Muscle Hypertrophy.Muscle Hypertrophy.Muscle Hypertrophy.Muscle Hypertrophy.

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1. Muscle Hypertrophy Roudy Alkhoury, MSc

2. Definition Hypertrophy is the increase in the CSA and muscle mass Hyperplasia in the nb of fibers (on steroids) Types of Hypertrophy: Transient (Fluid accumulation) Sarcoplasmic (Non-Functional) Myofibrillar (Functional) Think of Bodybuilder vs Athlete Recall Sliding Filament Theory, Type of Fibers.

3. Considerations and Factors MPS AND MPD: HYP or Atrophy MPD: 1. Immobilization 2. Disease (cancer, HIV, rheumatoid arthritis, renal failure,...) 3. Drug-related: glucocorticoids 4. Bad Nutrition 5. Sarcopenia Add a main point MPS: 1. Mechanical Tension: Tension and Stretch 2. Muscle Damage 3. Metabolic Stress 4. Nutrition 5. Anabolic Hormones

4. MPS: 1. Mechanical Tension: mechanoreceptors activate mTOR. 2. Muscle Damage: inflammation response so macrophages clean up damage and new growth occurs. Also T-Tubule deformation and release of Cytokins and GF. 3. Metabolic Stress: metabolite creates hypoxia and may lead to fiber degeneration and greater stimulation on mps. 4. Nutrition: Leucine, Isoleucine, veline (BCAA) stimulate mTOR. 5. Anabolic Hormones: IGF-1, MGF, TEST, GH activate satellite cell activation and mTOR.

5. Amino acids play a crucial role in muscle growth by activating the mTORC1 pathway, leading to increased protein synthesis. Mechanoreceptors are involved in mechanotransduction, translating mechanical forces during muscle contraction into cell signaling and protein synthesis. IGF-1, particularly the isoform MGF, is essential for muscle growth as it is produced locally in response to mechanical stimulation and activates signaling pathways that stimulate protein synthesis.

6. Linking them together: Anabolic hormones, influenced by factors like exercise and nutrition, activate signaling pathways such as mTOR and AR, promoting muscle protein synthesis and growth. Nutrition provides the necessary substrates for energy production during exercise and supplies amino acids for muscle protein synthesis. Mechanical tension from resistance training stimulates pathways like mTOR and NFAT, while muscle damage and metabolic stress further enhance these pathways, leading to muscle repair and growth. Muscle damage, induced by eccentric contractions or high-force exercise, initiates an inflammatory response and activates satellite cells for muscle repair and growth. Inflammatory mediators and growth factors released during muscle damage, such as IGF-1 and myostatin, influence signaling pathways like mTOR and NFAT Metabolic stress, experienced during high-repetition, low-rest workouts or occlusion training, contributes to muscle hypertrophy through mechanisms such as increased lactate production, decreased pH, and cell swelling. Metabolic stress activates pathways like mTOR and promotes muscle fiber recruitment and fatigue, stimulating hypertrophic adaptations

7. Satellite Cell

8. Muscle Protein Synthesis

9. Acute Adaptations to Resistance Training: Neural Adaptations: Increased Motor Unit Recruitment: During resistance training sessions, there's an acute increase in the recruitment of motor units, leading to enhanced force production. Improved Motor Unit Synchronization: Synchronization of firing patterns among motor units improves, enhancing coordination and efficiency of muscle contractions. Reduced Neural Inhibition: Resistance training decreases neural inhibition, allowing for greater activation of muscle fibers and improved force generation. Metabolic Responses: Increased Energy Demand: Resistance training induces a temporary increase in energy demand to fuel muscle contractions, leading to elevated metabolic rate during and after workouts. Lactate Accumulation: Intense resistance training can result in the accumulation of lactate, contributing to metabolic stress and signaling pathways involved in muscle growth. Mechanical Stress: Muscle Damage: Eccentric muscle actions and high-force contractions can cause microscopic muscle damage, triggering an inflammatory response and the subsequent repair and growth of muscle tissue. Cell Swelling: Resistance training leads to intracellular fluid accumulation and cell swelling, stimulating anabolic pathways and promoting muscle hypertrophy.

10. Chronic Adaptations to Resistance Training: Muscle Hypertrophy: Increased Muscle Fiber Size: Over time, resistance training induces muscle hypertrophy, characterized by an increase in the cross-sectional area of muscle fibers, particularly Type II fibers. Protein Synthesis: Chronic resistance training upregulates protein synthesis pathways, leading to the accretion of contractile proteins and structural components within muscle fibers. Strength Gains: Neuromuscular Adaptations: Continued resistance training results in neural adaptations, including enhanced motor unit recruitment, synchronization, and reduced neural inhibition, contributing to improvements in strength and power. Structural Changes: Muscle hypertrophy and changes in muscle architecture, such as increased pennation angle, contribute to greater force production capacity. Metabolic Improvements: Increased Metabolic Efficiency: Chronic resistance training enhances metabolic efficiency, leading to improved energy utilization, substrate oxidation, and glucose metabolism. Muscle Glycogen Storage: Regular resistance training increases muscle glycogen storage capacity, improving endurance and performance during high-intensity exercise. Connective Tissue Adaptations: Tendon and Ligament Strength: Resistance training promotes the remodeling and strengthening of tendons and ligaments, enhancing joint stability and reducing the risk of injury. Bone Density: Resistance training induces mechanical loading on bones, stimulating bone remodeling and increasing bone mineral density, reducing the risk of osteoporosis. Functional Adaptations: Movement Efficiency: Regular resistance training improves movement patterns, joint stability, and coordination, enhancing overall functional capacity and performance in daily activities and sports.

11. Selective Hypertrophy

12. RT PROGRAMMING