The purpose of this study was to determine whether satellite cell ablation within rat fast-twitch muscles exposed to chronic low-frequency stimulation (CLFS) would limit fast-to-slow fibre type transitions. Twenty-nine male Wistar rats were randomly assigned to one of three groups. Satellite cells of the left tibialis anterior were ablated by weekly exposure to a 25-Gy dose of -irradiation during 21-days of CLFS (IRR-Stim), whilst a second group received only 21-days of CLFS (Stim). A third group received weekly doses of -irradiation (IRR). Non-irradiated right legs served as internal controls. Continuous infusion of BrdU revealed that CLFS induced an 8.0-fold increase in satellite cell proliferation over control (mean±SEM: 23.9±1.7 vs. 3.0±0.5/mm2, P<0.0001) that was abolished by -irradiation. M-cadherin and myogenin staining were also elevated 7.7- and 3.8-fold (P<0.0001), respectively, in Stim compared with control, indicating increases in quiescent and terminally differentiating satellite cells; these increases were abolished by -irradiation. Myonuclear content was elevated 3.3-fold (P<0.0001) in Stim, but remained unchanged in IRR-Stim. Immunohistochemical analyses revealed attenuation of fast-to-slow fibre type transitions in IRR-Stim compared with Stim. Comparable changes were observed at the protein level by SDS-PAGE. It is concluded that although considerable adaptive potential exists within myonuclei, satellite cells play a role in facilitating fast-to-slow fibre type transitions.