Finger force (I: Index, M: Middle, R: Ring, L: Little, IMRL: Total force) during different phases (means ± standard errors are shown): A) general adjustments: pre-, during-, and post-perturbation, B) quick adjustments following PTUP and PTDN: Pre-Pert, Post-Pert50, Post- Pert100, Post-Pert150, Post-Pert500. Left and right plots show the TRACK and N-TRACK conditions, respectively. Pre-perturbation phase for the PTUP condition is the mean pre-perturbed cycles and pre-perturbation phase of PTDN condition is the mean of the last cycle before PTDN.