Phasic and tonic muscles

Phasic and tonic muscles are two types of muscle fibers that serve different functions:

Phasic Muscles:

1. Fast-twitch (FT) fibers

2. High-force, low-endurance

3. Rapid contraction and relaxation

4. Fatigable

5. Used for:

    - Explosive movements (e.g., sprinting, jumping)

    - High-intensity activities (e.g., weightlifting, powerlifting)

Examples of phasic muscles:

1. Biceps brachii

2. Quadriceps

3. Gastrocnemius

Tonic Muscles:

1. Slow-twitch (ST) fibers

2. Low-force, high-endurance

3. Slow contraction and relaxation

4. Non-fatigable

5. Used for:

    - Posture maintenance

    - Low-intensity activities (e.g., walking, standing)

    - Sustained contractions (e.g., holding a position)

Examples of tonic muscles:

1. Erector spinae

2. Trapezius

3. Rhomboids

4. Core muscles (e.g., abdominals, pelvic floor)

Key differences:

1. Contraction speed: Phasic muscles contract quickly, while tonic muscles contract slowly.

2. Endurance: Phasic muscles fatigue quickly, while tonic muscles can sustain contractions for longer periods.

3. Function: Phasic muscles are used for explosive movements, while tonic muscles are used for posture and low-intensity activities.