Maria C. Pereira

Effect of adding single-joint exercises to a multi-joint exercise resistance-training program on strength and hypertrophy in untrained subjects

The aim of this study was to examine the effect of adding single-joint (SJ) exercises to a multi-joint (MJ) exercise resistance-training program on upper body muscle size and strength. Twenty-nine untrained young men participated in a 10-week training session. They were randomly divided in 2 groups: the MJ group performed only MJ exercises (lat pulldown and bench press); the MJ+SJ group performed the same MJ exercises plus SJ exercises (lat pulldown, bench press, elbow flexion, and elbow extension). Before and after the training period, the muscle thickness (MT) of the elbow flexors was measured with ultrasound, and peak torque (PT) was measured with an isokinetic dynamometer. There was a significant (p < 0.05) increase in MT (6.5% for MJ and 7.04% for MJ+SJ) and PT (10.40% for MJ and 12.85% for MJ+SJ) in both groups, but there were no between-group differences. Therefore, this study showed that the inclusion of SJ exercises in a MJ exercise training program resulted in no additional benefits in terms of muscle size or strength gains in untrained young men.

Dissociated Time Course of Muscle Damage Recovery Between Single- and Multi-Joint Exercises in Highly Resistance-Trained Men

Abstract Soares, S, Ferreira-Junior, JB, Pereira, MC, Cleto, VA, Castanheira, RP, Cadore, EL, Brown, LE, Gentil, P, Bemben, MG, and Bottaro, M. Dissociated time course of muscle damage recovery between single- and multi-joint exercises in highly resistance-trained men. J Strength Cond Res 29(9): 2594–2599, 2015—This study compared the time course of elbow flexor muscle recovery after multi- and single-joint exercises in highly resistance-trained men. Sixteen men (24.5 ± 5.5 years) performed, in a counterbalanced order, 8 sets of 10 repetition maximum (RM) unilateral seated row exercise and 8 sets of 10RM unilateral biceps preacher curl exercise using the contralateral arm. Maximum isometric peak torque (PT) and delayed onset muscle soreness (DOMS) were recorded at baseline (pre), 10 minutes, 24, 48, 72, and 96 hours after each exercise protocol. There was a significant decrease (p ⩽ 0.05) in elbow flexor PT 10 minutes after both the multi- and single-joint exercise sessions. However, PT decrease was greater after single-joint (26.8%) when compared with multi-joint (15.1%) exercise (p ⩽ 0.05). In addition, elbow flexor PT was lower (8.4%) than baseline 24 hours after the single-joint exercise (p < 0.01), whereas PT returned to baseline 24 hours after the multi-joint exercise. Compared with baseline, DOMS increased at 24, 48, and 72 hours after single-joint exercise (p ⩽ 0.05). However, DOMS returned to baseline levels after 72 hours after multi-joint exercise. In addition, DOMS after single-joint exercise was greater (p ⩽ 0.05) than after multi-joint exercise at 24, 48, and 72 hours after exercise. Our data suggest that after a resistance training session, highly resistance-trained men experience dissimilar elbow flexor strength recovery between single-joint and multi-joint exercises. Likewise, elbow flexor DOMS is greater and takes longer to recover after single-joint exercise.

Análise eletromiográfica da pré-ativação muscular induzida por exercício monoarticular

OBJETIVO: Verificar se a execucao de um exercicio monoarticular de baixa intensidade para os extensores do joelho e uma estrategia eficaz para aumentar o numero de unidades motoras recrutadas no musculo vasto lateral durante a realizacao de um exercicio multiarticular subsequente. METODOS: Nove sujeitos saudaveis do sexo masculino (23,33±3,46 anos) foram submetidos a rotinas de treinamento nas quais os exercicios cadeira extensora e leg press 45° eram realizados em sequencia. Na rotina de baixa intensidade (R30), foram realizadas 15 extensoes unilaterais de joelho, seguidas de 15 repeticoes de leg press 45° com cargas de 30% e 60% de uma repeticao maxima (1-RM), respectivamente. Na rotina de alta intensidade (R60), a mesma sequencia foi executada, porem a carga dos dois movimentos foi de 60% de 1-RM. Uma serie simples de 15 repeticoes leg press 45° com carga de 60% de 1-RM foi utilizada como exercicio controle (RC). A eletromiografia de superficie foi registrada no musculo vasto lateral por meio de um arranjo linear de eletrodos. O valor RMS foi calculado para cada repeticao do leg press 45° e, a partir desses resultados, foram calculadas regressoes lineares. As inclinacoes das retas obtidas foram entao normalizadas pelos coeficientes lineares das equacoes de regressao e comparadas por meio da ANOVA de um fator para medidas repetidas. RESULTADOS: As inclinacoes observadas na rotina RC foram significativamente inferiores as de R30 e as de R60 (p<0,05). CONCLUSOES: Os resultados indicaram um recrutamento mais efetivo de unidades motoras nas rotinas de exercicio multiarticular precedidas de exercicio monoarticular. Artigo registrado na Australian New Zealand Clinical Trials Registry (ANZCTR) sob o numero ACTRN12609000413224.

Specific joint angle assessment of the shoulder rotators

BACKGROUND: Independent peak torque (IPT) ratios may lead to misinterpretation of shoulder rotator imbalances. OBJECTIVE: To compare shoulder rotator IPT conventional ratio (CR) and dynamic control ratio (DCR) with ten-degree angle specific torque (AST) CR and DCR. METHODS: Twenty healthy adult males (24.65 ± 2.4 yrs) performed concentric (C) and eccentric (E) internal rotation (IR) and external rotation (ER) of the right shoulder on an isokinetic dynamometer at 60 ◦ /s and 180 ◦ /s through 150 ◦ of ROM. RESULTS: IPT DCR was significantly different than AST DCR at several angles at both test speeds. IPT CR were not significantly different than any AST CR at either speed. The last 3 ten degree AST DCR were also compared. AST DCR was significantly different at two angles at 60 ◦ /s and at three angles at 180 ◦ /s. CONCLUSION: DCR analysis should use a ten degree AST interpretative approach in order to avoid erroneous interpretations of shoulder rotator strength imbalances. IPT ratio tests should only be used to calculate CR.

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

Abstract Martorelli, SS, Martorelli, AS, Pereira, MC, Rocha-Junior, VA, Tan, JG, Alvarenga, JG, Brown, LE, and Bottaro, M. Graduated compression sleeves: Effects on metabolic removal and neuromuscular performance. J Strength Cond Res 29(5): 1273–1278, 2015—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.

Comparison of upper body strength gains between men and women after 10 weeks of resistance 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.

The Effects of Graduated Compression Sleeves on Muscle Performance: A Randomised Controlled Trial

The purpose of this study was to examine the effects of graduated compression sleeves on muscle performance during high-intensity exercise. Twenty-four resistance trained men were randomly assigned to one of two groups: compression sleeve (GCS, n=11) or placebo sleeve (GPS, n=13). Participants performed 4 sets of 10 unilateral maximal eccentric/concentric elbow flexion repetitions on an isokinetic dynamometer at 120°s−1 with 1 min of inter-set rest. Average torque, work and power were measured during concentric and eccentric actions. ANOVA revealed no significant interactions or main effects for group for any variable. However, values decreased significantly across sets for average torque (1st = 46.55 ± 11.11 Nm to 4th = 36.75 ± 8.78 Nm), average work (1st = 78.83 ± 18.49 J to 4th = 53.26 ± 10.04 J) and average power (1st = 52.3 ± 12.03 W to 4th = 32.59 ± 8.82 W). Therefore, the use of a graduated compression sleeve appears not enhance isokinetic elbow flexion muscle performance.

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.

Reliability of normalized surface electromyographic signals of maximal upper-body isokinetic strength

BACKGROUND: Normalization in surface electromyography (SEMG) has been the object of numerous investigations. OBJECTIVE: The purpose of this study was to evaluate the reliability of normalized SEMG amplitude, as well as the reliability of different normalization coefficients during isokinetic upper-body strength assessment. METHODS: Thirteen male subjects performed a maximal isokinetic elbow flexion test and test-retest separated by 5 to 7 days. Three normalization coefficients were extracted from the tests: 1) mean value of the rectified SEMG signal (MeanTask); 2) peak value of the rectified SEMG signal (PeakTask); 3) maximal value of the rectified SEMG signal of the peak torque repetition (Isokinetic-specMVC). These normalization coefficients, as well as the root mean square value (RMS) of the signal before and after normalization by described coefficients (RMS-MeanTask; RMS-PeakTask; RMS-Isokinetic-specMVC) were evaluated in terms of absolute and relative reliability. RESULTS: None of the normalization coefficients presented acceptable levels of absolute reliability (bias range in limits of agreement greater than 27%). However MeanTask and Isokinetic-specMVC presented good levels of relative reliability (ICC > 0.80). RMS-MeanTask was the only amplitude parameter that demonstrated satisfactory indices of absolute (bias range lower than 5% and CV 0.80) reliability. CONCLUSIONS: Normalizing SEMG amplitude by MeanTask is a reasonable strategy to reduce day-to-day amplitude discrepancies during isokinetic upper-body strength assessment.

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.