Short-term neuromuscular, morphological, and architectural responses to eccentric quasi-isometric muscle actions
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ORIGINAL ARTICLE
Short‑term neuromuscular, morphological, and architectural responses to eccentric quasi‑isometric muscle actions Dustin J. Oranchuk1,2 · André R. Nelson2 · Adam G. Storey1 · Shelley N. Diewald1 · John B. Cronin1 Received: 18 May 2020 / Accepted: 21 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Eccentric quasi-isometric (EQI) contractions have been proposed as a novel training method for safely exposing the musculotendinous system to a large mechanical load/impulse, with few repetitions. However, understanding of this contraction type is rudimentary. We aimed to compare the acute effects of a single session of isotonic EQIs with isokinetic eccentric (ECC) contractions. Methods Fifteen well-trained men performed a session of impulse-equated EQI and ECC knee extensions, with each limb randomly allocated to one contraction type. Immediately PRE, POST, 24/48/72 h, and 7 days post-exercise, regional soreness, quadriceps swelling, architecture, and echo intensity were evaluated. Peak concentric and isometric torque, rate of torque development (RTD), and angle-specific impulse were evaluated at each time point. Results There were substantial differences in the number of contractions (ECC: 100.8 ± 54; EQI: 3.85 ± 1.1) and peak torque (mean: ECC: 215 ± 54 Nm; EQI: 179 ± 28.5 Nm). Both conditions elicited similar responses in 21/53 evaluated variables. EQIs resulted in greater vastus intermedius swelling (7.1–8.8%, ES = 0.20–0.29), whereas ECC resulted in greater soreness at the distal and middle vastus lateralis and distal rectus femoris (16.5–30.4%, ES = 0.32–0.54) and larger echogenicity increases at the distal rectus femoris and lateral vastus intermedius (11.9–15.1%, ES = 0.26––0.54). Furthermore, ECC led to larger reductions in concentric (8.3–19.7%, ES = 0.45–0.62) and isometric (6.3–32.3%, ES = 0.18–0.70) torque and RTD at medium-long muscle lengths. Conclusion A single session of EQIs resulted in less soreness and smaller reductions in peak torque and RTD versus impulse-equated ECC contractions, yet morphological shifts were largely similar. Long-term morphological, architectural, and neuromuscular adaptations to EQI training requires investigation. Keywords Acute · Angle-specific · Echo intensity · Force · Length-tension · Physiology · Rehabilitation · Resistance exercise · Torque · Ultrasound Abbreviations DOMS Delayed onset muscle soreness MT Muscle thickness Communicated by Olivier Seynnes. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00421-020-04512-4) contains supplementary material, which is available to authorized users. * Dustin J. Oranchuk [email protected] 1
Sports Performance Research Institute New Zealand, AUTMillennium, 17 Antares Place, Mairangi Bay, Auckland, New Zealand
Institute of Health and Sport, Victoria University, Melbourne, Australia
2
EI Echo intensity FL Fascicle length ROM Range of motion MVIT Maximal voluntary isometric torque EQI Eccentric
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