TRU PRO Tennis String Lab Testing Results (USRSA)

The United States Racquet Stringers Association explains the lab test procedure as follows: All strings were tensioned to 62 pounds and allowed to sit for 200 seconds. Then the string was hit five times with a force equivalent to hitting a 120 mph serve. The tension loss represents the total amount of the relaxation over both time and impact. The stiffness value is a calculation derived from the amount of force created at impact to stretch the string. Lower values represent softer strings and lower impact forces. Higher values represent stiffer strings and higher impact forces.