GLOSSARY

Muscle hypertrophy is an increase in muscle size, mainly resulting from enlargement of existing muscle fibres (an increase in their cross-sectional area), not from an increase in fibre number.

Mechanisms

• Mechanical tension: the primary driver of hypertrophy; through mechanotransduction and activation of the mTOR pathway, protein synthesis increases.
• Metabolic stress: accumulation of metabolites in high-repetition training; its role is supportive and still debated.
• Muscle damage: no longer considered a necessary driver of hypertrophy, and excessive damage may even slow growth.
• Satellite cells: add new nuclei in substantial hypertrophy.

Protein Balance