Muscle Hypertrophy & Resistance Training

Vocabulary flashcards summarizing the mechanisms, nutritional factors, and training variables influencing muscle hypertrophy.

Transient Hypertrophy

A short-term increase in muscle size immediately after exercise due to fluid accumulation from blood plasma.

Chronic Hypertrophy

A long-term increase in muscle size from consistent training, produced by larger fibers (fiber hypertrophy) or more fibers (fiber hyperplasia).

Fiber Hypertrophy

Growth in the cross-sectional area of existing muscle fibers through added myofibrils, actin, myosin, and new sarcomeres.

Fiber Hyperplasia

An increase in the number of muscle fibers, observed clearly in animals; evidence in humans is limited and usually <10% of growth.

Eccentric Contraction

Lengthening muscle action that is especially potent for increasing fiber cross-sectional area and strength, with high-velocity versions giving the greatest gains.

Low-Intensity Fatiguing Contractions

Light-load exercises taken to failure that can recruit maximal fibers despite <50% 1-RM resistance.

Muscle Protein Synthesis (MPS)

The cellular process of building new muscle proteins; falls during exercise and rises 3–5× for up to 24 h afterward.

Muscle Protein Degradation

The breakdown of muscle proteins; increases during exercise and continues after exercise, but is outweighed by elevated MPS in recovery.

Satellite Cells

Muscle stem cells that activate, migrate, and fuse to damaged fibers or each other to donate nuclei and aid growth or regeneration.

Early Strength Gains

Improvements in force output during the first weeks of training that come largely from heightened neural activation rather than hypertrophy.

Fiber Type Conversion

Shifts in muscle fiber subtype, commonly IIx → IIa or IIa → I, induced by chronic stimulation or resistance training.

Protein Intake Recommendation

Most lifters benefit from ~1.2–1.7 g protein·kg⁻¹·day⁻¹; intakes above 1.7 g·kg⁻¹ generally give no extra hypertrophy.

Post-Workout Protein Dose

About 20–25 g of high-quality protein consumed soon after resistance exercise optimally stimulates MPS.

Leucine

A branched-chain amino acid that strongly activates mTOR and is abundant in dairy, meat, and whey protein.

Protein Feeding Pattern

Multiple small protein doses over the day stimulate MPS better than one large bolus.

Carbohydrate After Training

Does not directly alter protein balance but aids glycogen resynthesis and overall recovery.

Mechanical Stretch

Primary intracellular signal triggered by resistance exercise that initiates hypertrophy pathways.

Intracellular IGF-1

Locally produced growth factor that activates the Akt/PKB → mTOR signaling cascade during muscle loading.

Akt/Protein Kinase B (PKB)

Kinase that relays growth signals from IGF-1 to mTOR, promoting protein synthesis.

mTOR (Mammalian Target of Rapamycin)

Master regulator of protein synthesis; integrates nutrients, insulin, and growth factors to control mRNA translation and ribosome production.

Insulin

An anabolic hormone that enhances amino-acid uptake, boosts RNA translation, and, via mTOR, stimulates protein synthesis.