Performance-based physical function tests

The stair climbing test (SCT) was used to assess functional mobility and the ability of the lower extremity muscles to generate concentric and eccentric forces. For the test, the time taken to ascend and descend a flight of stairs (12 steps; each step was 17-cm high and 25-cm wide) was measured [17].

The 6-minute walk test (6MWT), a measure of the distance (m) that an individual walks in 6 minutes, was used to assess the overall locomotor ability and locomotor fatigue. Patients were instructed to walk as far as possible for 6 minutes along a 50-m hallway that was marked with lines [18].

For the Timed Up and Go (TUG) test, patients began in a seated position in an armchair (seat height, 44 cm; depth, 45 cm; width, 49 cm; and armrest height, 64 cm). They were then instructed to rise, walk forward for 3 m, turn around, walk back to the chair, and sit back down without any physical assistance. The whole process was timed and evaluated the dynamic balance [19].

The maximal isometric strength of the bilateral knee extensors and flexors was measured using an isokinetic dynamometer (Computer Sports Medicine Inc., Stoughton, MA, USA). Before the test, all patients relaxed their muscles by performing light stretches [20]. Patients were instructed to grasp the sidebars of the apparatus during the test procedure. After a structured warm-up with the knee joint fixed at 60° of flexion (to generate maximal isometric force) [21], patients were instructed to perform maximal voluntary contractions until the torque did not increase by >5% on three successive attempts.

Spatiotemporal variables of gait were measured using a validated wireless inertial sensing device (BTS Bioengineering S.p.A., Milan, Italy). The first and last steps of the 8-m walk were removed from all calculations to eliminate the effects of abnormal patterns during the initiation of gait or psychological responses at the termination of gait [22].

Available knee ROM was measured using a standard long arm goniometer. Knee flexion was measured as the value of maximal active bend at the knee while the patient was lying in a supine position. Knee extension was measured as the angle of maximal active straightening with the patient’s heel placed on a 10-cm wooden block [23].