Table 1.

Summary of the physiological and biomechanical properties of deceleration and the implications for team sport athletes from injury and performance perspectives

Theoretical rationale	Injury and performance considerations
Biomechanical
↑ Magnitudes of horizontal braking impulse in the APFC and PFC relative to the FFC [15, 16, 40]	Injury ↓ Momentum and subsequent knee joint loading during steps prior to COD foot plant and subsequent ACL injury Performance ↑ Effective application of force for re-acceleration into new intended direction
↑ Impact peak forces and loading rates [34]	Injury ↑ Lower-body musculoskeletal loading Performance Rapid ↓ momentum in order to evade or pursue opponents based on impulse-momentum relationship
↑ Joint angular velocities of lower limbs [43]	Injury and performance ↑ Eccentric power absorption and rapid limb positioning of all three lower-limb joints to facilitate braking over multiple foot contacts
Physiological
↑ Forces for a given angular velocity during eccentric muscle actions compared to concentric or isometric [49–51]	Injury ↑ Forces lead to ↑ muscle damage and neuromuscular fatigue Performance ↑ Mechanical and metabolic efficiency for given work performed
↑ Quadriceps activation relative to MVC  ↑ Hamstring activation levels relative to quadriceps (improving hamstring:quadriceps ratio) [68]	Injury ↑ Internal (muscle) moments to counteract large external joint moments during ground contact ↓ Risk of anterior displacement of the tibia through hamstring co-contraction, ↓ risk of ACL injury Performance ↑ Production of internal moments contribute to ↑ braking force (impulse)
↑ Pre-impact muscle activation  ↑ Rate of eccentric force production [55, 71, 72]	Injury ↓ Rate of active muscle fascicle lengthening and eccentric/quasi-isometric force inputs (i.e., mechanical strain) to muscle fascicles Performance ↑ Ability to generate and attenuate rapid braking forces ↑ Technical ability to orientate braking forces
↑ Mechanical buffering capacity of tendon (stiffness qualities and precise neural activation patterns) [54, 55]	Injury ↓ Rate of active muscle fascicle lengthening and eccentric/quasi-isometric force inputs (i.e., mechanical strain) to muscle fascicles Performance ↑ MTU stiffness contributing to ↑ braking forces
↑ Co-coordinative proficiency and sensorimotor function [18, 99]	Injury ↓ Repetitive bouts of submaximal erroneous movement patterns and high-risk postures ↓ Likelihood of ‘mechanical fatigue failure’ Performance ↑ Movement skill and ability to perform sports-specific actions
↑ Positive architectural shifts in muscle fibres (i.e., ↑ sarcomeres in-series) and ↑ tissue tolerance to braking loads [88, 89]	Injury ↓ Muscle damage and negative effects of neuromuscular fatigue (i.e., repeated bout effect) Performance ↑ Expression of force–velocity characteristics

It is important to note that although horizontal decelerations may expose an athlete to an increased vulnerability through different mechanisms, it is frequent and optimised training that may offer a protective effect. As such, exposure to heightened mechanical loading is necessary to stimulate adaptation and protect the athlete against the damaging effects of high-intensity horizontal decelerations performed in competition

APFC antepenultimate foot contact, PFC penultimate foot contact, FFC final foot contact, COD change of direction, ACL anterior cruciate ligament, MVC maximal voluntary contraction, MTU muscle tendon unit