Influence of external ankle support on lower extremity joint mechanics during drop landings.

OBJECTIVE To investigate the effects of external ankle support (EAS) on lower extremity joint mechanics and vertical ground-reaction forces (VGRF) during drop landings. DESIGN A 1 x 3 repeated-measures, crossover design. SETTING Biomechanics research laboratory. PATIENTS 13 male recreationally active basketball players (age 22.3 +/- 2.2 y, height 177.5 +/- 7.5 cm, mass 72.2 +/- 11.4 kg) free from lower extremity pathology for the 12 mo before the study. INTERVENTIONS Subjects performed a 1-legged drop landing from a standardized height under 3 different ankle-support conditions. MAIN OUTCOME MEASURES Hip, knee, and ankle angular displacement along with specific temporal (TGRFz1, TGRFz2; s) and spatial (GRFz1, GRFz2; body-weight units [BW]) characteristics of the VGRF vector were measured during a drop landing. RESULTS The tape condition (1.08 +/- 0.09 BW) demonstrated less GRFz1 than the control (1.28 +/- 0.16 BW) and semirigid conditions (1.28 +/- 0.21 BW; P < .0001), and GRFz2 was unaffected. For TGRFz1, no-support displayed slower time (0.017 +/- 0.004 s) than the semirigid (0.014 +/- 0.001 s) and tape conditions (0.014 +/- 0.002 s; P < .05). For TGRFz2, no-support displayed slower time (0.054 +/- 0.006 s) than the semirigid (0.050 +/- 0.006 s) and tape conditions (0.045 +/- 0.004 s; P < .05). Semirigid bracing was slower than the tape condition, as well (P < .05). Ankle-joint displacement was less in the tape (34.6 degrees +/- 7.7 degrees) and semirigid (36.8 degrees +/- 9.3 degrees) conditions than in no-support (45.7 degrees +/- 7.3 degrees; P < .05). Knee-joint displacement was larger in the no-support (45.1 degrees +/- 9.0 degrees) than in the semirigid (42.6 degrees +/- 6.8 degrees; P < .05) condition. Tape support (43.8 degrees +/- 8.7 degrees) did not differ from the semirigid condition (P > .05). Hip angular displacement was not affected by EAS (F(2,24) = 1.47, P = .25). CONCLUSIONS EAS reduces ankle- and knee-joint displacement, which appear to influence the spatial and temporal characteristics of GRFz1 during drop landings.