Explanation: Training with low resistance, typically 35 to 40 repetitions until fatigue3.... Primarily results in increases in endurance3....

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Card 2: Muscle Size Changes

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Term: Sarcopenia4...

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Explanation: The loss of muscle mass that occurs due to the aging process, with the greatest decline typically after age 504.... It involves atrophy of type II fibers and a reduced number of both type I and type II fibers4.

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Term: Atrophy4...

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Explanation: A decrease in muscle size, often due to underuse or inactivity4.... Prolonged inactivity (like bedrest or casting) for as little as 20 to 30 days can cause a 20% to 30% reduction in muscle fiber size6....

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Term: Hyperplasia9...

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Explanation: An increase in the number of muscle fibers9.... It is unclear if hyperplasia occurs in humans, although it is observed in animals9....

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Term: Hypertrophy9...

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Explanation: An increase in the cross-sectional area (size) of muscle fibers9.... This is likely the dominant factor in resistance training-induced increases in muscle mass in humans9.... Hypertrophy is due to an increase in muscle proteins like actin and myosin10....

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Card 3: Neural Adaptations to Resistance Training

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Term: Neural Adaptations (in Resistance Training)9...

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Explanation: Changes within the nervous system that promote increases in muscular strength11.... These adaptations are largely responsible for the early gains in strength, particularly during the first 2 to 8 weeks of training9....

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Term: Evidence for Neural Adaptations11...

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Explanation: Evidence includes strength increases in the first two weeks without an increase in muscle fiber size11..., and the phenomenon of "cross education"11....

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Term: Cross Education11...

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Explanation: Training one limb results in increases of strength in the untrained limb11.... This is seen in strength training but not aerobic training11.

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Term: Increased Neural Drive9...

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Explanation: A key physiological adaptation within the nervous system due to resistance training9.... This involves an increased number of motor units recruited, an increased firing rate of motor units, increased motor unit synchronization, and improved neural transmission across the neuromuscular junction9....

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Card 4: Cellular Mechanisms of Muscle Growth (Hypertrophy)

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Term: Protein Synthesis6...

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Explanation: The process by which muscle cells create new proteins (like actin and myosin)10. Muscle growth (hypertrophy) depends on the balance between protein synthesis and protein degradation6.... Resistance training increases protein synthesis6....

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Term: Time Course of Protein Synthesis Response14...

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Explanation: After a single bout of resistance training, protein synthesis can increase by 50% to 140% within the first four hours14.... It remains elevated for 30 to 50 hours post-exercise in both trained and untrained individuals14.... Accumulation of this increased synthesis over weeks leads to hypertrophy20.

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Term: Ribosomes22...

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Explanation: Cellular organelles where protein synthesis occurs22. Resistance training causes an increase in the number of ribosomes, which elevates the muscle's protein synthesis capacity23.

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Term: mTOR15...

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Explanation: A protein kinase ("mechanistic target of rapamycin" or potentially "meosin target of rap relaxation" according to one mention, but commonly understood as the former)15.... It is the key factor accelerating protein synthesis following resistance training23 and is needed for protein synthesis15.

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Term: Satellite Cells12...

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Explanation: Stem cells located between the sarcolemma (muscle cell membrane) and the basal lamina12....

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Term: Role of Satellite Cells in Hypertrophy6...

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Explanation: Resistance training activates satellite cells to divide and fuse with muscle fibers12.... This fusion increases the number of myonuclei in the muscle fiber12.... More myonuclei are likely required to support increased protein synthesis in larger fibers and maintain the myonuclear domain (ratio of nucleus to fiber size)12.... Satellite cell activation is blunted in older individuals13.

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Term: Myonuclei6...

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Explanation: The nuclei within a muscle fiber12.... Muscle cells are multi-nucleated14. An increase in myonuclei, facilitated by satellite cells, allows for additional protein synthesis and supports muscle hypertrophy12....

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Card 5: Other Factors Influencing Hypertrophy

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Term: Anabolic Hormones (Circulating, e.g., IGF-1, Growth Hormone)14...

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Explanation: Hormones linked to mTOR activation with the potential to increase protein synthesis24. While resistance training causes small increases, increases in circulating anabolic hormones are not required for resistance training-induced hypertrophy14....

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Term: Anti-inflammatory Drugs (Nonsteroidal)14...

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Explanation: Over-the-counter drugs like ibuprofen and acetaminophen30. While some animal studies suggested blunting hypertrophy, recent human studies indicate they do not negatively impact strength gains or hypertrophy from resistance training14....

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Term: Genetic Influence on Hypertrophy15...

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Explanation: Approximately 80% of the difference in muscle mass between individuals is due to genetic variation15.... 47 different genes play a key role, many linked to the mTOR pathway15.... Variations in these genes lead to large differences in hypertrophy magnitude28.

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Term: Non-responders, Moderate-responders, High-responders (Genetic)15...

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Explanation: Classifications for individuals based on their genetic potential for resistance training-induced skeletal muscle hypertrophy15.... Non-responders have low potential, moderate-responders have moderate potential, and high-responders have high potential15....

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Term: Free Radicals7...

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Explanation: Molecules whose increased production occurs in muscle fibers during skeletal muscle inactivity, causing oxidative stress7.... They promote muscle atrophy by depressing protein synthesis and increasing protein degradation7....

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Card 6: Detraining and Concurrent Training

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Term: Detraining (following Strength Training)8...

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Explanation: Cessation of resistance training results in muscle atrophy and a loss of strength15.... The rate of strength loss is slower compared to endurance training detraining15....

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Term: Muscle Memory6...

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Explanation: The ability for previously trained individuals to make a rapid recovery of strength during retraining after prolonged inactivity8.... Research suggests this is due to the myonuclei added during training not being lost during detraining, providing an advantage for rapid protein synthesis upon retraining6....

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Term: Prolonged Skeletal Muscle Inactivity6...

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Explanation: Periods like bedrest or casting a limb6.... Leads to rapid fiber atrophy6..., caused by decreased protein synthesis and increased protein breakdown6.... Increased free radicals contribute by depressing synthesis and increasing degradation7....

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Term: Concurrent Training25...

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Explanation: Performing both endurance and resistance training26.... There is a potential for interference between the adaptations26..., meaning it can impair strength gains compared to strength training alone26.... The degree of interference depends on the intensity, volume, and frequency of the endurance training26....

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Term: Mechanisms for Concurrent Training Interference25...

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Explanation: Potential mechanisms include:

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Neural factors: Limited evidence for impaired motor unit recruitment25....

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Overtraining: No direct evidence it specifically impairs strength gains in concurrent training25....

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Depressed protein synthesis: Endurance training signaling (often via AMPK) can inhibit mTOR, thereby interfering with the protein synthesis needed for hypertrophy25....

Note