Interpreting Signal Amplitudes in Surface Electromyography Studies in Sport and Rehabilitation Sciences

Vigotsky, Andrew D.; Halperin, Israel; Lehman, Gregory J; Trajano, Gabriel S.; Vieira, Taian

doi:10.3389/fphys.2017.00985

Cited by 322 publications

(281 citation statements)

References 111 publications

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“…Cook and colleagues (19) infer that this might be related to a greater degree of motor unit recruitment and/or firing rates with HL. However, the interpretation of electromyography (EMG) regarding both factors is difficult since various variables including motor unit synchronization, fatigue, and motor unit cycling contribute to changes in EMG amplitude (23,55,57). Another frequently used method to investigate neural drive is the twitch interpolation technique (27).…”

Section: Muscle Propertiesmentioning

confidence: 99%

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training

Centner

Lauber

Seynnes

et al. 2019

Journal of Applied Physiology

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Low-load blood flow restriction (LL-BFR) training has gained increasing interest in the scientific community by demonstrating that increases in muscle mass and strength are comparable to conventional high-load (HL) resistance training. Although adaptations on the muscular level are well documented, there is little evidence on how LL-BFR training affects human myotendinous properties. Therefore, the aim of the present study was to investigate morphological and mechanical Achilles tendon adaptations after 14 wk of strength training. Fifty-five male volunteers (27.9 ± 5.1 yr) were randomly allocated into the following three groups: LL-BFR [20–35% of one-repetition maximum (1RM)], HL (70–85% 1RM), or a nonexercising control (CON) group. The LL-BFR and HL groups completed a resistance training program for 14 wk, and tendon morphology, mechanical as well as material properties, and muscle cross-sectional area (CSA) and isometric strength were assessed before and after the intervention. Both HL (+40.7%) and LL-BFR (+36.1%) training induced significant increases in tendon stiffness ( P < 0.05) as well as tendon CSA (HL: +4.6%, LL-BFR: +7.8%, P < 0.001). These changes were comparable between groups without significant changes in Young’s modulus. Furthermore, gastrocnemius medialis muscle CSA and plantar flexor strength significantly increased in both training groups ( P < 0.05), whereas the CON group did not show significant changes in any of the evaluated parameters. In conclusion, the adaptive change in Achilles tendon properties following low-load resistance training with partial vascular occlusion appears comparable to that evoked by high-load resistance training. NEW & NOTEWORTHY Low-load blood flow restriction (LL-BFR) training has been shown to induce beneficial adaptations at the muscular level. However, studies examining the effects on human tendon properties are rare. The findings provide first evidence that LL-BFR can increase Achilles tendon mechanical and morphological properties to a similar extent as conventional high-load resistance training. This is of particular importance for individuals who may not tolerate heavy training loads but still aim for improvements in myotendinous function.

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Section: Muscle Propertiesmentioning

confidence: 99%

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training

Centner

Lauber

Seynnes

et al. 2019

Journal of Applied Physiology

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“…In addition to the limitations surrounding NJM analysis, differences in quadriceps utilization between squatting widths should not be inferred solely based on EMG results. 26 Based on anecdotal evidence, squatting in substantially wider position (ie, at or above ~1.5× greater trochanter width) can hinder depth and knee flexion. Greater knee flexion angles have been suggested to be a larger determinant of quadriceps utilization than external load when observing angle-specific relative muscular efforts in the squat.…”

Section: Net Joint Momentsmentioning

confidence: 99%

Effects of barbell back squat stance width on sagittal and frontal hip and knee kinetics

Lahti

Hegyi

Vigotsky

et al. 2018

Scandinavian Med Sci Sports

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Different stance widths are commonly utilized when completing the barbell back squat during athletic general preparedness training. Width manipulation is thought to influence sagittal plane stimuli to the hip and knee extensors, the primary extensor musculature in the squat. However, how width manipulation affects frontal plane stimuli is less understood. Knowledge of hip and knee net joint moments (NJM) could improve exercise selection when aiming to improve sport-specific performance and prevent injuries. Fourteen adult amateur rugby athletes were recruited for this study. After a familiarization period, participants performed wide- (WIDE, 1.5× greater trochanter width) and narrow-stance (NARROW, 1× greater trochanter width) barbell back squats to femur parallel depth, using relative loads of 70% and 85% of one-repetition maximum. Sagittal and frontal plane hip and knee kinetics and kinematics were compared between widths. A Bonferroni-corrected alpha of 0.01 was employed as the threshold for statistical significance. Knee flexion angle was statistically greater in NARROW than WIDE (P < 0.0001, d = 2.56-2.86); no statistical differences were observed for hip flexion angle between conditions (P = 0.049-0.109, d = 0.33-0.38). Hip-to-knee extension NJM ratios and knee adduction NJMs were statistically greater in WIDE than NARROW (P < 0.007, d = 0.51-1.41). At femur parallel, stance width manipulation in the barbell back squat may provide substantial differences in biomechanical stimulus in both the sagittal plane and the frontal plane. In certain contexts, these differences may have clinically relevant longitudinal implications, from both a performance and a injury prevention standpoint, which are discussed.

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“…In exercise physiology, the type of EMG used is usually surface EMG with bipolar electrodes applied on the skin over the working muscles. In surface EMG research, the amplitude is often used to infer the level of “neural drive” to the muscles, although the limitations of surface EMG for this purpose have been known for several decades (reviewed by Duchateau et al, Farina et al, and Vigotsky et al). For example, Moritani et al cautioned that the change in the surface EMG should not automatically be attributed to changes in either motor unit recruitment or in firing rates as the EMG amplitude is further influenced by the individual muscle fibre potential, degree of motor unit synchronization, and fatigue.…”

Section: Methods To Investigate Muscle Fibre Activation and Usementioning

confidence: 99%

Muscle fibre activation and fatigue with low‐load blood flow restricted resistance exercise—An integrative physiology review

Wernbom

Aagaard

2019

Acta Physiologica

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Blood flow-restricted resistance exercise (BFRRE) has been shown to induce increases in muscle size and strength, and continues to generate interest from both clinical and basic research points of view. The low loads employed, typically 20%-50% of the one repetition maximum, make BFRRE an attractive training modality for individuals who may not tolerate high musculoskeletal forces (eg, selected clinical patient groups such as frail old adults and patients recovering from sports injury) and/or for highly trained athletes who have reached a plateau in muscle mass and strength. It has been proposed that achieving a high degree of muscle fibre recruitment is important for inducing muscle hypertrophy with BFRRE, and the available evidence suggest that fatiguing low-load exercise during ischemic conditions can recruit both slow (type I) and fast (type II) muscle fibres. Nevertheless, closer scrutiny reveals that type II fibre activation in BFRRE has to date largely been inferred using indirect methods such as electromyography and magnetic resonance spectroscopy, while only rarely addressed using more direct methods such as measurements of glycogen stores and phosphocreatine levels in muscle fibres. Hence, considerable uncertainity exists about the specific pattern of muscle fibre activation during BFRRE. Therefore, the purpose of this narrative review was (1) to summarize the evidence on muscle fibre recruitment during BFRRE as revealed by various methods employed for determining muscle fibre usage during exercise, and (2) to discuss reported findings in light of the specific advantages and limitations associated with these methods. K E Y W O R D Sfatigue, ischemia, motor units, muscle hypertrophy, occlusion 4 of 48 | WERNBOM aNd aaGaaRd 3.5.), which in turn can raise the recruitment threshold of the highest threshold units (discussed in Section 3.4.). As a result, the approximate upper limit for motor unit recruitment during more normal and physiologically relevant contraction durations (eg, 1-3 seconds) remains to be fully defined.

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Interpreting Signal Amplitudes in Surface Electromyography Studies in Sport and Rehabilitation Sciences

Cited by 322 publications

References 111 publications

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training

Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training

Effects of barbell back squat stance width on sagittal and frontal hip and knee kinetics

Muscle fibre activation and fatigue with low‐load blood flow restricted resistance exercise—An integrative physiology review

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