The role of eccentric muscle actions in the increase of strength and muscle mass

An increased muscle mass and strength are the main adjustments to strength training. It seems that the tension level of the muscle action plays a major role. It has been demonstrated that tension is affected by muscle action type. During an excentric action the muscle produces tension with increase of its length resulting in damage to the muscle structure. Considering that excentric training causes greater changes in strength gains and muscle mass, exercise induced damage has been seen as training stimulus. This paper will present mechanical and neural characteristics of the excentric actions e how they may contribute to the skeletal muscle adaptations to the strength training stimuli.Os principais ajustes ao treinamento de força são o aumento da massa e da força dos músculos esqueléticos. O grau de tensão da ação muscular é determinante destes ajustes e ele é influenciado pelo tipo da ação. Na ação excêntrica o músculo gera tensão com aumento de seu comprimento resultando em danos à musculatura. Visto que o treinamento excêntrico causa grande hipertrofia e ganho de força, o dano também pode ser considerado um estímulo de treinamento. Neste artigo serão apresentadas as características mecânicas e neurais das ações excêntricas e como elas podem contribuir para o que músculo esquelético se ajuste de maneira mais eficiente aos estímulos oferecidos pelo treinamento de força

Affective feelings and perceived exertion during a 10-km time trial and head-to-head running race

Purpose: Our aim was to verify the affective feelings (AF) and rating of perceived exertion (RPE) responses during a 10-km competitive head-to-head (HTH) and compare it to a time-trial (TT) running race. Methods: Fourteen male runners completed 2 x 10-km runs (TT and HTH) on different days. Speed, RPE and AF were measured every 400-m. For pacing analysis races were 14 divided into four stages: I) first 400 m (F400); II) 401m to 5000m (M1); III) 5001m and 9600m (M2) and; IV) the last 400m (final sprint [FS]). Results: Improvement of performance was observed (39:32 ± 02:41 min:s vs 40:28 ± 02:55 min:s; p = 0.03; ES = - 0.32) in HTH compared to TT. There were not differences in either pacing strategy or RPE between conditions. AF were higher during the HTH,being different in M2 when compared to TT (2.09 ± 1.81 vs 0.22 ± 2.25; p = 0.02; ES = 0.84). Conclusion: AF are directly influenced by the presence of opponents during a HTH race and a more positive AF could be involved in the dissociation between RPE and running speed and consequently, the overall race performance

MECANISMOS DE ADAPTAÇÃO AO TREINAMENTO COM ELETROESTIMULAÇÃO TRANSCUTÂNEA A ALTAS E MÉDIAS FREQÜÊNCIAS

A eletroestimulação transcutânea (ETC) vem sendo utilizada com êxito na reabilitação após períodos de imobilização ou inatividade. Esta técnica de treinamento começou a ser estudada no esporte a partir da década de 70 na União Soviética e mostrou-se capaz de causar ganhos na força muscular em indivíduos atletas e sedentários. Os mecanismos responsáveis por esses ganhos de força ainda não estão totalmente elucidados. Os objetivos do presente trabalho são: 1) discutir as especificidades do treinamento com ETC e 2) identificar os possíveis mecanismos de adaptação responsáveis pelos ganhos de força após treinamento de ETC a médias e altas freqüências. A intensidade de estímulo determina o número de unidades motoras (UM) que são ativadas, quanto maior a intensidade maiores os ganhos de força. A freqüência de estimulação é outro fator que interfere diretamente nos resultados observados. Baixas freqüências (1-49Hz) tornam as fibras musculares mais lentas e resistentes. Já freqüências médias (50-200Hz) e altas (>200Hz) podem causar elevação da força e da velocidade de contração da fibra muscular. A ETC causa um recrutamento preferencial das UM rápidas, o que pode favorecer a obtenção de ganhos de força muscular. Assim como no treinamento com contrações voluntárias, a ETC pode causar adaptações morfológicas ou neurais. Contudo, a temporalidade dessas adaptações deve ser determinada. TRAINING ADAPTATION AFTER TRANSCUTANEOUS ELECTRICAL SIMULATION WITH HIGH AND MEDIUM FREQUENCY Abstract Electrical stimulation (ES) has been used for reabilithation and after inactivity periods to recover strength. Its effects started to be studied in athletes and sedentaries in the 70s by the former CCPP. The aims of this review were: 1) discuss ES training characteristics, and 2) identify the possible strength adaptations at high and medium frequencies. Strength gains are modulated by two factors: Stimuli intesity, which modulates the number of activated motor units, and the frequency of stimulation. Muscle fibers become slower and increase time to fatigue with low frequency stimulation (1-49Hz). On the other hand, medium (50-200Hz) and high frequencies (>200Hz) increase muscle fiber force and speed. Electrical stimulation seems to produce a reversal in motor unit recruitment, which may produce greater strength gains. The mechanisms responsible for these strength gains are both morphological and neural. The time frame of each one of these adaptations has to be determined

Efeito de dois métodos de treinamento no desenvolvimento da força máxima e da potência muscular de membros inferiores

Força máxima e potência são considerados métodos de treinamento complementares para a preparação de um atleta. No entanto, há evidências de desempenhos semelhantes em resposta a treinamentos de força máxima (TF) e potência (TP). O objetivo deste estudo foi realizar uma comparação entre os dois métodos de treino descritos quanto à eficiência em aumentar a força máxima e a potência no exercício meio agachamento. Vinte e quatro sujeitos fisicamente ativos (peso 76 ± 8,4 kg, estatura 178,2 ± 5,3 cm), com no mínimo seis meses de interrupção no treinamento de força para membros inferiores, foram divididos nos grupos TF e TP. Foram realizados pré e pós-treinamento o teste de força dinâmica máxima (1 RM) e de potência muscular de membros inferiores no exercício meio agachamento com carga de 30% 1 RM. Após oito semanas de treinamento (3x/semana) observou-se que a força máxima aumentou significante (p < 0,001) e similarmente, 23% e 16% para os grupos TF e TP, respectivamente. A potência relativa concêntrica média aumentou quando considerados os dois grupos em conjunto (p < 0,05). Os principais achados foram que TF e TP aumentaram tanto a força máxima quanto a potência de maneira semelhante.Maximum strength and power are considered complementary training methods in an athlete's training program. However, there are evidences of similar performance improvements in response to maximum strength training (ST) and power training (PT). The purpose of the present study was to compare the two training methods described in relation to their efficiency in increasing maximum strength and power in the half squat exercise. Twenty four physically active subjects (weight 76 ± 8.4 kg, height 178.2 ± 5.3 cm), with at least six months of strength training wash-out, were divided into two training groups, ST and PT. Pre and pos-training testing involved maximum dynamic strength (1 RM) and half squat power test with 30% 1 RM. After eight weeks of training (3x/week) we found that maximum strength increased significantly (p < 0.001) and similarly, 23% e 16% for ST and PT, respectively. Relative mean concentric power increased when both groups were pooled (p < 0.05). The main findings of this study were that ST and PT increased similarly both maximum strength and power

Effect of classical massage on subjective perceived soreness, edema, range of motion and maximum strength after delayed onset muscle soreness induced by exercise

O treino de força com cargas elevadas tem induzido indivíduos a apresentarem sintomas de dano muscular que incluem a dor muscular tardia. Na tentativa de diminuir sintomas e desconforto da DOMS, estratégias têm sido utilizadas, entre elas, a massagem. O objetivo do presente estudo foi verificar os efeitos da massagem clássica na percepção subjetiva de dor (DOMS), circunferência do braço (CIR), amplitude de movimento (ADM) e força máxima (1RM) após protocolo para indução de DOMS. Para isso, 18 adultos jovens saudáveis do gênero masculino foram divididos em três grupos (G1 = massagem; G2 = protocolo; G3 = protocolo + massagem) equalizados pelo teste de uma força máxima de flexão de cotovelo no banco Scott. O protocolo de indução de DOMS consistiu de 30 ações excêntricas musculares supramáximas (seis séries de cinco repetições a 110% de 1RM). A massagem foi realizada no grupo G3 imediatamente após o protocolo durante seis minutos. As variáveis dependentes (DOMS, CIR, ADM) foram avaliadas 24, 48, 72 e 96 horas após o protocolo, enquanto a força máxima, apenas após 48 e 96 horas. Os resultados indicaram aumento na DOMS e diminuição na ADM e 1RM, similar aos de outros estudos que utilizaram protocolos semelhantes. No entanto, não houve diferenças entre os grupos G2 e G3 em nenhuma das variáveis analisadas. Pode-se concluir que com esse design experimental o protocolo utilizado foi eficaz para provocar as alterações nas variáveis analisadas e a massagem não causou nenhum benefício na recuperação das funções musculares nem na percepção subjetiva de dor.Heavy resistance training induces to symptoms of muscle damage which include delayed onset muscle soreness (DOMS). Some strategies (i.e. massage) have been used to attenuate these symptoms and to reduce discomfort associated with DOMS. This study aimed to investigate the effects of classical massage on DOMS perception, limb girth (CIR), range of motion (ADM) and maximum strength performance (1-RM) after a muscle damage protocol. Eighteen males were divided into three groups (G1= massage-only, G2= protocol-only, G3= protocol + massage) according to their 1-RM values. DOMS-inducing protocol consisted of 30 supramaximal eccentric contractions (6 sets of 5 repetitions at 110% 1RM). Immediately after the protocol, classical massage was performed in G3 for 6 minutes. DOMS, CIR, ADM were assessed 24, 48, 72 and 96 hours after the muscle damage protocol, and maximum strength was evaluated only after 48 and 96 hours. Results showed increase in DOMS and reduction in ADM and 1-RM values, in agreement with other studies using similar procedures. However, there was no difference between G2 and G3 in any of the assessed variables. It can be concluded that the muscle damage protocol used in this study was effective in causing alteration in the dependent variables observed. However, classical massage was not effective to minimize the symptoms associated to exercise induced muscle damage

Using the bar-velocity to predict the one-repetition maximum in the power clean from the knee

This study investigated the predictive validity and reliability of the load-velocity relationship with the one-repetition maximum test (1RM) in power clean from the knee exercise (PC). Initially, 12 healthy young males, with no PC experience, underwent eight sessions to learn the PC technique. After the learning period, the participants visited the laboratory on four more occasions with intervals between the visits from 72 to 96 h. The first two sessions were dedicated to the actual 1RM tests, while the last two sessions were performed to measure the barbell’s load-velocity relationship at 30%, 45%, 60%, 75%, and 90% of PC 1RM. The highest peak velocity recorded at each load was used to establish the linear regression equation and, consequently, to predict 1RM values. As a result, a low validity was observed between the highest actual 1RM value and the predicted 1RM in sessions 1 and 2 (typical errors = 3.6 to 5.0 kg, coefficients of variation = 6.03 to 8.21%, effect sizes = -1.23 to -1.00, and Bland-Altman bias = 8.5 to 11.7 kg). For reliability, higher measurement errors (intraclass correlation coefficient, typical error, coefficient of variation, and width of limits of agreement at 95%) were observed for the predicted 1RM compared to the actual 1RM test. In conclusion, the load-velocity relationship was not able to predict the 1RM value with high accuracy in the PC from the knee. Moreover, the predicted 1RM presented inferior reliability than the actual 1RM test

Muscle power in basketball and volleyball players: relationship between isokinetic dynamometry and vertical jump

The aims of this study were: 1) to determine the anthropometric characteristics and body compositon of players; 2) to evaluate the maximal muscle power of the knee extensors muscles with the isokinetic dynamometry; 3) to determine the relationships between the test of isokinetic power and the vertical jum p test; 4) to compare the results between sports. A sample of 12 basketball players and 13 volleyball players was evaluated in several anthropometric measures and in two tests of muscle power. Body composition was determined through the equation by Jackson &amp; Pollock (1978). Vertical jum p test was made without the arm movements, and the isokinetic muscle power test of the knee extensors was made in four speeds: 60, 180, 240 and 300°/sec.The results showed that the basketball players were taller, heavier and fatter than the volleyball players. There were no significant diferences in power output. When power was related to body weight, volleyball players showed higher values in the vertical jum p test and the isokinetic power test at 60°/sec. and in the vertical jump test when corrected by lean body mass. Relationships between maximal power tests showed from moderate to high degree between isokinetic power test at 180 and 300°/sec. and the vertical jum p test for basketball players. Volleyball players showed similar results at 180 and 300°/sec. Similar results were found when tests were corrected for body weight and lean body mass for basketball players, but in volleyball players relationships were from low to moderateOs objetivos do estudo foram: 1) determinar as características antropométricas e a composição corporal dos jogadores, 2) avaliar a potência máxima dos músculos extensores do joelho com a dinamometria isocinética, 3) verificar a relação entre o teste isocinético e o teste de salto vertical e 4) comparar os dois grupos de jogadores. Uma amostra de 12 jogadores de basquetebol e 13 de voleibol foi submetida a uma avaliação antropométrica e dois testes de potência muscular. A composição corporal foi calculada a partir da equação de Jackson &amp; Pollock (1978). O teste de salto vertical foi realizado sem o auxílio dos membros superiores e a dinamometria isocinética executada no movimento de extensão do joelho às velocidades de 60, 180, 240 e 300°/seg. Nos jogadores de basquetebol foram encontrados valores mais altos para estatura peso e quantidade de gordura comparados com os voleibolistas. Os dois grupos apresentaram desempenho neuromuscular semelhante em termos absolutos. Relativo ao peso corporal os voleibolistas foram superiores no salto vertical e na potência à 60°/seg. e também no salto vertical relativo à massa magra. Na relação entre os dois testes em termos absolutos, correlações moderadas para altas foram encontradas à 180 e 300°/seg. para os jogadores de basquete e 180 e 240°/seg. para os de voleibol. Resultados semelhantes ocorreram nos praticantes de basquetebol relativo ao peso corporal e a massa magra, contudo, para os voleibolistas as relações foram de baixas para moderada

Blood-Flow-Restriction-Training-Induced Hormonal Response is not Associated with Gains in Muscle Size and Strength

The aim of this study was to determine whether increases in post-exercise endocrine response to low-load resistance exercise with blood flow restriction and high-load resistance exercise would have association with increases in muscle size and strength after an 8-week training period. Twenty-nine untrained men were randomly allocated into three groups: low-load resistance exercise with (LL-BFR) or without blood flow restriction (LL), and high-load resistance exercise (HL). Participants from LL-BFR and LL groups performed leg extension exercise at 20% of one repetition maximum (1RM), four sets of 15 repetitions and the HL group performed four sets of eight repetitions at 80% 1RM. Before the first training session, growth hormone (GH), insulin-like growth factor 1 (IGF-1), testosterone, cortisol, and lactate concentration were measured at rest and 15 min after the exercise. Quadriceps CSA and 1RM knee extension were assessed at baseline and after an 8-week training period. GH increased 15 min after exercise in the LL-BFR (p = 0.032) and HL (p \u3c 0.001) groups, with GH concentration in the HL group being higher than in the LL group (p = 0.010). There was a time effect for a decrease in testosterone (p = 0.042) and an increase in cortisol (p = 0.005), while IGF-1 remained unchanged (p = 0.346). Both muscle size and strength were increased after training in LL-BFR and HL groups, however, these changes were not associated with the acute post-exercise hormone levels (p \u3e 0.05). Our data suggest that other mechanisms than the acute post-exercise increase in systemic hormones induced by LL-BFR and HL produce changes in muscle size and strength

Concurrent validity and reliability of the load-velocity relationship to predict the one-repetition maximum during three weightlifting derivatives

The study investigated the concurrent validity and reliability of the load-velocity relationship to predict the one-repetition maximum (1RM) of the power clean from the knee (PCK), high pull from the knee (HPK), and mid-thigh clean pull (MTCP). For each exercise, 12 participants performed two 1RM sessions tests and two sessions to measure the barbell’s load-velocity relationship at 30, 45, 60, 75, and 90% of 1RM. The velocity recorded at each load was used to establish the linear regression equation and, consequently, to predict 1RM value. A low validity between the 1RM direct test and predicted 1RM was observed for PCK (typical error [TE]=3.96 to 4.50 kg, coefficient of variation [CV]=4.68 to 5.27%, effect size [ES]=-0.76 to -0.58, Bland-Altman bias [BAB]=9.83 to 11.19 kg), HPK (TE=4.58 to 5.82 kg, CV=6.44 to 8.14%, ES=-0.40 to -0.39, BAB=3.52 to 4.17 kg), and MTCP (TE=6.33 to 8.08 kg, CV=4.78 to 6.16%, ES=-0.29 to -0.19, BAB=3.98 to 6.17 kg). Adequate reliability was observed for the 1RM direct test and for the predicted 1RM. However, based on Bland-Altman limits of agreement, lower measurement errors were obtained for the 1RM direct test in comparison to the predicted 1RM for all the exercises. In conclusion, the load-velocity relationship was not able to predict 1RM values with high accuracy in the PCK, HPK, and MTCP. Moreover, the 1RM direct test was the most reliable for PCK, HPK and MTCP