Detailed Study Notes on Muscle Actions and Training

Eccentric and Concentric Muscle Actions

• Definitions:

  • Eccentric Muscle Action: Muscle fibers lengthen while producing force.
  • Concentric Muscle Action: Muscle fibers shorten while producing force.

• Examples of Muscle Actions:

  • Bicep Curl:
  • Going from full extension to full flexion (concentric).
  • Lowering the weight involves controlling the descent (eccentric).

• Strength Differences:

  • Greater force production during eccentric actions due to actin and myosin binding being stretched apart rather than contracted.

Muscle Soreness and Hypertrophy

• Delayed Onset Muscle Soreness (DOMS):
  • Occurs 24-48 hours post-exercise, especially after unaccustomed eccentric activity.
• Hypertrophy vs. Hyperplasia:
  • Hypertrophy: Increase in muscle fiber size.
  • Hyperplasia: Increase in the number of muscle fibers, more common in laboratory animals than in humans.

Metabolic Adaptations to Training

• ATP Production and Training:
  • Endurance training enhances mitochondria and energy pathways.
  • Resistance training leads to specific adaptions such as increases in storage of creatine phosphate (up to 45%).
• Glycolytic Enzymes:
  • Changes depend on the type of training; typical low-repetition workouts may not enhance glycolytic enzymes due to less demand.

Types of Strength Testing

• Isometric Strength:

  • Specific to joint angle; force production relates to actin-myosin overlap.
  • Optimal overlap produces maximum force, while too much overlap reduces force.

• Isokinetic Testing:

  • Measures torque at various angles, providing a torque curve which is beneficial for tracking strength across the range of motion.

Torque-Velocity Relationship

• General Curve:

  • Eccentric muscle action typically produces higher torque than concentric at various velocities.
  • As speed increases, concentric strength tends to decrease (decay curve).

• Eccentric Torque Behavior:

  • Increased torque production with velocity until certain limit, where the actin-myosin binding becomes less effective.

Practical Applications

• In resistance training, vary the type of muscle actions to address muscle hypertrophy and maximize strength benefits.
• Understanding how muscle actions work can guide exercise programming for better results and prevention of injuries.