Published online Dec 18, 2016. doi: 10.5312/wjo.v7.i12.801
Peer-review started: July 21, 2016
First decision: September 5, 2016
Revised: September 6, 2016
Accepted: October 5, 2016
Article in press: October 7, 2016
Published online: December 18, 2016
To investigate the impact of extrinsic visual feedback and additional cognitive/physical demands on single-limb balance in individuals with ankle instability.
Sixteen subjects with ankle instability participated in the study. Ankle instability was identified using the Cumberland Ankle Instability Tool (CAIT). The subject’s unstable ankle was examined using the Athletic Single Leg Stability Test of the Biodex Balance System with 4 different protocols: (1) default setting with extrinsic visual feedback from the monitor; (2) no extrinsic visual feedback; (3) no extrinsic visual feedback with cognitive demands; and (4) no extrinsic visual feedback with physical demands. For the protocol with added cognitive demands, subjects were asked to continue subtracting 7 from a given number while performing the same test without extrinsic visual feedback. For the protocol with added physical demands, subjects were asked to pass and catch a basketball to and from the examiner while performing the same modified test.
The subject’s single-limb postural control varied significantly among different testing protocols (F = 103; P = 0.000). Subjects’ postural control was the worst with added physical demands and the best with the default condition with extrinsic visual feedback. Pairwise comparison shows subjects performed significantly worse in all modified protocols (P < 0.01 in all comparisons) compared to the default protocol. Results from all 4 protocols are significantly different from each other (P < 0.01) except for the comparison between the “no extrinsic visual feedback” and “no extrinsic visual feedback with cognitive demands” protocols. Comparing conditions without extrinsic visual feedback, adding a cognitive demand did not significantly compromise single-limb balance control but adding a physical demand did. Scores from the default protocol are significantly correlated with the results from all 3 modified protocols: No extrinsic visual feedback (r = 0.782; P = 0.000); no extrinsic visual feedback with cognitive demands (r = 0.569; P = 0.022); no extrinsic visual feedback with physical demands (r = 0.683; P = 0.004). However, the CAIT score is not significantly correlated with the single-limb balance control from any of the 4 protocols: Default with extrinsic visual feedback (r = -0.210; P = 0.434); no extrinsic visual feedback (r = -0.450; P = 0.081); no extrinsic visual feedback with cognitive demands (r = -0.406; P = 0.118); no extrinsic visual feedback with physical demands (r = -0.351; P = 0.182).
Single-limb balance control is worse without extrinsic visual feedback and/or with cognitive/physical demands. The balance test may not be a valid tool to examine ankle instability.
Core tip: Single-limb balance control with the Biodex Balance System (BBS) was significantly worse without extrinsic visual feedback and with cognitive or physical demands in those with ankle instability. Clinicians should consider a patient’s activity and incorporate proper additional demands in ankle stability testing. In addition, the Athletic Single Leg Stability Test of the BBS may not be a valid tool to examine ankle instability. Further research is needed to examine the validity and reliability of the Athletic Single Leg Stability Test in testing ankle instability.