Body Segment	Description	References
Hamstring Strength and Activation	The protection of the ACL is significantly supported by mechanisms that mitigate knee shear forces, enhance knee flexion, and reduce both anterior tibial shear forces and ground reaction forces. These factors collectively reduce strain on the ACL during dynamic movements, thereby enhancing joint stability. Such protective effects are especially critical during activities involving rapid changes in direction or high-impact landings, where improper force distribution can compromise the integrity of the ACL A critical contributor to ACL vulnerability is the imbalance in muscular strength and activation patterns. Deficiencies in medial hamstring strength, particularly when accompanied by excessive activation of the vastus lateralis, are strongly linked to increased risk of ACL injuries. This imbalance alters the natural load-sharing mechanisms within the lower limb, resulting in greater reliance on the ACL to resist excessive anterior tibial translation and valgus forces The hamstrings, especially the semitendinosus muscle, play a vital role in reducing ACL loading by generating significant braking forces during deceleration and propulsion forces during acceleration. These actions are primarily facilitated during hip extension, where the hamstrings counteract anterior tibial translation and help stabilize the knee. This dual functionality underscores the importance of the semitendinosus in both efficient movement and injury prevention, as it not only aids in force transmission but also protects against excessive strain on passive structures like the ACL Training programs focused on strengthening the medial hamstrings and improving neuromuscular control can significantly reduce the risk of ACL injuries. This includes exercises targeting eccentric hamstring strength, which has been shown to enhance the ability to control anterior tibial shear forces, as well as strategies to reduce over-reliance on the quadriceps during high-stress movements. Such interventions are vital for maintaining joint integrity and optimizing movement efficiency.	(Weinhandl et al., 2014; Donnelly et al., 2012; Lloyd & Buchanan, 2001; Maniar et al., 2020). (Smeets et al., 2019; Zebis et al., 2009). (Besier et al., 2003; Maniar et al., 2019).
Quadriceps Strength and Activation	Plays a significant role in facilitating effective braking during eccentric contractions and generating propulsion during concentric contractions, while also aiding knee flexor moments during the phase of weight acceptance in gait and movement. These coordinated actions are critical for maintaining joint stability and efficient force transfer during dynamic activities. Insufficient quadriceps strength can lead to compensatory alterations in movement mechanics, such as increased hip and trunk flexion, which redistribute mechanical loads onto the hamstrings. This compensatory mechanism places additional stress on the hamstrings, thereby heightening the risk of strain or injury during activities that require rapid or forceful movements. Understanding these dynamics underscores the importance of balanced strength across muscle groups for reducing injury risk and optimizing biomechanical efficiency.	(Besier et al., 2003; Lloyd & Buchanan, 2001; Maniar et al., 2019) (Mateus et al., 2020; Warrener et al., 2021)
Soleus Strength and Activation	Generates posterior shear forces that play a critical role in stabilizing the knee joint, particularly by counteracting anterior tibial translation during dynamic activities. This mechanism is essential for maintaining knee integrity under high loads, such as those encountered during landing and propulsion phases of movement. Additionally, these forces contribute to controlled deceleration (braking) upon ground contact and effective force generation required for propulsion, ensuring optimal joint alignment and load distribution. The posterior shear forces, primarily mediated by the hamstring muscles, work synergistically with other stabilizing structures like the anterior cruciate ligament (ACL) to minimize shear stress on the knee. This integrated action is crucial for mitigating injury risk during high-impact and high-velocity activities, emphasizing the importance of muscular strength and neuromuscular coordination in functional joint stability.	(Maniar et al., 2018; Sinclair et al., 2019)
Peroneus Longus and Tibialis Anterior Activation	Facilitates ankle stability by regulating critical movements such as inversion, supination, and internal rotation, thereby maintaining proper alignment and reducing the risk of joint misalignment or injury. This stabilizing function is particularly essential during dynamic activities where rapid changes in direction or uneven surfaces are encountered. The regulation of these movements is primarily achieved through coordinated neuromuscular control and the activation of ankle stabilizers, including the peroneal muscles, tibialis posterior, and intrinsic foot muscles. These structures work in synergy to counter excessive or maladaptive forces, ensuring smooth transitions between movements and protecting the ligaments, such as the anterior talofibular ligament (ATFL) and calcaneofibular ligament, from undue strain. Additionally, proprioceptive feedback from mechanoreceptors within the ankle joint capsule and surrounding soft tissues plays a crucial role in maintaining dynamic stability. This sensory input allows for real-time adjustments to movement patterns, minimizing the risk of sprains or chronic instability. Enhancing the strength and proprioceptive capacity of the ankle stabilizers can therefore significantly improve functional performance and reduce the incidence of ankle-related injuries in both athletic and everyday activities.	(Fong et al., 2009; Konradsen & Ravn, 1991)
Intrinsic Foot and Toe Flexor Strength	Plays a pivotal role in the storage and return of elastic energy during dynamic activities, acting as a spring-like system to optimize efficiency and reduce energy expenditure. This elastic function is particularly critical during activities such as running, jumping, and walking, where the cyclical stretching and recoiling of tendons, such as the Achilles tendon and plantar fascia, contribute to energy conservation and effective force transmission. In addition to its role in energy dynamics, it provides crucial structural support to the medial longitudinal arch of the foot. This support helps maintain the arch’s shape under load, distributing forces evenly across the foot and protecting against conditions such as overpronation or flatfoot. The preservation of the medial arch also enhances gait stability and efficiency, ensuring smooth transitions during the stance phase. Furthermore, it significantly enhances propulsion by improving the transfer of forces from the lower limbs to the ground, thereby enabling powerful forward motion. The interaction of the foot and ankle stabilizing muscles, such as the tibialis posterior, peroneals, and intrinsic foot muscles, contributes to ankle stability, reducing excessive movements like eversion or inversion. This coordination is essential not only for efficient movement but also for minimizing injury risks in high-impact and repetitive activities.	(Kelly et al., 2019; Tourillon et al., 2019; Fraser et al., 2016) (Kelly et al., 2019; Tourillon et al., 2019; Fraser et al., 2016)
Adductor Strength and Activation	During the push-off phase of movement, the coordination of hip extension and pelvic rotation toward the direction of travel is critical for generating propulsion and forward momentum. This dynamic interaction involves the synchronized action of multiple muscle groups, including the gracilis, which plays a significant role in stabilizing the pelvis and assisting in hip adduction and flexion during this phase. The gracilis, given its anatomical structure and functional properties, operates at high lengthening velocities under eccentric loading conditions, making it particularly susceptible to strain. The eccentric contraction of the gracilis during the deceleration and redirection of the lower limb places significant mechanical stress on its fibers. This stress, combined with the high demands of dynamic activities that involve rapid changes in direction or explosive power generation, can lead to an increased risk of groin muscle injuries. Such injuries are particularly common in sports requiring repeated push-off and cutting movements, highlighting the gracilis's vulnerability under high loading conditions. Additionally, the gracilis functions synergistically with other adductor muscles and the core musculature to maintain pelvic stability and alignment during movement. Any dysfunction or weakness in this coordination can exacerbate the risk of injury, not only to the gracilis but also to the surrounding musculature. Targeted strengthening and flexibility training aimed at improving the eccentric strength and length-tension properties of the gracilis can help mitigate injury risk and enhance athletic performance.	(Dupré et al., 2021; Markovic et al., 2020; Moreno-Pérez et al., 2019) (Dupré et al., 2021; Markovic et al., 2020; Moreno-Pérez et al., 2019)
Dynamic Trunk Control	Trunk, comprising roughly half of the body’s mass, serves as a critical component in maintaining stability, particularly during high-demand movements like change of direction (COD) tasks. Effective trunk stabilization on a single limb during these tasks is essential for optimizing movement efficiency and reducing injury risk. The trunk's position and control directly influence the biomechanics of the lower limbs, especially under high accelerative and decelerative forces. Lateral trunk flexion significantly alters the frontal-plane mechanics by increasing the moment arm distance, which amplifies the forces acting on the knee joint. This shift also modifies the orientation of the ground reaction force (GRF) vector, contributing to higher knee joint loads during COD movements. Such increased loads, especially when combined with dynamic instability, can compromise knee joint integrity and elevate the risk of ACL injuries. Lateral trunk instability has been strongly correlated with a greater likelihood of ACL injuries, as unstable trunk movements increase medial-lateral forces and knee valgus moments. Computational simulations reinforce this, showing that shifting the center of mass medially reduces knee valgus loads and enhances stability. In contrast, a medial trunk lean has been associated with improved biomechanical performance during COD tasks. By aligning the trunk more medially, athletes can optimize force application and maintain better control, improving speed and efficiency. Medial trunk positioning not only enhances performance but also helps to mitigate undue stress on the knee joint. Additionally, anterior trunk flexion plays a unique role, particularly during the braking phases of movement. This forward-leaning posture increases the loading demands on the hamstrings, allowing these muscles to play a more prominent role in deceleration and control. Proper hamstring engagement in this context is crucial for maintaining lower-limb stability and preventing injuries. Thus, the interplay between trunk positioning, GRF orientation, and muscle engagement highlights the importance of trunk control in athletic performance and injury prevention.	(Donnelly et al., 2012; Hewett & Myer, 2011) (Zazulak et al., 2007) (Donnelly et al., 2012) (Dos’Santos, 2020; Marshall et al., 2014) (Kerin et al., 2022)
Pelvic Control	Pelvic obliquity, defined as the asymmetrical tilting of the pelvis in the frontal plane, can significantly affect the angles of lateral trunk flexion. This interplay between the pelvis and trunk is crucial for achieving proper alignment and stability during dynamic movements. When pelvic obliquity is well-controlled, it facilitates an optimal lateral trunk lean, aligning the center of mass effectively over the base of support. This alignment not only enhances movement efficiency but also aids in shifting the body’s momentum in the intended direction, making it particularly beneficial during tasks requiring rapid changes in movement, such as cutting or turning. The influence of pelvic obliquity on trunk flexion angles is mediated by the coordination of the lumbopelvic musculature, including the obliques, quadratus lumborum, and gluteus medius. These muscles work together to stabilize the pelvis and trunk, ensuring that lateral flexion does not result in excessive frontal-plane deviation or compromise lower-limb mechanics. Proper trunk alignment also helps to maintain an optimal ground reaction force (GRF) vector, reducing unnecessary joint loads and minimizing the risk of injuries, such as knee valgus collapse or ankle instability. In dynamic athletic movements, controlled pelvic obliquity allows for smooth transitions in weight distribution, enabling the trunk to lean appropriately toward the direction of travel. This adjustment optimizes force application during propulsion and braking phases, enhancing performance. Conversely, poor control of pelvic obliquity can result in excessive lateral trunk flexion, disrupting alignment and increasing the likelihood of compensatory mechanics that strain the lower extremities. Training strategies aimed at improving core and pelvic stability, as well as functional neuromuscular control, can help athletes maintain optimal pelvic and trunk alignment. Such interventions are critical not only for improving movement efficiency but also for reducing injury risk by promoting biomechanical harmony across the trunk, pelvis, and lower limbs.	(Staynor et al., 2018) (Staynor et al., 2018)
External Hip Rotator (Gluteal) Strength and Activation	The external hip rotators play a crucial role in maintaining proper knee alignment by reducing the knee abduction angle (KAA), knee abduction moment (KAM), and frontal-plane moment arms. These adjustments are essential for minimizing excessive lateral forces acting on the knee, which can destabilize the joint during dynamic activities. The ability of the external rotators to control these biomechanical parameters is especially significant given that increased knee valgus angles and moments are strongly associated with a heightened risk of anterior cruciate ligament (ACL) injuries. Among the external rotators, the gluteal muscles—particularly the gluteus medius—play a pivotal role in counteracting knee valgus forces and rotational moments. Adequate gluteal strength is essential for maintaining proper lower-limb alignment, as the gluteus medius stabilizes the pelvis and femur, preventing inward collapse of the knee. Conversely, insufficient activation of the gluteus medius has been linked to elevated knee abduction moments, increasing the strain on the ACL and other joint structures. The gluteal muscles, particularly the hip extensors, also contribute to generating large hip flexion moments, which are critical for powerful propulsion and deceleration. These muscles stabilize the trunk and lower limb during braking phases and provide the force required for trunk stabilization in dynamic movements. Proper function of the gluteal muscles ensures that the load is evenly distributed across the lower kinetic chain, preventing compensatory mechanisms that can lead to injury. Deficits in isometric hip external rotation strength have been specifically associated with an increased risk of non-contact ACL injuries. Weakness in this area compromises the ability to resist rotational and valgus forces at the knee, leaving the joint vulnerable during high-stress movements such as landing, cutting, and pivoting. Strengthening the hip external rotators, particularly through targeted resistance and neuromuscular training, is therefore a key strategy for reducing ACL injury risk and enhancing athletic performance.	(Hewett et al., 2005; McLean et al., 2004) (Hewett et al., 2005) (Maniar et al., 2018; Ueno et al., 2020) (Dos’Santos et al., 2019). (Khayambashi et al., 2016)