Implementation of perturbation training for elderly requires a validated measure to quantify someone’s ability to recover when encountering a perturbation. A quantified recovery performance has been constructed for the anteroposterior (QRPAP) and for mediolateral (QRPML) plane, the QRPAP and QRPML reflect the amount of deviation of the center of pressure trajectory from the unperturbed walking pattern. The QRPAP and QRPML were calculated for eleven elderly subjects (>65 years), who experienced 66 perturbations (accelerations and decelerations) during treadmill walking. The constructed QRPAP and QRPML were validated in this study (1) by comparing them to the rated recovery performance (RRT) as provided by physiotherapists and (2) by studying how they were affected by an increased specified difficulty (SpD) of perturbations. The used perturbation characteristics for the SpD’s were validated with the perceived difficulty (PD) as reported by the subjects for each perturbation. A positive relation confirmed the increase of PD with an increase of SpD. Both for the QRPAP and the QRPML a positive relation was found with the RRP and a negative relation was found with the SpD. The QRPAP showed a stronger relation with the RRP and was found to be more sensitive when compared to the QRPML. The relation of the QRPAP with the RRP was consistent across physiotherapists. Implementation of the QRPAP during perturbation training will decrease the attention demanded of physiotherapists and will remove the offset observed across physiotherapists. Progress can be monitored objectively and training difficulty can be adjusted accordingly.