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 following training. This study investigated the contribution of multiple underpinning neural [agonist EMG (QEMG), antagonist EMG (HEMG)] and morphological variables [total quadriceps volume (QUADS), and muscle fascicle pennation angle (QUADSθ )], 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) and antagonist (HEMG). In addition QUADS was determined with MRI and QUADSθ with B-mode ultrasound.

RESULTS

Percentage changes (∆) in MVT were correlated to ∆QEMG (r = 0.576, P = 0.001), ∆QUADS (r = 0.461, P = 0.014), and pre-training MVT (r = -0.429, P = 0.023), but not ∆HEMG (r = 0.298, P = 0.123) or ∆QUADSθ (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 (30.6%), ∆QUADS (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.