The contribution of muscle hypertrophy to strength changes following resistance training

Eur J Appl Physiol. 2014 Jun;114(6):1239-49. doi: 10.1007/s00421-014-2855-4. Epub 2014 Mar 9.


Purpose: Whilst skeletal muscle hypertrophy is considered an important adaptation to resistance training (RT), it has not previously been found to explain the inter-individual changes in strength after RT. This study investigated the contribution of hypertrophy to individual gains in isometric, isoinertial and explosive strength after 12 weeks of elbow flexor RT.

Methods: Thirty-three previously untrained, healthy men (18-30 years) completed an initial 3-week period of elbow flexor RT (to facilitate neurological responses) followed by 6-week no training, and then 12-week elbow flexor RT. Unilateral elbow flexor muscle strength [isometric maximum voluntary force (iMVF), single repetition maximum (1-RM) and explosive force], muscle volume (V(m)), muscle fascicle pennation angle (θ(p)) and normalized agonist, antagonist and stabilizer sEMG were assessed pre and post 12-week RT.

Results: Percentage gains in V(m) correlated with percentage changes in iMVF (r = 0.527; P = 0.002) and 1-RM (r = 0.482; P = 0.005) but not in explosive force (r ≤ 0.243; P ≥ 0.175). Percentage changes in iMVF, 1-RM, and explosive force did not correlate with percentage changes in agonist, antagonist or stabilizer sEMG (all P > 0.05). Percentage gains in θ(p) inversely correlated with percentage changes in normalized explosive force at 150 ms after force onset (r = 0.362; P = 0.038).

Conclusions: We have shown for the first time that muscle hypertrophy explains a significant proportion of the inter-individual variability in isometric and isoinertial strength gains following 12-week elbow flexor RT in healthy young men.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Humans
  • Male
  • Muscle Strength*
  • Muscle, Skeletal / anatomy & histology
  • Muscle, Skeletal / innervation
  • Muscle, Skeletal / physiology*
  • Organ Size
  • Resistance Training*