, 165.9 ± 6.4 cm, 68.6 ± 11.8 kg) without prior structured resistance training experience volunteered for this study. Body composition (BodPod), rectus femoris muscle thickness (B-mode Ultrasound), vertical jump, back squat 1RM and bench press 1RM were assessed pre- and post-training. Following 1 week of familiarization training, subjects were matched for body composition and squat strength, and randomly assigned to either a betaine (2.5 g/day; n = 11) or placebo (n = 12) group that completed 3 sets of 6-7 exercises per day performed to momentary muscular failure. Training was divided into two lower and one upper body training sessions per week performed on non-consecutive days for 8 weeks, and weekly volume load was used to analyze work capacity.

RESULTS

Significant main effects of time were found for changes in lean mass (2.4 ± 1.8 kg), muscle thickness (0.13 ± 0.08 cm), vertical jump (1.8 ± 1.6 cm), squat 1RM (39.8 ± 14.0 kg), and bench press 1 RM (9.1 ± 7.3 kg); however, there were no significant interactions. A trend (p = .056) was found for greater weekly training volumes for betaine versus placebo. Significant interactions were found for changes in body fat percentage and fat mass: body fat percentage and fat mass decreased significantly more in betaine (- 3.3 ± 1.7%; - 2.0 ± 1.1 kg) compared to placebo (- 1.7 ± 1.6%; - 0.8 ± 1.3 kg), respectively.

CONCLUSIONS

The results of this study indicated that betaine supplementation may enhance reductions in fat mass, but not absolute strength, that accompany a resistance training program in untrained collegiate females.

Positive, limited and negative responders: The variability in physical fitness adaptation to basic military training

OBJECTIVES

To investigate the heterogeneity of physical adaptation in Australian Army recruits completing a 12-week basic military training regimen.

DESIGN

A prospective research design.

METHODS

Volunteer recruits (n=195) completed 12-weeks of basic military training. Recruit physical fitness was assessed at week 1, weeks 6-8 and week 12. Recruits in the upper (75th) and lower (25th) quartiles for each assessment were then analysed using a repeated measures two-way ANOVA. The relative magnitude of recruit adaptions were classified as positive response (R_positive, ≥5%), limited response (R_limited, >-5% to <5%) and negative response (R_negative, ≤-5%); Chi-square analysis determined the proportional differences in the distribution of each quartile.

RESULTS

An interaction (p<0.001) was observed in the lower and upper recruit quartiles for all assessments of physical fitness at each time point. After 12 weeks of military training the mean difference of the highest quartile was; 20-m multi-stage fitness test 7.4mL·kg^-1·min^-1, (CI:5.8:9.1), 2-min push-ups 20.1 reps, (CI:16.2:23.9), 1RM box lift 5.6kg, (CI:2.6:5.8) and load carriage 222.1s, (CI:174.7:269.4) compared to the lowest recruit quartile. The highest quartile demonstrated no improvement in 1RM box lift (-4%, -1%) and push-ups (2%, 0%) performance at weeks 6-8 and week 12 respectively. In contrast, adaptations in the lowest quartile for 1RM box lift (16%, 21%) and push-ups (46%, 46%) over the same time periods were observed.

CONCLUSIONS

A significant proportion of recruits may complete basic military training with a decline in physical performance. Higher relative-intensity cardiorespiratory and resistance exercise should be considered to facilitate physical adaptation in all recruits.

High- and Low-Load Resistance Training: Interpretation and Practical Application of Current Research Findings

Our current state of knowledge regarding the load (lighter or heavier) lifted in resistance training programmes that will result in 'optimal' strength and hypertrophic adaptations is unclear. Despite this, position stands and recommendations are made based on, we propose, limited evidence to lift heavier weights. Here we discuss the state of evidence on the impact of load and how it, as a single variable, stimulates adaptations to take place and whether evidence for recommending heavier loads is available, well-defined, currently correctly interpreted or has been overlooked. Areas of discussion include electromyography amplitude, in vivo and in vitro methods of measuring hypertrophy, and motor schema and skill acquisition. The present piece clarifies to trainers and trainees the impact of these variables by discussing interpretation of synchronous and sequential motor unit recruitment and revisiting the size principle, poor agreement between whole-muscle cross-sectional area (CSA) and biopsy-determined changes in myofibril CSA, and neural adaptations around task specificity. Our opinion is that the practical implications of being able to self-select external load include reducing the need for specific facility memberships, motivating older persons or those who might be less confident using heavy loads, and allowing people to undertake home- or field-based resistance training intervention strategies that might ultimately improve exercise adherence.

Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis

Schoenfeld, BJ, Grgic, J, Ogborn, D, and Krieger, JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res 31(12): 3508-3523, 2017-The purpose of this article was to conduct a systematic review of the current body of literature and a meta-analysis to compare changes in strength and hypertrophy between low- vs. high-load resistance training protocols. Searches of PubMed/MEDLINE, Cochrane Library, and Scopus were conducted for studies that met the following criteria: (a) an experimental trial involving both low-load training [≤60% 1 repetition maximum (1RM)] and high-load training (>60% 1RM); (b) with all sets in the training protocols being performed to momentary muscular failure; (c) at least one method of estimating changes in muscle mass or dynamic, isometric, or isokinetic strength was used; (d) the training protocol lasted for a minimum of 6 weeks; (e) the study involved participants with no known medical conditions or injuries impairing training capacity. A total of 21 studies were ultimately included for analysis. Gains in 1RM strength were significantly greater in favor of high- vs. low-load training, whereas no significant differences were found for isometric strength between conditions. Changes in measures of muscle hypertrophy were similar between conditions. The findings indicate that maximal strength benefits are obtained from the use of heavy loads while muscle hypertrophy can be equally achieved across a spectrum of loading ranges.

Adaptations to Endurance and Strength Training

The capacity for human exercise performance can be enhanced with prolonged exercise training, whether it is endurance- or strength-based. The ability to adapt through exercise training allows individuals to perform at the height of their sporting event and/or maintain peak physical condition throughout the life span. Our continued drive to understand how to prescribe exercise to maximize health and/or performance outcomes means that our knowledge of the adaptations that occur as a result of exercise continues to evolve. This review will focus on current and new insights into endurance and strength-training adaptations and will highlight important questions that remain as far as how we adapt to training.

Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis

BACKGROUND

A number of resistance training (RT) program variables can be manipulated to maximize muscular hypertrophy. One variable of primary interest in this regard is RT frequency. Frequency can refer to the number of resistance training sessions performed in a given period of time, as well as to the number of times a specific muscle group is trained over a given period of time.

OBJECTIVE

We conducted a systematic review and meta-analysis to determine the effects of resistance training frequency on hypertrophic outcomes.

METHODS

Studies were deemed eligible for inclusion if they met the following criteria: (1) were an experimental trial published in an English-language refereed journal; (2) directly compared different weekly resistance training frequencies in traditional dynamic exercise using coupled concentric and eccentric actions; (3) measured morphologic changes via biopsy, imaging, circumference, and/or densitometry; (4) had a minimum duration of 4 weeks; and (5) used human participants without chronic disease or injury. A total of ten studies were identified that investigated RT frequency in accordance with the criteria outlined.

RESULTS

Analysis using binary frequency as a predictor variable revealed a significant impact of training frequency on hypertrophy effect size (P = 0.002), with higher frequency being associated with a greater effect size than lower frequency (0.49 ± 0.08 vs. 0.30 ± 0.07, respectively). Statistical analyses of studies investigating training session frequency when groups are matched for frequency of training per muscle group could not be carried out and reliable estimates could not be generated due to inadequate sample size.

CONCLUSIONS

When comparing studies that investigated training muscle groups between 1 to 3 days per week on a volume-equated basis, the current body of evidence indicates that frequencies of training twice a week promote superior hypertrophic outcomes to once a week. It can therefore be inferred that the major muscle groups should be trained at least twice a week to maximize muscle growth; whether training a muscle group three times per week is superior to a twice-per-week protocol remains to be determined.

Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy

The present study investigated the effects of different intensities of resistance training (RT) on elbow flexion and leg press one-repetition maximum (1RM) and muscle cross-sectional area (CSA). Thirty men volunteered to participate in an RT programme, performed twice a week for 12 weeks. The study employed a within-subject design, in which one leg and arm trained at 20% 1RM (G20) and the contralateral limb was randomly assigned to one of the three conditions: 40% (G40); 60% (G60), and 80% 1RM (G80). The G20 started RT session with three sets to failure. After G20 training, the number of sets was adjusted for the other contralateral limb conditions with volume-matched. CSA and 1RM were assessed at pre, post-6 weeks, and post-12 weeks. There was time effect for CSA for the vastus lateralis (VL) (8.9%, 20.5%, 20.4%, and 19.5%) and elbow flexors (EF) (11.4%, 25.3%, 25.1%, and 25%) in G20, G40, G60, and G80, respectively (p > .05). G80 showed higher CSA than G20 for VL (19.5% vs. 8.9%) and EF (25% vs. 11.4%) at post-12 weeks (p < .05). There was time effect for elbow flexion and unilateral leg press strength for all groups post-12 weeks (p < .05). However, the magnitude of increase was higher in G60 and G80. In conclusion, when low to high intensities of RT are performed with volume-matched, all intensities were effective for increasing muscle strength and size; however, 20% 1RM was suboptimal in this regard, and only the heavier RT intensity (80% 1RM) was shown superior for increasing strength and CSA compared to low intensities.

Effects of Insect Protein Supplementation during Resistance Training on Changes in Muscle Mass and Strength in Young Men

During prolonged resistance training, protein supplementation is known to promote morphological changes; however, no previous training studies have tested the effect of insect protein isolate in a human trial. The aim of this study was to investigate the potential effect of insect protein as a dietary supplement to increase muscle hypertrophy and strength gains during prolonged resistance training in young men. Eighteen healthy young men performed resistance training four day/week for eight weeks. Subjects were block randomized into two groups consuming either an insect protein isolate or isocaloric carbohydrate supplementation within 1 h after training and pre-sleep on training days. Strength and body composition were measured before and after intervention to detect adaptions to the resistance training. Three-day weighed dietary records were completed before and during intervention. Fat- and bone- free mass (FBFM) improved significantly in both groups (Mean (95% confidence interval (CI))), control group (Con): (2.5 kg (1.5, 3.5) p < 0.01), protein group (Pro): (2.7 kg (1.6, 3.8) p < 0.01) from pre- to post- leg and bench press one repetition maximum (1 RM) improved by Con: (42.0 kg (32.0, 52.0) p < 0.01) and (13.8 kg (10.3, 17.2) p < 0.01), Pro: (36.6 kg (27.3, 45.8) p < 0.01) and (8.1 kg (4.5, 11.8) p < 0.01), respectively. No significant differences in body composition and muscle strength improvements were found between groups. In young healthy men, insect protein supplementation did not improve adaptations to eight weeks of resistance training in comparison to carbohydrate supplementation. A high habitual protein intake in both Con and Pro may partly explain our observation of no superior effect of insect protein supplementation.

Total training load may explain similar strength gains and muscle hypertrophy seen in aged rats submitted to resistance training and anabolic steroids

This study aimed to quantify training parameters and analyze the morphological response of aged muscles submitted to resistance training and anabolic steroids. Aged Wistar rats were divided into groups: C - initial control; CF - final control; CAS - control with anabolic steroid, RT - resistance training, and RTA - resistance training with anabolic steroid. Maximum carried load, absolute and relative loads increased significantly in RT and RTA. RTA demonstrated greater relative load than RT. Average total volume, total climbing volume, relative total volume, relative total climbing volume, and mean climbing volume were similar between groups RT and RTA. For soleus, CAS, RT, and RTA enlarged cross-sectional area of type I fibers and nuclear ratio. As for type II fibers, RTA was higher than C and CF. For plantaris, RT and RTA showed significant increases in myofibers type I compared to C and CF. For type II fibers, RTA showed a significant increase compared to C and CF. Regarding the nuclear ratio, RT and RTA showed a higher ratio than C, CF, and CAS. Our results demonstrated that both RT and RTA were not different among the analyzed morphological parameters. This fact can be explained by the absence of differences found in the training variables analyzed.

Interpreting Signal Amplitudes in Surface Electromyography Studies in Sport and Rehabilitation Sciences

Surface electromyography (sEMG) is a popular research tool in sport and rehabilitation sciences. Common study designs include the comparison of sEMG amplitudes collected from different muscles as participants perform various exercises and techniques under different loads. Based on such comparisons, researchers attempt to draw conclusions concerning the neuro- and electrophysiological underpinning of force production and hypothesize about possible longitudinal adaptations, such as strength and hypertrophy. However, such conclusions are frequently unsubstantiated and unwarranted. Hence, the goal of this review is to discuss what can and cannot be inferred from comparative research designs as it pertains to both the acute and longitudinal outcomes. General methodological recommendations are made, gaps in the literature are identified, and lines for future research to help improve the applicability of sEMG are suggested.

Imbalances in the Development of Muscle and Tendon as Risk Factor for Tendinopathies in Youth Athletes: A Review of Current Evidence and Concepts of Prevention

Tendons feature the crucial role to transmit the forces exerted by the muscles to the skeleton. Thus, an increase of the force generating capacity of a muscle needs to go in line with a corresponding modulation of the mechanical properties of the associated tendon to avoid potential harm to the integrity of the tendinous tissue. However, as summarized in the present narrative review, muscle and tendon differ with regard to both the time course of adaptation to mechanical loading as well as the responsiveness to certain types of mechanical stimulation. Plyometric loading, for example, seems to be a more potent stimulus for muscle compared to tendon adaptation. In growing athletes, the increased levels of circulating sex hormones might additionally augment an imbalanced development of muscle strength and tendon mechanical properties, which could potentially relate to the increasing incidence of tendon overload injuries that has been indicated for adolescence. In fact, increased tendon stress and strain due to a non-uniform musculotendinous development has been observed recently in adolescent volleyball athletes, a high-risk group for tendinopathy. These findings highlight the importance to deepen the current understanding of the interaction of loading and maturation and demonstrate the need for the development of preventive strategies. Therefore, this review concludes with an evidence-based concept for a specific loading program for increasing tendon stiffness, which could be implemented in the training regimen of young athletes at risk for tendinopathy. This program incorporates five sets of four contractions with an intensity of 85–90% of the isometric voluntary maximum and a movement/contraction duration that provides 3 s of high magnitude tendon strain.

Ability to predict repetitions to momentary failure is not perfectly accurate, though improves with resistance training experience

‘Repetitions in Reserve’ (RIR) scales in resistance training (RT) are used to control effort but assume people accurately predict performance a priori (i.e. the number of possible repetitions to momentary failure (MF)). This study examined the ability of trainees with different experience levels to predict number of repetitions to MF. One hundred and forty-one participants underwent a full body RT session involving single sets to MF and were asked to predict the number of repetitions they could complete before reaching MF on each exercise. Participants underpredicted the number of repetitions they could perform to MF (Standard error of measurements [95% confidence intervals] for combined sample ranged between 2.64 [2.36–2.99] and 3.38 [3.02–3.83]). There was a tendency towards improved accuracy with greater experience. Ability to predict repetitions to MF is not perfectly accurate among most trainees though may improve with experience. Thus, RIR should be used cautiously in prescription of RT. Trainers and trainees should be aware of this as it may have implications for the attainment of training goals, particularly muscular hypertrophy.

Upper-Body Muscular Endurance Training Improves Performance Following 50 min of Double Poling in Well-Trained Cross-Country Skiers

This study investigated the effect of muscular endurance training on O₂-cost and performance in double poling (DP) on a rollerski treadmill. Twenty-two well-trained cross-country skiers (31 ± 4 years, 77 ± 9 kg, 181 ± 8 cm, VO_2max running: 64 ± 5 mL·kg⁻¹·min⁻¹) were counter-balanced to either a combined muscular endurance and running interval training group [MET; n = 11 (♂ = 9, ♀ = 2)], or an endurance running interval training group [ET; n = 11 (♂ = 9, ♀ = 2)]. Both groups continued their normal low-and moderate intensity training, but replaced 2 weekly high intensity-training sessions with two project-specific sessions for 6 weeks. In these sessions, MET combined upper-body muscular endurance training (4 × 30 repetitions, 90 s rest between sets) and running intervals (3 × 4 or 2 × 6 min, 3 min rest), while ET performed running intervals only (6 × 4 or 4 × 6 min, 3 min rest). The DP test-protocol consisted of 50 min submaximal poling for O₂-cost measurement, followed by a self-paced 1,000-m performance test. In addition, subjects performed a VO_2max test in running. MET increased muscular endurance (P < 0.05) and 1RM in simulated DP (P < 0.01) more than ET. Further, MET reduced the 1,000-m time and O₂-cost compared to baseline values (P < 0.05), and tended to improve the 1,000-m time more than ET (P = 0.06). There were no changes in VO_2max running or VO_2peak DP in either MET or ET. In conclusion, 6 weeks of muscular endurance training increased both muscular endurance and 1RM in simulated DP. Further, specific upper-body muscular endurance training improved DP performance and thus, seems as a promising training model to optimize performance in well-trained cross-country skiers.

Effect of low-intensity resistance training with heat stress on the HSP72, anabolic hormones, muscle size, and strength in elderly women

BACKGROUND

Several recent studies have reported that heat stress stimulates the activation of heat shock protein 72 (HSP72), leading to an increase in muscle synthesis. Some studies suggested that low-intensity resistance training combined with heat stress could improve muscle size and strength.

AIM

This study aimed to identify the effect of low-intensity resistance training with heat stress over 12 weeks on the HSP72, anabolic hormones, muscle size, and strength in elderly women.

METHODS

The subjects were physically healthy women of 65-75 years, who were randomly assigned to one of three groups: a low-intensity resistance training with heating sheet group (HRT group, n = 8), a moderate-intensity resistance training (RT group, n = 6), and a heating sheet group (HEAT group, n = 7). Computed tomography scans, 1-repetition maximum (1RM), and blood samples were taken pre- and post-training.

RESULTS

The HSP72 did not vary significantly between the different groups and times. The IGF-1 and 1RM had significantly increased in all three groups after the training (respectively, p < 0.05). Moreover, the cross-sectional area (CSA) of the quadriceps showed a significantly greater increase in the HRT group than in the HEAT group (p < 0.05).

CONCLUSIONS

We found that low-intensity training with heat stress stimulated the anabolic hormones of elderly women, improving their muscle strength and hypertrophy. We believe that low-intensity training with heat stress is an effective way to prevent muscle atrophy and to improve muscle strength in elderly women.

O USO DE BARRA OU HALTERE NÃO ALTERA A ATIVAÇÃO MUSCULAR DURANTE O EXERCÍCIO PULLOVER

RESUMO Introdução: Inúmeras variações de exercícios têm sido aplicadas nas rotinas de treinamento de força, com o objetivo de otimizar os ganhos de força e hipertrofia e, entre os exercícios usados, podemos destacar o pullover. Objetivo: Comparar a atividade eletromiográfica da parte clavicular do músculo peitoral maior (PMC), parte esternocostal do peitoral maior (PME), cabeça longa do tríceps braquial (TBL), do deltoide anterior (DA), deltoide posterior (DP), latíssimo do dorso (LD) e serrátil anterior (SA) entre os exercícios pullover barra (PB) e pullover haltere (PH). Método: Participaram do estudo 11 homens treinados (idade, 24,50 ± 4,34 anos; percentual de gordura = 13,63 ± 1,94; estatura = 1,76 ± 0,04 m; massa corporal total = 73,12 ± 6,10 kg). A primeira fase do estudo consistiu em avaliações antropométricas e teste e re-teste de 10 repetições máximas (RM). A segunda fase do estudo foi composta pela coleta dos sinais eletromiográficos nos exercícios propostos. Para tal, foi realizada uma série com cargas ajustadas a 90% de 10 RM. Para verificar as diferenças na ativação dos respectivos músculos estudados entre os exercícios PB e PH adotou-se o teste t de Student pareado para amostras dependentes. Resultados: Não foram observadas mudanças na ativação de nenhum dos músculos analisados nos exercícios propostos (P > 0,05). Conclusão: Concluiu-se que a realização do exercício pullover com barra ou com o haltere não altera a participação/ativação dos músculos envolvidos.

The effects of supramaximal versus submaximal intensity eccentric training when performed until volitional fatigue

PURPOSE

Our purpose was to compare supramaximal versus submaximal intensity eccentric training performed until volitional fatigue.

METHODS

Thirty-two young adults (19 males) were randomized into one of three groups: (1) ECC110 performed eccentric (ECC) only contractions at 110% of concentric (CON) 1-repetition maximum (1RM); (2) ECC80 performed ECC only contractions at 80% of CON 1RM; (3) a control group. Training progressed from 3 to 6 sets of unilateral ECC training of the elbow flexors over 8 weeks, with each set performed until volitional fatigue. Elbow flexors muscle thickness (via ultrasound) and 1RM were assessed pre- and post-training. Rating of perceived exertion (RPE) and muscle soreness was self-reported.

RESULTS

Both ECC110 (+0.25 cm) and ECC80 (+0.21 cm) showed a greater post-training increase in muscle thickness compared to control (-0.01 cm) (p < 0.05), with no differences between ECC110 and ECC80. ECC80 (+1.23 kg) showed a greater post-training increase in strength compared to control (p < 0.05), while ECC110 (+0.76 kg) had no significant difference post-training vs. control (-0.01 kg). ECC80 had significantly lower average RPE scores than ECC110 (p < 0.05).

CONCLUSIONS

Both supramaximal intensity eccentric training and submaximal intensity eccentric training are effective for increasing muscle size, but submaximal eccentric training is perceived to require less exertion than supramaximal training. These findings suggest that submaximal eccentric training may be an ideal strategy to increase muscle size and strength in individuals whose needs warrant training at a lower level of exertion.

Resistance training prescription with different load-management methods improves phase angle in older women

The purpose of the present study was to investigate the effect of two different resistance training (RT) prescription methods on phase angle (PA) in older women. Seventy-six older women (68.5 ± 5.7 years) were randomly assigned to one of three groups: two training groups that performed an eight-week RT programme either in a constant load (CT, n = 25) or an ascending pyramidal load (PR, n =  26) routine three times per week, or a control group (CG, n =  25) that performed no exercise. The CT programme consisted of three sets of 8-12 repetition maximum (RM) with a constant load for the three sets, whereas the PR training consisted of three sets of 12/10/8 RM with incremental loads for each set. PA was assessed by whole-body spectral bioelectrical impedance. After the RT period, both CT and PR achieved higher (P < .05) values of PA (CT =  5.76 ± 0.59°, PR =  5.63 ± 0.61°, CG =  5.48 ± 0.46°) compared to the CG; however, there was no difference (P > .05) between trained groups. The results suggest that eight weeks of RT based on a PR and CT load routines promote an improvement in PA, and both prescription methods performed similarly.

The Effect of Different Resistance Training Load Schemes on Strength and Body Composition in Trained Men

The purpose of this study was to evaluate the impact of moderate-load (10 RM) and low-load (20 RM) resistance training schemes on maximal strength and body composition. Sixteen resistance-trained men were randomly assigned to 1 of 2 groups: a moderate-load group (n = 8) or a low-load group (n = 8). The resistance training schemes consisted of 8 exercises performed 4 times per week for 6 weeks. In order to equate the number of repetitions performed by each group, the moderate load group performed 6 sets of 10 RM, while the low load group performed 3 sets of 20 RM. Between-group differences were evaluated using a 2-way ANOVA and independent t-tests. There was no difference in the weekly total load lifted (sets × reps × kg) between the 2 groups. Both groups equally improved maximal strength and measures of body composition after 6 weeks of resistance training, with no significant between-group differences detected. In conclusion, both moderate-load and low-load resistance training schemes, similar for the total load lifted, induced a similar improvement in maximal strength and body composition in resistance-trained men.

Role of metabolic stress for enhancing muscle adaptations: Practical applications

Metabolic stress is a physiological process that occurs during exercise in response to low energy that leads to metabolite accumulation [lactate, phosphate inorganic (Pi) and ions of hydrogen (H⁺)] in muscle cells. Traditional exercise protocol (i.e., Resistance training) has an important impact on the increase of metabolite accumulation, which influences hormonal release, hypoxia, reactive oxygen species (ROS) production and cell swelling. Changes in acute exercise routines, such as intensity, volume and rest between sets, are determinants for the magnitude of metabolic stress, furthermore, different types of training, such as low-intensity resistance training plus blood flow restriction and high intensity interval training, could be used to maximize metabolic stress during exercise. Thus, the objective of this review is to describe practical applications that induce metabolic stress and the potential effects of metabolic stress to increase systemic hormonal release, hypoxia, ROS production, cell swelling and muscle adaptations.

Greater Neural Adaptations following High- vs. Low-Load Resistance Training

We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 1RM; n = 13) resistance training group and completed leg extension resistance training to failure 3 times per week for 6 weeks. Testing was completed at baseline, 3, and 6 weeks of training. During each testing session, ultrasound muscle thickness and echo intensity, 1RM strength, maximal voluntary isometric contraction (MVIC) strength, and contractile properties of the quadriceps femoris were measured. Percent voluntary activation (VA) and electromyographic (EMG) amplitude were measured during MVIC, and during randomly ordered isometric step muscle actions at 10–100% of baseline MVIC. There were similar increases in muscle thickness from Baseline to Week 3 and 6 in the 80 and 30% 1RM groups. However, both 1RM and MVIC strength increased from Baseline to Week 3 and 6 to a greater degree in the 80% than 30% 1RM group. VA during MVIC was also greater in the 80 vs. 30% 1RM group at Week 6, and only training at 80% 1RM elicited a significant increase in EMG amplitude during MVIC. The peak twitch torque to MVIC ratio was also significantly reduced in the 80%, but not 30% 1RM group, at Week 3 and 6. Finally, VA and EMG amplitude were reduced during submaximal torque production as a result of training at 80% 1RM, but not 30% 1RM. Despite eliciting similar hypertrophy, 80% 1RM improved muscle strength more than 30% 1RM, and was accompanied by increases in VA and EMG amplitude during maximal force production. Furthermore, training at 80% 1RM resulted in a decreased neural cost to produce the same relative submaximal torques after training, whereas training at 30% 1RM did not. Therefore, our data suggest that high-load training results in greater neural adaptations that may explain the disparate increases in muscle strength despite similar hypertrophy following high- and low-load training programs.

Effects of 4 weeks of low-load unilateral resistance training, with and without blood flow restriction, on strength, thickness, V wave, and H reflex of the soleus muscle in men

PURPOSE

To test the effects of 4 weeks of unilateral low-load resistance training (LLRT), with and without blood flow restriction (BFR), on maximal voluntary contraction (MVC), muscle thickness, volitional wave (V wave), and Hoffmann reflex (H reflex) of the soleus muscle.

METHODS

Twenty-two males were randomly distributed into three groups: a control group (CTR; n = 8); a low-load blood flow restriction resistance training group (BFR-LLRT; n = 7), who were an inflatable cuff to occlude blood flow; and a low-load resistance training group without blood flow restriction (LLRT; n = 7). The training consisted of four sets of unilateral isometric LLRT (25% of MVC) three times a week over 4 weeks.

RESULTS

MVC increased 33% (P < 0.001) and 22% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. The soleus thickness increased 9.5% (P < 0.001) and 6.5% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. However, neither MVC nor thickness changed in either of the legs tested in the CTR group (MVC -1 and -5%, and muscle thickness 1.9 and 1.2%, for the control and trained leg, respectively). Moreover, V wave and H reflex did not change significantly in all the groups studied (V_wave/M _wave ratio -7.9 and -2.6%, and H _max/M _max ratio -3.8 and -4%, for the control and trained leg, respectively).

CONCLUSIONS

Collectively, the present data suggest that in spite of the changes occurring in soleus strength and thickness, 4 weeks of low-load resistance training, with or without BFR, does not cause any change in neural drive or motoneuronal excitability.

Free leucine supplementation during an 8-week resistance training program does not increase muscle mass and strength in untrained young adult subjects

The purpose of this study was to examine the effects of free leucine supplementation on changes in skeletal muscle mass and strength during a resistance training (RT) program in previously untrained, young subjects. In a double-blind, randomized, placebo-controlled study, 20 healthy young (22 ± 2 years) participants were assigned to two groups: a placebo-supplement group (PLA, N = 10) or a leucine-supplement group (LEU, N = 10). Both groups underwent an 8-week hypertrophic RT program (2 days/week), consuming an equivalent amount of leucine (3.0 g/day in a single post-training dose) or placebo (cornstarch). Quadriceps muscle strength, cross-sectional area (CSA) of the vastus lateralis (VL), and rectus femoris (RF), as well as the habitual dietary intake were assessed before and after the 8-week intervention period. There was a similar improvement in muscle strength (Leg press, LEU: +33% vs. PLA: +37%; P > 0.05, and knee extension, LEU: +31% vs. PLA: 34%; P > 0.05) and CSA (VL, LEU: 8.9% vs. PLA: 9.6%; P > 0.05, and RF, LEU: +21.6% vs. PLA: + 16.4%; P > 0.05) in the both groups from pre- to post-training. In addition, there was no significant (P > 0.05) difference in daily dietary intake between the LEU and PLA groups before and after the intervention period. Free leucine supplementation (3.0 g/day post-training) does not increase muscle strength or CSA during RT in healthy young subjects consuming adequate dietary protein intake.

Intramuscular Anabolic Signaling and Endocrine Response Following Resistance Exercise: Implications for Muscle Hypertrophy

Maintaining skeletal muscle mass and function is critical for disease prevention, mobility and quality of life, and whole-body metabolism. Resistance exercise is known to be a major regulator for promoting muscle protein synthesis and muscle mass accretion. Manipulation of exercise intensity, volume, and rest elicit specific muscular adaptations that can maximize the magnitude of muscle growth. The stimulus of muscle contraction that occurs during differing intensities of resistance exercise results in varying biochemical responses regulating the rate of protein synthesis, known as mechanotransduction. At the cellular level, skeletal muscle adaptation appears to be the result of the cumulative effects of transient changes in gene expression following acute bouts of exercise. Thus, maximizing the resistance exercise-induced anabolic response produces the greatest potential for hypertrophic adaptation with training. The mechanisms involved in converting mechanical signals into the molecular events that control muscle growth are not completely understood; however, skeletal muscle protein synthesis appears to be regulated by the multi-protein phosphorylation cascade, mTORC1 (mammalian/mechanistic target of rapamycin complex 1). The purpose of this review is to examine the physiological response to resistance exercise, with particular emphasis on the endocrine response and intramuscular anabolic signaling through mTORC1. It appears that resistance exercise protocols that maximize muscle fiber recruitment, time-under-tension, and metabolic stress will contribute to maximizing intramuscular anabolic signaling; however, the resistance exercise parameters for maximizing the anabolic response remain unclear.

Myoeletric indices of fatigue adopting different rest intervals during leg press sets

INTRODUCTION

The purpose of this study was to examine the acute effect of different rest intervals between multiple sets of the 45° angled leg press exercise (LP45) on surface electromyographic (SEMG) spectral and amplitude indices of fatigue.

METHODS

Fifteen recreationally trained females performed three protocols in a randomized crossover design; each consisting of four sets of 10 repetitions with 1 (P1), 3 (P3), or 5 (P5) minute rest intervals between sets. Each set was performed with 70% of the LP45 ten-repetition maximum load. The SEMG data for biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles was then evaluated.

RESULTS

The SEMG amplitude change in the time coefficient (CRMS) and spectral fatigue index (Cf5) indicated higher levels of fatigue for all muscles evaluated during the P3 protocol versus the P1 and P5 protocols (p ≤ 0.05), respectively. The RF and VL muscles showed greater fatigue levels by the second and third sets; whereas, greater fatigue was shown in the VM and BF muscles by the fourth set (p ≤ 0.05).

CONCLUSIONS

A three-minute rest interval between sets might represent a neuromuscular window between a fatigue stated and fully recovered state in the context of neural activation. Moreover, a three minute rest interval between sets might allow for consistent recruitment of high threshold motor units over multiple sets, and thus promote a more effective stimulus for strength gains.

Repetition Performance and Blood Lactate Responses Adopting Different Recovery Periods Between Training Sessions in Trained Men

Miranda, H, Maia, MF, Paz, GA, de Souza, JAAA, Simão, R, Farias, DA, and Willardson, JM. Repetition performance and blood lactate responses adopting different recovery periods between training sessions in trained men. J Strength Cond Res 32(12): 3340-3347, 2018-The purpose of this study was to examine the effect of different recovery periods (24, 48, and 72 hours) between repeated resistance training (RT) sessions for the upper-body muscles on repetition performance and blood lactate responses in trained men. Sixteen recreationally trained men (age: 26.1 ± 3.1 years; height: 179 ± 4.5 cm; body mass: 82.6 ± 4.0 kg, 4.5 ± 2.2 years of RT experience) participated in this study. Eight repetition maximum (8RM) loads were determined for the bench press (BP), 30° incline bench press (BP30), and 45° incline bench press (BP45) exercises. To assess the effects of different recovery periods between repeated training sessions, 3 protocols were performed in randomized order, including 24 hours (P24), 48 hours (P48), and 72 hours (P72). Each RT session consisted of performing 4 repetition maximum sets of the BP, BP30, and BP45 with 8RM loads and 2-minute rest intervals between sets. Blood lactate levels were measured presession (PRE), immediately postsession (POST), 3 minutes postsession (P3), and 5 minutes postsession (P5). For the P24 protocol, significant decreases in repetition performance were found between sessions for the BP, BP30, and BP45 exercises, respectively. When considering session 2 only, the total work (repetition × sets) was significantly higher under P48 and P72 compared with P24 for the BP30 and BP45 exercises. Blood lactate levels (i.e., POST, P3, and P5) significantly increased for session 2 under the P24 compared with the P48 and P72 protocols, respectively. Therefore, coaches and practitioners who need to accomplish a higher training volume for the upper-body muscles should adopt recovery periods longer than 24 hours between sessions that train the same or similar muscle groups.

Pre- versus post-exercise protein intake has similar effects on muscular adaptations

The purpose of this study was to test the anabolic window theory by investigating muscle strength, hypertrophy, and body composition changes in response to an equal dose of protein consumed either immediately pre- versus post-resistance training (RT) in trained men. Subjects were 21 resistance-trained men (>1 year RT experience) recruited from a university population. After baseline testing, participants were randomly assigned to 1 of 2 experimental groups: a group that consumed a supplement containing 25 g protein and 1 g carbohydrate immediately prior to exercise (PRE-SUPP) (n = 9) or a group that consumed the same supplement immediately post-exercise (POST-SUPP) (n = 12). The RT protocol consisted of three weekly sessions performed on non-consecutive days for 10 weeks. A total-body routine was employed with three sets of 8–12 repetitions for each exercise. Results showed that pre- and post-workout protein consumption had similar effects on all measures studied (p > 0.05). These findings refute the contention of a narrow post-exercise anabolic window to maximize the muscular response and instead lends support to the theory that the interval for protein intake may be as wide as several hours or perhaps more after a training bout depending on when the pre-workout meal was consumed.

Effect of Training Leading to Repetition Failure on Muscular Strength: A Systematic Review and Meta-Analysis

BACKGROUND

It remains unclear whether repetitions leading to failure (failure training) or not leading to failure (non-failure training) lead to superior muscular strength gains during resistance exercise. Failure training may provide the stimulus needed to enhance muscular strength development. However, it is argued that non-failure training leads to similar increases in muscular strength without the need for high levels of discomfort and physical effort, which are associated with failure training.

OBJECTIVE

We conducted a systematic review and meta-analysis to examine the effect of failure versus non-failure training on muscular strength.

METHODS

Five electronic databases were searched using terms related to failure and non-failure training. Studies were deemed eligible for inclusion if they met the following criteria: (1) randomised and non-randomised studies; (2) resistance training intervention where repetitions were performed to failure; (3) a non-failure comparison group; (4) resistance training interventions with a total of ≥3 exercise sessions; and (5) muscular strength assessment pre- and post-training. Random-effects meta-analyses were performed to pool the results of the included studies and generate a weighted mean effect size (ES).

RESULTS

Eight studies were included in the meta-analysis (combined studies). Training volume was controlled in four studies (volume controlled), while the remaining four studies did not control for training volume (volume uncontrolled). Non-failure training resulted in a 0.6-1.3% greater strength increase than failure training. A small pooled effect favouring non-failure training was found (ES = 0.34; p = 0.02). Significant small pooled effects on muscular strength were also found for non-failure versus failure training with compound exercises (ES = 0.37-0.38; p = 0.03) and trained participants (ES = 0.37; p = 0.049). A slightly larger pooled effect favouring non-failure training was observed when volume-uncontrolled studies were included (ES = 0.41; p = 0.047). No significant effect was found for the volume-controlled studies, although there was a trend favouring non-failure training. The methodological quality of the included studies in the review was found to be moderate. Exercise compliance was high for the studies where this was reported (n = 5), although limited information on adverse events was provided.

CONCLUSION

Overall, the results suggest that despite statistically significant effects on muscular strength being found for non-failure compared with failure training, the small percentage of improvement shown for non-failure training is unlikely to be meaningful. Therefore, it appears that similar increases in muscular strength can be achieved with failure and non-failure training. Furthermore, it seems unnecessary to perform failure training to maximise muscular strength; however, if incorporated into a programme, training to failure should be performed sparingly to limit the risks of injuries and overtraining.

The role of volume-load in strength and absolute endurance adaptations in adolescent's performing high- or low-load resistance training

This study compared high- (HL) and low-load (LL) resistance training (RT) on strength, absolute endurance, volume-load, and their relationships in untrained adolescents. Thirty-three untrained adolescents of both sexes (males, n = 17; females, n = 16; 14 ± 1 years) were randomly assigned into either (i) HL (n = 17): performing 3 sets of 4-6 repetitions to momentary concentric failure; or (ii) LL (n = 16): performing 2 sets of 12-15 repetitions to momentary concentric failure. RT was performed for 2×/week for 9 weeks. Change in maximum strength (1 repetition maximum) and absolute muscular endurance for barbell bench press was assessed. Weekly volume-load was calculated as sets (n) × repetitions (n) × load (kg). Ninety-five percent confidence intervals (CIs) revealed that both groups significantly increased in strength and absolute endurance with large effect sizes (d = 1.51-1.66). There were no between-group differences for change in strength or absolute endurance. Ninety-five percent CIs revealed that both groups significantly increased in weekly volume-load with large effect sizes (HL = 1.66, LL = 1.02). There were no between-group differences for change in volume-load though average weekly volume-load was significantly greater for LL (p < 0.001). Significant Pearson's correlations were found for the HL group between average weekly volume-load and both strength (r = 0.650, p = 0.005) and absolute endurance (r = 0.552, p = 0.022) increases. Strength and absolute endurance increases do not differ between HL and LL conditions in adolescents when performed to momentary concentric failure. Under HL conditions greater weekly volume-load is associated with greater strength and absolute endurance increases.

Effects of blood-flow restriction on biomarkers of myogenesis in response to resistance exercise

We investigated the acute myogenic response to resistance exercise with and without blood-flow restriction (BFR). Six men and women (age, 22 ± 1 years) performed unilateral knee extensions at 40% of 1-repetition maximum with or without (CNTRL) BFR applied via pressure cuff inflated to 220 mm Hg. Muscle biopsies were collected at 4 h and 24 h postexercise. Addition of BFR increased myoD and c-Met messenger RNA expression relative to CNTRL. Expression of hepatocyte growth factor protein was significantly higher following CNTRL.