A, slopes of steady-state firing. No differences were found in comparing fast versus slow motoneurones, or unweighted versus weight-bearing conditions. B, significant main effects of minimum current required for steady-state firing. Motoneurones of hindlimb unweighted (HU; •) rats had significantly higher minimum currents than weight-bearing (WB) rats (○, P = 0.027), and fast (•) had higher currents than slow (○) motoneurones (P = 0.018).