Analyzing Movements: Joint Actions and Muscle Contractions

Understanding Movement Patterns

When we analyze any movement in sports or daily activities, we need to look at two key components:

1. Joint Actions - How our joints move and in what directions
2. Muscle Contractions - How our muscles work together to create these movements

Always break down complex movements into individual joint actions and muscle contractions to better understand the biomechanics involved.

Joint Actions

Types of Joint Movements

1. Flexion and Extension
   • Flexion: Decreasing the angle between bones (like bending your elbow)
   • Extension: Increasing the angle between bones (like straightening your arm)
2. Abduction and Adduction
   • Abduction: Moving a limb away from the body's midline
   • Adduction: Moving a limb toward the body's midline
3. Rotation
   • Internal (Medial) Rotation: Rotating toward the body's midline
   • External (Lateral) Rotation: Rotating away from the body's midline

In a basketball jump shot:

• Ankle plantar flexion (pointing toes down)
• Knee extension
• Hip extension
• Shoulder flexion
• Elbow extension

Muscle Contractions

Types of Muscle Contractions

1. Isotonic Contractions
   • Concentric: Muscle shortens while contracting (like lifting a weight)
   • Eccentric: Muscle lengthens while contracting (like lowering a weight)
2. Isometric Contractions
   • Muscle generates force without changing length
   • Example: Holding a plank position

Multiple muscles work together in most movements through different types of contractions.

Muscle Roles

1. Agonist (Prime Mover)
   • Main muscle performing the movement
   • Example: Biceps during elbow flexion
2. Antagonist
   • Opposes the agonist
   • Relaxes to allow movement
   • Example: Triceps during elbow flexion
3. Synergist
   • Assists the agonist
   • Provides stability
   • Example: Brachialis helping biceps during elbow flexion

Don't assume a muscle always plays the same role - it can be an agonist in one movement and an antagonist in another!

Practical Analysis Example

Analyzing a Squat Movement

1. Descent Phase (Eccentric)
   • Hip flexion (Gluteus Maximus lengthening)
   • Knee flexion (Quadriceps lengthening)
   • Ankle dorsiflexion (Gastrocnemius lengthening)
2. Rising Phase (Concentric)
   • Hip extension (Gluteus Maximus shortening)
   • Knee extension (Quadriceps shortening)
   • Ankle plantar flexion (Gastrocnemius shortening)

When analyzing movements, always consider both the descending and ascending phases, as they often involve the same muscles working in opposite ways.

Practical Applications

Understanding movement analysis helps in:

• Improving technique
• Preventing injuries
• Designing training programs
• Rehabilitating injuries

When analyzing any sport movement, start with the major joints involved, then identify the muscles working at each joint.