Hypertrophy vs Hyperplasia in Muscle Growth

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What is the main difference between hypertrophy and hyperplasia?

Hypertrophy increases muscle cell size, while hyperplasia increases overall muscle fibers.

Which component changes with hypertrophy?

Increase in myofibrils (actin & myosin filaments)

What causes Delayed Onset Muscle Soreness (DOMS)?

Eccentric activities

Which skeletal muscle adaptation is responsible for improved delivery of oxygen and nutrients around the body?

Increased capillary density

What does mitochondrial density adaptation in skeletal muscles aim to achieve?

Enhance oxidative metabolism

Which adaptation allows the body to rely more on oxidative pathways and fully metabolize carbs/fats?

Increased MCT Transporters

Study Notes

Hypertrophy vs Hyperplasia

  • Hypertrophy: existing muscle cells get larger, increasing muscle cross-sectional size
  • Hyperplasia: increase in overall muscle fibers
  • Difference: hypertrophy involves muscle cell growth, while hyperplasia involves an increase in the number of muscle fibers

Role of Satellite Cells

  • Myogenic stem cells that mediate hypertrophy and hyperplasia
  • Migrate to damaged cells and donate nucleus to help repair and grow
  • Become active due to skeletal muscle stimulus

Components of Hypertrophy

  • Increase in myofibrils (actin and myosin filaments)
  • Increased sarcoplasm
  • More connective tissue

Types of Hypertrophy

  • Transient: short-term "muscle pump", muscle swelling due to blood flow to tissue
  • Chronic: long-term changes that withstand over time, generally contribute to strength training

General Mechanisms of Hypertrophy

  • Exercise causes muscle tension, sarcomere disruption, and metabolic stress (increase in H+ ions)
  • Stimulus serves as a trigger for muscle growth due to overcompensation of protein synthesis

Delayed Onset Muscle Soreness (DOMS)

  • Caused by eccentric activities
  • Occurs 12-48 hours after strenuous exercise

Skeletal Muscle Adaptations to Aerobic Training

  • Mitochondrial density: creates more energy (ATP) for the cell
  • Mitochondria size: more efficient, with more ETC along the membrane, increasing ATP production
  • Increased oxidative enzymes: more enzymes in the Krebs Cycle and ETC used earlier, allowing the body to rely on oxidative pathways and fully metabolize carbs and fats
  • Increased MCT transporters: training increases lactate production, requiring more transporters to manage blood lactate levels via the Carnitine Shuttle
  • Increased myoglobin: more oxygen carried to the muscle and made available to mitochondria for oxidative metabolism
  • Increased capillary density: greater surface area for gas exchange, decreasing diffusion distance
  • Increased blood volume: improved delivery of oxygen, lipids, and glucose around the body
  • Lower lactate levels: lactate threshold reached at a higher VO2 max due to being better at using oxidative energy systems to metabolize lactate
  • Reduced glycogen depletion: glycogen used when we can’t rely on lipids for energy, with more glycogen available for anaerobic energy production

Learn about the differences between hypertrophy and hyperplasia in muscle growth. Understand the role of satellite cells in mediating hypertrophy and hyperplasia, as well as the changes in muscle components that occur with hypertrophy.

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