Prediction equation of hip external rotators maximum torque in healthy adults and older adults using the measure of hip extensors maximum torque

•Hip extensors (HEX) torque was able to predict hip external rotators (HER) torque.•Both measures were strongly correlated in adults and older individuals.•There is no difference between directly measured and predicted values of HER torque.•The prediction equation was valid and accurate to estimate HER torque. The use of predictive equation of muscular torque can reduce physical effort and time spent during evaluation. To establish, validate, and test the accuracy of a prediction equation to estimate the hip external rotators (HER) torque in adults and older adults by means of hip extensors (HEX) torque measurement. Eighty-three healthy adults (development set) were assessed to test the association of HEX and HER torques and to establish the prediction equation. A separate 36 adults and 15 older adults (validation sets) were assessed to test the ability of the equation to estimate HER torque. Hip isometric strength was assessed by a handheld dynamometer. Simple linear regression analysis revealed that HEX torque was associated with HER torque (r=0.80; p