Muscle Physiology

• Muscles make up more than 40% of body mass
• Skeletal muscles act not only to produce movement but also to stop movement such as resisting gravity to maintain posture
• Each skeletal muscle has three layers of connective tissue (mysia) that enclose it and provide structure to the muscle as a whole, and also compartmentalize the muscle fibers within the muscle.
• Each muscle is wrapped in a sheath of dense, irregular connective tissue called the epimysium, which allows a muscle to contract and move powerfully while maintaining its structural integrity
• The epimysium also separate muscle from other tissues and organs in the area, allowing the muscle to move independently
• Inside each skeletal muscle, muscle fibers are organized into individual bundles, each called a fascicle, by a middle layer of connective tissue called the perimysium
• The fascicular organization is common in muscles of the limbs; it allows the nervous system to trigger a specific movement of a muscle by activating a subset of muscle fibers within a bundle, or fascicle of the muscle
• Inside each fascicle, each muscle fiber is encased in a thin connective tissue layer of collagen and reticular fibers called the endomysium.
• The endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue.

• Muscle fiber: single muscle cell, usually classified according to strength, speed of contraction, and energy source
• Myofibrils: protein structures that make up muscle fibers
• Hypertrophy: increased size of muscle fiber
• Atrophy: decrease in size of muscle fiber
  • Atrophy over time due to aging is known as sarcopenia
• Hyperplasia: increase in number of muscle fibers

Muscle Fiber Types

Muscle Units

• Motor unit: a motor nerve (one that initiates movement) connected to one or more muscle fibers
• Muscle learning: improvement in the body’s ability to recruit motor units, brought about through strength training

Resistance Exercises

• Eccentric (pliometric) loading: placing load on the muscle while it is lengthening
• Plyometrics: rapid stretching of a muscle group undergoing eccentric stress (the muscleis exerting force while it lengthens), followed by a rapid concentric contraction
• Speed loading: moving a load as rapidly as possible
• Kettlebell: a type of speed loading using an iron ball with a connected handle; highly ballistic

Resistance Terms

• Tendon: tough band of fibrous tissue; connects a muscle to a bone or other body part and transmits force exerted by muscle
• Ligament: tough band of tissue; connects ends of bones or supports organs
• Cartilage: tough, resilient tissue that acts as a cushion between the bones in a joint
• Testosterone: principal male hormone responsible for secondary sex characteristics and increasing muscle size
• Power: ability to exert force rapidly

Muscular Adaptations

• Increased strength of tendons, ligaments, and bones
• Increased storage of fuel in muscles- Increased resistance to muscle fatigue
• Increased muscle endurance
• Increased size of fast-twitch muscle fibers (from a high-resistance program)
• Increased size of slow-twitch muscle fibers (from a high-repetition program)
• Improved coordination of motor units
• Increased utilization of motor units during muscle contractions

Citation: https://www.acsm.org/all-blog-posts/certification-blog/acsm-certified-blog/2019/07/31/acsm-guidelines-for-strength-training-featured-download

Weight Training Safety

• Use proper lifting technique
• Use spotters and collars with free weights
• Be alert for injuries
• Report injuries to your instructor or physician
• R-I-C-E (Rest, Ice, Compression, Elevation)
• Possible signs of overtraining include a lack of progress, chronic fatigue, decreased coordination, and chronic muscle soreness
• Consult a physician if unusual symptoms occur

Strength Training Programs Criteria

• Repetition maximum (RM): maximum amount of resistance that can be moved a specified number of times
• 1-RM is the maximum amount of weight that can be lifted one time; 5-RM is the maximum weight that can be lifted five times
• Repetitions: number of times an exercise is performed during one set
• Set: group of repetitions followed by rest
• The length of a rest interval depends on the amount of resistance/training goal
• If you desire greater increases in strength, increase the load and the number of sets and decrease the number of reps
• For endurance, choose 40–60% of your maximum 1 RM to perform more reps
• Periodization (cycle training) in which the sets, reps, and intensity of exercise vary, may be useful for gaining strength
• ACSM recommends two or more non-consecutive days a week for weight training
• Allow at least one day of rest
• A complete weight training program works all the major muscle groups
• Important to balance exercises between antagonistic muscle groups
• Exercise the large-muscle groups first and then the small-muscle groups
• Order exercises to work opposing muscle groups in sequence
• Do a general warm-up and a specific warm-up for the exercises by doing repetitions with lighter weights
• For cool-down, relax for 5 to 10 minutes after exercising
• Post-exercise stretching may prevent post-exercise soreness

Citation: https://www.acsm.org/all-blog-posts/certification-blog/acsm-certified-blog/2019/07/31/acsm-guidelines-for-strength-training-featured-download

References

• https://www.acsm.org/all-blog-posts/certification-blog/acsm-certified-blog/2019/07/31/acsm-guidelines-for-strength-training-featured-download