This study aimed to investigate the effect of task difficulty on the effectiveness of BT in community-dwelling older adults and determined the optimal challenge point for BT in this population.
This study included 40 community-dwelling older adults with independence in activities of daily living and without medical conditions that could interfere with task performance. BT was performed on a balance board that tilted left and right, and movements were measured using a system equipped with a three-axis accelerometer and a three-axis gyroscope. Task difficulty was adjusted by modifying the shape of the board’s support components. Task performance was evaluated using the stability index, which reflects the average tilt angle of the board per unit time during task execution. The participants were randomly assigned to two groups—low and high—based on the level of difficulty. Each group practiced balancing tasks for nine 20-s trials. A pre-test and a retention test, each consisting of three 20-s trials, were conducted before and after the practice sessions. Subjective task difficulty was assessed immediately after each practice session using the NASA task load index (TLX), as described previously (Akizuki & Ohashi, 2015). The stability index was analyzed by analysis of variance using a 2 (groups: high-difficulty versus low-difficulty) × 3 (blocks) factorial design with repeated measures on the last factor for the practice sessions and a 2 (groups) × 2 (tests: pre-test versus retention test) design with repeated measures on the last factor for the test sessions. The learning rate was defined as the rate of improvement from the pre-test to the retention test and was analyzed by curvilinear regression analysis using NASA-TLX subscales. Statistical analysis was performed using SPSS Statistics version 29 (IBM Corp, Armonk, NY), and the significance level was set at 5%.
There was no significant between-group difference in the stability index during the pre-test. Nonetheless, the stability index in the retention test was significantly higher in the low-difficulty group than in the high-difficulty group (p 0.001). Additionally, some NASA-TLX subscales were significantly correlated with task performance during practice, and the performance dimension of the NASA-TLX showed significantly associated with the learning rate (R2 = 0.410, p 0.001).
The effectiveness of BT can be improved by adjusting the functional task difficulty. Nonetheless, better methods for adjusting and measuring task difficulty during BT are warranted.
For physical therapists conducting BT for fall prevention in community-dwelling older adults, the effectiveness of BT can be increased by adjusting the task difficulty based on NASA-TLX.
balance training
optimal task difficulty
