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The role of volume-load in strength and absolute endurance adaptations in adolescent’s performing high- or low-load resistance training
Abstract
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: 1) HL (n=17): performing 3 sets of 4-6 repetitions to momentary concentric failure; or 2) LL (n=16): performing 3 sets of 12-15 repetitions to momentary concentric failure. RT was performed 2x/week for 9 weeks. Change in maximum strength (1 RM) and absolute muscular endurance for barbell bench press was assessed. Weekly volume-load was calculated as sets [no.] x repetitions [no.] x load [kg]. 95% confidence intervals (CIs) revealed 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. 95%CIs revealed 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.
... By contrast, a follow-up study from Faigenbaum et al. and another study by Steele et al. found no training-related differences in strength gains (e.g. 1RM chest press/ 15RM leg press and 1RM bench press/ muscular strength endurance bench press, respectively) with high intensities and low repetitions versus training with lower intensities and higher repetitions [49,51]. Surprisingly, in an early study, Rarick and Larsen did not even detect a difference in maximal static/isometric strength when performing daily low intensity and low volume compared to high intensity and high volume training for the wrist flexors in male adolescents for four weeks [116]. ...
... While the majority of the above cited studies [47,49,51] examined untrained children, Gonzalez-Badillo et al. looked at strength gains in 16-year-old well-trained weight lifters [52]. Comparative studies of resistance and plyometric training in youth These authors observed that a high volume protocol over ten weeks did not induce greater adaptations (e.g. ...
... Even though no group differences for muscular endurance gains (15RM leg press) were observed, only the higher repetition protocol resulted in larger improvements compared to the control group, thus favouring higher repetitions [49]. In contrast, Steele et al. did not observe protocol specific effects on muscular endurance (bench press repetitions with 70% of 1RM) when training was conducted with two sets of either low (4-6) or high (12)(13)(14)(15) repetitions to momentary failure in adolescents [51]. They argued that there appears to be a minimum threshold for both volume and intensity which is necessary to optimize adaptations. ...
Introduction
To date, several meta-analyses clearly demonstrated that resistance and plyometric training are effective to improve physical fitness in children and adolescents. However, a methodological limitation of meta-analyses is that they synthesize results from different studies and hence ignore important differences across studies (i.e., mixing apples and oranges). Therefore, we aimed at examining comparative intervention studies that assessed the effects of age, sex, maturation, and resistance or plyometric training descriptors (e.g., training intensity, volume etc.) on measures of physical fitness while holding other variables constant.
Methods
To identify relevant studies, we systematically searched multiple electronic databases (e.g., PubMed) from inception to March 2018. We included resistance and plyometric training studies in healthy young athletes and non-athletes aged 6 to 18 years that investigated the effects of moderator variables (e.g., age, maturity, sex, etc.) on components of physical fitness (i.e., muscle strength and power).
Results
Our systematic literature search revealed a total of 75 eligible resistance and plyometric
training studies, including 5,138 participants. Mean duration of resistance and plyometric
training programs amounted to 8.9 ± 3.6 weeks and 7.1±1.4 weeks, respectively. Our findings showed that maturation affects plyometric and resistance training outcomes differently, with the former eliciting greater adaptations pre-peak height velocity (PHV) and the latter around- and post-PHV. Sex has no major impact on resistance training related outcomes (e.g., maximal strength, 10 repetition maximum). In terms of plyometric training, around- PHV boys appear to respond with larger performance improvements (e.g., jump height, jump distance) compared with girls. Different types of resistance training (e.g., body weight, free weights) are effective in improving measures of muscle strength (e.g., maximum voluntary contraction) in untrained children and adolescents. Effects of plyometric training in untrained youth primarily follow the principle of training specificity. Despite the fact that only 6 out of 75 comparative studies investigated resistance or plyometric training in trained individuals, positive effects were reported in all 6 studies (e.g., maximum strength and vertical jump height, respectively).
Conclusions
The present review article identified research gaps (e.g., training descriptors, modern alternative training modalities) that should be addressed in future comparative studies.
... Investigating other outcomes may help to elucidate the potential influence of EO manipulation on RT-induced muscular adaptations, such as the training volume and load (25,27,32,42), and the anabolic hormonal response to RT (2,19,20,30). In regard to EO and its influence on these variables, the performance of MJ-to-SJ in comparison with the opposite order may confer higher total training volume (28,38,40) and acute anabolic hormonal concentrations (36,44). ...
... However, a greater VL was observed favoring MJ-SJ regardless of whether the exercise was MJ or SJ. Because 1RM strength gains may be greater when training is performed with a higher VL (42), and considering the MJ-SJ group presented higher VL in all exercises, this may help to explain the somewhat more pronounced ES differences in muscle strength favoring MJ-SJ. However, it remains questionable whether the higher VL achieved in MJ-SJ would have practical value to long-term strength development in our study's target population. ...
The purpose of the present study was to analyze the effects of resistance-training (RT) exercise order on muscle strength, hypertrophy, and anabolic hormones in older women. Forty-four older women were randomly assigned to one of three groups: a non-exercise control group (CON, n=15) and two RT groups that performed a 12-weeks RT program in a multi-joint to single-joint order (MJ-SJ, n=14), or in a single-joint to multi-joint order (SJ-MJ, n=15). The RT protocol (3x/week) encompassed eight exercises, with three sets of 10-15 repetitions performed per exercise. 1RM tests were used to evaluate muscle strength; DXA was used to estimate lean soft tissue. Both training groups showed significant and similar increases in muscle strength (MJ-SJ=16.4%; SJ-MJ=12.7%) and mass (MJ-SJ=7.5%; SJ-MJ=6.1%), whereas there were no significant changes in testosterone and IGF-1. The results suggest that both approaches are similarly effective in eliciting morphofunctional improvements in older women.
... Many studies have shown that gains in muscle strength and size can occur with the utilization of low loads [7][8][9][10] and even during nonorthodox resistance activities, like walking [11] and cycling [12]. These studies suggest that effort, and not external load or total work might be the key determinant to training adaptations [10,13]. ...
... Many studies have shown that gains in muscle strength and size can occur with the utilization of low loads [7][8][9][10] and even during nonorthodox resistance activities, like walking [11] and cycling [12]. These studies suggest that effort, and not external load or total work might be the key determinant to training adaptations [10,13]. One of the most pertinent results seemed to come from a recent study by Counts et al. [14]. ...
Objectives:
To explore the acute effects of training status, movement velocity, dominance, and visual feedback on muscle activation and rating of perceived exertion (RPE) during resistance training with no external load (no-load resistance training; NLRT).
Methods:
Thirty-three men (17 untrained and 16 trained), performed elbow flexions in four NLRT sessions: 1) slow velocity with EMG visual feedback, 2) slow velocity without EMG visual feedback, 3) fast velocity with EMG feedback, and 4) fast velocity without EMG feedback. RPE was measured using the Borg Discomfort scale. EMG for the biceps and triceps were recorded for both arms.
Results:
EMG feedback had no influence on RPE. The peak and mean EMG values were not different for the biceps (93.8±11.5% and 50±13.1%) and triceps (93.7±23.9% and 49.6±16.2%). The results revealed a difference in the training status, with higher peak EMG for untrained than for trained participants (96.9±20% vs. 90.2±15.6%). However the values for mean EMG were not different between the untrained and trained (50.3±15.7% vs. 49.2±13.7%) participants. There was no difference in the peak (92.8±19% vs. 94.7±20.4%) and mean (49.8±15.0% vs. 49.7±14.5%) EMG values for the dominant and non-dominant sides. Peak EMG values were not different between faster and slower velocities (93.6±19.6% and 93.9±17.8%). However, mean EMG was higher for slower (50.5±14.4%) than for faster (48.5±15.4%) velocities. The peak and mean EMG during contractions with (93.3±17.5% and 49.5±14.1%) and without visual feedback (94.2±19.9% and 50±15.4%) were not significantly different.
Conclusion:
NLRT produces high levels of muscle activation independent of training, status, dominance, movement velocity, and visual feedback.
... The total training load was represented by the total volume in each phase (n° repetitions X n° series X weight of the kettlebell) [35], the weight of the kettlebell relative to body mass (%BM), and the percentage of the maximum heart rate reached in the sessions (%HR max ). ...
Introdução: Apesar da prática de exercício ser benéfica para a saúde, mulheres apresentam níveis elevados de inatividade física. A falta de tempo e as respostas afetivas (RAs) negativas ao exercício podem ser barreiras à aderência aos programas de treinamento para essa população. Assim, é importante que estudos investiguem as RAs decorrentes de protocolos de exercício de curta duração. Nesse sentido, treinamento com kettlebell de alta intensidade pode ser uma alternativa interessante. Objetivo: O objetivo deste estudo foi caracterizar as RAs agudas e crônicas de mulheres jovens submetidas a um programa de treinamento com kettlebell de alta intensidade. Métodos: Onze voluntárias (idade = 25 ± 3 anos) participaram por 10 semanas de treinamento com kettlebell de alta intensidade (3x por semana). O programa foi aplicado utilizando um período de familiarização, seguidos por três fases utilizando os exercícios swing e agachamento. Resultados: Não foram observadas diferenças significativas quando comparadas as RAs obtidas antes da sessão com as medidas de 5,10 e 20 min após a sessão na fase aguda (p > 0,05). Ainda, não foram observadas diferenças significativas ao longo das 10 semanas de treinamento (Pré = 2,13 ± 0,26 / 5 min= 1,92 ± 0,42 / 10 min = 1,89 ± 0,43 / 20 min = 1,93 ± 0,44) (p > 0,05). Conclusão: O programa de treinamento com kettlebell de alta intensidade com aumento progressivo e individualizado de carga pode manter RAs positivas na fase aguda, e após 10 semanas de treino.
... A large number of studies exploring the effects of resistance training on muscular endurance have required subjects to perform sets to momentary failure or to an assigned number of RM. [14][15][16]23,25,33 Since subjects were not required to perform all sets to momentary failure in the present study, it is possible that the training stimuli varied between subjects and impacted on the results. Differences in the maximum number of repetitions performed at specific relative loads between trainers has previously been demonstrated. ...
Background:
A paucity of research exists examining whether resistance training with a greater number of sets per exercise enhances the development of muscular endurance. The aim of this study was to investigate the effects of ten sets versus five sets of resistance training on muscle endurance.
Methods:
Fifteen healthy males (age 23.7 ± 4.6 y) with at least 1 year resistance training experience were randomly assigned to 6 weeks of 10 sets (10-SET) or 5 sets (5-SET) of 10 repetitions at 60-80% one-repetition maximum (1RM) for specific compound resistance exercises with rest intervals between sets of 60-90 s and 60 s between exercises, performed 3 times per week. Relative muscle endurance test was assessed via maximal repetitions using 70% 1RM for the bench press, lat pulldown and leg press.
Results:
There was a significant increase in the number of repetitions to failure in the muscle endurance test for the leg press in 10-SET (40.9%, p = 0.04) and 5-SET (27.9%; p = 0.03), although no statistical differences between groups in the post-intervention results. Both groups increased volume-load in the muscle endurance test for the bench press (≥14.3%, p<0.05) and leg press (≥36.7%, p<0.05), but there were no statistical differences between groups in the post-intervention results.
Conclusions:
Findings suggest that performing 10 sets compared to 5 sets of resistance training does not enhance the development of relative muscle endurance. The volume-load accrued within an individual set rather than across sets may be of greater importance when targeting muscular endurance.
... Previous studies have compared the sex-specific differences in muscle form and function between children, adolescents, and adults (22,34,35,85,88,89,92,99,100), however, to our knowledge, no previous studies have examined these potential sex-specific adaptations over the course of growth and development in a longitudinal study design. Furthermore, numerous previous studies have studied the effects of resistance training on young males and females (4,17,25,26,31,36,37,76,83,103), however, to our knowledge no studies have examined the sexspecific, longitudinal adaptations of skeletal muscle to resistance training over the growth and development years. To better understand the sex-specific changes in muscle form and function during growth and development, longitudinal studies measuring muscle strength, size, and neuromuscular function, as well as adaptations to resistance training programs, across growth and development are warranted. . ...
The purpose of this study was to compare measurements of muscle strength, size, and neuromuscular function of the forearm flexors in pre- and post-pubescent males and females. Forty pre-pubescent (mean ± 95% confidence interval, age = 9.79 ± 0.35 yrs, n = 10 males, n = 10 females) and post-pubescent (age = 17.23 ± 0.58 yrs, n = 10 males, n = 10 females) participants completed this study. Biceps brachii muscle cross-sectional area (CSA) and muscle volume (MV) were quantified from ultrasound images. Participants completed maximal voluntary isometric contractions (MVICs) of the forearm flexors and extensors, and submaximal isometric step muscle actions at 30, 50, and 70% of the peak MVIC, as well as one absolute low-level torque step muscle action that equaled 5 Nm. Participants also completed isometric ramp muscle actions at a constant rate of torque increase (7.5 Nm∙s-1). Percent voluntary activation (VA) was quantified during the MVIC and submaximal isometric step muscle actions, while EMG amplitude and MMG amplitude were quantified during the isometric ramp muscle actions. MVIC strength was expressed in absolute terms and normalized to CSA and MV to examine the influence of muscle size on differences in strength between groups. The post-pubertal males were 130% stronger, had 78% greater CSA, 374% greater MV, and 17% greater maximal VA than the pre-pubertal males, while the post-pubertal females were 72% stronger, had 63% greater CSA, 270% greater MV, and 23% greater maximal VA than the pre-pubertal females. Normalizing MVIC strength to CSA and MV accounted for a greater proportion of the difference in strength between males than females. The collective responses for VA, EMG amplitude, and MMG amplitude across intensity reflected differences in muscle activation and motor unit recruitment strategies between pre- and post-pubertal males and females. These results suggest that muscle size may account for a greater proportion of the growth and development-related differences in strength among males, while females may be more affected by changes in muscle activation. However, regardless of sex, changes in muscle size and neuromuscular function occur during growth and development. Advisor: Joel T. Cramer
... Interestingly, in our study AAS users performed higher total training volumes than non-users. Whilst the association between increases in training volume and increases in muscle strength are controversial (Steele, Fisher, Assunção, Bottaro, & Gentil, 2017), the higher performance due to AAS use might help to explain our results. ...
The purpose of the present study was to compare the changes in anthropometric measures and muscle performance in users and non-users of androgenic anabolic steroids (AAS) performing resistance training (RT) programmes involving only multiple joint (MJ) exercises or a combination of MJ and single joint (SJ) exercises. Thirty recreational bodybuilders were divided into 4 groups: non-AAS users performing only MJ exercises (MJ), non-AAS users performing MJ + SJ (MJ + SJ), AAS users performing only MJ exercises (AAS − MJ) and AAS users performing MJ + SJ exercises (AAS − MJ + SJ). Before and after 8 weeks of training, the participants were tested for 10 repetition maximum (10RM) in different RT exercises. Flexed arm circumference (FAC), biceps and triceps skinfolds were measured. No interactions were found between time and the performance of SJ exercise in any variable (p > .05). However, there was a significant interaction between AAS use and time (p < .001), such that AAS users showed greater 10RM gains in all exercises, skinfold decreases and increases in FAC than non-users. In conclusion, our study shows that the addition of SJ exercises to MJ exercises brings no additional benefit in terms of muscle performance and anthropometric changes in trained men, either if they were using AAS or not. These results suggest that trained men can save time not including SJ in their routines and still achieve optimal results. Moreover, our results show that AAS use is associated with greater increases in muscle strength and FAC and greater reductions in biceps and triceps skinfold thickness.
... They reported increasing VOL-L as well as BLa and cortisol with decreasing training loads. In a further study, Steele, et al. 23 reported larger weekly VOL-L for a light-load group performing 2 sets of 12-15RM to momentary failure compared to a heavy-load group performing 3 sets of 4-6RM to momentary failure (LL = 1142.4 ± 341.8 kg, HL = 696.4 ...
Objective: A growing area of discourse within sports medicine and resistance training is that of periodization. This has been represented as variation in load and subsequently repetitions as well as volume, with a view to maximize strength and hypertrophy adaptations. A number of recent review articles have attempted to draw overarching conclusions from the present body of literature in an effort to provide definitive guidelines. However, there are numerous variables within resistance training that are often overlooked, and in the context of periodization, might significantly impact adaptation. Design & Methods: Narrative Review Results: The present piece confers need for clarity in terminology of effort rather than intensity, as well as discussing how variety of load might impact volume-load, discomfort, muscle damage and recovery. Furthermore, this article discusses often overlooked variables such as variety in exercise selection, detraining periods, and supervision, which are all evidenced to impact strength and hypertrophy adaptations. Conclusions: Our opinion is that without inclusion of these variables any guidelines surrounding periodization for strength or hypertrophy are limited in application. We conclude by highlighting areas for future research, as well as practical recommendations within this field.
... Related to the above points, a further limitation of the current body of literature is the relatively high number of researchers who did not incorporate a control group into their study design. Several studies [64][65][66][67] were excluded on the basis that they did not provide any control group data, fulfilling other inclusion criteria. This study design feature takes on added significance in interventions in youth given that rapid changes in maturation status can result in both increases or decreases in physical capabilities [68,69]. ...
Background: Resistance training is an effective way to enhance strength in female youth but, to date, no researcher has meta-analysed its effect on muscular strength in that population.
Objectives: This meta-analysis characterised female youths’ adaptability to resistance training (RT). A second objective was to highlight the limitations of the body of literature with a view to informing future research.
Data sources: Google Scholar, PubMed, Web of Science
Study eligibility criteria: Resistance training interventions in healthy females with a mean age between 8 and 18 years. Programmes of between 4 and 16 weeks duration that included a control group.
Study appraisal and synthesis methods: The inverse-variance random effects model for meta-analyses was used because it allocates a proportionate weight to trials based on the size of their individual standard errors and facilitates analysis whilst accounting for heterogeneity across studies. Effect sizes, calculated from a measure of muscular strength, are represented by the standardised mean difference and are presented alongside 95% confidence intervals.
Results: The magnitude of the main effect was ‘small’ (0.54, 95% confidence interval: 0.23, 0.85). Effect sizes were larger in older (> 15 yrs; ES = 0.72 [0.23, 1.21] vs. 0.38 [-0.02, 0.79]), taller (>163cm; ES = 0.67 [0.20, 1.13] vs. 0.55 [0.08, 1.02]) and heavier (<54kg; ES = 0.67 [0.30, 1.03] vs. 0.53 [-0.00, 1.06]) participants.
Conclusions and implications of key findings: Resistance training is effective in female youth. These findings can be used to inform the prescription of RT in female youth.
... A equação: (nº de séries x nº de repetições x carga) foi utilizada para quantificar o VT para cada exercício. O trabalho total (TT) foi calculado como o somatório das repetições no decorrer das quatro séries para cada exercício 19 . ...
Introdução: O método pareado agonista-antagonista (PAA) consiste em estimular previamente a musculatura antagonista do grupo muscular que se deseja otimizar, aumentando a ativação neural e força dos músculos agonistas. Objetivo: Comparar o método tradicional vs PAA sobre o trabalho total (TT) e volume de treinamento (VT) no exercício cadeira extensora (CE). Métodos: Doze mulheres treinadas realizaram dois protocolos experimentais randomizados: método tradicional - quatro séries da CE até a falha concêntrica; método PAA: quatro séries de mesa flexora (MF) + CE até a falha concêntrica. Foi dado um intervalo de 30 segundos entre os dois exercícios. Resultados: Pôde-se observar diferença significativa tanto no TT como VT, para o método PAA quando comparado ao tradicional. Conclusão: Sugere-se assim que o método PAA apresenta-se como melhor estratégia para otimização do desempenho de repetições máximas se comparado ao método tradicional, além de apresentar possibilidade de redução no tempo despendido para o treinamento.
... 9,10 Indeed, success in the bench press is determined by optimising the kinematics of the lift where not only can the shortest bar path be achieved in order to be biomechanically efficient 11 , but also economical in terms of neuromuscular effort 12 . Further, practising such a skill at high volumes may help to further facilitate adaptation 10,13 . ...
Objective: To examine whether using the Slingshot will enable participants to perform a greater volume-load during bench press repetitions with a maximal load and increase set volume-load compared to an unaided condition. Summary of Background Data: Literature suggests that increased volume-loads during training may aid in improving strength, and further maximises mechanical tension and metabolic stress potentially leading to increased hypertrophy. It has been suggested that a new piece of equipment, called the Slingshot could be used in training to improve performance in the bench press by enabling individuals to increase their training volume whilst using maximal loads. Method: Nine trained male participants volunteered to participate. Each participant performed a bench press one repetition maximum (1RM) test before completing repetitions to momentary failure using the Slingshot one week later. Volume-load for each condition was calculated as repetitions (n) x load (kg). Results: A paired samples t-Test comparing between conditions revealed a significant difference (p < 0.001) between volume loads performed unaided (96.1±14.6 kg) and with the Slingshot (350±103.7 kg). Conclusion: Using the slingshot in training does allow individuals to perform greater volume-loads with a maximal load; however longitudinal research must be conducted to ascertain the magnitude of any potential benefit from using it.
... The greater magnitude improvements in power measures with power vs. strength training corresponds with the training specificity principle (Sale and MacDougall, 1981;Behm, 1988Behm, , 1995Behm and Sale, 1993). Training specificity dictates that training adaptations are greater when the training mode, (Hettinger, 1958;Funato et al., 1986;Sewall and Micheli, 1986;Weltman et al., 1986;Blimkie, 1989;Ozmun et al., 1994;DeRenne et al., 1996;Gorostiaga et al., 1999;Sadres et al., 2001;Flanagan et al., 2002;Pikosky et al., 2002;Tsolakis et al., 2004;Drinkwater et al., 2005;Benson et al., 2007;Faigenbaum et al., 2007aFaigenbaum et al., , 2014Faigenbaum et al., , 2015Channell and Barfield, 2008;Rhea et al., 2008;Teng et al., 2008;Chelly et al., 2009;Dorgo et al., 2009;Lubans et al., 2010;Velez et al., 2010;Wong et al., 2010;Ebada, 2011;Granacher et al., 2011aGranacher et al., ,b, 2014Granacher et al., , 2015Ignjatovic et al., 2011;Muehlbauer et al., 2012;Santos and Janeira, 2012;Moore et al., 2013;Moraes et al., 2013;Sander et al., 2013;Coskun and Sahin, 2014;Ferrete et al., 2014;Pesta et al., 2014;Piazza et al., 2014;Dalamitros et al., 2015;Gonzalez-Badillo et al., 2015;dos Santos Cunha et al., 2015;Sarabia et al., 2015;Tran et al., 2015;Eather et al., 2016;Harries et al., 2016;Lloyd et al., 2016;Negra et al., 2016;Prieske et al., 2016;Rodriguez-Rosell et al., 2016;Contreras et al., 2017;Steele et al., 2017;Weakley et al., 2017). Step up 65.5 7.6 76. (Hewett et al., 1996;Cossor et al., 1999;Witzke and Snow, 2000;Diallo et al., 2001;Matavulj et al., 2001;Martel et al., 2005;Szymanski et al., 2007;Meylan and Malatesta, 2009;Thomas et al., 2009;Buchheit et al., 2010;King and Cipriani, 2010;Potdevin et al., 2011;Santos and Janeira, 2011;Lloyd et al., 2012;Noyes et al., 2012Noyes et al., , 2013Marques et al., 2013;Michailidis et al., 2013;Ramirez-Campillo et al., 2013, 2015aMarta et al., 2014;Piazza et al., 2014;Sohnlein et al., 2014;Attene et al., 2015;Chelly et al., 2015;Pereira et al., 2015;Alves et al., 2016;Arabatzi, 2016;Borges et al., 2016;de Hoyo et al., 2016;Fernandez-Fernandez et al., 2016;Hall et al., 2016;McCormick et al., 2016;Moran et al., 2016;Rosas et al., 2016). ...
Numerous national associations and multiple reviews have documented the safety
and efficacy of strength training for children and adolescents. The literature highlights
the significant training-induced increases in strength associated with youth strength
training. However, the effectiveness of youth strength training programs to improve
power measures is not as clear. This discrepancy may be related to training and
testing specificity.Most prior youth strength training programs emphasized lower intensity
resistance with relatively slow movements. Since power activities typically involve higher
intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics),
there is a conflict between the training medium and testing measures. This meta-analysis
compared strength (e.g., training with resistance or body mass) and power training
programs (e.g., plyometric training) on proxies of muscle strength, power, and speed.
A systematic literature search using a Boolean Search Strategy was conducted in the
electronic databases PubMed, SPORT Discus,Web of Science, and Google Scholar and
revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for
inclusion in this systematic review and meta-analysis. The meta-analysis showed small to
moderate magnitude changes for training specificity with jump measures. In other words,
power training was more effective than strength training for improving youth jump height.
For sprint measures, strength training was more effective than power training with youth.
Furthermore, strength training exhibited consistently large magnitude changes to lower
body strength measures, which contrasted with the generally trivial, small and moderate
magnitude training improvements of power training upon lower body strength, sprint
and jump measures, respectively. Maturity related inadequacies in eccentric strength
and balance might influence the lack of training specificity with the unilateral landings
and propulsions associated with sprinting. Based on this meta-analysis, strength training
should be incorporated prior to power training in order to establish an adequate
foundation of strength for power training activities.
The effect of resistance training with higher- and lower-loads on muscle mass and strength has been extensively studied while changes in muscle endurance have received less attention. This trial aimed to assess the effect of training load on absolute (AME) and relative muscle endurance (RME). Sixteen untrained women (22.7±3.3 yr: mean ± SD) had one arm and leg randomly assigned to train with higher-loads (HL; 80-90% 1RM), and the contralateral limbs trained with lower-loads (LL; 30-50% 1RM) thrice weekly to volitional fatigue for 10 weeks. Heavy and light load AME and RME, strength, and muscle mass were assessed pre- and post-training. Strength increased more in the HL compared to LL leg (P = <0.01), but similar increases in strength were observed between upper body conditions (P = 0.46). Lower body heavy and light load AME improved in both conditions, but HL training induced a larger improvement in heavy load AME (HL, 9.3±4.3, vs. LL, 7.5±7.1 repetitions, Time × Limb P < 0.01) and LL training induced a larger improvement in light load AME (LL, 24.7±22.2, vs. HL, 15.2±16.7 repetitions, Time × Limb P = 0.04). In the upper body, HL and LL training induced similar increases in both heavy (Time × Limb P = 0.99), and light load (Time × Limb P = 0.16) AME. Dual-energy x-ray absorptiometry showed no change in leg fat-and-bone-free mass (FBFM) for either condition, and an increase in only LL arm FBFM. AME improved in a manner specific to the training loads used. ClinicalTrials.gov (NCT04547972).
Background:
Excessive gag reflex could be problematic for adequate dental care. Although various factors may increase the susceptibility to gagging, its contributing factors have not been fully determined.
Objective:
This study aimed to determine whether gag reflex was associated with tactile sensitivity and psychological characteristics.
Methods:
15 volunteers of healthy males and females each were recruited for this study. After completing a questionnaire describing the self-perceived gag reflex activity, a disposable saliva ejector was inserted along the palate into the mouth until gagging was evoked. The ratio of the insertion depth to the palatal length was used as an index for the gagging threshold. The two-point discrimination (TPD) and Semmes-Weinstein monofilament (SWM) tests were performed to assess the tactile sensitivity of the palatal regions (hard palate, anterior and posterior soft palate). The Symptom Checklist-90-Revised was used to investigate the relationship between the gagging threshold and the psychological status.
Results:
Our findings showed that the gagging threshold had a significant positive correlation with the TPD and SWM thresholds on the hard palate. The psychological profiles of psychoticism and hostility score were also significantly correlated with the gagging threshold. However, there were no significant differences in the tactile and gagging thresholds, as well as the psychological profiles, between males and females.
Conclusion:
Our results suggested that the tactile sensitivity of the anterior palate is a determining factor for the gagging threshold and implied that the initial response of the oral entry site to stimulation may lead to the development of gag reflex.
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.
Muscle strength is often measured through the performance of a one-repetition maximum (1RM). However, we that feel a true measurement of ‘strength’ remains elusive. For example, low-load alternatives to traditional resistance training result in muscle hypertrophic changes similar to those resulting from traditional high-load resistance training, with less robust changes observed with maximal strength measured by the 1RM. However, when strength is measured using a test to which both groups are ‘naive’, differences in strength become less apparent. We suggest that the 1RM is a specific skill, which will improve most when training incorporates its practice or when a lift is completed at a near-maximal load. Thus, if we only recognize increases in the 1RM as indicative of strength, we will overlook many effective and diverse alternatives to traditional high-load resistance training. We wish to suggest that multiple measurements of strength assessment be utilized in order to capture a more complete picture of the adaptation to resistance training.
Background:
It has been hypothesized that the ability to increase volume load (VL) via a progressive increase in the magnitude of load for a given exercise within a given repetition range could enhance the adaptive response to resistance training.
Objectives:
The purpose of this study was to compare changes in volume load (VL) over eight weeks of resistance training (RT) in high-versus low-load protocols.
Materials and methods:
Eighteen well-trained men were matched according to baseline strength were randomly assigned to either a low-load RT (LOW, n = 9) where 25 - 35 repetitions were performed per exercise, or a high-load RT (HIGH, n = 9) where 8 - 12 repetitions were performed per exercise. Both groups performed three sets of seven exercises for all major muscles three times per week on non-consecutive days.
Results:
After adjusting for the pre-test scores, there was a significant difference between the two intervention groups on post-intervention total VL with a very large effect size (F (1, 15) = 16.598, P = .001, ηp(2) = .525). There was a significant relationship between pre-intervention and post-intervention total VL (F (1, 15) = 32.048, P < .0001, ηp(2) = .681) in which the pre-test scores explained 68% of the variance in the post-test scores.
Conclusions:
This study indicates that low-load RT results in greater accumulations in VL compared to high-load RT over the course of 8 weeks of training.
Resistance training (RT) offers benefits to both men and women. However, the studies about the differences between men and women in response to an RT program are not conclusive and few data are available about upper body strength response. The aim of this study was to compare elbow flexor strength gains in men and women after 10 weeks of RT. Forty-four college-aged men (22.63 ± 2.34 years) and forty-seven college-aged women (21.62 ± 2.96 years) participated in the study. The RT program was performed two days a week for 10 weeks. Before and after the training period, peak torque (PT) of the elbow flexors was measured with an isokinetic dynamometer. PT values were higher in men in comparison to women in pre- and post-tests (
p
< 0.01). Both males and females significantly increased elbow flexor strength (
p
< 0.05); however, strength changes did not differ between genders after 10 weeks of RT program (11.61 and 11.76% for men and women, respectively;
p
> 0.05). Effect sizes were 0.57 and 0.56 for men and women, respectively. In conclusion, the present study suggests that men and women have a similar upper body strength response to RT.
EMERGING EVIDENCE SUGGESTS THAT TYPE I FIBERS DISPLAY A SUBSTANTIAL PROPENSITY FOR GROWTH IF THEY ARE SELECTIVELY TARGETED VIA LOW-LOAD TRAINING. THE PURPOSE OF THIS ARTICLE WILL BE TO REVIEW THE RESEARCH REGARDING FIBER TYPE-SPECIFIC HYPERTROPHY AND DRAW EVIDENCE-BASED CONCLUSIONS AS TO THEIR IMPLICATIONS FOR PROGRAM DESIGN. Copyright © National Strength and Conditioning Association.
The purpose of this study was to compare early muscular fitness adaptations in children in response to low repetition maximum (LRM) and high repetition maximum (HRM) resistance training. Twenty-three girls and 20 boys between the ages of 8.0 and 12.3 years (mean age 10.6 ± 1.3 years) volunteered to participate in this study. Children performed one set of 6 to 10 RM ( n = 12) or one set of 15 to 20 RM ( n = 19) on child-size exercise machines twice weekly over 8 weeks. Children in the control group ( n = 12) did not resistance train. Maximum strength (1 RM) on the chest press, local muscular endurance (15 RM) on the leg press, long jump, vertical jump, and v-sit flexibility were assessed at baseline and posttraining. The LRM and HRM groups made significantly greater gains in 1-RM strength (21% and 23%, respectively) as compared with the control group (1%). Only the HRM group made significantly greater gains in 15-RM local muscular endurance (42%) and flexibility (15%) than that recorded in the control group (4% and 5%, respectively). If children perform one set per exercise as part of an introductory resistance training program, these findings favor the prescription of a higher RM training range.
This investigation examined peak motor unit activity during sets which differed in resistance (50, 70, or 90% 1-Repetition Maximum (1RM)). Ten resistance trained men (age, 23±3 yr; height, 187±7 cm; body mass, 91.5±6.9 kg; squat 1RM, 141±28 kg) were assessed by electromyography (EMG) on the vastus lateralis and vastus medialis muscles in a randomized, within-subject design experiment consisting of two test visits: a drop set day and a single set day using only the 50% of 1 RM intensity performed to failure. At the start of each day, subjects performed two submaximal repetition sets (50% 1RM X 10 repetitions and 70% 1RM X 7 repetitions). On the drop set day, subjects performed three consecutive maximal repetition sets at 90%, 70%, and 50% 1RM to failure with no rest periods in between. On the single set day, subjects performed a maximal repetition set at 50% 1RM to failure. Overall, the maximal repetition sets to failure at 50% and 70% 1RM resulted in higher peak EMG amplitude than during submaximal repetition sets with the same resistance. However, peak EMG amplitude was significantly (P ≤ 0.05) greater in the maximal 90% 1RM set than all other sets performed. When sets were performed to failure, ratings of perceived exertion (CR-10) did not differ over the intensity range of loads and suggests a perception is not capable of accurately detecting the actual amounts of motor unit recruitment. The results of this investigation indicate that using higher external resistance is a more effective means of increasing motor unit activity than increasing the number of repetitions performed with lighter weights even when the end point is muscular failure. Accordingly, previous recommendations for the use of heavier loads during resistance training programs to stimulate the maximal development of strength and hypertrophy are further supported.
No abstract.
Copyright © 2015, Journal of Applied Physiology.
The purpose of this study was to investigate electromyographic amplitude (EMG AMP), EMG mean power frequency (MPF), exercise volume (VOL), total work and muscle activation (iEMG), and time under concentric load (TUCL) during, and muscle cross-sectional area (mCSA) before and after 3 sets to failure at 80 vs. 30 % 1RM resistance exercise.
Nine men (mean ± SD, age 21.0 ± 2.4 years, resistance training week(-1) 6.0 ± 3.7 h) and 9 women (age 22.8 ± 3.8 years, resistance training week(-1) 3.4 ± 3.5 h) completed 1RM testing, followed by 2 experimental sessions during which they completed 3 sets to failure of leg extension exercise at 80 or 30 % 1RM. EMG signals were collected to quantify EMG AMP and MPF during the initial, middle, and last repetition of each set. Ultrasound was used to assess mCSA pre- and post-exercise, and VOL, total work, iEMG, and TUCL were calculated.
EMG AMP remained greater at 80 % than 30 % 1RM across all reps and sets, despite increasing 74 and 147 % across reps at 80 and 30 % 1RM, respectively. EMG MPF decreased across reps at 80 and 30 % 1RM, but decreased more and was lower for the last reps at 30 than 80 % 1RM (71.6 vs. 78.1 % MVIC). mCSA increased more from pre- to post-exercise for 30 % (20.2-24.1 cm(2)) than 80 % 1RM (20.3-22.8 cm(2)). VOL, total work, iEMG and TUCL were greater for 30 % than 80 % 1RM.
Muscle activation was greater at 80 % 1RM. However, differences in volume, metabolic byproduct accumulation, and muscle swelling may help explain the unexpected adaptations in hypertrophy vs. strength observed in previous studies.
The purpose of this study was to compare the effect of low- versus high-load resistance training (RT) on muscular adaptations in well-trained subjects. Eighteen young men experienced in RT were matched according to baseline strength, and then randomly assigned to 1 of 2 experimental groups: a low-load RT routine (LL) where 25-35 repetitions were performed per set per exercise (n = 9), or a high-load RT routine (HL) where 8-12 repetitions were performed per set per exercise (n = 9). During each session, subjects in both groups performed 3 sets of 7 different exercises representing all major muscles. Training was carried out 3 times per week on non-consecutive days, for 8 total weeks. Both HL and LL conditions produced significant increases in thickness of the elbow flexors (5.3 vs. 8.6%, respectively), elbow extensors (6.0 vs. 5.2%, respectively), and quadriceps femoris (9.3 vs. 9.5%, respectively), with no significant differences noted between groups. Improvements in back squat strength were significantly greater for HL compared to LL (19.6 vs. 8.8%, respectively) and there was a trend for greater increases in 1RM bench press (6.5 vs. 2.0%, respectively). Upper body muscle endurance (assessed by the bench press at 50% 1RM to failure) improved to a greater extent in LL compared to HL (16.6% vs. -1.2%, respectively). These findings indicate that both HL and LL training to failure can elicit significant increases in muscle hypertrophy among well-trained young men; however, HL training is superior for maximizing strength adaptations.
Purpose:
This study investigates the impact of two different intensities and different volumes of low-load resistance training (LLRT) with and without blood flow restriction on the adaptation of muscle strength and size.
Methods:
The sample was divided into five groups: one set of 20 % of one repetition maximum (1RM), three sets of 20 % of 1RM, one set of 50 % of 1RM, three sets of 50 % of 1RM, or control. LLRT was performed with (OC) or without (NOC) vascular occlusion, which was selected randomly for each subject. The maximal muscle strength (leg extension; 1RM) and the cross-sectional area (quadriceps; CSA) were assessed at baseline and after 8 weeks of LLRT.
Results:
1RM performance was increased in both groups after 8 weeks of training: OC (1 × 50 % = 20.6 %; 3 × 50 % = 20.9 %; 1 × 20 % = 26.6 %; 3 × 20 % = 21.6 %) and NOC (1 × 50 % = 18.6 %; 3 × 50 % = 26.8 %; 1 × 20 % = 18.5 %; 3 × 20 % = 21.6 %; 3 × 20 % = 24.7 %) compared with the control group (−1.7 %). Additionally, the CSA was increased in both groups: OC (1 × 50 % = 2.4 %; 3 × 50 % = 3.8 %; 1 × 20 % = 4.6 %; 3 × 20 % = 4.8 %) and NOC (1 × 50 % = 2.4 %; 3 × 50 % = 1.5 %; 1 × 20 % = 4.3 %; 3 × 20 % = 3.8 %) compared with the control group (−0.7 %). There were no significant differences between the OC and NOC groups.
Conclusion:
We conclude that 8 weeks of LLRT until failure in novice young lifters, regardless of occlusion, load or volume, produces similar magnitudes of muscular hypertrophy and strength.
Abstract There has been much debate as to optimal loading strategies for maximising the adaptive response to resistance exercise. The purpose of this paper therefore was to conduct a meta-analysis of randomised controlled trials to compare the effects of low-load (≤60% 1 repetition maximum [RM]) versus high-load (≥65% 1 RM) training in enhancing post-exercise muscular adaptations. The strength analysis comprised 251 subjects and 32 effect sizes (ESs), nested within 20 treatment groups and 9 studies. The hypertrophy analysis comprised 191 subjects and 34 ESs, nested with 17 treatment groups and 8 studies. There was a trend for strength outcomes to be greater with high loads compared to low loads (difference = 1.07 ± 0.60; CI: -0.18, 2.32; p = 0.09). The mean ES for low loads was 1.23 ± 0.43 (CI: 0.32, 2.13). The mean ES for high loads was 2.30 ± 0.43 (CI: 1.41, 3.19). There was a trend for hypertrophy outcomes to be greater with high loads compared to low loads (difference = 0.43 ± 0.24; CI: -0.05, 0.92; p = 0.076). The mean ES for low loads was 0.39 ± 0.17 (CI: 0.05, 0.73). The mean ES for high loads was 0.82 ± 0.17 (CI: 0.49, 1.16). In conclusion, training with loads ≤50% 1 RM was found to promote substantial increases in muscle strength and hypertrophy in untrained individuals, but a trend was noted for superiority of heavy loading with respect to these outcome measures with null findings likely attributed to a relatively small number of studies on the topic.
Purpose
It has been hypothesized that lifting light loads to muscular failure will activate the full spectrum of MUs and thus bring about muscular adaptations similar to high-load training. The purpose of this study was to investigate EMG activity during low- versus high-load training during performance of a multi-joint exercise by well-trained subjects.
Methods
Employing a within-subject design, 10 young, resistance-trained men performed sets of the leg press at different intensities of load: a high-load (HL) set at 75 % of 1-RM and a low-load (LL) set at 30 % of 1-RM. The order of performance of the exercises was counterbalanced between participants, so that half of the subjects performed LL first and the other half performed HL first, separated by 15 min rest. Surface electromyography (EMG) was used to assess mean and peak muscle activation of the vastus medialis, vastus lateralis, rectus femoris, and biceps femoris.
Results
Significant main effects for trials and muscles were found (p
Objective: There is considerable interest in attaining muscular hypertrophy in recreational gym-goers, bodybuilders, older adults, and persons suffering from immunodeficiency conditions. Multiple review articles have suggested guidelines for the most efficacious training methods to obtain muscular hypertrophy. Unfortunately these included articles that inferred hypertrophy markers such as hormonal measurements, used older techniques that might not be valid (e.g. circumference) and failed to appropriately consider the complexity of training variables.
Methods: The present commentary provides a narrative review of literature, summarising main areas of interest and providing evidence-based guidelines towards training for muscular hypertrophy.
Conclusions: Evidence supports that persons should train to the highest intensity of effort, thus recruiting as many motor units and muscle fibres as possible, self-selecting a load and repetition range, and performing single sets for each exercise. No specific resistance type appears more advantageous than another, and persons should consider the inclusion of concentric, eccentric and isometric actions within their training regime, at a repetition duration that maintains muscular tension. Between set/exercise rest intervals appear not to affect hypertrophy, and in addition the evidence suggests that training through a limited range of motion might stimulate similar results to full range of motion exercise. The performance of concurrent endurance training appears not to negatively affect hypertrophy, and persons should be advised not to expect uniform muscle growth both along the belly of a muscle or for individual muscles within a group. Finally evidence suggests that short (~3 weeks) periods of detraining in trained persons does not incur significant muscular atrophy and might stimulate greater hypertrophy upon return to training.
Key words: muscular size, bodybuilding, intensity, genetics, concurrent, endurance
The current manuscript is a translation of the Position statement on youth resistance training: the 2014 International Consensus. The original manuscript was adapted from the oficial position statement of the UK Strength and Conditioning Association on youth resistance training. It was subsequently reviewed and endorsed by leading professional organisations within the fields of sports medicine, exercise science and paediatrics. The authorship team for this article was selected from the fields of paediatric exercise science, paediatric medicine, physical education, strength and conditioning and sports medicine.
Training attendance is an important variable for attaining optimal results after a resistance training (RT) program, however, the association of attendance with the gains of muscle strength is not well defined. Therefore, the purpose of the present study is to verify if attendance would affect muscle strength gains in healthy young males.
Ninety two young males with no previous RT experience volunteered to participate in the study. RT was performed 2 days a week for 11 weeks. One repetition maximum (1RM) in the bench press and knee extensors peak torque (PT) were measured before and after the training period. After the training period, a two step cluster analysis was used to classify the participants in accordance to training attendance, resulting in three groups, defined as high (92 to 100%), intermediate (80 to 91%) and low (60 to 79%) training attendance.
According to the results, there were no significant correlations between strength gains and training attendance, however, when attendance groups were compared, the low training attendance group showed lower increases in 1RM bench press (8.8%) than the other two groups (17.6% and 18.0% for high and intermediate attendance, respectively).
Although there is not a direct correlation between training attendance and muscle strength gains, it is suggested that a minimum attendance of 80% is necessary to ensure optimal gains in upper body strength.
Recently in BJSM, Dr Berkoff1 highlighted some ‘hot topics’ in sports and exercise medicine. A variety of topics were covered, all of which were ‘hot’. Of particular interest, however, was the fact that Dr Berkoff preceded his article with a definition of ‘hot’. Within sports and exercise medicine, and indeed in all scientific disciplines, definitions are of great importance. In fact, “The primary advantage of operational definitions lies in the unification of science and the resolution of controversy.”2 It is the definition and use of a term within a topic that might also be deemed as ‘hot’ that this editorial attempts to address: Intensity in resistance training (RT). Recent publications regarding RT have attempted to offer clarification on the definition of intensity.3 ,4 Fisher and Smith3 wrote regarding the use of the term intensity within RT suggesting that it is better representative of effort, whereas other authors have considered it synonymous with load.4 Fisher and Smith2 are not the first to suggest that the use of intensity to refer to load in RT is inappropriate. Others have previously attempted to instigate a change in the language used by researchers and practitioners.5 ,6 Despite previously finding myself supporting this view (that intensity is better defined as effort and not load) regarding the use of the term and having published as such,6 ,7 further consideration has left me doubting the value of both interpretation of intensity as synonymous with load or effort. Thus, this editorial seeks to ask the readers of BJSM, and the wider community involved in RT, to consider the use of the term intensity as it stands and whether both sides of the disagreement are defending inappropriate idioms. More specifically, however, it …
To explore the extent to which muscular strength in adolescence is associated with all cause and cause specific premature mortality (<55 years).
Prospective cohort study.
Sweden.
1 142 599 Swedish male adolescents aged 16-19 years were followed over a period of 24 years.
Baseline examinations included knee extension, handgrip, and elbow flexion strength tests, as well as measures of diastolic and systolic blood pressure and body mass index. Cox regression was used to estimate hazard ratios for mortality according to muscular strength categories (tenths).
During a median follow-up period of 24 years, 26 145 participants died. Suicide was a more frequent cause of death in young adulthood (22.3%) than was cardiovascular diseases (7.8%) or cancer (14.9%). High muscular strength in adolescence, as assessed by knee extension and handgrip tests, was associated with a 20-35% lower risk of premature mortality due to any cause or cardiovascular disease, independently of body mass index or blood pressure; no association was observed with mortality due to cancer. Stronger adolescents had a 20-30% lower risk of death from suicide and were 15-65% less likely to have any psychiatric diagnosis (such as schizophrenia and mood disorders). Adolescents in the lowest tenth of muscular strength showed by far the highest risk of mortality for different causes. All cause mortality rates (per 100 000 person years) ranged between 122.3 and 86.9 for the weakest and strongest adolescents; corresponding figures were 9.5 and 5.6 for mortality due to cardiovascular diseases and 24.6 and 16.9 for mortality due to suicide.
Low muscular strength in adolescents is an emerging risk factor for major causes of death in young adulthood, such as suicide and cardiovascular diseases. The effect size observed for all cause mortality was equivalent to that for well established risk factors such as elevated body mass index or blood pressure.
ACSM Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Adults. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 975-991, 1998. The combination of frequency, intensity, and duration of chronic exercise has been found to be effective for producing a training effect. The interaction of these factors provide the overload stimulus. In general, the lower the stimulus the lower the training effect, and the greater the stimulus the greater the effect. As a result of specificity of training and the need for maintaining muscular strength and endurance, and flexibility of the major muscle groups, a well-rounded training program including aerobic and resistance training, and flexibility exercises is recommended. Although age in itself is not a limiting factor to exercise training, a more gradual approach in applying the prescription at older ages seems prudent. It has also been shown that aerobic endurance training of fewer than 2 d·wk-1, at less than 40-50% of V˙O2R, and for less than 10 min-1 is generally not a sufficient stimulus for developing and maintaining fitness in healthy adults. Even so, many health benefits from physical activity can be achieved at lower intensities of exercise if frequency and duration of training are increased appropriately. In this regard, physical activity can be accumulated through the day in shorter bouts of 10-min durations.
In the interpretation of this position stand, it must be recognized that the recommendations should be used in the context of participant's needs, goals, and initial abilities. In this regard, a sliding scale as to the amount of time allotted and intensity of effort should be carefully gauged for the cardiorespiratory, muscular strength and endurance, and flexibility components of the program. An appropriate warm-up and cool-down period, which would include flexibility exercises, is also recommended. The important factor is to design a program for the individual to provide the proper amount of physical activity to attain maximal benefit at the lowest risk. Emphasis should be placed on factors that result in permanent lifestyle change and encourage a lifetime of physical activity.
Resistance training produces an array of health benefits, as well as the potential to promote muscular adaptations of strength, size, power and endurance. The American College of Sports Medicine (ACSM) regularly publish a position stand making recommendations for optimal achievement of the desired training goals. However, the most recent position stand (as well as previous ones) has come under heavy criticism for misrepresentation of research, lack of evidence and author bias. Therefore this paper proposes a set of scientifically rigorous resistance training guidelines, reviewing and summarising the relevant research for the purpose of proposing more logical, evidence-based training advice. We recommend that appreciably the same muscular strength and endurance adaptations can be attained by perform-ing a single set of ~8-12 repetitions to momentary muscular failure, at a repetition duration that maintains muscular tension throughout the entire range of motion, for most major muscle groups once or twice each week. All resistance types (e.g. free-weights, resistance machines, bodyweight, etc.) show potential for increases in strength, with no significant difference between them, although resistance machines appear to pose a lower risk of injury. There is a lack of evidence to suggest that balance from free weights or use of unstable surfaces shows any transfer-ence to sporting improvement, and explosive movements are also not recommended as they present a high injury risk and no greater benefit than slow, controlled weight training. Finally, we consider genetic factors in relation to body type and growth potential.
We have reported that the acute postexercise increases in muscle protein synthesis rates, with differing nutritional support, are predictive of longer-term training-induced muscle hypertrophy. Here, we aimed to test whether the same was true with acute exercise-mediated changes in muscle protein synthesis. Eighteen men (21 ± 1 yr, 22.6 ± 2.1 kg/m(2); means ± SE) had their legs randomly assigned to two of three training conditions that differed in contraction intensity [% of maximal strength (1 repetition maximum)] or contraction volume (1 or 3 sets of repetitions): 30%-3, 80%-1, and 80%-3. Subjects trained each leg with their assigned regime for a period of 10 wk, 3 times/wk. We made pre- and posttraining measures of strength, muscle volume by magnetic resonance (MR) scans, as well as pre- and posttraining biopsies of the vastus lateralis, and a single postexercise (1 h) biopsy following the first bout of exercise, to measure signaling proteins. Training-induced increases in MR-measured muscle volume were significant (P < 0.01), with no difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3= 7.2 ± 1.9%, P = 0.18. Isotonic maximal strength gains were not different between 80%-1 and 80%-3, but were greater than 30%-3 (P = 0.04), whereas training-induced isometric strength gains were significant but not different between conditions (P = 0.92). Biopsies taken 1 h following the initial resistance exercise bout showed increased phosphorylation (P < 0.05) of p70S6K only in the 80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.
Children differ from adults in many muscular performance attributes such as size-normalized strength and power, endurance, fatigability and the recovery from exhaustive exercise, to name just a few. Metabolic attributes, such as glycolytic capacity, substrate utilization, and VO2 kinetics also differ markedly between children and adults. Various factors, such as dimensionality, intramuscular synchronization, agonist-antagonist coactivation, level of volitional activation, or muscle composition, can explain some, but not all of the observed differences. It is hypothesized that, compared with adults, children are substantially less capable of recruiting or fully employing their higher-threshold, type-II motor units. The review presents and evaluates the wealth of information and possible alternative factors in explaining the observations. Although conclusive evidence is still lacking, only this hypothesis of differential motor-unit activation in children and adults, appears capable of accounting for all observed child-adult differences, whether on its own or in conjunction with other factors.
The aim of this study was to evaluate the effects of integrative neuromuscular training (INT) during physical education (PE) class on selected measures of health- and skill-related fitness in children. Forty children from two 2nd grade PE classes were cluster randomized into either an INT group (n = 21) or a control (CON) group (n = 19). INT was performed 2×/wk during the first ~15 min of each PE class and consisted of body weight exercises. INT and CON participants were assessed for health- and skill-related fitness before and after 8 wks of PE with or without INT, respectively. A significant interaction of group by time was observed in INT participants with improvements noted in push-ups, curl-ups, long jump, single leg hop, and 0.5 mile (0.8 km) run performance (p < .05). These data indicate that INT is an effective and time-efficient addition to PE as evidenced by improvements in health- and skill-related fitness measures in children.
One possible reason for the continued neglect of statistical power analysis in research in the behavioral sciences is the inaccessibility of or difficulty with the standard material. A convenient, although not comprehensive, presentation of required sample sizes is provided. Effect-size indexes and conventional values for these are given for operationally defined small, medium, and large effects. The sample sizes necessary for .80 power to detect effects at these levels are tabled for 8 standard statistical tests: (1) the difference between independent means, (2) the significance of a product-moment correlation, (3) the difference between independent rs, (4) the sign test, (5) the difference between independent proportions, (6) chi-square tests for goodness of fit and contingency tables, (7) 1-way analysis of variance (ANOVA), and (8) the significance of a multiple or multiple partial correlation.
The quest to increase lean body mass is widely pursued by those who lift weights. Research is lacking, however, as to the best approach for maximizing exercise-induced muscle growth. Bodybuilders generally train with moderate loads and fairly short rest intervals that induce high amounts of metabolic stress. Powerlifters, on the other hand, routinely train with high-intensity loads and lengthy rest periods between sets. Although both groups are known to display impressive muscularity, it is not clear which method is superior for hypertrophic gains. It has been shown that many factors mediate the hypertrophic process and that mechanical tension, muscle damage, and metabolic stress all can play a role in exercise-induced muscle growth. Therefore, the purpose of this paper is twofold: (a) to extensively review the literature as to the mechanisms of muscle hypertrophy and their application to exercise training and (b) to draw conclusions from the research as to the optimal protocol for maximizing muscle growth.
A literature review was employed to evaluate the current epidemiology of injury related to the safety and efficacy of youth resistance training. Several case study reports and retrospective questionnaires regarding resistance exercise and the competitive sports of weightlifting and powerlifting reveal that injuries have occurred in young lifters, although a majority can be classified as accidental. Lack of qualified instruction that underlies poor exercise technique and inappropriate training loads could explain, at least partly, some of the reported injuries. Current research indicates that resistance training can be a safe, effective and worthwhile activity for children and adolescents provided that qualified professionals supervise all training sessions and provide age-appropriate instruction on proper lifting procedures and safe training guidelines. Regular participation in a multifaceted resistance training programme that begins during the preseason and includes instruction on movement biomechanics may reduce the risk of sports-related injuries in young athletes. Strategies for enhancing the safety of youth resistance training are discussed.
Velocity specificity of resistance training has demonstrated that the greatest strength gains occur at or near the training velocity. There is also evidence that the intent to make a high speed contraction may be the most crucial factor in velocity specificity.
The mechanisms underlying the velocity-specific training effect may reside in both neural and muscular components. Muscular adaptations such as hypertrophy may inhibit high velocity strength adaptations due to changes in muscle architecture. However, some studies have reported velocity-specific contractile property adaptations suggesting changes in muscle kinetics. There is evidence to suggest velocity-specific electromyographic (EMG) adaptations with explosive jump training. Other researchers have hypothesised neural adaptations because of a lack of electrically evoked changes in relation to significant voluntary improvements. These neural adaptations may include the selective activation of motor units and/or muscles, especially with high velocity alternating contractions. Although the incidence of motor unit synchronisation increases with training, its contribution to velocity-specific strength gains is unclear. However, increased synchronisation may occur more frequently with the premovement silent period before ballistic contractions. The preprogrammed neural circuitry of ballistic contractions suggests that high velocity training adaptations may involve significant neural adaptations. The unique firing frequency associated with ballistic contractions would suggest possible adaptations in the frequency of motor unit discharge. Although co-contraction of antagonists increases with training and high velocity movement, its contribution is probably related more to joint protection than the velocity-specific training effect.
In order to stimulate further adaptation toward a specific training goal(s), progression in the type of resistance training protocol used is necessary. The optimal characteristics of strength-specific programs include the use of both concentric and eccentric muscle actions and the performance of both single- and multiple-joint exercises. It is also recommended that the strength program sequence exercises to optimize the quality of the exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher intensity before lower intensity exercises). For initial resistances, it is recommended that loads corresponding to 8-12 repetition maximum (RM) be used in novice training. For intermediate to advanced training, it is recommended that individuals use a wider loading range, from 1-12 RM in a periodized fashion, with eventual emphasis on heavy loading (1-6 RM) using at least 3-min rest periods between sets performed at a moderate contraction velocity (1-2 s concentric, 1-2 s eccentric). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 d x wk(-1) for novice and intermediate training and 4-5 d x wk(-1) for advanced training. Similar program designs are recommended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion, with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training, and 2) use of light loads (30-60% of 1 RM) performed at a fast contraction velocity with 2-3 min of rest between sets for multiple sets per exercise. It is also recommended that emphasis be placed on multiple-joint exercises, especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (> 15) using short rest periods (< 90 s). In the interpretation of this position stand, as with prior ones, the recommendations should be viewed in context of the individual's target goals, physical capacity, and training status.
The present review introduces the notion of statistical power and the hazard of under-powered studies. The problem of how to calculate an ideal sample size is also discussed within the context of factors that affect power, and specific methods for the calculation of sample size are presented for two common scenarios, along with extensions to the simplest case.
Whereas many definitions of fatigue include externally measurable decrements in force or performance, fatigue can be present with no change in the external output of the muscle. The maintenance of submaximal forces can be considered a compromise between neuromuscular force enhancement and competing inhibitory influences. An example of a muscle facilitatory process includes postactivation potentiation that results in an increased sensitivity to Ca++. The neuromuscular system copes with metabolic disruption and subsequent loss of force by recruiting additional motor units and increasing the firing frequency. If the contraction persists, firing frequency may decrease so as to optimize the stimulus rate with the prolonged duration of the muscle fibre action potential (muscle wisdom). The insertion of additional neural impulses into the train of stimuli can result in force potentiation (catch-like properties). Furthermore, there is evidence of neural potentiation and a dissociation of muscle activity with submaximal fatigue. Conversely, inhibition may be derived supraspinally or at the spinal level. While there may be some evidence of intrinsic motoneuronal fatigue, inhibitory afferent influences from chemical, tensile, pressure, and other factors play an important role in the competing influences on force output.
There is a large public and scientific interest concerning resistance training in youth. Main interests are focussed on injury risk, the effectiveness of resistance training, in particular before puberty, and on mechanisms which are responsible for strength gain. Historically, resistance training was not recommended for children. It was generally believed that the lack of circulating androgens would preclude any strength improvement. Moreover, due to the fear of overuse and injuries it was considered to be useless and dangerous. Nowadays, there is enough evidence that resistance training in children and adolescents is effective and harmless given that it is performed age-adapted and appropriately supported. After a short introduction about muscle growth and strength progression during growth and development, the results of resistance training studies on strength and bone health as well as possible mechanisms of neuro-muscular adaptations are discussed. It is shown that resistance training is save and bears a minimum risk for injuries if guidelines are respected. At the end, we will give some practical recommendations for an age-appropriate, safe and effective resistance training.
The purpose of this study was to analyze the specific training load during a resistance training (RT) programme designed to increase muscular hypertrophy in men and women. Thirty-four women (22.7 ± 4.1 years, 58.8 ± 11.9 kg, 162.6 ± 6.2 cm and 22.1 ± 3.6 kg.m −2) and 30 men (22.7 ± 4.4 years, 68.4 ± 9.0 kg, 174.5 ± 6.6 cm and 22.5 ± 2.4 kg.m −2) underwent a supervised RT programme that was divided into two phases of 8 weeks each. Training consisted of 10–12 exercises performed with three sets of 8–12 repetitions at repetition maximum resistances performed 3 times per week on nonconsecutive days. There was a significant (P < 0.05) main effect for gender by time interaction for average training load of all the exercises performed in the first 8 weeks of RT with women showing a higher relative increase than men (+43.6% vs. +32.5%, respectively). This result was not observed during the second 8-week phase of the RT programme during which no significant gender by time interaction (P > 0.05) was shown with both genders having a similar relative increase (+28.7% vs. +24.3%, respectively). Women had a higher increase than men in specific average training load of the upper limb exercises during both the first 8 weeks of training (+30.2% vs. +26.6%, respectively) and the second 8 weeks of training (+31.1% vs. +25.3%, respectively). We conclude that the adaptation in specific training load is influenced by gender.
The activity pattern of low-threshold human trapezius motor units was examined in response to brief, voluntary increases in contraction amplitude ('EMG pulse') superimposed on a constant contraction at 4-7 % of the surface electromyographic (EMG) response at maximal voluntary contraction (4-7 % EMGmax). EMG pulses at 15-20 % EMGmax were superimposed every minute on contractions of 5, 10, or 30 min duration. A quadrifilar fine-wire electrode recorded single motor unit activity and a surface electrode recorded simultaneously the surface EMG signal. Low-threshold motor units recruited at the start of the contraction were observed to stop firing while motor units of higher recruitment threshold stayed active. Derecruitment of a motor unit coincided with the end of an EMG pulse. The lowest-threshold motor units showed only brief silent periods. Some motor units with recruitment threshold up to 5 % EMGmax higher than the constant contraction level were recruited during an EMG pulse and kept firing throughout the contraction. Following an EMG pulse, there was a marked reduction in motor unit firing rates upon return of the surface EMG signal to the constant contraction level, outlasting the EMG pulse by 4 s on average. The reduction in firing rates may serve as a trigger to induce derecruitment. We speculate that the silent periods following derecruitment may be due to deactivation of non-inactivating inward current ('plateau potentials'). The firing behaviour of trapezius motor units in these experiments may thus illustrate a mechanism and a control strategy to reduce fatigue of motor units with sustained activity patterns.
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
Although physiologic benefits of resistance training for children and adolescents have been well documented, the impact of age and maturity on trainability of muscle strength remains poorly understood.
To assess the effects of resistance training in different age groups and maturity levels.
We searched electronic bibliographic databases, key journals, and reference lists of reviews, book chapters, and articles. Two independent reviewers evaluated the effects of resistance training on muscle strength for prepubertal and postpubertal healthy children and adolescents (younger than 18 years) by using the results of randomized and nonrandomized controlled trials. Assessments of muscle endurance and motor performance tests (eg, vertical jump) were excluded. The influence of continuous and categorical moderator variables was assessed by meta-regression and subgroup analyses, respectively.
The overall weighted effect size of 1.12 (95% confidence interval: 0.9-1.3) was significantly greater than 0 (P < .01). Subgroup analyses revealed "maturity" to be a significant categorical moderator variable (z = 2.50; P = .01) and positive correlation coefficients were found for the continuous variables "duration" (r = 0.28; P = .02) and "frequency" (r = 0.26; P = .03).
The results of our analysis indicate that the ability to gain muscular strength seems to increase with age and maturational status, but there is no noticeable boost during puberty. Furthermore, study duration and the number of performed sets were found to have a positive impact on the outcome.
The purpose of the present study was to compare the changes in muscle strength in nontrained young males performing resistance training under different supervision ratios. One hundred twenty-four young men were randomly assigned to groups trained under a high (HS, 1:5 coach to athlete ratio) or low (LS, 1:25) supervision ratio. Both groups performed identical resistance training programs. Subjects were tested for maximum bench press 1 repetition maximum (1RM) and knee extensor torque before and after 11 weeks of training. According to the results, only HS lead to a significant increase (11.8%) in knee extensor torque. Both groups significantly increased bench press 1RM load; the increases were 10.22% for LS and 15.9% for HS. The results revealed significant differences between groups for changes in knee extensor torque and 1RM bench press, with higher values for the HS group. There were no differences between groups for the increases in bench press and leg press work volume or training attendance. The proportion of subjects training with maximum intensity was higher in HS for both bench press and leg press exercises. In addition, the distribution of subjects training with maximal intensity was higher for the bench press than for the leg press exercise in both groups. The primary findings of the present study are that the strength gains for both lower- and upper-body muscles are greater in subjects training under higher supervision ratios, and this is probably because of higher exercise intensity. These results confirm the importance of direct supervision during resistance training.
The RMS amplitude of the surface electromyogram (EMG) and the frequency of discharge of motor units was examined throughout the duration of isometric contractions of the adductor pollicis muscles sustained to fatigue at tensions of 25, 40, and 55% of the maximum voluntary strength (MVC) of eight male subjects during fatiguing isometric contractions. The maximum strength of the muscle and the EMG above the adductor pollicis muscles was also assessed during 3 s of voluntary and electrically induced isometric contractions interposed at 25, 50, 75, and 100% of the duration of the fatiguing contractions. At the point of fatigue from submaximal isometric contractions, the RMS amplitude of the surface EMG was highest for contractions at 55 as compared to 40 and 25% MVC. The lower RMS amplitude of the EMG during contractions at lower as compared to higher tensions at the point of fatigue was paralleled by a lower discharge frequency of the alpha motor neurons in the fatigued muscle during contractions at 25% as compared to 40 and 70% MVC. The reduction in discharge frequency was probably of a sufficient order of magnitude to account for the lower amplitude of the EMG at the end of fatiguing isometric contractions at lower tensions.
The effect of learning a throwing skill with the body in one position on performing the skill in a different position was investigated. 40 normal women, aged 20 to 34 years, were randomly assigned to experimental or control groups. Subjects threw darts from two positions, sitting on a Balans chair or reclined on a slanted table. Practice and transfer sessions each included 4 sets of 5 throws. Performance was significantly poorer after switching positions than when remaining in the same position. Performance after practice in an alternate position was significantly worse than performance after no practice. These findings suggest that practicing a skill in one position may not improve learners' ability to perform that skill in a different position.
There has been considerable debate concerning the benefits of children participating in weight training programs. With the potential benefits of such training in specific rehabilitation regimens, the safety/efficacy of weight training is a topic in need of scientific study. Fifty-two experimental and 39 control subjects participated in this study. A 2 x 2 x 2 (gender by treatment by Tanner stage) ANOVA was used to examine pre- to post-test differences in six strength measures, eight anthropometric measures, five motor performance measures, and one flexibility measure associated with participation in a 12-week progressive resistance programme. In addition, safety of the weight training programme was examined. For strength differences, there were two significant main effects favouring strength gains in males and four favouring the experimental group. For anthropometric changes, 3-way interactions occurred that were not easily explained. However, the predominant main effect was treatment; the experimental group generally experienced gains in body segment girths with decreases in skinfold thickness. For motor performance, the experimental group had greater improvements in three of five parameters. The experimental group also had significantly greater gains in flexibility. The weight training programme was associated with only one injury. These findings support the general observation that physical benefits can be gained safely by children who participate in a weight training programme.
Previous research has shown that children can increase their muscular strength and muscular endurance as a result of regular participation in a progressive resistance training program. However, the most effective exercise prescription regarding the number of repetitions remains questionable.
To compare the effects of a low repetition-heavy load resistance training program and a high repetition-moderate load resistance training program on the development of muscular strength and muscular endurance in children. Design. Prospective, controlled trial.
Community-based youth fitness center.
Eleven girls and 32 boys between the ages of 5.2 and 11.8 years.
In twice-weekly sessions of resistance training for 8 weeks, children performed 1 set of 6 to 8 repetitions with a heavy load (n = 15) or 1 set of 13 to 15 repetitions with a moderate load (n = 16) on child-size exercise machines. Children in the control group (n = 12) did not resistance train. One repetition maximum (RM) strength and muscular endurance (repetitions performed posttraining with the pretraining 1-RM load) were determined on the leg extension and chest press exercises.
One RM leg extension strength significantly increased in both exercise groups compared with that in the control subjects. Increases of 31.0% and 40.9%, respectively, for the low repetition-heavy load and high repetition-moderate load groups were observed. Leg extension muscular endurance significantly increased in both exercise groups compared with that in the control subjects, although gains resulting from high repetition-moderate load training (13.1 +/- 6.2 repetitions) were significantly greater than those resulting from low repetition-heavy load training (8.7 +/- 2.9 repetitions). On the chest press exercise, only the high repetition-moderate load exercise group made gains in 1-RM strength (16.3%) and muscular endurance (5.2 +/- 3.6 repetitions) that were significantly greater than gains in the control subjects.
These findings support the concept that muscular strength and muscular endurance can be improved during the childhood years and favor the prescription of higher repetition-moderate load resistance training programs during the initial adaptation period.
The muscular wisdom hypothesis proposed that the slowing of the motor unit discharge rate during sustained maximal isometric contractions serves to minimize fatigue. The purpose of this review is to examine the applicability of the muscular wisdom hypothesis during other forms of contraction, i.e., prolonged submaximal isometric or dynamic contractions.
Motor-unit firing patterns were studied in the vastus lateralis muscle of five healthy young men [21.4 +/- 0.9 (SD) yr] during a series of isometric knee extensions performed to exhaustion. Each contraction was held at a constant torque level, set to 20% of the maximal voluntary contraction at the beginning of the experiment. Electromyographic signals, recorded via a quadrifilar fine wire electrode, were processed with the precision decomposition technique to identify the firing times of individual motor units. In repeat experiments, whole-muscle mechanical properties were measured during the fatigue protocol using electrical stimulation. The main findings were a monotonic decrease in the recruitment threshold of all motor units and the progressive recruitment of new units, all without a change of the recruitment order. Motor units from the same subject showed a similar time course of threshold decline, but this decline varied among subjects (mean threshold decrease ranged from 23 to 73%). The mean threshold decline was linearly correlated (R2 >or= 0.96) with a decline in the elicited peak tetanic torque. In summary, the maintenance of recruitment order during fatigue strongly supports the notion that the observed common recruitment adaptations were a direct consequence of an increased excitatory drive to the motor unit pool. It is suggested that the increased central drive was necessary to compensate for the loss in force output from motor units whose muscle fibers were actively contracting. We therefore conclude that the control scheme of motor-unit recruitment remains invariant during fatigue at least in relatively large muscles performing submaximal isometric contractions.
The schema theory for discrete motor skill learning (Schmidt, 1975), originally published in 1975, has generated considerable interest and received strong challenges over its lifetime. In this paper, I focus on the findings generated since 1975 that bear on the theory and highlight those that produce difficulties for it and will be motivators for differing theoretical viewpoints in the future. At the same time, I examine other lines of evidence that seem to bolster the original lines of thinking. Finally, I provide some suggestions for a much needed new generation of motor learning theory, pointing out particular features from the schema theory that could be included and suggesting gaps and omissions that will need additional data and theorizing in future attempts.
Using the size principle to model peripheral muscle fatigue [abstract] International Society of Electrophysiology and Kinesiology Conference Analysis of the training load during a hypertrophytype resistance training programme in men and women
- J Potvin
- A Fuglevand
- A S Chicago Ribiero
- A Avelar
- B J Schoenfeld
- S J Fleck
- M F Souza
- C S Padilha
Potvin, J., and Fuglevand, A. 2016. Using the size principle to model peripheral
muscle fatigue [abstract]. International Society of Electrophysiology and
Kinesiology Conference; Chicago
Ribiero, A.S., Avelar, A., Schoenfeld, B.J., Fleck, S.J., Souza, M.F., Padilha,
C.S., and Cyrino, E.S. 2015. Analysis of the training load during a hypertrophytype resistance training programme in men and women. Eur. J. Sport. Sci.
Effects of different resistance training protocols on upper
- W L Westcott
Westcott, W.L. 2001. Effects of different resistance training protocols on upper-Page 24 of 38