Intensity and generalization of treadmill slip training: High or low, progressive increase or decrease?

The purpose of this study was to investigate the efficacy of different treadmill slip training protocols on the transfer of reactive and proactive control of center of mass stability to a novel, over-ground slip. Four training protocols were investigated: high-intensity (HI; acceleration of all treadmill slips=12 m/s2), low-intensity (LO; acceleration of all treadmill slips=6 m/s2), progressively increasing intensity (INCR; acceleration of treadmill slips increasing from 6 m/s2 to 12 m/s2 over the course of training), and progressively decreasing intensity (DECR; acceleration of treadmill slips decreasing from 12 m/s2 to 6 m/s2 over the course of training). From a pool of 36 young subjects, nine were randomly assigned to each training protocol (HI, LO, INCR, and DECR). In each protocol, subjects underwent a series of 24 treadmill slips before they experienced a novel slip during over-ground walking. Measures from these subjects were compared across groups and to data from control subjects (CTRL, n=9) who had experienced a novel over-ground slip without treadmill training as part of a previous experiment. The results showed that treadmill slip training improved balance control on over-ground slip and had a larger effect on subjects׳ reactive control of stability (44.3%) than on proactive control (27.1%) in comparison with the CTRL group. HI yielded stronger generalization than LO, while INCR was only marginally better than DECR. Finally, the group means of stability displayed a clear ascending order from CTRL, LO, DECR, INCR, to HI.