The four phases of movement are the preparatory phase, force-production phase, critical instant, and follow-through/recovery phase. Together, they provide a framework for analysing how a sporting skill is prepared, executed, completed, and controlled.
How the phases work
In IB SEHS subtopic B.2.3, movement analysis divides a skill into meaningful stages so that technique and performance can be evaluated.
| Phase | Function and example |
|---|---|
| Preparatory phase | The performer adopts an effective starting position and may create a countermovement or backswing. Before a tennis serve, the player positions the feet, tosses the ball, bends the knees, and takes the racket back to prepare for efficient force generation. |
| Force-production phase | The performer produces and transfers force through coordinated joint actions. In a serve, the legs extend, the trunk rotates, and the shoulder and arm accelerate the racket. Effective sequencing through the kinetic chain increases the final segment's or implement's velocity. |
| Critical instant | This decisive moment most directly determines the skill's outcome and may be contact, release, take-off, or landing. In the serve, racket: ball contact is critical because racket velocity, angle, and contact position determine ball trajectory. |
| Follow-through/recovery phase | After the critical instant, continued movement decelerates the limbs, dissipates forces, maintains balance, and prepares the performer for the next action. After serving, the racket continues across the body as the player regains a ready position. |
A common misconception is that the critical instant must be a long phase. It is usually one decisive moment, while the other phases occur over time. Boundaries may vary with the skill being analysed.