###### Abstract  
The body's postural control system is responsible for responding to perturbations of balance and keeping the body upright. During quiet standing, the center of pressure oscillates about the center of mass, counteracting imbalances. These oscillations can be analyzed to determine the degree of stability, which could be helpful in quantifying the effects of brain injuries. In this research, the center of pressure was recorded for stances with feet together and feet tandem, with eyes opened and eyes closed, in neurotypical participants. These signals were analyzed using indices of approximate entropy and velocity to determine how sensitive the measures were in tracking changes to stability levels. One-way ANOVA test results showed increased approximate entropy in anterior/posterior and medial/lateral directions (\(p\) = 1.21 \(\times\) 10\({}^{-11}\), 3 \(\times\) 10\({}^{-14}\)) and increased velocity in both directions (\(p\) = 2.87 \(\times\) 10\({}^{-6}\), 4.87 \(\times\) 10\({}^{-7}\)) during conditions with decreased stability. [PERSON]'s post hoc testing indicated that approximate entropy was significantly greater in all the less stable feet tandem trials in comparison to the most stable eyes open, feet together condition with \(p\) < 0.001 in nearly every participant and that velocity was significantly greater in the least stable eyes closed, feet tandem trials in comparison to the most stable condition with \(p\  
may be lost without the implementation of adaptations such as stepping or movement of the arms [5]. Many studies have analyzed the methods of postural control in humans during quiet standing for the purpose of understanding the way that the body maintains balance [2; 4; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20]. One main takeaway is the general oscillatory pattern that the COM and COP can be expected to follow under typical neurologic function. For example, if the COM of a person in a quiet standing position with their feet together moves posteriorly, a person would fall backward without intervention. As the COM moves farther from the COP, angular acceleration and velocity increase, causing the body to fall more quickly. To stop this motion and an eventual fall, the body pivots about the ankle, causing a posterior angular velocity and acceleration of the body. This moves the COP back and toward the COM due to the moment resulting from the weight acting downward at the COM and the ground reaction force acting upward at the COP. While the body sways backward, the COP and COM line up and the person is no longer at risk of falling backward. This pattern continues indefinitely as the body sways back and forth [4]. The inverted pendulum model, as described by [PERSON] [4], is the basis of human oscillation. In this model, the ankles are the pivot point of the body, which acts as the pendulum. Although some studies have shown that postural control involves compensation at the knee and hip, as well, and is not exclusive to the ankle [21; 22; 23; 24; 25; 26], other studies have demonstrated that the single inverted pendulum model, which only considers the ankle, is functionally acceptable for the experimental description of COP oscillations [27; 28]. The understanding of COP oscillations above allows for studies to explore how behavior changes under varying neurological conditions, such as concussion. People suffering from brain injuries like concussion have sustained damage to their central nervous system, both locally and diffusely, which results in symptoms of dizziness and balance impairment [29]. This damage is reflected in the COP due to the alteration of the central and peripheral control response mechanisms, leading to changes in the way the body responds to perturbations of balance. If not provided sufficient time to heal, the brain can be further damaged, particularly in athletes who return to play too soon.