The increase in surface EMG could be a misleading measure of neural adaptation during the early gains in strength

Arabadzhiev, Todor I.; Dimitrov, Vladimir G.; Dimitrov, George

doi:10.1007/s00421-014-2893-y

Cited by 26 publications

(22 citation statements)

References 67 publications

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“…Traditionally, training-induced increases in EMG amplitude have been interpreted as increases in neural drive to the muscle (Komi et al, 1978; Moritani and deVries, 1979; Hakkinen and Komi, 1983; Thepaut-Mathieu et al, 1988). While caution is warranted when interpreting changes in surface EMG amplitude in this way, normalizing to the M-wave helps to control for peripheral adaptations and/or changes in electrode placement that may influence the EMG signal (Folland and Williams, 2007; Arabadzhiev et al, 2014), allowing EMG QAMP to be considered an indirect indicator of efferent drive (Lepers et al, 2001; Trezise et al, 2016). In combination with the increase in VA, the increase in EMG QAMP observed in the present study seem to reflect greater motor unit excitation following training at 80% 1RM.…”

Section: Discussionmentioning

confidence: 99%

“…The EMG amplitude was expressed as the root mean square value in μV during the isometric muscle actions. In order to reduce error due to electrode relocation, subcutaneous fat, and the influence of peripheral factors on the EMG signal (Folland and Williams, 2007; Arabadzhiev et al, 2014), the absolute EMG amplitude values during MVIC and at 10–100% of MVIC at Baseline, Week 3, and Week 6 were normalized to the M PP values at Baseline, Week 3, and Week 6, respectively (Behrens et al, 2015) and was thus considered an indicator of central efferent drive to the quadriceps femoris muscles (Lepers et al, 2001; Trezise et al, 2016). Furthermore, EMG amplitude was average across the VL, VM, and RF to calculate quadriceps femoris muscle activation (EMG QAMP ) (Trezise et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

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Greater Neural Adaptations following High- vs. Low-Load Resistance Training

et al. 2017

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We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 1RM; n = 13) resistance training group and completed leg extension resistance training to failure 3 times per week for 6 weeks. Testing was completed at baseline, 3, and 6 weeks of training. During each testing session, ultrasound muscle thickness and echo intensity, 1RM strength, maximal voluntary isometric contraction (MVIC) strength, and contractile properties of the quadriceps femoris were measured. Percent voluntary activation (VA) and electromyographic (EMG) amplitude were measured during MVIC, and during randomly ordered isometric step muscle actions at 10–100% of baseline MVIC. There were similar increases in muscle thickness from Baseline to Week 3 and 6 in the 80 and 30% 1RM groups. However, both 1RM and MVIC strength increased from Baseline to Week 3 and 6 to a greater degree in the 80% than 30% 1RM group. VA during MVIC was also greater in the 80 vs. 30% 1RM group at Week 6, and only training at 80% 1RM elicited a significant increase in EMG amplitude during MVIC. The peak twitch torque to MVIC ratio was also significantly reduced in the 80%, but not 30% 1RM group, at Week 3 and 6. Finally, VA and EMG amplitude were reduced during submaximal torque production as a result of training at 80% 1RM, but not 30% 1RM. Despite eliciting similar hypertrophy, 80% 1RM improved muscle strength more than 30% 1RM, and was accompanied by increases in VA and EMG amplitude during maximal force production. Furthermore, training at 80% 1RM resulted in a decreased neural cost to produce the same relative submaximal torques after training, whereas training at 30% 1RM did not. Therefore, our data suggest that high-load training results in greater neural adaptations that may explain the disparate increases in muscle strength despite similar hypertrophy following high- and low-load training programs.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Greater Neural Adaptations following High- vs. Low-Load Resistance Training

et al. 2017

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“…Caution should be used when interpreting increases in surface EMG amplitude. Simulation studies have shown that peripheral factors seem to have a larger effect on the gross EMG signal than neural factors (Arabadzhiev et al 2014) and that lower amplitude cancellation could account for an increased EMGrms independent to neural drive (Keenan et al 2006). There is some experimental evidence to suggest that this is possible (Maffiuletti and Martin 2001) due to relatively slow, submaximal load training such as that used in the present study.…”

Section: Discussionmentioning

confidence: 99%

Medium-intensity, high-volume “hypertrophic” resistance training did not induce improvements in rapid force production in healthy older men

Walker

Peltonen

Häkkinen

2015

AGE

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The aim of the study was to determine whether it is possible to improve both maximum and rapid force production using resistance training that is typically used to induce muscle hypertrophy in previously untrained older men. Subjects (60-72 years) performed 20 weeks of "hypertrophic" resistance training twice weekly (n = 27) or control (n = 11). Maximum dynamic and isometric leg press, as well as isometric force over 0-100 ms, and maximum concentric power tests were performed pre- and post-intervention. Muscle activity was assessed during these tests by surface electromyogram of the vastus lateralis and medialis muscles. Muscle hypertrophy was assessed by panoramic ultrasound of the vastus lateralis. The intervention group increased their maximum isometric (from 2268 ± 544 to 2538 ± 701 N) and dynamic force production (from 137 ± 24 to 165 ± 29 kg), and these changes were significantly different to control (isometric 12 ± 16 vs. 1 ± 9 %; dynamic 21 ± 12 vs. 2 ± 4 %). No within- or between-group differences were observed in rapid isometric force or concentric power. Relative increases in vastus lateralis cross-sectional area trended to be statistically greater in the intervention group (10 ± 8 vs. 3 ± 6 %, P = 0.061). It is recommendable that resistance training programs for older individuals integrate protocols emphasizing maximum force/muscle hypertrophy and rapid force production in order to induce comprehensive health-related and functionally important improvements in this population.

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“…It has been suggested that sEMG should be normalized to the CMAP P‐P amplitude. By subtracting out potential changes within the muscle and technical factors that may vary across test sessions, the remaining sEMG signal should be a true estimate of central drive . Although conceptually appealing, the normalization procedure poses two problems.…”

Section: Discussionmentioning

confidence: 99%

“…By subtracting out potential changes within the muscle and technical factors that may vary across test sessions, the remaining sEMG signal should be a true estimate of central drive. 43,44 Although conceptually appealing, the normalization procedure poses two problems. First, the ratio score combines the measurement error of two variables and can redistribute the variance.…”

Section: Discussionmentioning

confidence: 99%