The aim of this study was to examine the impact of weekly swimming training distance upon the ergogenicity of inspiratory muscle training (IMT). Thirty-three youth swimmers were recruited and separated into a LOW and HIGH group based on weekly training distance (< 31 km.wk-1 and > 41 km.wk-1, respectively). The LOW and HIGH groups were further subdivided into control and IMT groups for a 6-week IMT intervention giving a total of four groups: LOWcon, LOWIMT, HIGHcon, HIGHIMT. Before and after the intervention period, swimmers completed maximal effort 100 m and 200 m front crawl swims, with maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively) assessed before and after each swim. IMT increased PImax (but not PEmax) by 36% in LOWIMT and HIGHIMT groups (P < 0.05) but 100 m and 200 m swims were faster only in the LOWIMT group (3% and 7% respectively, P < 0.05). Performance benefits only occurred in those training up to 31 km.wk-1 and indicate that the ergogenicity of IMT is affected by weekly training distance. Consequently, training distances are important considerations, among others, when deciding whether or not to supplement swimming training with IMT.