Kinetics is the branch of mechanics concerned with the forces that cause or result from motion. While kinematics describes what movements occur, kinetics explains why they occur by examining the forces, torques, and energies involved.
In biomechanical analysis, kinetic measurements include:
- Forces: External forces (like ground reaction forces) and internal forces (like muscle forces)
- Torques/Moments: Rotational forces acting around joints
- Work: Force applied over a distance
- Power: The rate at which work is performed
- Energy: Kinetic energy of moving segments and potential energy from position
Common kinetic analyses in sports and clinical settings:
- Ground Reaction Forces: Forces exerted by the ground on the body during activities like running, jumping, or landing
- Joint Moments: The torques acting at joints during movement
- Muscle Forces: The forces generated by muscles to produce movement
- Impact Forces: Forces experienced during collisions or landings
Kinetic data typically requires specialized equipment like force plates, pressure sensors, or electromyography (EMG). However, when combined with kinematic data from video analysis, inverse dynamics calculations can estimate joint forces and moments.
Understanding kinetics is crucial for:
- Injury prevention (identifying dangerous force patterns)
- Performance enhancement (optimizing power output)
- Rehabilitation (ensuring safe loading during recovery)
- Equipment design (creating better protective gear or training tools)