Exogenous Caffeine Ingestion Does Not Increase Plantarflexor Torque in Older or Younger Men.

Aging is associated with neurodegeneration and a loss of muscle function, especially in lower-limb muscles. While caffeine may augment muscle force generation through multiple effects on the central nervous system, no studies have yet compared the effects of caffeine on force-generating capacity between younger and older men, who might respond differently due to age-related changes in the structures on which caffeine acts. In a double-blind, controlled trial, 22 younger (25 ± 5 years) and 21 older (68 ± 6 years) men were tested for isometric plantarflexor torque on two separate days (2-7 days apart) before and 60 min after ingesting 3 mg/kg (∼2 cups of coffee) of caffeine or placebo. No effects of caffeine ingestion on peak torque or rate of torque development were detected in either older or younger men. Therefore, 3 mg/kg of caffeine may not acutely counteract age-related decreases in force capacity of the functionally important plantarflexor muscles.

Evidence of validity and reliability of Jumpo 2 and MyJump 2 for estimating vertical jump variables.

Background: We investigated the concurrent validity and test-retest reliability of the Jumpo 2 and MyJump 2 apps for estimating jump height, and the mean values of force, velocity, and power produced during countermovement (CMJ) and squat jumps (SJ). Methods: Physically active university aged men (n = 10, 20 ± 3 years, 176 ± 6 cm, 68 ± 9 kg) jumped on a force plate (i.e., criterion) while being recorded by a smartphone slow-motion camera. The videos were analyzed using Jumpo 2 and MyJump 2 using a Samsung Galaxy S7 powered by the Android system. Validity and reliability were determined by regression analysis, typical error of estimates and measurements, and intraclass correlation coefficients. Results: Both apps provided a reliable estimate of jump height and the mean values of force, velocity, and power. Furthermore, estimates of jump height for CMJ and SJ and the mean force of the CMJ were valid. However, the apps presented impractical or poor validity correlations for velocity and power. Compared with criterion, the apps underestimated the velocity of the CMJ. Conclusions: Therefore, Jumpo 2 and MyJump 2 both provide a valid measure of jump height, but the remaining variables provided by these apps must be viewed with caution since the validity of force depends on jump type, while velocity (and as consequence power) could not be well estimated from the apps.

Acute effects of different rest intervals between agonist-antagonist paired-sets in the neuromuscular system performance of young adults.

INTRODUCTION: The agonist-antagonist paired-sets (APS) is a resistance training that involves alternating between exercises for agonist/antagonist muscles of a joint, with little or no rest between then. There is evidence that APS is more strenuous than traditional methods, but evidence on the optimal RI between agonist-antagonist actions is unknown. OBJECTIVE: The aim of this study was to compare different rest intervals between agonist-antagonist actions during APS in young adults. METHOD: Fifty healthy men (mean age 23.2 ± 2.8 years; 1.76 ± 0.1m height, 78.03 ± 8.1 kg) were included and performed three different agonist-antagonist paired-sets protocols separated by 72h, consisting of 4 sets of 10 repetitions. The protocols differed in terms of the rest interval between the knee flexion and extension movements: 0s (no rest); 60s and 120s. The rest intervals between exercise sets were standardized at 60s. Total work, peak torque, neuromuscular efficiency, surface EMG amplitude (sEMG, root mean square) and fatigue index obtained by processing of sEMG signal, were compared between rest intervals and exercise sets within each protocol. RESULTS: There were no significant differences between rest intervals for total work, peak torque and neuromuscular efficiency (P > 0.05), but significant differences were found for sEMG and fatigue (P < 0.01), in which the protocol with 60s interval resulted in greater fatigue. CONCLUSION: We showed that peak torque, total work and neuromuscular efficiency were not different between RI. The 60s RI showed a lower sEMG and a greater muscle fatigue. Although there were no significant differences, the NME was higher in the 60s interval.

Effects of Horizontal and Incline Bench Press on Neuromuscular Adaptations in Untrained Young Men.

The aim of the current study was to investigate the effects of horizontal and incline bench press as well as the combination of both exercises on neuromuscular adaptation in untrained young men. Forty-seven untrained men were randomly assigned to one of the three groups: 1) a horizontal bench press group (n= 15), 2) an incline bench press group (n= 15), and 3) a combination (horizontal + incline) group (n= 17). Training was conducted once a week for eight weeks, with equalized number of sets among groups. Muscle thickness, isometric strength and electromyography (EMG) amplitude of the pectoralis major were measured one week before and after the training period. There was no difference between groups for the change in horizontal bench press isometric strength (~ 10 kg increase, p=0.776) or incline bench press isometric strength (~ 11 kg increase, p=0.333). Changes in muscle thickness differed only in one of the three sites. The changes in the second intercostal space of the pectoralis major was greatest in the incline pressure group compared with the horizontal [mean difference (95% CI) of 0.62 (0.23, 1.0) cm, p=0.003] and combination groups [mean difference (95% CI) of 0.50 (0.14, 0.86) cm, p=0.008]. The change in EMG amplitude following training differed between groups in only one out of the four sites. The present results indicate that strength and conditioning professionals might consider that horizontal and incline bench press exercises, or a combination of both exercises can render similar change in general strength.

Could inter-set stretching increase acute neuromuscular and metabolic responses during resistance exercise?

This study investigated the acute effects of inter-set static stretching (ISS) during resistance exercise (RE) on the subsequent neuromuscular and metabolic responses. Twelve resistance-trained men performed three different knee extension RE protocols comprised of seven sets of 10 repetitions in a counterbalanced fashion. The three protocols were: 1) ISS (subjects performed 25 sec of quadriceps stretching between sets during 40 sec rest interval); 2) control (CON, subject passively rested between sets for 40 sec); 3) traditional (TRA, subject passively rested between sets for 120 sec). Total work was lower (p < 0.05) in ISS than CON and TRA (p <0.05). The fatigue index was greater (p < 0.05) in ISS compared with CON and TRA. ISS also resulted in lower (p < 0.05) electromyography (EMG) amplitude during the 6th and 7th sets compared with TRA. Additionally, EMG frequency was lower (p < 0.05) from the 3rd to 5th sets during ISS compared to CON, and from the 3rd to 7th sets compared to TRA. Muscle swelling and blood lactate similarly increased (p > 0.05) in response to all protocols. These results indicate that ISS negatively impacts neuromuscular performance, and does not increase the metabolic stress compared to passive rest intervals.

Effects of Synergist vs. NonSynergist Split Resistance Training Routines on Acute Neuromuscular Performance in Resistance-Trained Men.

Castanheira, RPM, Ferreira-Junior, JB, Celes, RS, Rocha-Junior, VA, Cadore, EL, Izquierdo, M, and Bottaro, M. Effects of synergist vs. nonsynergist split resistance training routines on acute neuromuscular performance in resistance-trained men. J Strength Cond Res 31(12): 3482-3488, 2017-The aim of this study was to evaluate the effects of synergist (SN) vs. nonsynergist (NS) split resistance training routines on the acute neuromuscular performance of the elbow flexors in resistance-trained men. Fifteen resistance-trained men (age: 23.2 ± 4.0 years, height: 173.0 ± 0.08 cm, and body mass: 78.38 ± 9.31 kg) randomly performed 3 training routines separated by an interval of 7 days: (a) pull-pull exercises (SN), which included 6 sets of 10 repetition maximum (RM) of a seated row exercise followed by 4 sets of 10RM of the preacher biceps curl exercise; (b) push-pull exercises (NS), which included 6 sets of 10RM of the bench press exercise followed by 4 sets of 10RM of the preacher biceps curl exercise; and (c) Control, which included 4 sets of 10RM of the preacher biceps curl exercise. Elbow flexors peak torque, total work, and the amplitude of electromyography signal (EMG root mean square) were measured during the elbow flexor isokinetic exercise. Peak torque was 10.2 and 3.9% higher during Control condition when compared with the SN and NS conditions, respectively (p ≤ 0.05). Peak torque was also 6.0% greater in the NS condition than the SN condition (p ≤ 0.05). Moreover, total work was 5.1% greater in the NS condition than the SN condition. Additionally, EMG findings did not differ among conditions (p > 0.05). In conclusion, a push and pull NS split routine is recommended to maximize elbow flexor training performance (i.e., lower acute loading effect) in trained subjects.

Parâmetros eletromiográficos em exercícios fatigantes realizados com diferentes tipos de resistência / Estándares electromiográficos en ejercicios extenuantes empleando distintos tipos de resistencia / Electromyographic parameters in fatiguing exercises performed with different types of resistance

RESUMO Buscou-se investigar os parâmetros eletromiográficos da fadiga muscular durante exercício dinâmico realizado com resistência variável (elástica) e resistência fixa (polia). Dez homens treinados participaram voluntariamente do estudo. Foram realizadas duas contrações voluntárias isométricas máximas (CVIM) de flexão do cotovelo com 5 segundos de duração cada e 2 minutos de intervalo entre as mesmas. Em seguida, os voluntários realizaram a flexão unilateral do cotovelo até a exaustão, utilizando resistência fixa e elástica com ritmo pré-estabelecido de 2 segundos para cada fase do movimento. A resistência constante foi realizada na polia a 30% da CVIM. Para a resistência elástica, o controle de carga era baseado na percepção subjetiva de esforço do participante. A ordem do exercício foi randomizada, e o sinal de eletromiografia do músculo bíceps braquial foi registrado durante as contrações. A partir do sinal eletromiográfico referente a cada execução de movimento, foram traçadas retas de regressão linear para as variáveis RMS e frequência de potência mediana (FPM). As inclinações das retas normalizadas pelo coeficiente linear das equações de regressão foram comparadas por meio do teste t pareado. Não foram observadas diferenças significativas entre os tipos de resistência (elástica e polia). Os parâmetros eletromiográficos de fadiga não foram diferentes durante o exercício de flexão do cotovelo realizado com resistência elástica e polia. A percepção de esforço durante o exercício com implemento elástico não influencia no padrão do sinal eletromiográfico (RMS e FPM).

RESUMEN En esta investigación se pretendió estudiar los estándares electromiográficos de fatiga muscular durante la realización de ejercicio dinámico con resistencia variable (elástico) y resistencia fija (polea). Han participado voluntariamente diez varones entrenados. Se llevó a cabo dos contracciones voluntarias máximas (CVIM) de flexión de codo, cada cual de cinco segundos de duración y dos minutos de intervalo entre las mismas. Después los voluntarios hicieron la flexión unilateral del codo hasta sentirse cansados, y emplearon la resistencia fija y elástica con ritmo prestablecido de dos segundos para cada fase del movimiento. Se llevó a cabo la resistencia constante en la polea a 30% de la CVIM. Relativo a la resistencia elástica, el control de carga se basaba en una percepción subjetiva del esfuerzo empleado por el participante. El orden del ejercicio fue aleatorio, y se registró la señal electromiográfica del músculo bíceps durante las contracciones. Desde la señal electromiográfica relativa a cada ejecución del movimiento se dibujó rectas de regresión lineal para las variables RMS y la frecuencia de potencia media (FPM). Se confirmó las inclinaciones de rectas normalizadas por el coeficiente lineal de las ecuaciones de regresión a través de la prueba t pareada. No se observaron diferencias significantes entre los tipos de resistencia (elástica y polea). Los estándares electromiográficas de fatiga durante la práctica de ejercicios de flexión de codo empleando resistencia elástica y polea no fueron distintos. La percepción del esfuerzo durante la práctica de ejercicio con elástico no trae consecuencias al estándar de señal electromiográfico (RMS y FPM).

ABSTRACT The present study sought to investigate the electromyographic parameters of muscle fatigue during dynamic exercise conducted with variable resistance (elastic) and fixed resistance (pulley). Ten trained men participated voluntarily in the study. Two maximum voluntary isometric contractions (MVIC) of the elbow flexors were performed for 5 seconds and a two minutes interval rest was given between reps. Then, the volunteers performed unilateral elbow flexion repetitions until the exhaustion using fixed and elastic resistance with a pre-established rhythm of two seconds for each phase of the movement. Constant resistance was carried out at the pulley at 30% of MVIC. For the elastic resistance, load control was based on the subjective perception of the participant's effort. The exercise order was randomized, and electromyography signal of the biceps brachii muscle was recorded during contractions. From the electromyographic signal related to every movement, linear regression lines were drawn for root mean square (RMS) variables and median power frequency (MPF). The inclination of the lines normalized by the linear coefficient of regression equations were compared using the paired t-test. No significant differences between the types of resistance (elastic and pulley) were found. During elbow flexion exercise performed with elastic resistance and pulley, electromyographic parameters of fatigue did not differ. Effort perception during the exercise with an elastic implement does not influence the electromyographic signal pattern (RMS and MPF).

Neuromuscular and blood lactate responses to squat power training with different rest intervals between sets.

Studies investigating the effect of rest interval length (RI) between sets on neuromuscular performance and metabolic response during power training are scarce. Therefore, the purpose of this study was to compare maximal power output, muscular activity and blood lactate concentration following 1, 2 or 3 minutes RI between sets during a squat power training protocol. Twelve resistance-trained men (22.7 ± 3.2 years; 1.79 ± 0.08 cm; 81.8 ± 11.3 kg) performed 6 sets of 6 repetitions of squat exercise at 60% of their 1 repetition maximum. Peak and average power were obtained for each repetition and set using a linear position transducer. Muscular activity and blood lactate were measured pre and post-exercise session. There was no significant difference between RI on peak power and average power. However, peak power decreased 5.6%, 1.9%, and 5.9% after 6 sets using 1, 2 and 3 minutes of RI, respectively. Average power also decreased 10.5% (1 min), 2.6% (2 min), and 4.3% (3 min) after 6 sets. Blood lactate increased similarly during the three training sessions (1-min: 5.5 mMol, 2-min: 4.3 mMol, and 3-min: 4.0 mMol) and no significant changes were observed in the muscle activity after multiple sets, independent of RI length (pooled ES for 1-min: 0.47, 2-min: 0.65, and 3-min: 1.39). From a practical point of view, the results suggest that 1 to 2 minute of RI between sets during squat exercise may be sufficient to recover power output in a designed power training protocol. However, if training duration is malleable, we recommend 2 min of RI for optimal recovery and power output maintenance during the subsequent exercise sets. Key pointsThis study demonstrates that 1 minute of RI between sets is sufficient to maintain maximal power output during multiple sets of a power-based exercise when it is composed of few repetitions and the sets are not performed until failure. Therefore, a short RI should be considered when designing training programs for the development of muscular power.Short RI may be more practical for strength coaches under time constraints (i.e. 1 minute of RI required only 7 minutes to complete an exercise session, while with 2 minutes take 12 minutes, and 17 minutes with 3 minutes of RI).Future research is needed to examine the longitudinal effects of interval rest in training programs designed for the development of muscular power.

Graduated compression sleeves: effects on metabolic removal and neuromuscular performance.

The aim of this study was to examine the effects of upper-body graduated compression sleeves (CS) on neuromuscular and metabolic responses during a power training. Fifteen resistance trained men (age: 23.07 ± 3.92 years; body mass: 76.13 ± 7.62 kg; height: 177 ± 6 cm) performed 2 separate power training protocols, either wearing CS or placebo sleeves (PS), in a counterbalanced fashion. Participants first performed a familiarization session and a bench press 1 repetition maximum (1RM) test. The training protocol consisted of 6 sets of 6 repetitions of bench press with a load of 50% 1RM. Statistical analysis compared mean power, peak power, blood lactate, muscle activation, isometric strength, and repetitions to failure. Mean and peak power significantly (p ≤ 0.05) decreased with increasing sets. However, there was no significant difference (p > 0.05) on mean and peak power between protocols. Blood lactate clearance was also not significantly different (p > 0.05) between CS and PS. Muscle activation was not different between PRE and POST (p > 0.05) for any of the muscles analyzed. Isometric strength decreased from PRE to POST (p ≤ 0.05) and was not different between CS and PS. Repetitions to failure were not different between protocols (p > 0.05). These results demonstrate no positive performance effects when wearing graduated CS during power exercise in young trained men.

Study of muscle fatigue in isokinetic exercise with estimated conduction velocity and traditional electromyographic indicators

INTRODUCTION: In the study of human biomechanics, it is often desirable to evaluate fatigue in the muscles that are involved in performing a particular task. Identifying the phenomena responsible for this condition is a problem that in most cases is complex and requires appropriate research mechanisms. Isokinetic dynamometry (ID) and surface electromyography (SEMG) are two techniques widely used in studies on strength and muscle fatigue. Their effectiveness is conditioned upon a good understanding of their limitations and the adoption of procedures to fully exploit the potential of each one. The main goal of the present study is to verify whether the electromyographic parameters, especially the conduction velocity (CV), are sensitive to the fatigue instauration process within sets of maximal isokinetic contractions. CV is a basic physiological parameter directly related to muscle activity and still little explored in experiments combining ID and SEMG. METHODS: Instrumentation architecture that combines ID and SEMG was used to estimate electromyographic and biomechanical parameters in protocols of maximum intensity isokinetic knee extension exercises. This architecture allows for limiting the parameter estimates to a specific region of isokinetic exercise, called the isokinetic load range (ILR), where one can consider that the angular velocity is constant and the SEMG signals are cyclo-stationary. Electromyographic signals were acquired using an array of electrodes. CONCLUSION: The results suggest that CV and the other SEMG parameters, including amplitude and frequency descriptors, are sensitive to detect a fatigue process only in protocols that restrict the analysis to ILR and that also bring the subject to a state of fatigue quickly.

Fadiga muscular entre séries de exercícios isocinéticos em mulheres jovens / Muscle fatigue between isokinetic exercises sets in young women

OBJETIVO: Avaliar o efeito de dois Intervalos de Recuperação (IR) no pico de torque (PT) e no trabalho total (TT) isocinético em mulheres jovens. MÉTODOS: 17 mulheres, destreinadas, (27,2 ± 4,1 anos; 56,8 ± 6,9 kg; 162,6 ± 7,0 cm) realizaram três séries de 10 extensões isocinéticas do joelho a 60° e 180°/s, com um e dois minutos de IR. A análise estatística foi a ANOVA dois x três [IR (um e dois minutos) x série (1ª, 2ª e 3ª)] com α < 0.05. RESULTADOS: Um minuto de IR não foi suficiente para manter o PT e o TT ao longo das séries (p<0,05) a 60º (redução de 15,7% no PT e 19,8% no TT) e 180º/s (redução de 3,6% no PT e de 5,6% no TT). Dois minutos foram suficientes apenas a 180º/s. Contudo, a 60°/s, dois minutos de IR possibilitou um maior PT na segunda e na terceira série em relação a um minuto (p<0,05). CONCLUSÃO: Dois minutos são suficientes para manutenção do PT em um protocolo de treinamento isocinético a 180º/s, mas não a 60º/s em mulheres jovens.

OBJECTIVE: To examine the effect of two rest interval (RI) on isokinetic Peak Torque (PT) and total work (TW) produced by young women. METHODS: 17 untrained women (27.2 ± 4.1 yrs; 56.8 ± 6.9 kg; 162.6 ± 7.0 cm) performed three sets of 10 unilateral isokinetic knee extension repetitions at 60° and 180°/s with one and two minutes of RI. Statistical evaluation was performed using a two x three ANOVA [RI (one and two minutes) x set (1st, 2nd, 3rd)] with α < 0.05. RESULTS: One minute was not enough to keep PT and TW between sets (p<0.05) at 60º (reduction of 15.7% in PT and 19.8% in TW) and 180º/s (reduction of 3.6% in PT and 5.6% in TT). Two minutes was enough only at 180º/s. However, two minutes of RI was greater (p<0.05) than one minutes at 60°/s for PT during the 2nd and 3rd sets. CONCLUSION: Two minutes is sufficient to keep PT within typical isokinetic resistance training protocols at 180º/s, but not at 60º/s in young women.

Relationship between ventilatory threshold and muscle fiber conduction velocity responses in trained cyclists.

The relationship between surface electromyography (SEMG) amplitude and the ventilatory threshold has been extensively studied. However, previous studies of muscle fiber conduction velocity (MFCV) are scarce and present insufficient evidence concerning the relationship between MFCV and metabolic responses during cycling. Based on that fact, the purpose of this study is twofold: (1) to investigate the existence of a MFCV threshold (MFCVT) during cycling and (2) to verify if this possible breakpoint is correlated with the ventilatory threshold (VT) and the SEMG threshold (SEMGT). Eight trained male cyclists (age 36.0±9.7years) performed an incremental cycling test with initial workload of 150W gradually incremented by 20Wmin(-1) until the exhaustion. Gas analyses were conducted using a breath-by-breath open-circuit spirometry and SEMG were registered from vastus lateralis in each pedaling cycle with a linear array of electrodes. A bi-segmental linear regression computer algorithm was used to estimate VT, MFCVT and SEMGT respectively in the carbon dioxide production (VCO2), MFCV and electromyography root mean square (EMG RMS) curves. The one way ANOVA for repeated measures did not reveal any significant difference among VT (77.1±7.5% of VO2max), MFCVT (80.3±10.4% of VO2max) and SEMGT (81.9±11.7% of VO2max). The Bland and Altman procedure confirmed a good concordance between SEMGT and VT (Bias=5.5 of %VO2max) as well as MFCVT and VT (Bias=5.2 of %VO2max). The present findings suggest that muscle fiber conduction velocity threshold is a valid and reliable non-invasive tool to obtain information about ventilatory threshold in trained cyclists.

Electromyographic analyses of muscle pre-activation induced by single joint exercise.

OBJECTIVE: To investigate whether performing a low-intensity, single-joint exercises for knee extensors was an efficient strategy for increasing the number of motor units recruited in the vastus lateralis muscle during a subsequent multi-joint exercises. METHODS: Nine healthy male participants (23.33+/-3.46 yrs) underwent bouts of exercise in which knee extension and 45 degrees , and leg press exercises were performed in sequence. In the low-intensity bout (R30), 15 unilateral knee extensions were performed, followed by 15 repetitions of the leg presses at 30% and 60% of one maximum repetition load (1-MR), respectively. In the high-intensity bout (R60), the same sequence was performed, but the applied load was 60% of 1-MR for both exercises. A single set of 15 repetitions of the leg press at 60% of 1-MR was performed as a control exercise (CR). The surface electromyographic signals of the vastus lateralis muscle were recorded by means of a linear electrode array. The root mean square (RMS) values were determined for each repetition of the leg press, and linear regressions were calculated from these results. The slopes of the straight lines obtained were then normalized using the linear coefficients of the regression equations and compared using one-way ANOVAs for repeated measures. RESULTS: The slopes observed in the CR were significantly lower than those in the R30 and R60 (p<0.05). CONCLUSIONS: The results indicated that the recruitment of motor units was more effective when a single-joint exercise preceded the multi-joint exercise. Article registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) under the number ACTRN12609000413224.

Análise eletromiográfica da pré-ativação muscular induzida por exercício monoarticular / Electromyographic analyses of muscle pre-activation induced by single joint exercise

OBJETIVO: Verificar se a execução de um exercício monoarticular de baixa intensidade para os extensores do joelho é uma estratégia eficaz para aumentar o número de unidades motoras recrutadas no músculo vasto lateral durante a realização de um exercício multiarticular subsequente. MÉTODOS: Nove sujeitos saudáveis do sexo masculino (23,33±3,46 anos) foram submetidos a rotinas de treinamento nas quais os exercícios cadeira extensora e leg press 45° eram realizados em sequência. Na rotina de baixa intensidade (R30), foram realizadas 15 extensões unilaterais de joelho, seguidas de 15 repetições de leg press 45° com cargas de 30 por cento e 60 por cento de uma repetição máxima (1-RM), respectivamente. Na rotina de alta intensidade (R60), a mesma sequência foi executada, porém a carga dos dois movimentos foi de 60 por cento de 1-RM. Uma série simples de 15 repetições leg press 45° com carga de 60 por cento de 1-RM foi utilizada como exercício controle (RC). A eletromiografia de superfície foi registrada no músculo vasto lateral por meio de um arranjo linear de eletrodos. O valor RMS foi calculado para cada repetição do leg press 45° e, a partir desses resultados, foram calculadas regressões lineares. As inclinações das retas obtidas foram então normalizadas pelos coeficientes lineares das equações de regressão e comparadas por meio da ANOVA de um fator para medidas repetidas. RESULTADOS: As inclinações observadas na rotina RC foram significativamente inferiores às de R30 e às de R60 (p<0,05). CONCLUSÕES: Os resultados indicaram um recrutamento mais efetivo de unidades motoras nas rotinas de exercício multiarticular precedidas de exercício monoarticular.

OBJECTIVE: To investigate whether performing a low-intensity, single-joint exercises for knee extensors was an efficient strategy for increasing the number of motor units recruited in the vastus lateralis muscle during a subsequent multi-joint exercises. METHODS: Nine healthy male participants (23.33±3.46 yrs) underwent bouts of exercise in which knee extension and 45°, and leg press exercises were performed in sequence. In the low-intensity bout (R30), 15 unilateral knee extensions were performed, followed by 15 repetitions of the leg presses at 30 percent and 60 percent of one maximum repetition load (1-MR), respectively. In the high-intensity bout (R60), the same sequence was performed, but the applied load was 60 percent of 1-MR for both exercises. A single set of 15 repetitions of the leg press at 60 percent of 1-MR was performed as a control exercise (CR). The surface electromyographic signals of the vastus lateralis muscle were recorded by means of a linear electrode array. The root mean square (RMS) values were determined for each repetition of the leg press, and linear regressions were calculated from these results. The slopes of the straight lines obtained were then normalized using the linear coefficients of the regression equations and compared using one-way ANOVAs for repeated measures. RESULTS: The slopes observed in the CR were significantly lower than those in the R30 and R60 (p<0.05). CONCLUSIONS: The results indicated that the recruitment of motor units was more effective when a single-joint exercise preceded the multi-joint exercise.

Effects of exercise order on upper-body muscle activation and exercise performance.

With the purpose of manipulating training stimuli, several techniques have been employed to resistance training. Two of the most popular techniques are the pre-exhaustion (PRE) and priority system (PS). PRE involves exercising the same muscle or muscle group to the point of muscular failure using a single-joint exercise immediately before a multi-joint exercise (e.g., peck-deck followed by chest press). On the other hand, it is often recommended that the complex exercises should be performed first in a training session (i.e., chest press before peck-deck), a technique known as PS. The purpose of the present study was to compare upper-body muscle activation, total repetitions (TR), and total work (TW) during PRE and PS. Thirteen men (age 25.08 +/- 2.58 years) with recreational weight-training experience performed 1 set of PRE and 1 set of PS in a balanced crossover design. The exercises were performed at the load obtained in a 10 repetition maximum (10RM) test. Therefore, chest press and peck-deck were performed with the same load during PRE and PS. Electromyography (EMG) was recorded from the triceps brachii (TB), anterior deltoids, and pectoralis major during both exercises. According to the results, TW and TR were not significantly different (p > 0.05) between PRE and PS. Likewise, during the peck-deck exercise, no significant (p > 0.05) EMG change was observed between PRE and PS order. However, TB activity was significantly (p < 0.05) higher when chest press was performed after the peck-deck exercise (PRE). Our findings suggest that performing pre-exhaustion exercise is no more effective in increasing the activation of the prefatigued muscles during the multi-joint exercise. Also, independent of the exercise order (PRE vs. PS), TW is similar when performing exercises for the same muscle group. In summary, if the coach wants to maximize the athlete performance in 1 specific resistance exercise, this exercise should be placed at the beginning of the training session.

Comparação entre a atividade EMG do peitoral maior, deltóide anterior e tríceps braquial durante os exercícios supino reto e crucifixo / Comparación entre la actividad EMG del pectoral mayor, deltoide anterior y tríceps braquial durante los ejercicios supino recto y cruz / Comparison among the EMG activity of the pectoralis major, anterior deltoidis and triceps brachii during the bench press and peck deck exercises

A identificação das peculiaridades de cada movimento e sua adequação aos objetivos do treinamento é uma tarefa que exige a interação de vários conhecimentos. Tal tarefa é fundamental para o sucesso nas diversas modalidades esportivas e programas de treinamento com fins de reabilitação e/ou estética. O objetivo do presente estudo foi comparar a atividade eletromiográfica (EMG) dos músculos peitoral maior (PM), deltóide anterior (DA) e tríceps braquial (TB) durante a execução dos exercícios supino reto com barra (SP) e crucifixo na máquina (CR). As atividades EMG dos músculos PM, DA e TB foram avaliadas durante a realização de 10 repetições máximas no CR e SP em 13 homens treinados. Os resultados não revelaram diferenças na atividade do PM e DA entre os exercícios. A atividade do TB foi maior na realização do SP em comparação com o CR. Durante o SP, a atividade do PM foi maior em relação ao TB, sem diferenças entre PM e DA ou DA e TB. No CR, a atividade do PM e a do DA foram maiores em relação ao TB, sem diferenças entre DA e PM. De acordo com os resultados obtidos no presente estudo pode-se concluir que, caso o objetivo do treinamento seja promover estímulos para o DA ou PM, ambos os exercícios podem ser usados, dependendo da disponibilidade de materiais e/ou da especificidade da atividade motora na qual se procura melhorar a performance.

The identification of the characteristics of each movement and its adjustment to the training goals are tasks that demand the interaction of many knowledge areas. These tasks are essential to the success in sports activities and training programs designed with athletic, aesthetic or healthy purposes. The objective of the present study was to compare the electromyograhic (EMG) activity of the pectoralis major (PM), anterior deltoids (DA) and triceps brachii (TB) muscles during the barbell bench press (SP) and the peck deck (PD) exercises. EMG activity of TB, PM and DA were assessed during 10 maximum repetitions performed in SP and PD in 13 trained men. The results did not show any differences between exercises for PM and DA activity; however, TB activity was higher for SP than PD exercise. During SP, the PM muscle activity was higher than TB. There were no differences between PM and DA, or between DA and TB. During the PD exercise, the PM and DA muscle activities were higher than TB. There were no differences between PM and DA. It was concluded that the prime movers of both exercise are DA and PM, and there are no differences between them. Therefore, both PD and SP could be performed with the purpose to stimulate DA and PM muscles, depending on the availability of the equipments and/or the specificity of the motor tasks.

La identificación de las peculiaridades de cada movimiento y su adecuación a los objetivos de entrenamiento es una tarea que exige la interacción de varias áreas de conocimiento. Tal tarea es fundamental para el éxito en las diversas modalidades deportivas y programas de entrenamiento con fines de rehabilitación y/o estética. El objetivo del presente estudio ha sido comparar la actividad electromiográfica (EMG) de los músculos pectoral mayor (PM), deltoides anterior (DA) y tríceps braquial (TB) durante la ejecución de los ejercicios supino recto con barra (SP) y de cruz en máquina (CR). Las actividades EMG de los músculos PM, DA y TB fueron evaluados durante la realización de 10 repeticiones máximas en CR y SP en 13 hombres entrenados. Los resultados no revelaron diferencias en la actividad de PM y DA entre los ejercicios. La actividad de TB fue mayor en la realización de SP en comparación con CR. Durante SP, la actividad de PM fue mayor en relación a TB, sin diferencias entre PM y DA o DA y TB. En CR, la actividad de PM y DA fueron mayores en relación a TB, sin diferencias entre DA y PM. De acuerdo con los resultados obtenidos en el presente estudio se puede concluir que en caso de que el objetivo de entrenamiento sea promover estímulos para DA o PM, ambos ejercicios pueden ser usados, dependiendo de la disponibilidad de materiales y/o de la especificidad de la actividad motora en la cual se procure mejorar el desempeño.