Push-Up: Plane of Motion, Biomechanics, and Training Implications

What Plane of Motion is a Push-Up?

A push-up is primarily a sagittal plane movement, characterized by the forward and backward motion of the body relative to its midline, involving flexion and extension at the elbow and shoulder joints, and scapular protraction and retraction.

Understanding the Cardinal Planes of Motion

To accurately classify any exercise, it's crucial to understand the three cardinal planes of motion that divide the human body. These planes help us describe movement in three-dimensional space:

• Sagittal Plane: Divides the body vertically into left and right halves. Movements in this plane are typically forward and backward, such such as flexion (decreasing the angle between bones) and extension (increasing the angle between bones). Examples include bicep curls, squats, and walking.
• Frontal (Coronal) Plane: Divides the body vertically into front and back halves. Movements in this plane are side-to-side, such as abduction (moving away from the midline) and adduction (moving towards the midline). Examples include lateral raises, side bends, and jumping jacks.
• Transverse (Horizontal) Plane: Divides the body horizontally into upper and lower halves. Movements in this plane involve rotation around a vertical axis. Examples include trunk twists, throwing motions, and internal/external rotation of joints.

The Push-Up: A Sagittal Plane Dominant Movement

The push-up is a quintessential bodyweight exercise, and its primary actions firmly place it within the sagittal plane. When performing a push-up:

• Body Movement: The body moves vertically towards and away from the floor in a straight line, representing a forward and backward motion relative to the body's horizontal orientation.
• Joint Actions:
  • Elbow Joint: Undergoes flexion during the eccentric (lowering) phase and extension during the concentric (pushing up) phase. These are classic sagittal plane actions.
  • Shoulder Joint: While often perceived as a horizontal pushing movement, the humerus (upper arm bone) moves through a range of flexion (as the body lowers, the humerus moves relatively forward) and extension (as the body pushes up, the humerus moves relatively backward) relative to the torso.
  • Scapulothoracic Joint: The scapulae (shoulder blades) perform retraction (moving closer to the spine) during the lowering phase and protraction (moving away from the spine) during the pushing phase. These are also sagittal plane movements.

Deeper Dive: Muscular Actions and Biomechanics

The muscles primarily responsible for the push-up's sagittal plane motion are:

• Pectoralis Major: Responsible for shoulder flexion and horizontal adduction (which in the context of a push-up, contributes to the forward-backward motion of the arm relative to the body).
• Anterior Deltoid: Assists with shoulder flexion.
• Triceps Brachii: The primary elbow extensor.
• Serratus Anterior: Crucial for scapular protraction, stabilizing the scapula against the rib cage and preventing "winging."
• Core Musculature: While not directly moving the limbs, the core (rectus abdominis, obliques, transverse abdominis) acts as an isometric stabilizer to prevent unwanted movement in other planes, maintaining the rigid plank position. This stability ensures the push-up remains a sagittal plane dominant exercise.

Minor Contributions from Other Planes

While the push-up is overwhelmingly sagittal, minor stabilizing contributions or compensatory movements can involve other planes:

• Transverse Plane:
  • Shoulder Internal/External Rotation: Though not a primary driver, the rotator cuff muscles work to stabilize the humeral head in the glenoid fossa, resisting unwanted rotation.
  • Trunk Rotation: Ideally, there should be no trunk rotation. However, weakness in the core or unilateral variations might introduce minor transverse plane movement.
• Frontal Plane:
  • Shoulder Abduction/Adduction: The arms do not significantly move away from or towards the midline in the frontal plane.
  • Lateral Flexion/Hip Drop: Core stability prevents the hips from dropping or the trunk from laterally flexing, which would be frontal plane movements.

These contributions are secondary and primarily for stabilization, not for the main concentric or eccentric actions of the exercise. A well-executed push-up minimizes movement in the frontal and transverse planes.

Practical Implications for Training

Understanding the push-up's classification as a sagittal plane movement has several important implications for training:

• Targeted Strength: Push-ups are excellent for developing pushing strength in the sagittal plane, targeting the chest, shoulders, and triceps.
• Balanced Programming: To ensure comprehensive strength and injury prevention, it's crucial to incorporate exercises that challenge the body in the other planes of motion.
  • Frontal Plane Examples: Lateral raises, side planks, lateral lunges.
  • Transverse Plane Examples: Russian twists, rotational throws, wood chops, cable rotations.
• Progression and Regression: While variations like incline, decline, or single-arm push-ups modify the challenge or muscle activation, the fundamental joint actions remain within the sagittal plane.

Conclusion

The push-up stands as a fundamental exercise, primarily operating within the sagittal plane due to the dominant flexion and extension movements at the elbows and shoulders, coupled with scapular protraction and retraction. Recognizing this classification is vital for fitness enthusiasts, personal trainers, and kinesiologists alike, providing a clearer understanding of its biomechanical demands and informing well-rounded exercise programming that addresses all planes of human movement.