Inset: Drawing of spinal gray matter divided into radial sectors for measure of quadriceps motoneuron radial dendritic extent. Radial extents of quadriceps dendrites in untreated animals (black bars), saporin-injected animals that either received no further treatment (SAP, white bars) or were given ad lib exercise (SAP+EXERCISE, light gray bars), and intact animals given ad lib exercise (intact+EXERCISE, dark gray bars). For graphic purposes, dendritic extent measures have been collapsed into 6 bins of 60° each. Extent measures did not differ across groups. Bar heights represent means ± SEM.