Gender and age effects on elbow joint stiffness in healthy subjects

Objective To investigate the effect of demographic factors on upper-limb pendulum tests in healthy subjects. Design Experimental. Upper-limb pendulum tests were performed on healthy subjects. Biomechanical parameters of the elbow joint were estimated. The body weight, forearm length, gender, and age of subjects were recorded. The relationships among the biomechanical parameters and demographic factors were investigated. Setting A referral medical center in Taiwan. Participants Healthy subjects (N=192). Intervention Upper-limb pendulum test. Main Outcome Measures Number of swings, relaxation indices calculated from the angle trajectories, and stiffness constants and damping coefficients estimated from the elbow model were used as the biomechanic parameters of elbow joints. Results Age had little effect on the biomechanic parameters. Both mean stiffness constant and damping coefficient were larger in men. However, when the influence of body weight was corrected, the biomechanic parameters were the same for both genders. Forearm length had similar but weaker effects on stiffness constant and damping coefficient. Conclusions In healthy subjects, the mechanical properties of the elbow joints were similar in men and women of comparable body weights and did not deteriorate significantly until subjects reached the age of 70 years.