Neglected in sport science. Research and applied practice have predominantly focused on assessing and developing acceleration and maximum velocity sprinting capabilities, neglecting the necessity to be able to decelerate.
Contextualise deceleration relative to entry velocity. Challenges for assessment include standardising acceleration distance or total distance, and expressing deceleration performance (distance [m], time [s] or m/s²) in the context of the maximum velocity attained in the acceleration phase.
Velocity must drop to zero. Deceleration tests must be designed so the velocity drops to an instantaneous zero, providing a definitive endpoint. This includes “acceleration to stop at a point” or “acceleration-deceleration to re-acceleration in 90°–180° turns” — all measured using a validated device that can measure instantaneous velocity.
Commands must ensure maximal effort. Test design must ensure the necessity to accelerate to the highest possible velocity within the constraints of the test (set distance). Inherently, this velocity and momentum will be different for all athletes.
Test both limbs. Designing deceleration test batteries that require each leg to act as both penultimate and final contact limbs can give further insights into preferential load distribution and identify deficiencies in lower extremity strength and coordination.
Two main protocol categories: Acceleration-Deceleration Ability (ADA) tests and forward Change of Direction (COD) tests (≥90°). Both require whole body velocity to drop to instantaneous zero. Red area indicates the exit zone for forward COD tests.
Athletes sprint a set distance then decelerate to a full stop or to a pre-set line. Approach distances studied: 4.5m, 5m, 9.14m, 10m, 15m, 18.29m, 20m, 30m.
Advantage: Reduces task complexity — pure deceleration without whole body rotation. Preferred during earlier phases of field-based rehabilitation.
Tip: A familiarisation session is recommended prior to any ADA test to reduce potential learning effects.
Sharp COD tests (90°–180°) require substantial braking over multiple foot contacts. The modified 505 (5m approach) and traditional 505 (15m approach) are common options.
Caution: Pure deceleration qualities may be contaminated by the skill required to execute a turn with whole body rotation. Using completion time alone is an oversimplification.
Instantaneous velocity–time profiles in the modified 505 (lower entry velocity) vs. traditional 505 (higher entry velocity) COD tests, showing deceleration phase sub-divisions: DECEarly and DECLate.
Tracks specific target (lower back), less spurious reflections
No pre-calibration required
High sampling frequency >100 Hz
Indoor & outdoor use
Restricted to linear (uniplanar) tasks only
High cost
Wide measuring span; quick setup
3D radar devices permit multi-planar COD tasks
Indoor & outdoor use
Manual data processing; inter-rater reliability risk
Wide span means moving objects can contaminate signal
Highest sampling frequency
Instantaneous feedback; integrates into training
Valid for 180° COD turns and ADA tests
Involves external load — may alter natural kinematics
Cannot measure unloaded condition; high cost
Most teams already use GNSS routinely in training
Multiple athletes assessed simultaneously
Invisible monitoring integrated into sessions
Outdoor only; lower sampling frequency limits accuracy
Requires custom filtering (4th-order Butterworth, 2 Hz)
Cost-effective; available on most smartphones
Provides kinematic technique analysis
AI pose-recognition enables fast processing
Single camera must be in sagittal plane
Limited validity/reliability data for AI-based tools
Step-by-step force insights without large force plates
Not restricted to laboratory environment
Indoor & outdoor use
IMU drift; calibration required before use
Reliability decreases at higher movement speeds
Comparison of braking step forces (g) preceding a 180° turn in a 505 COD test captured using the Xsens IMU system. Data highlight the heightened loading of early deceleration steps. * = significant difference from final foot contact; # = significant difference from penultimate foot contact.
Velocity–time profile during an ADA test. Deceleration phase starts at VMax and ends at VLow. The 50% VMax threshold divides the early (DECEarly) and late (DECLate) deceleration sub-phases.
Ability to maintain high deceleration across the entire phase. Most commonly reported metric for comparing athletes.
Highest instantaneous deceleration. Strongly influenced by sampling frequency and filtering. Could indicate both better deceleration capacity AND heightened injury risk.
Early = VMax to 50% VMax. Late = 50% VMax to VMin. Ratio near 1 suggests balanced strategy. Athletes with poor early decel may “slam the brakes” late, elevating ACL risk.
Shorter values are highly advantageous: athletes can approach COD at faster speeds. Note: anthropometric characteristics (leg length) can influence DTS independently of deceleration ability.
Entry momentum (mass × VMax) drives deceleration demands. Faster and heavier athletes face greater braking challenges — must be accounted for when benchmarking longitudinally.
Key kinematic markers across the antepenultimate, penultimate, and ultimate foot contacts: (1) touchdown distance / leg placement angle, (2) peak hip & knee flexion, (3) step kinematics, (4) shin angle, (5) trunk angle, (6) knee flexion at touchdown, (7) COM height.
Frontal plane kinematic markers: (1) knee abduction at touchdown & peak knee flexion — elevated angles increase knee joint loading; (2) frontal plane pelvic alignment; (3) frontal plane trunk alignment.
Foot placed in front of COM to increase horizontal braking impulse. Heel contact in earlier braking steps maximises braking effect. A larger leg placement angle (relative to vertical) increases potential for braking impulse.
Trunk should “lean back” or be upright at touchdown. A partially flexed knee (~30°) helps lower multi-planar joint loads. Forward trunk flexion with an extended knee lengthens hamstrings — a compensatory, not desired movement pattern.
At the penultimate and ultimate foot contacts, the rear foot remains in contact with the ground providing dual support — greater stability, load sharing, longer braking time (no propulsion phase), and greater braking impulse.
Phase 1 — ADA tests first. ADA tests are more suitable during earlier field-based rehabilitation phases. Athletes demonstrate the ability to safely decelerate before introducing COD demands.
Phase 2 — Shorter sprint distances. When decelerating from higher velocity, early braking steps generate very high-impact peak forces and loading rates. Shorter approach distances reduce these demands during rehabilitation.
Phase 3 — COD integration. COD tests integrated in the periods prior to and following return to sport, once deceleration capacity is demonstrated.
Deceleration Index. Proposed metric = deceleration time relative to acceleration time, measuring the rate at which a player can slow down relative to their ability to accelerate. Identified as a missing link in injury rehabilitation.
● Elevated knee abduction angle at touchdown → elevated knee joint loading
● Reduced knee flexion (“shock absorption”) → higher knee abduction moment
● Forward trunk flexion + extended knee → hamstring overload risk
● Poor early deceleration → “slamming the brakes” in late phase → ACL risk at final foot contact
● Upright braking strategy (less negative shin angle) → more steps required to reduce momentum