Immediate and latent interlimb transfer of gait stability adaptation following repeated exposure to slips

Abstract

The authors trained 21 participants by using blocked-and-mixed exposure to right-side slips and then caused them to slip unexpectedly on the untrained left side. Authors retested participants with a right slip and a left slip at 1 week, 2 weeks, 1 month, and 4 months. The authors found that preslip stability on the first untrained left slip improved and was significantly greater than that on the first right slip, which probably contributed to the reduction in incidence of falls from approximately 30% to approximately 10%. Postslip stability and base of support (BOS) slip velocity were similar to those on the first right slip and much lower than those on the last right slip. Increases in pre- and postslip stabilities and BOS slip velocity during the left slip led to reductions in backward balance loss (BLOB) from approximately 95% on initial left slip to approximately 60% and to approximately 25% on the 1st and 3rd retest sessions, respectively. In contrast, BLOB remained at a constant approximately 40% level on the right slip of the same retest sessions. The results indicate a partial immediate transfer and a possible latent transfer.

FIGURE 1

Schematic diagram of the experimental setup with approximate position of the participant at touchdown of the training (right limb). Unfilled circles indicate positions of passive–reflective markers on the body segments and movable platform. Solid and dotted lines joining the markers represent the body-segment links used to calculate the whole-body center of mass. The I-beam and safety harness system were much higher than shown (9 m above the ground). The I-beam extended the length of the 7-m walkway. The two sliding devices were placed side by side to enable inducing the bilateral slips. The low-friction, nonmotorized movable top plates were mounted on a frame with linear bearings. Once released, the movable platforms were free to slide along the track on the linear bearings. These devices were locked and embedded in a 7-m walkway and made less apparent by the stationary decoy platforms.

FIGURE 2

Incidence of balance loss for the first and last training (right) side slips (R-1 and R-24, respectively) and the slip on the untrained (left) side slip (L-1) from the initial session (Hypothesis 1–H₁). Also shown are the slip trials from the right and left sides for the 4 retest sessions conducted about 1 week, 2 weeks, 1 month, and 4 months after the initial training session (Hypothesis 2–H₂). ^* indicates p < .05 for left side comparisons; ⁺⁺ and ^†† indicate, p < .001 for right and interlimb comparisons, respectively. A solid line connecting 2 data points without symbols or an asterisk indicates p > .05.

FIGURE 3

Group means (± 1 SD) of (A) pre- and (B) postslip stability for the first and last training (right) side slips (R-1 and R-24, respectively) and the slip on the untrained (left) side (L-1) from the initial session (Hypothesis 1–H₁). Also shown are the slip trials from the right and left sides for the 4 retest sessions conducted about 1 week, 2 weeks, 1 month, and 4 months after the initial training session (Hypothesis 2–H₂). The preslip stability is also demonstrated for the right and left limbs (at touchdown) during a regular (Reg-1) walking trial prior to the first right slip and prior to the first left slip (Reg-2). ^* and ^† indicate p < .05 for left and interlimb comparisons, respectively; ⁺⁺, ^** and ^†† indicate for right, left, and interlimb comparisons, p < .001. Less negative values of stability indicate higher stability. A solid line connecting 2 data points without symbols indicates p > .05.

FIGURE 4

Group means (± 1 SD) of (A) BOS velocity (Ẋ BOS) and (B) foot angle for the first and last training (right) side slips (R-1 and R-24, respectively) and the slip on the untrained (left) side (L-1) from the initial session (Hypothesis 1–H₁). Also shown are the slip trials from the right and left sides for the 4 retest sessions conducted about 1 week, 2 weeks, 1 month, and 4 months after the initial training session (Hypothesis 2–H₂). Foot angle was obtained at pre-slip touchdown of the slipping limb and BOS was obtained at postslip liftoff of the contralateral, trailing limb. * and ^† indicate p < .05 for left and interlimb comparisons, respectively; ⁺⁺ and ** indicate for right and left comparisons, respectively, p < .001. A solid line connecting 2 data points without any symbols indicates p > .05.