chapter 14

Muscular Strength

The maximal force that a muscle group can generate.

Muscular Endurance

The ability to make repeated contractions against a submaximal load.

Strength Training

Training with high resistance, typically 6 to 10 repetitions until fatigue, resulting in strength increases.

Low-Resistance Training

Training with low resistance, typically 35 to 40 repetitions until fatigue, resulting in increases in endurance.

Sarcopenia

The loss of muscle mass that occurs due to the aging process, with the greatest decline typically after age 50.

Atrophy

A decrease in muscle size often due to underuse or inactivity.

Hyperplasia

An increase in the number of muscle fibers, although it is unclear if it occurs in humans.

Hypertrophy

An increase in the cross-sectional area (size) of muscle fibers, dominant in resistance training-induced muscle mass increases.

Neural Adaptations

Changes within the nervous system that promote increases in muscular strength.

Evidence for Neural Adaptations

Strength increases in the first two weeks without an increase in muscle fiber size, including the phenomenon of 'cross education'.

Cross Education

Training one limb results in increases of strength in the untrained limb.

Increased Neural Drive

A physiological adaptation within the nervous system due to resistance training that involves increased motor unit recruitment and firing rate.

Protein Synthesis

The process by which muscle cells create new proteins, key for muscle growth.

Time Course of Protein Synthesis Response

Protein synthesis can increase by 50% to 140% within the first four hours after a resistance training session.

Ribosomes

Cellular organelles where protein synthesis occurs.

mTOR

A protein kinase that is a key factor accelerating protein synthesis following resistance training.

Satellite Cells

Stem cells located between the muscle cell membrane and basal lamina, vital for muscle growth.

Role of Satellite Cells in Hypertrophy

Satellite cells activate to divide and fuse with muscle fibers, increasing myonuclei for protein synthesis.

Myonuclei

The nuclei within a muscle fiber, supporting protein synthesis and hypertrophy.

Anabolic Hormones

Hormones linked to mTOR activation that have the potential to increase protein synthesis.

Anti-inflammatory Drugs

Over-the-counter drugs that do not significantly impact strength gains or hypertrophy from resistance training.

Genetic Influence on Hypertrophy

Approximately 80% of muscle mass difference between individuals is due to genetic variation.

Non-responders, Moderate-responders, High-responders

Classifications based on genetic potential for resistance training-induced muscle hypertrophy.

Free Radicals

Molecules that can cause oxidative stress and promote muscle atrophy by affecting protein synthesis.

Detraining

Cessation of resistance training that results in muscle atrophy and loss of strength.

Muscle Memory

The ability for previously trained individuals to rapidly regain strength during retraining after inactivity.

Prolonged Skeletal Muscle Inactivity

Periods of inactivity leading to rapid fiber atrophy due to decreased protein synthesis.

Concurrent Training

Performing both endurance and resistance training which may interfere with strength gains.

Mechanisms for Concurrent Training Interference

Potential mechanisms include neural factors, overtraining, and depressed protein synthesis.