Prevention of Slip-Related Backward Balance Loss: The Effect of Session Intensity and Frequency on Long-Term Retention

Schematic diagram of the experimental setup with the approximate position of the subject at touchdown of the training (right limb). The unfilled circles indicate positions of passive-reflective markers on the body segments and movable platform. The solid (right side) and dotted (left side) gray 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 are much higher than shown (9m above the ground). The I-beam extends the length of the 7-m walkway 49. The low-friction, nonmotorized moveable top plates (right and left) are mounted on a frame with linear bearings. These devices were locked and embedded in a 7-m walkway and made less apparent by the stationary decoy platforms. Once released, the right moveable platform was free to slide on along the sliding track on the linear bearings. The left plate remained locked and served as a decoy.

The instantaneous gait stability for an instantaneous COM state (diamond) is the shortest distance (double-headed arrow) between the boundary and the COM state. The COM state consists of the anterioposterior COM position and its velocity relative to the BOS (X_COM/BOS, Ẋ_COM/BOS, respectively). The thick black line represents the boundary for backward loss of balance. The X_COM/BOS, Ẋ_COM/BOS are normalized to foot length and , respectively, where g is acceleration because of gravity, and h is the body height.

Incidence of backward balance loss in percentage (%) shown on the first slip of the initial session (Initial) and the 4-month retest slip (4-mo) for the 4 participating groups: High-intensity, high-frequency (HI_HF); high-intensity, low-frequency (HI_LF); low-intensity, high-frequency (LI_HF); and low-intensity, low-frequency (LI_LF). *A significant level of P<.05 for the independent and paired t tests performed. The exact values for P<.10 have been reported as well for these comparisons.

Means and SDs of (A) preslip stability, (B) postslip stability, and (C) hip height on the first slip of the initial session (initial) and the 4-month retest slip (4-month) for the 4 participating groups: high-intensity, high-frequency (HI_HF); high-intensity, low-frequency (HI_LF); low-intensity, high-frequency (LI_HF); and low-intensity, low-frequency (LI_LF). Note that the preslip stability was obtained at instant of preslip touchdown of the slipping (right) limb. Postslip stability and hip height were obtained at the instant of postslip liftoff of the contralateral (left) limb. Hip height was normalized to body height (bh). More positive values of stability indicate greater stability. *A significant level of P<.05 for the independent and paired t tests performed. The exact values for P<.10 have been reported as well for these comparisons.