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The Effects of Muscle Actions Upon Strength Gains

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De Carvalho Nogueira A., De Souza Vale R., Colado J., Tella V., Garcia-Massó X., Dantas E.

Human Movement

2011

vol. 12

issue 4

331-336

Purpose. The purpose of this study was to compare the effects of concentric with eccentric muscle actions on strength gains. Methods. Forty-two untrained men were randomly divided into three groups: the concentric experimental (CE), the eccentric experimental (EE) and a control (C). The CE group performed only concentric muscle actions at 80% of one repetition maximum (1 RM) and the EE group performed only eccentric muscle actions at 120% of 1 RM. Both groups trained by performing three sets of 10-12 repetitions for eight weeks of biceps curl (BC) and bench press (BP) exercises. The C group did not engage in any type of training. Results. Analyses performed within the CE group found that there were significant improvements in muscle strength in the eighth week of BP (Δ % = 26.9%, p = 0.01) and in the fourth and eighth week of BC (Δ % = 22.1%, p = 0.00 and Δ% = 32.1%, p = 0.00, respectively). Analyses of the EE group found that there were significant improvements in muscle strength in the fourth and eighth week of BP (Δ% = 13.7%, p = 0.00 and Δ% = 28.4%, p = 0.00, respectively). Between the two groups (CE versus EE), comparisons showed that the CE group performed significantly better than the EE group in the fourth and eighth week of BC (p = 0.00 and p = 0.00, respectively). Conclusions. These findings indicate that those who do not train should perform concentric muscle actions in the first 8 weeks of training in order to generate accelerated strength improvement.

Maximal Isokinetic Peak Torque and EMG Activity Determined by Shorter Ranges of Motion

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Oliveira A., Corvino R., Gonçalves M., Caputo F., Denadai B.

Human Movement

2012

vol. 13

issue 2

102-108

Purpose. Isokinetic tests are often applied to assess muscular strength and EMG activity, however the specific ranges of motion used in testing (fully flexed or extended positions) might be constrictive and/or be painful for patients with injuries or under-going rehabilitation. The aim of this study was to examine the effects of different ranges of motion (RoM) when determining maximal EMG during isokinetic knee flexion and extension with different types of contractions and velocities. Methods. Eighteen males had EMG activity recorded on the vastus lateralis, vastus medialis, semitendinosus and biceps femoris muscles during five maximal isokinetic concentric and eccentric contractions for the knee flexors and extensors at 60° · s-1 and 180° · s-1. The root mean square of EMG was calculated at three different ranges of motion: (1) a full range of motion (90°-20° [0° = full knee extension]); (2) a range of motion of 20° (between 60°-80° and 40°-60° for knee extension and flexion, respectively) and (3) at a 10° interval around the angle where peak torque is produced. EMG measurements were statistically analyzed (ANOVA) to test for the range of motion, contraction velocity and contraction speed effects. Coefficients of variation and Pearson's correlation coefficients were also calculated among the ranges of motion. Results. Predominantly similar (p > 0.05) and well-correlated EMG results (r > 0.7, p ≤ 0.001) were found among the ranges of motion. However, a lower coefficient of variation was found for the full range of motion, while the 10° interval around peak torque at 180° · s-1 had the highest coefficient, regardless of the type of contraction. Conclusions. Shorter ranges of motion at around the peak torque angle provides a reliable indicator when recording EMG activity during maximal isokinetic parameters. It may provide a safer alternative when testing patients with injuries or undergoing rehabilitation.

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2 Human Movement

1 2012

1 2011

1 Caputo F.

1 Colado J.

1 Corvino R.

1 Dantas E.

1 De Carvalho Nogueira A.

1 De Souza Vale R.

1 Denadai B.

1 Garcia-Massó X.

1 Gonçalves M.

1 Oliveira A.

1 Tella V.

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The Effects of Muscle Actions Upon Strength Gains

Maximal Isokinetic Peak Torque and EMG Activity Determined by Shorter Ranges of Motion