Introduction: Ice hockey is a physically demanding sport that requires a combination of aerobic and anaerobic capacities, as well as specific on-ice skills. This study aimed to compare the effectiveness of individualized interval training on a slide board with training on a cyclo-ergometer, focusing on aerobic capacity and specific fitness in elite ice hockey players. Materials and Methods: Thirty players were randomly divided into an experimental (slide board) and a control (cyclo-ergometer) group. Both groups underwent a 6-week training program with the same intensity and volume. Results: The results showed that both forms of training led to significant improvements in aerobic capacity, as indicated by VO2max and VO2 lactate thresholds. The slide board training group demonstrated higher effect sizes (d = 1.49, 1.62) than the cyclo-ergometer one (0.76, 0.43). Specific on-ice performance tests showed that slide board training resulted in faster skating times (p = 0.0002), suggesting a greater transfer of training effects to on-ice skills. Conclusions: This study highlights the benefits of incorporating slide board interval training into the off-season training regimen of elite ice hockey players. Slide board training improves specific on-ice skills, which are crucial for high-level hockey performance. These findings provide valuable insights for coaches and strength and conditioning specialists working with elite ice hockey players.