Changes in agonist neural drive, hypertrophy and pre-training strength all contribute to the individual strength gains after resistance training

Purpose Whilst neural and morphological adaptations following resistance training (RT) have been investigated extensively at a group level, relatively little is known about the contribution of specific physiological mechanisms, or pre-training strength, to the individual changes in strength followin...

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Published in:	European journal of applied physiology Vol. 117; no. 4; pp. 631 - 640
Main Authors:	Balshaw, Thomas G., Massey, Garry J., Maden-Wilkinson, Thomas M., Morales-Artacho, Antonio J., McKeown, Alexandra, Appleby, Clare L., Folland, Jonathan P.
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer Berlin Heidelberg 01-04-2017 Springer Nature B.V
Subjects:	Adult Arthritis Biomedical and Life Sciences Biomedicine Case-Control Studies Electromyography Evoked Potentials, Motor Human Physiology Humans Investigations Isometric Contraction Magnetic resonance imaging Male Morphology Muscle Strength Occupational Medicine/Industrial Medicine Original Article Physiology Quadriceps Muscle - diagnostic imaging Quadriceps Muscle - innervation Quadriceps Muscle - physiology Random Allocation Resistance Training Sports Medicine Strength training Variables United Kingdom > UK Neural drive Muscle architecture Between-individual variability Strength training Muscle volume
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Summary:	Purpose Whilst neural and morphological adaptations following resistance training (RT) have been investigated extensively at a group level, relatively little is known about the contribution of specific physiological mechanisms, or pre-training strength, to the individual changes in strength following training. This study investigated the contribution of multiple underpinning neural [agonist EMG (QEMG MVT ), antagonist EMG (HEMG ANTAG )] and morphological variables [total quadriceps volume (QUADS VOL ), and muscle fascicle pennation angle (QUADS θ p )], as well as pre-training strength, to the individual changes in strength after 12 weeks of knee extensor RT. Methods Twenty-eight healthy young men completed 12 weeks of isometric knee extensor RT (3/week). Isometric maximum voluntary torque (MVT) was assessed pre- and post-RT, as were simultaneous neural drive to the agonist (QEMG MVT ) and antagonist (HEMG ANTAG ). In addition QUADS VOL was determined with MRI and QUADS θ p with B-mode ultrasound. Results Percentage changes (∆) in MVT were correlated to ∆QEMG MVT ( r = 0.576, P = 0.001), ∆QUADS VOL ( r = 0.461, P = 0.014), and pre-training MVT ( r = −0.429, P = 0.023), but not ∆HEMG ANTAG ( r = 0.298, P = 0.123) or ∆QUADS θ p ( r = −0.207, P = 0.291). Multiple regression analysis revealed 59.9% of the total variance in ∆MVT after RT to be explained by ∆QEMG MVT (30.6%), ∆QUADS VOL (18.7%), and pre-training MVT (10.6%). Conclusions Changes in agonist neural drive, quadriceps muscle volume and pre-training strength combined to explain the majority of the variance in strength changes after knee extensor RT (~60%) and adaptations in agonist neural drive were the most important single predictor during this short-term intervention.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1439-6319 1439-6327
DOI:	10.1007/s00421-017-3560-x