The Relationship Between Core Stability, Extremity Proprioception, and Dynamic Balance in Young Adults

Introduction Core musculature comprises a complex anatomical structure, including the hips and pelvic floor at the base, the diaphragm superiorly, the oblique muscles laterally, the gluteal and paraspinal muscles posteriorly, and the abdominal muscles anteriorly. This integrated system plays a vital role in balancing biomechanical forces acting on the body, enhancing force production in the extremities, and optimizing movement efficiency. Furthermore, by surrounding the trunk, it contributes significantly to spinal stability and the maintenance of upright posture. The core muscles, which play a key role in stabilizing the trunk and pelvis, also constitute the center of the kinetic chain. Core muscles play a crucial role in transmitting energy and force from the proximal to the distal segments through this chain, facilitating effective force transfer to the extremities. These functions enhance peripheral joint stability and decrease the risk of injury during physical activity. Core stability is defined as the capacity to control trunk position and movement relative to the pelvis effectively, and it plays a pivotal role in maintaining postural control. The core is considered a functional unit comprising muscle groups that collaboratively contribute to spinal stabilization. This stability emerges through the integrated action of motor control systems and muscular strength. Enhanced core stability promotes efficient force transmission throughout the kinetic chain, increases trunk muscle endurance, and supports both static and dynamic balance performance.

Balance is defined as the ability to maintain a stable posture by regulating the body's position in space. While static balance refers to sustaining postural stability in the absence of external disturbances, dynamic balance involves the capacity to restore and preserve stability during or following voluntary movement. Both components of balance are closely associated with trunk stability and reflect the efficiency of postural control systems. Trunk stability refers to the capacity to maintain control of the trunk both at rest and during dynamic or fine motor tasks. This control relies on two fundamental yet interrelated mechanisms: maintaining the projection of the body's center of gravity within the base of support and aligning body segments along the vertical axis. Enhancing core muscle strength contributes to postural control by minimizing deviations in the center of mass and reducing trunk sway. The efficiency of this postural mechanism is strongly influenced by neuromuscular control.

Neuromuscular control is closely associated with the proprioceptive component of the sensorimotor system. Proprioception refers to the transmission of afferent signals from mechanoreceptors located in muscles, ligaments, facet joints, and intervertebral discs to the central nervous system. Among these structures, the paraspinal muscles, which contain a high density of muscle spindles, play a critical role in regulating trunk movements. Disruptions in the proprioceptive signaling pathway can impair the development of accurate motor patterns and reduce overall movement quality.

Despite extensive literature on core stability and postural control, the relationship between core endurance and proprioceptive acuity in the upper and lower extremities remains underexplored. Clarifying this association is of particular interest in both clinical rehabilitation and athletic performance contexts. Therefore, the present study aims to investigate the effects of core muscle endurance on proprioceptive function in the shoulder and hip joints, and to examine how these variables relate to dynamic balance performance in healthy young adults.

Materials and Methods Participants This study included 60 healthy volunteers (37 females, 23 males; mean age: 20.9 ± 2.46 years). In this study, the sample size was determined by considering both the findings from previous studies and the need to compensate for data losses and preserve statistical power. In a similar study in the literature, a regression analysis that investigated the association between core endurance and dynamic balance found R² = 0.24. Based on this value, when the effect size was estimated using the formula f² = R² / (1 - R²), f² = 0.31 was obtained. An a priori power analysis conducted using G*Power (α = 0.05, power = 0.80, 5 predictor variables) determined that a minimum of 48 participants was needed to detect this effect size. The sample was planned to consist of at least 60 people, considering a potential attrition rate of 25% during the data collection phase. After completing the study, researchers performed post hoc power analysis for core endurance tests and found the lowest R² value of 0.19 in regression analyses. Using this value, researchers calculated the effect size as 0.24 with the f² = R² / (1 - R²) formula researchers made. Given these data (α = 0.05, f² = 0.24; predictors = 5; n = 60), statistical power was confirmed to be 0.80. These results indicate that the sample size was sufficient both during the planning phase and upon post-hoc verification.