Effect of age-related hyperkyphosis on open and closed-loop postural control in older adults

Center-of-pressure (CoP) oscillations represent the neuromuscular system's response to control the body's center of mass. In older adults, hyperkyphosis alters body alignment, increases sway, and impairs proprioception. While some studies have explored hyperkyphosis effects on CoP displacements, the underlying neuromuscular mechanisms remain underexplored. This studyinvestigated hyperkyphosis impacts on the postural control using the stabilogram diffusion analysis (SDA) to assess interplay between open and closed-loop control. Thirty-eight older adults with a mean kyphosis angle of 57.8 ± 8.4° and 34 controls with a mean kyphosis angle of 38.4 ± 4.9°, participated. CoP parameters, including trajectory range, velocity in the anterior-posterior (AP), mediolateral (ML), and planar (R) directions, sway area per unit time, and SDA, were measured during bipedal standing in eyes-open (EO) and eyes-closed (EC) conditions. Results showed significantly higher short-term effective diffusion coefficients in the ML (p = 0.016), AP (p = 0.011), and R-directions (p = 0.007), as well as critical displacement in the AP-direction (p = 0.048), and CoP velocity in R-direction (p = 0.046) in the hyperkyphotic group. Conversely, critical time interval in R-direction (p = 0.034) was lower compared to controls. EC increased short-term effective diffusion coefficient in all directions, critical displacement in the AP, and R-directions, sway area per unit time, CoP velocity in all directions, trajectory range in the AP (p < 0.001) and ML-directions (p = 0.047). EO showed higher long-term diffusion coefficients in the AP and R-directions (p < 0.001), and critical time intervals in the AP (p = 0.014) and R-direction (p = 0.003). Hyperkyphosis impairs open-loop control and reliance on closed-loop mechanisms, potentially delays responses and increases fall risk in older adults.