This study investigated the impact of a 4-week dry-land short sprint interval program (sSIT) on a swim ergometer, when incorporated into long aerobic-dominant in-water swimming training, on the physiological parameters, hormonal factors, and swimming performance of well-trained swimmers. Sixteen participants (age = 25 ± 6 years, height = 183 ± 6 cm, weight 78 ± 6 kg, body fat = 10.6 ± 3.1%) were randomized to either a long aerobic-dominant in-pool training plus three sessions/week of sSIT or a control group (CON) who didn’t engage in SIT. sSIT consisted of 3 sets of 10 × 4 s, 10 × 6 s, and 10 × 8 s all-out sprints interspersed by 15, 60, and 40 s recovery between each sprint, respectively. Pre- and post-training assessments included peak oxygen uptake (V̇O₂peak), O₂pulse (V̇O₂/HR), ventilation at V̇O₂peak (V̇_E@V̇O₂peak), peak and average power output, and freestyle swim performance at 50, 100, and 200-m distances, stroke rate, as well as testosterone and cortisol. sSIT resulted in significant improvements in V̇O₂peak (5.8%), O₂pulse (4.7%), V̇_E@V̇O₂peak (7.1%), peak and average power output (6.7% and 13.8%, respectively), total testosterone (20%), testosterone to cortisol ratio (16.1%), and 50, 100, and 200-m freestyle swimming performance (-2.2%, -1.2%, and -1.1%, respectively). Furthermore, the observed alterations in the physiological, biochemical, and performance adaptations were significantly more substantial in the sSIT group than the CON group (p ≤ 0.05), demonstrating no modifications during the 4-week long aerobic-dominant in-water swimming without sSIT. The current research effectively established that supplementing standard long aerobic-dominant in-water swim training with three weekly dry-land sSIT sessions triggers adaptive mechanisms that foster enhancements in the aerobic and anaerobic capacity and swimming performance in well-trained swimmers.

• Incorporating dry-land sSIT into swimmers’ typical long aerobic-dominant in-water swim training triggers adaptive mechanisms that foster enhancements in the aerobic and anaerobic capacity and swimming performance in well-trained swimmers.

• The changes in hormonal responses suggest an anabolic adaptation to such intervention indicating a favorable training response.

• The swim ergometer is a discipline-specific practical modality for SIT. Utilizing an ergometer allows swimmers to achieve maximum anaerobic power quickly and perform trials at maximal intensity.

• The integration of sSIT into long aerobic-dominant in-water swim training allows swimmers and their coaches to harness the potential of such programs to maximize the quality and efficiency of their training. This approach brings about positive physiological improvements and performance enhancements.