Kinematics is the branch of mechanics that describes the motion of bodies without reference to the forces that cause the motion. It focuses purely on the geometry of movement, including position, displacement, velocity, and acceleration.
In biomechanics, kinematic analysis examines:
- Position: Where body segments are located in space
- Displacement: How far and in what direction segments move
- Velocity: How fast segments are moving (both linear and angular)
- Acceleration: How quickly velocity changes
Kinematic analysis answers questions like "what happened?" rather than "why did it happen?" For example:
- What was the peak velocity of the hand during a tennis serve?
- What joint angles were present at ball release?
- What was the trajectory of the center of mass during a jump?
Video analysis is the primary tool for kinematic assessment, using cameras to capture movement and software to track and measure positions over time. Both 2D analysis (single camera view) and 3D analysis (multiple synchronized cameras) are common approaches.
Kinematic data is essential for:
- Technique analysis and coaching
- Movement pattern identification
- Comparison between trials or athletes
- Documentation of movement quality
Kinematics is often paired with kinetics (the study of forces) to provide a complete understanding of human movement.