The effects of age, fitness, and health on the passive stiffness of the intact low back and its impact on seated work in a healthy, working, female population.

Age is associated with increased tissue stiffness and a higher risk of low back pain, particularly in older, sedentary workers who spend long periods sitting. This study explored how trunk stiffness changes with age and its relationship with posture during prolonged sitting in a sample of 37 women aged 20-65 years. Age was assessed as both Chronological Age and Fitness Age, with trunk stiffness measured using a passive trunk flexion apparatus. Participants sat at a computer workstation for 60 minutes, and spine posture was recorded every 10 minutes. The study found that trunk stiffness significantly increased with age, especially when considering Fitness Age (r = 0.517, p = 0.003). Additionally, trunk stiffness was negatively correlated with spine motion during sitting (r = -0.435, p = 0.023). These findings suggest that workers with poorer health move less while sitting and could be more susceptible to the deleterious effects of sedentary work.