Background/Purpose
To determine the effects of augmented visual feedback on dynamic balance performance at two different stability levels using the Biodex Balance System.
Method
The Biodex Balance System (Biodex Medical Systems, Shirley, NY) is a stabilometer consisting of an instrumented circular tilt board that moves simultaneously about the anterior-posterior and medial-lateral axes with maximum tilt to 20¨¬ from horizontal in all directions. Changing the resistance force applied to the platform varies platform stability. Stability levels are 1 to 8 with 8 being the most stable (least difficult). Levels 2 and 7 were used in the present study with the degrees from horizontal for each trial measured and a stability index calculated. This index was used as the dependent variable with a low score representing the better performance. Forty male volunteers (21.1 ± 4.1 yr; 73.6 ± 14.7 kg, 169.51 ± 6.2 cm) without disorder participated. Participants were randomly assigned to one of four groups consisting of 10 subjects each. A familiarization trial was performed after which each participant then completed nine 20 second trials. The mean stability index score was used as datum. The independent variable was augmented visual feedback via screen display tracings versus non-augmented feedback (i.e., participant looked at covered screen).
Analysis/Results
Separate statistical analyses were conducted for level 2 and level 7. Mean augmented and non-augmented stability scores were compared using Independent t-tests; a = .05. For level 7, a significant t-value (t = 3.11, p = .005), favoring augmented visual feedback was found (M = 2.29 ± .90; no feedback: M = 3.5 ± 1.6). No mean differences (t = .221, p = .828) between augmented visual feedback (M = 9.67 ± 2.5) and non-augmented feedback (M = 9.95 ± 3.4) were found at level 2.
Conclusions
Findings were interpreted in terms of open versus closed motor-loop control. At the less stable level 2, compensatory movements to maintain platform balance may have been performed faster because of less resistance, thus there was not sufficient time to use visual feedback causing open loop responses. For the more stable level 7, movements were slower because of greater resistance allowing time for the use of augmented visual feedback. The implication for Biodex balance training is that different motor control mechanisms may be used at the different levels of stability.